LIBRARY Michigan State J Univertsfy “—— ----—... ... ‘ n$...-.,._, | ‘CI a ~ ‘ ' M. '.'"- I ~ I i . . U'. ' ~ I . ‘ . y‘ ‘ . N o .’ ‘| l - .- Iq‘..'~ '5‘ I ‘ 0 3". . ‘ ‘ h ; '~ I ‘ ' ' . . I I“; ' 1 1 V .. t ’7‘ . ‘ . x. ' \ '. N. I v“ o ' A ' . ' ‘~ ‘ .‘9 Q‘ ~ :_.‘I~Io‘ - . I ”I . - '. I I, ' I .‘ .1 I ' _ ’ .‘ I? J" " r , I JJ'. “0 I ' . ‘ 1.11"." .' .>' — " .I.. :-I . ‘ o A .. , ‘. ‘ , s 1 , . -. . s . V 5 P ‘ e. .- -' .3 ’r ‘ < “ . ' ~§ ‘ JI “ ‘ , .t' r' ' I . , " .‘ ~‘ , ~ ' . . ’Iv.‘ u ' “‘ ‘ v - -" .-' ‘f r " .g "" ~ .- .‘ - \ ' '8.-~‘€ ---r t o u; . 'a I I! - ‘ I" J ' ‘I ‘q. 0 q“ s. I u ) ‘. . k. '. \ ,4 ‘ , . I I. ‘ ' ' -¢ ‘ N, .' I'.’ 3‘ K 7 'I. .'g ”3‘ . 1 A .1I4' y: g, II..~1.,-. .1~ _ i'..‘ n?”- ' l " ~‘ ‘ _ . .0 ' ' h“ n: \ " '; I "J-" a' '1’ I h.) ._ a L "“ I“ ' ‘4‘ '4 ‘ “ ' '- ’I h ' ‘ ' ' ’ \‘v G“ '\ ' \‘L )5; '4=~I {1- )1 y“.- . .r -' . N. .’ jh' ‘. ' _‘. f - ‘J! -\.J ' , -r, = ; 'y' . . . ,. I Hf”. ‘Jt , 1H '4 ‘ (awn *r' .3- ‘ a“ s -‘ ‘ -. - A“h "fibhfif 7-" ~73“? I ~— - - .5 ' A. ‘ . _I ’ . 1‘ , 2 ”r. f‘.” I I! . ..;4 ‘~ ~31; } ‘ 41 .‘(> x“ .t$:" -_ I ItIII I‘ . -I I. . .- u! , v _ \ . O J, , : II A I ‘ ‘0" ‘ . ’ . ‘ r.- E, u; 3‘- ~. ' -' «3% ‘ an - v» Icy-3.42... . .' .. ,r‘A ; _- I - -¢‘.-;.' ‘_ .-. ‘ . ' ‘ '. -‘\. ".3“ 93’s v: 3-: ‘ . \r-i "1‘ -. :1 $115.;- . -‘ - \ ~ ~ . I 1 ('° \ 2 t u" f .i . -. ‘ ,.I. .II. 1 ' I. ~\' ’f\( ‘ - k -l'.‘ ,, . .3- . A. I . .' X. n \f‘ ~. .>,.‘; ‘ 4 If” . 'N' ,‘.-.I- "W“, -'. f ._. . r. ."3 u,‘_'(',);I. ‘ I n ‘ ". , .I, .. :J “\"l' I" y—r ‘ II , . r 1.] .‘ L .*\5 .’¢6 ‘u‘ r ' . v . .I .’ ‘. . - x - .". .' *‘I v.IA. , I I , . I ‘1‘. . ..".;1~.-"7‘»g1-‘.'« P‘. .I:.‘.I I, .. ‘L; ’Vlé ‘ .. I. ~. . ‘. I‘, , ‘1 . ’. 0 ~ 4. Q I.~.IDIK;-. ‘;.‘ I. u . , . ' “. I" . ' ,’ I ,‘ . I - §.~ I'I I ‘ ‘ - . . ' I ‘ . I ‘ . ;- ,s . ‘ I“ ' ‘ _ _. A s ‘I .' I" I, . J“. h _ I . _ , 53‘ [15V L ‘4 L“) .‘ :3", .3 ‘xh I F.“ ‘I {a . \ FA. ' . fin. _. . 'I ","?- '.I I _ II n . \ . l ‘V\ I 5 #1. .I }_ ‘59 .3’ , .r,’ (I ,‘v.,u' I u . 0 .‘ J‘ ‘ ' * ’. ’v".'_ t. N ' .‘ I “V 1‘ ‘ ' 1.}. r" ‘ - -‘ ‘tng'ulv '- ;*,' it"s. I. “V . I’ """ljl‘101'fitfiy; W"; -' s I: V I f‘ {*(U'. " ”t" I ‘ ' . - ' , J: r v I I..' " I‘,J>".\ ' f«;\.~1'~ ~ .‘ $1“ 0 ' J . -',‘ o .f‘;’:“ly.l.“\> \ " h‘ \a "‘. 'u-"l‘lx" ‘ . k’,‘ ‘ W‘. -‘ "I . d-. I . s ,. -. ; . - .um .310 ,- . g a 2 5" As '0‘ . ‘.'I. ‘I '3‘; I_ 3‘ ' .1.I‘¥:\ II’ ‘~: 14‘...’ . f I \ ~ -.’ ' .I v "p 15 ‘ II- - Eff“ . "3“. ”1'“ (a. l ' ‘ . :fi‘. ' ' ? ..-~ . '~ ~ ', 0‘5‘ a.‘ ‘ '- ' I . .w, ‘ - ,r. . -.,, v I , m- g‘ . , ‘ . - .63 . . x. __ is '~» ‘4‘. f" . r . " ._ I .5 ‘1'?“ ,_ . . ,. . . . .‘ 25.1": 5'-" , ' t g . ‘J. a} '9 ¥ - ‘ ' ’y' ' 4 '\ of’l‘ ‘ ‘i' .‘ > I - I . | " I . ~ I fi‘N.‘ w. a. ' . "' k I” . ‘ ‘ ~ » » . ' v . A] 3'" - l. l ‘l ' ‘ .W . ' ' . 3*" F» dry"! ‘ . .§‘ . . .. “I“.:‘.‘ I;;,-. . . ." .. ' o 1": rfl~ '2 ‘; L,» .1 “*fi'. I‘ I. .I - _ . " _‘..\ ,- "W. $4,..." I I T ." J-I , x1 .'I . fl. II I- . ,~_ \h._ “n“ - $3 .- . . ._ ‘- -~{.“ - ‘\ Lt“! ’.{1‘§¥' ‘I ”Big-‘52 a 31;“: .. , I -,~. 1 ,. I {4" 'v-. II . _ I . .l‘ .I. l. ‘3‘. I J3- . ~ . _ - ' .~. . ‘ - . ‘ -' a, V . I . . 9 ' Ow" ’. . a I ~.. II .Q. o Ig- I: ' .‘Il I’TI‘V"‘*.“ ll: ' I ‘ O ' . .iI . I f. _ .. _ I . u . y .I" . “_ ‘ ‘-‘ = . I . . ‘ . .. . . .h; I ' '. . . :. II n ..' y I , ‘.'- V. ‘ v. ’k. '. I , A ‘v ‘ . I o _ I'I . .. . . : < . . « . I I " ' ‘ ' “ ' ‘. ¢ “ 'K' III". Vfi ‘1'??? i 0' " . j .' I " .4 ' ‘ ' .' n . ' - . AI. ' ' . -. ' ‘ - . . :-‘, l‘ . I‘ V i V”. " r .‘ ," . - . . I. - ‘ . ' ‘ . "‘ ' ~ _. . ' ,. I I u A T. \ ;, . “I ( v1 4*. '- - .' .' . , . ' . ' ”'3 . .\ . - 'n .- ' n; I-s . I "' ‘ - ‘ _' n " ..‘ I ‘, ‘.-'."1"e-'.'~ ‘ '.~\' - ‘ ~ I ." - . - _ , . I-I I . , I a -‘o.. \‘I . » ' , . . ' ‘ in"? . ‘ ' .' . ~ - 7. . . "'2 ' - -\,q‘o. . - v . ‘ . ' ' . ‘ ". - - . . _ ‘ O . f .‘ ,- "Nd. . I . - 4 . ~ -_ ~ ~ ' l 'f w. c ‘ I'I . u , r. I. . l .‘ . \ ‘ I . new“ . , _. I ‘ ‘ d‘.’ ‘ ‘31.”. .‘ r 1 . c ( ‘ .7“ .— .. 1 . .I_- . . ' u C d "'- u. ‘ c- ‘ l‘. v‘. | v ' I '. '. ." - - t' ,1 ' . I o 'I ‘v -‘v ' ' I“ , . {’3}; r\ r , . ."I .4. ' ., - ‘ '4’ . 7- . .4 7' I): , ‘ . ,‘ ‘ ’I|’.\. ' I : .1 .m ..... , . ‘3' f. . ‘ .1 ' I . g ' Q — c "v‘- I .I - . v ." . ‘ IO VI . , jv .‘ I'.. .. - I . z ‘ . - . Q I 5 . ) ' -o.‘. ‘- ‘I ‘- ' . ,' I, . ~ . oI ,'.' v ‘ "' 1‘ - - u ‘ ' ' ’5‘ ‘ I n O l | I . I g, ‘ s" . I o, . - ~ ‘ ‘$~‘4.“' , . ‘ .. _ . . ,. - I I II , ._, ‘ I _ . . .- . . I -. . , 'I $.f ’ . -_ .‘ I. ” . ' . y“ a ‘ ‘fi - ‘ .'\- . 1'. . . A, I .. t f' . I . ‘ . ' . ‘ i ‘ ’ b - \. ',. H . . r'. , c ‘ K . “ w - , - . j . I- . v, A ' '. ‘ II‘ “ :11. l u ' _ - a ‘l ‘ _ '9 m x ' ‘ . I ‘~ .c ‘ ~ ' ‘l v .‘ I-‘I . I” \' ’3 ' ~ 0 ‘ '. ‘ . r ' x. -.I.I“t.~’ . \_. . 3 "3' .‘a: . I . . , ' ' 1 U "rv‘ju‘. .‘ I - I,” _. I _. . ' .. I’. ' . . I—p" I . b '_-_, I . ' " " " ‘ .' . I ‘. l \/ ‘ ‘ '."I.I JI. 4 '. v § '.\ ' ‘ ‘ A u ! o_ o ‘ y I. , t“ -" -: e'. ‘.z I I . n \ .' u. I; I ‘ . . I . . . ‘ ..‘. . .. . - 'A - - ‘ - .. l \ .- 4-.A. , ' ‘ . .' ‘ ' \ '. .. ‘, ' ’ ' . - . . - ' Mu * ‘1 . ‘ ‘ V. ' . ’ . ' ' 9' r I ' . . . . ‘II I‘IJY‘:'-- . 'L .5 ,II 3" I b ' Cr; II I. ., _ I}. . -,-o hu‘. ' ‘ ‘- ' ‘ n " ' ' ' , ' ‘ '- - ’ . ‘* .-. ‘\ , ’ ‘ . .' , - I I , I-_ n . . , ' - v ‘ V. . I _..‘ ,— '¢ I 7M! ,' _ .II.. 1 - . I' ' r ”i . I._»..£‘3‘ . . I -', I .. '. . . . . . I. I . ,‘I . II I I _ I __ . I ,. _ . I . _ -. 3. '.I . I_ “I - I I '. 9 o 7, 3-} .. I“: ‘5‘“ A, ' , . . ‘. -.I 34;?“ ‘_ . '. _ ~. I.. _ I. . - -u' . . I . , I . I I . . . ' . 2 4I . ‘ . kf .' - -- . . A . ”it'll“ ' . a’h . ‘ I . V 4" {.' "' ? - I. n 1‘ -. M ‘ V‘ ‘ 1‘ ', )t t ' - V - I p ‘ _ ‘ ”.5 ,vITI‘.‘ 3,: "1“.) ' s 9 -- I . I. , - ' |.- I ~-. . . '., I" ,.A.‘ .‘ . M" I '- ‘ . . . V I .. 'rfl‘ ‘ ‘1 3‘3“": ‘ ‘ M " 25-: ’5! M I. :w'\,.‘ I ‘ ' ."_I . . I-, ~. ,"" .. . "... 5". STUDIES ON TRAPPED MIIK (M"S$ELA VISON MIKE) IN SOUTHEfiN MICHIGAN. by John Arthur §§alander A THESIS Submitted to the Graduate School of Michigan State College of Agriculture and Anolied Science in partial fulfilment of the requirements for the fiegree of MASTER OF SCIEKCE Department of Zoology 19h2 W28 time author wishes to express his deepest appreciation to Mr. B. 1‘. Ostenson for counsel and guidance during the course of this study and in the preparation of the manuscript. Sincere thanks are extended to ur. Wham». Dr. 9. 1. Tech, and Dr. R. A. roman of the Department of Zoolog tor the information, helpful suggestions, and constructive criticisms which they have offered. ' Gratitude is expressed to Professor A. I. Ioodhead, of the Univer- sity of lichigan, for providing me with a umber of stanachs collected during the winters of 1938 and 1939. For aid in identifying some of the parasites the writer is indebted to tire. Virginia Stoney of the Game Division Laboratory of the Hichigan Department of Conservation and to Dr. 8. I. Price, Ir. J. T. Luther, and Mr. Allen HcIntosh d the Zool- ogieal Division, Bureau of Animal Industry. Acknowledgement is also due to the Michiw Dapartment of Conservation and to members of the . Gare Division for the information which they have placed at nor disposal. The writer has greatly appreciated the splendid cooperation of the many fur-buyers encountered in the field who provided the material used in this study. The photographs appearing in this thesis were taken by Dr. P. I. fleck of the Zoology Department. Do all others who have given aid and encouragement in this under- taking, the writer extends his thanks and appreciation. mor CONTENTS Page Introduction.......................... ..... . ..... ..... ..... ........ 9 laterials and Methods........................... ...... . .......... .. 12 Source of Material and General Procedure...................... 12 Measurements... ........... ... 11+ AntOpsies.............. ..... ........ ................. ......... 15 Visceral Analysis........... ......... ..... 16 Stanachs....... .......... . ......... ........... . 16 Intestines........ ..... ...... . .............. ...... 18 Dead nebits................ ............. . ....................... ... 19 Discussion of Results....... ........ ............ ........ ...... 20 Nonfood Items.................. ...... ............... ..... 31 Sex Differences in food Habits................................ 33 Predation..................... ..... . .............. . ......... .. 1‘1 Annotated mu or load Items. 1+8 Manuals" ................... .. 51 Burden..." .................... . ....... . .......... ...... 52 Reptiles...................................... ......... .. 52 Amphibians........ ............... ... 53 Dish....... .................... . ................... ...... 53 Crayfish“... ...... . ...... ...... .. ......... . ....... .. 53 Insects................ ...................... .... ..... ... 53 Other Items.... 53 M List of Food Ito. found in Stomachs and Intestines..... 5h Mito. ”dD1.°aa°'...........OOOOOO....0.... ..... O ....... 00.... 56 68 memEOOOOOCOOOOOOOO..OOOOOOOOOO ......... OOOOOOOOOOOOOOOOOOOOOOQC P863 [signs and neasuxements........................................... 72 Identification of Sex by Heasurements......................... 76 Separation oflge Groups............. ............... .......... 81 Oman"... ...... ............... 87 Oonclusions................. .............. . ..................... ... 89 EflanIssssoosooossooo.o........................................ 91 mnuOOOOOOCOOO...O0.0.......O. ....... .... 000000000 ......O..... 1 TABLES . Page Table l. Percentages by frequency and by volume of the food items found in the stomachs of 102 winter mink. 1938-19u1.......... 21 Table 2. Percentages by frequency and by volume of the food items found in the intestines of 101 winter mink. 19140-19h1........ 23 Table 3. Percentages by frequency and by volume of the food items found in the stanachs of 55 male mink. 1938.19u1............. 3h Table h». Percentages by frequean and by volume of the food items found in the stanachs of 1‘3 female mink. 1938-19h1........... 35 Table 5. Percentages by frequency and by volume of the food items found in the intestines of 57 male mink. 19110-19h1........... 36 Table 6. Percentages by frequency and by volume of the food items found in the intestines of 37 female mink. '191‘0-19’41......... 37 Table 7. Tests of sigtificance of the difference in rate of occur- rence of prey items found in the stomachs of 55 male as can- pared to 143 female mink..... ..... . 38 Table 8. Tests of significance of the difference in rate of occur- rence of prey items found in the intestines of 57 male as can- pared to 37 female mink....................................... 39 Table 9. Computed hills of muskrats, cottontails, and mink for 18 southern Michigan counties compiled from hunters. and trap- pers' reports for the period from 1938 to 19ul................ 10’. Table 10. Average precipitation in inches for the months of July, August, and September in zone In from 1933 to 19h1........... 1m Table 11. Embers and percentages of four major food items found in the stomachs of 102 winter mink from 1938 to 1931.......... ”9 Page Table 12. Incidence of some helminth parasites found in trapped mink taken curing the trapping seasons of 19130 and 191F1....... 58 Table 13. Tests of significance of the difference in percentage of infestation with some helminth parasites of mink taken during the trapping seasons of 1940 and 19h1........,.,.,..... 59 Table 1’4. Smarty of the weights and measurements of 157 mid: collected in southern Michigan...u........................... 73 Table 15. Sumner); of the skull measurements of 126 min]: collected in southern Michigan"... 7‘4 Table 16. Tests of significance of the difference in body measure- ments of mink collected in 19% as compared to those collected Table 17. The detemination of the predicting equation for weight loss due to skinning.......................................... 77 Table 18. Emery of baculum measurements of 80 mink collected in .Outharn niaimoooeeeeoeeeoeeeeeseeeeeeeeeeeeeeeeeeeeeeee... 8} IIIUSTEATIONS P889 figure 1. lap of the study area...... 11 figure 2. Graph showing the relative prOportions of different classes of annals found in the stomachs of winter mink....... 26 figure 3. Graph showing the' relative proportions of different classes of animals found in the intestines of winter mink..... 2‘! figure it. Graph showing the relative preportions of different genera of mammals identified in the stomachs of winter mink....28 figure 5. Graph showing the relative preportions of different genera of manmals identified in the intestines of winter mink. 29 figure 6. Graph showing computed kills of muskrat, mink, and cottontails in the study area as indicated by trappers' and hunters' reports.............................................. ‘15 l'igure 7. Graph showing computed muskrat kill as compared to average July precipitation.................................... ‘47 figure 8. Graph showing the percentage by volume of four major food items in the winter diet of the mink over a four year period........................................................ 50 figure 9. Lungworms, l'ilaroides bronchialis, in the lungs of a mink (courtesy of the Michigan Dopartment of Conservation).... 61 Figure 10. A mink infected with the giant kidney worm, Dioctom 52921.3. The infected kidney is opened to show the worm in place. (courtesy of the Michigan Department of Conservation).. 63 Figure 11. rrequency distribution of testes volume of 68 mink..... 'PO page figure 12. bequency distribution of hind foot measurements of 61 female and 93 male mini: 79 Iigure 13. Graph showing the comparative chances which an animal at a given measurement has of being a male or female.......... so figure 1’4. Iroquency distribution of the lateral diameters of the base of the bacula of 77 mink sit figure 15. Iroquency distribution of the weights of the bacula of 76 minkOOOOOeseeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeecoco... 85 IITRONOTIOD ”111881 of the literature on mustelids reveals that to date pub- lished information concerning the status of the mink in the wild is rel- atively incomplete. The accounts of cones (1877), Seton (1926), and Bailey (1926) are of a general nature while the many articles published in veterinary and fur-trade Journals stress, chiefly, the practical aspects of mink ranching. A considerable body of literature is contain- ed in fur-breeding sections of sporting mapsines and in periodicals catering to the for industry but much of this materiel is difficult of access and, in new cases, of rather dubious amthenticity. Other pub- lished information existent does not, by any means, satisfactorily ans- war the new questions which arise concerning the relationships of this animal in the wild. he mink is one of Iiohigan's most important fur-bearers, generally ranking about second in annual fur value. Approximately fifty percent of the mink trapped in llichigan are taken from the southern Inlf of the Lower Peninsula. his region, which includes most of the good agricul- hired land of the state, annually produces the majority of the crap of furs harvested by Michigan trappera (Kayne, 191a). Thus, along with other fur-bearers, the mink augnents the incomes of people in rural sec-- tions to no mall degree during the trapping season. In view of its importance as a fur-bearer, the mink has received surprisingly little attention. This may be due in part to the fact that, unlike some other fur-hearers, it has hen able to survive and even increase despite intensive trappinG. hunting, and reduction of suit- able habitats in agricultural areas. According to trappers and fur- buyers the mink has been increasing rapidly in nunbers during the last 10 few years and all are vociferous in their complaints about the inroads being made upon the muskrat population. There is a tendency on the part of the trappers and fur-buyers to attribute this increase to the law which prohibits the disturbance or molestation of any hoaver, musk- rat, racoon, or rabbit house, hole, burrow or den. Bocause the min): frequents and uses the same situations as do the aforementioned mammals the trapper is virtually prevented from hunting them with dogs. The trends in computed kills, as indicated by compilation of data from trappers' report cards, tend to substantiate their conclusions in re- spect to a population increase. However, a coincident upward trend in the computed kill of most other fur-bearers, including muskrat, is also indicated and hence caution is necessary in searching for the cause of such trends. The only available studies of the species in Michigan are those by Dearborn (1932) relating to food habits, and by Harshall (1936) describ- ing winter activities. Other published information concerning the mink in Michigan is only fragnentary. The object of this research was to accumulate as much information concerning the species, from the available material, as was practicable and to interpret the data as correctly as possible in the ligit of known facts since the preper evaluation of data concerning food habits, parasites, and the like is of fundamental inportance in determining sound management practices for a species. In contbucting the laboratory examinations, standard procedures were followed as a rule. However, whenever it seemed feasible special techniques were adapted in order to secure additional information. :1; J} TLH J1 TL] 1 gar s %' u—a MAP OF THE STUDY AREA.- Large dots indicate The localities from which specimens were secured. figure 1. lap of the study area. ammo All) names Since this investigation was largely confined to the laboratory, the writer deemed it expedient, from the start, to glean as Inch inform- ation as possible, relating in any manner to the animal in the wild, from the material available which consisted of entire carcasses of nit besides a number of individml stmnachs. To this end a specimen record (see Appendix) was prepared upen which all observations concerning each individual specimen were entered. As the individual records were cas- pleted they were cataloged in chronological order. has all observ- ation pertaining to a single specimen were conveniently placed to- gether while the records would also be easily sorted to assemble parti- cular groups of data for inspect ion. be principle techniques employed in gathering the data pertinent to the problem will be described here. liner procedures and special techniques which were adapted to the securing of more specific inform- ation will be discussed in the teat wherever it seems feasible to do so. m 2: ans—4am awaken ' a large portiOn of the material used in this study was obtained during the months of December 1910 and December 1911 from southern Iichian fur-buyers (see fig. 1). Previous to the trapping season the fur-buyers were visited and containers left with them. a five percent fonnalin solution was placed in each of the containers and the car- casses of nit beugit from trappers were placed in this solution by the fur-buyers. ate bwers were requested to place a tag, bearing locality and approximate date of capture, upon each specimen before immersing it in the fomelin solution. they were also instructed to slit the wall of the abdesen to allow quifi and thorougi penetration of the preserv- ative to all parts of the body. he carcasses were collected at intervals during the trapping season from the fur-Wen in order to secure as reliable data as pose- ihle and to decrease the loss of specimens throng: improper handling. In a few cases, it was found necessary to discard specimens which were extrasly dessicated and undergoing deconposition because of incomplete insrsien in the preservative. However, when the carcasses were proper- ly handled the formalin solution proved sufficiently strong to insure good preservation and there was no appreciable loss of specimens. In most instances when the dealer operated on a small scale the carcasses secured represented catches of local trappers. However, some of the larger dealers who were contacted secured animals from trappers located within a 25-50 mile radius. this fact was kept in mind when blocking out the limits of the stew area. County boundaries have been followed in delimiting the area in order that available population date upon fur-bearers, for the various counties, might be better utilised. In addition to 158 carcasses collected from fur-buyers, a total of ii} stomachs were kindly turned over to the writer by Professor 1.. I. . Ioodhead, of the University of Michigan, who has been engaged for sane time in the stuw of the life cycle of the giant kidney worm, m 29.93.. in the mink. i'hese stosachs were taken from mink collected in southern Iichigan during the winters of 1938 and 1939 and have been in- corporated into the study. Stmachs and intestinal tracts fras several mink taken in the winter of 1910 were also received from Ir. Don w. anne of the Michigan State College Department of Zoology. After collection from the fur-buyers the carcasses were brouait back to the laboratory and transferred to a ten percent formalin solution. Iach specimen was assigned. a collector's anchor and this together with locality and date of capture was recorded in india it upon a parchsent tag. file data pertaining to each specimen was then recorded under a corresponding series of numbers in a catalogue at the time of examination. me: After removal from the preservative, each specimen was weighed to the nearest gran on a trip Nance. Care was taken to drain the body cavity thoroughly and to remove all excess fluid with absorbent towel- ling before doing an actual weighing. Standard bob measurements were taken on all specimens before autopeying them. mess measurements are as follows: total length, on bow stretched out to its full length, from tip of nose to tip of last tail vertebrae: length of tail, from a central point in sharp me on upper side at base where tail can be bent at right angles to hck, to tip of last tail vertebrae: length of hind foot, with sole flat, at Mt angles to leg, from hinder-est surface of heel to tip of longest claw: length of ear fun notch to tip (taken on unskinned specimens). Since the nasal cartilages and nose pads were lacking in the skinned specimens the measurements of total length are free five to ten milli- meters less than those taken on unskinned‘ specimens. After the bodv measurements were telcen the head was severed frme the bow at the Jincture between the occipital condylee and the atlas vertebra. All excess flesh was then removed from the skull before taking cranial measurements. me cranial measurements taken were as follows: condylobasal length, from posterior edge of occipital con- files to the anterior border of the upper incisors: mastoidal breadth, greatest transverse dimension of skull across the mastoidal processes: least interorbital width, breadth of cranium across the frontals at 15 narrowest place above the orbits: length of upper molar-premolar row, from posterior margin of alveolus of last molar to anterior nmrgin of alveolus of premolar. After removing all of the flash from the bacula, a umber of measure- ments were taken. miles are as follows: greatest length measured in a straiglt line fro: the proximal end of the base to the tip of the shaft: greatest done-ventral diameter of the base: greatest lateral diameter ~ of the base: greatest dorm-ventral disaster of the median portion of the shaft: greatest lateral diameter of the median portion of the shaft. me hcula were also'weighed to the nearest milligram on an analytical balance. Before ”idling, the bacula were deg-eased in xylol, dehydrat- ed in 95 percent alcohol, and then left in a dessicator for an hours in order that all excess moisture would be eliminated. Volumes of testes (including epididymis) and ovaries were determin- ed by water displacement. Length and breadth of these crane were also measured in millimeters. The measurement of volme was found to be unu- eatisfactory for the. ovaries since the volume was so small that it could not be accurately measured. _ . All of the linear measurements, with the exception of total length and tail length, were taken with a Vernier caliper to the nearest 0.1 of a millimeter. be total length and tail length were measured to the nearest millimeter with a meter stick. mtmies Autopsies were performed upon 158 animals during the course of the investigation. he specMens were first inspected for any outward signs of disease or parasitism. lest, the body cavity was laid open with a pair of heavy share and the general condition of the viscera noted. Stomach and intestines were removed and tied in cheesecloth together with the specimsn tag. They were then placed in ten percent formalin to be mined at a later date. The other organs were mined very carefully for evidences of parasitism or for anything of a gross patho- logical nature. lhen parasites were found, a amber were usually saved for identification and a count or estimate of the number present in each orpn was nude. In addition to the organs in the body cavity, the nasal passages and frontal sinuses were opened to permit inspection for parasites. u... M W a total of 216 stomachs examined, 93 were espty and 21 contained unrecognisable amorphous material, vegetation, and trap debris. Included in the trap debris were such items as dirt, sticks, trap pads, and toes chewed off w the animal while in the trap. This left a total of 102 stomachs upon which to base an appraisal of the winter diet of the mint. In staining the stomachs it was usually noted that a single item of food was represented. lateral exceptions to this were recorded, how- ever, eons of the stcnachs containing from three to four different items. has material in the stomachs was usually chewed into pieces which were one-half inch or mealler in sise. Usually the fleshy material was at least partially digested. Small manuals, fish, and crayfish always appeared to be thoroughly chewed while larger prey was appuently swall- owed in larger chunks. he volune of the conthts of the stomach was determined to the nearest 0.1 ml. by water displacement. Volumes under 0.1 ml. were re- corded as traces. nae contents of the stomach were washed into a white 1? enmeel pan to render the food items more visible. If more than one item was represented the volume of each was determined after the contents had been carefully separated. Ihen a large amount of fat or grease was pre- sent which tended to obscure the identity of dimosfic items, hot water was used to remove the excess. a series of sieves of varying mesh proved useful in separating food particles of various sises making it possible to separate diagnostic items rather easily. Ligit colored or white ob- Jects often were readily picked out by washing the contents of the stem-- ach into a large culture dish and placing this over a black background. i'he mini-n timbers of individuals (as indicated by counts of appendages, bones, etc.) of each item represented in a staunch were alwavs recorded. In all cases identifications were as specific as possible. Ihen items could not be imediately identified, diagnostic parts such as hairs, scales, claws, etc., were placed in an envelope together with the catalogue number of the specimen and identified later. Diagnostic items which proved most useful in making determinations were the hairs, teeth, and claws of manuals: feathers of birds: scales of reptiles and fish: skin and feet of sulphibians: and the herd chitinous parts of crayfish and insects. Cross sections, medullary patterns, and cuticular scale patterns of guard hairs were utilised in identifying male. In most instances determination to genera was possible by casparison with know emples and through the use of keys. The publications of lathiek (1938), lilliams (1938), Dearborn (1939), and Hardy and Plitt (19‘10) were es- pecially valuable in this respect and were constantly used. Studs' h'east feather key to the orders of birds north of flezico (tight, 1939) proved useful in same cases for confirming the identification of feath- ers. no action of digestive Juices upon the feathers often mitipted 18 the value of this key, however, and direct comparison of feather color and pattern with known specimens proved more trustworthy. Action of digestive tuices upon fish scales, resulting in their partial dissol- ution, made it practicable to determine them to family only, even though a usher of the better preserved scales could be identified to species. Other items were determined as accurately as possible depending won their condition. Intestines—ad total of 166 intestines were examined. 30 of these were empty and 35 contained unrecognisable material, vegetation, and trap debris, leaving 101 intestines from which the frequency and bulk percentages were computed. frequency percentages are based on 101 in- testines while bulk percentages have been computed from 69 intestines. m intestines were slit lengthwise and the contents washed out into a pan. The contents of the pan were then poured into a umber so mesh screen. nae material was concentrated by the removal of all excess water by thorough draining and by absorption through the screen with towelling. Due to the fineness of the screen, a negligible loss of feed particles occurred. Volume of the contents was then determined to the nearest 0.1 ml. by water displacement. Ihen more than one item was represented a bulk estimation of the relative proportions of each item to the total bulk was made by inspection since the material in the intestines smld not be easily separated. Hence there is a wider margin of error in the volumetric measurement of food items in the intestines than in the stomachs. Identification of food itqns was essentially the same for the in- testines as for the stomachs. Because of a greater amount of amorphous material and debris in the intestines, a more thorough straining W sieves of various meshes was necessary to uncover diagnostic items. m name he economic status of an animal is determined to a considerable (extent by its food habits. Is it destructive or beneficial! 130 that extent is its choice of food determined by availability! How do its food preferences affect other one or fur animals? !he 'final decision as to the animal's economic position is dependent 'upon the silvers to these as well as to other related questions. be present study, based on winter mink only, is admitteny lacking in the canpleteness which a year-round study would provide. However,- the studies of nearborn (1932) and. Hamilton (1936, who) should serve to bridge this hiatus satisfactorily. Since the study covers the critical period during the winter when animal pepulations are on the anus, it is . felt that some lidit niat be shed upon the problem of predation by the mint, particularly upon the mush-at. Also a food habits study over a period of years allows for a better interpretation of results by making it possible to empare abundance and availability of food items as well as to appraise the effects of certain external factors affecting the animal's activities. i'o facilitate comparison with other studies, both volueetric and frequency percentages of prey items are given. the amber of indivi- dulls of each prey item represented in the diet is also included to melee a couparison of stmnachs and intestines possible and to allow a proper evaluation to be placed an the small» itans in the diet. me percentage occurrence index tends to place more emphasis upon items which appear in many stomaChs even though lacking in bulk but does not tabs into account the fact that two or more mall items of the sun hind may occur in one stomach. fiance the relative numbers of small item taken by an animal are often not properly emphasised either by volume or by frequency. From an economic standpoint the nmsbers of the various items conemed are often more inportant than either volume or frequency since they allow canparison with figures on abundance of prey, economic status, etc., all of which are measured by individuals. The volmaetric method on the other hand gives the best indication of which foods furnished the bulk of the animal's sustenance. Intestinal amlysis has been used to supplement stomach analysis in so far as possible. i'he combined data for the four year period are not strictly comparable, however, since intestinal analysis was made only on the specimens taken during 19% and 19141. lbs results of the stomach and intestinal analyses are presented in tables 1 and 2. Discussion 9!. results As lelson (1918, p. l+72) has aptly stated, “few species are more psi-teeny adapted to a double mode of life than the mint. It is equal- ly at home slyly searching thickets and bottomland forests for prey or seeking it with otter-like prowess beneath the water.“ i'hie double mode of existence is amply borne out by the results of both stomach and in- testinal analyses since aquatic and non-aquatic prey items are about eqmlly represented in the diet. All of the min]: examined appeared to b exclusively carnivorous. Grass and other debris when found in stom- achs and intestines was present only in very mall quantities and was usually associated with the smaller prey items suggesting that it was bolted along with the food. fherefore such material was seemed to have been incidentally ingested and is not considered as a regular part of t]! diets Table as Porcentages by frequency and by volume of the food items found in the intestines of 101 winter mink. 19140-191u. nunber of indivi-I percentage percentage gem (1113.1; items m volume occurrence Mammals: volume-«53.90 f frequency-«$5.314 f unmet, 0ndatra 21* 17.61 23.76 Cottontail, yivngggg 16 11.38 15.811 Meadow Mouse, Hicrotus 8 10.08 7.98 Deer Mouse, r scus 1‘ 6.18 3.96 Pine louse, m 2 3.0“ 1.98 Short-tailed Shrew, Blarina h 2.71 3.96 Star—nosed Mole, Conglura 2 1.30 1.98 Long-tailed Shrew, m 1 .91 .99 Snowshoe Hare, 31929.9. 1 .08 .99 House House, _1tu_g_ 1 .00 .99 Brown Bat, m l .00 .99 Unidentified 2 .98 1.98 Birds: volume—5.20 f ..— frequency—7.92 5 Domestic Chicken, M 2 1.30 1.98 pheasant, zhasianus 2 .33 1.93 miffed Grouse, £22133 1 .00 .99 lg (Domestic Chicken) 1 .5’4 .99 Unidentified 2 3.014 1.98 mules: volume-«22$ frequency-99 fl Snakes (unidentified) 1 .21 .99 Table 1. (cont e) lumber of indivi- Percentage Percentage 1193; dual items by volume occurgggg m1 l'rog, fig 3 2.511 2.98 Spring reaper, 113 1 .05 .98 Unidentified (frogs) 8 2.02 7.811 fish: ”lune-«5.89 f frequency-40.78 fi Gentrarchids 6 3.22 5.88 Catastomids 2 1.18 1.96 Cyprinids 1 1.15 .98 Unidentified 2 .35 1.96 ArthroEods: veinne~1.8h g frequency-«5.88 fl Crayfish, dentures 6 1.811 5.88 Totals. . . ........................ 131 100.00 123.53 25 Representation by classes shows that in both stomachs and intestines manuals constitute well over half of all the food eaten. Graphic pre- sgntation of these data are given in Iigures 2 and 3. The amber and relative proportions of the different genera of mammals occurring in both stomachs and intestines did not differ greatly (see rigs. h and 5). It is noticeable, however, that the volumetric percentages for slall manuals tend to be larger in the intestines than in the stunachs, whereas for the cottontail and the makrat the opposite seems to hold true. this seems to be the case for fish, frogs, and crayfish as well. Since chiefly the fleshy parts of larger manuals appear to be eaten while smaller manuals are apparently eaten entire, it seems reasonable to accuse that the change in relative proportions by veins are the result of digestive action. ' fhe fleslw parts of auskrats and cottontails eaten by mink may be expect- ed to decrease in bulk as they traverse the digestive tract. mall mam- mals vhioh are eaten whole, however, have a relatively larger proportion of indigestible parts such as hair, skin, and bones, and hence would be expected to increase proportionately in volume as they pass from the stomach into the intestine where digestion is completed. the hard, chit- inous emosheletons of crayfish and insects, and the scales and bones of fish, being relatively indigestible, likewise tend to form a larger per- centage by bull: in the intestine than in the stanach while frogs which consist largely of soft parts show a decrease. In capturing scat, in- testinal, and staunch analyses, then, this sort of evidence mist be kept in mini. } me volunetrio percentages, on the whole, appear to be far more re- liable for staunch analyses than for intestinal analyses and in general it may be said that percentages of occurrence are more consistent, as a FREQUENCY AND VDLUMETRIC INDICES OF DIFFERENT CLASSES DFANIMALS IDENTIFIED IN THE STOMACHS or 102 WINTER MINK. 100 SDI: 80- B Frequency Indices .Volume‘tric Indices Em a § Mammals Birds Snakes Frogs Fish Crayfish l'igure 2. Graph showing the relative preportions of different classes of animals found in the stomachs of winter mink. FREQUENCY AND VDLUMETRIC INDICES OF DIFFERENT CLASSES DFANIMALS IDENTIFIED IN THE INTESTINES OF 101 WINTER MINK. a} Frequency Indices W Volumetric Indices V '//////////////////////////////////////////// 4— § kkrfi ls Birds Snakes Frogs Fish Crayfish Insects Mom 3' Figure 3. Graph showing the relative proportions of different classes of animals found in the intestines of winter mink. VDLUMETRIC AND FREQUENCY INDICES OF DIFFERENT GENERA 0F MAMMALS IDENTIFIED IN THE STDMACHS OF 102 WINTER MINK. IOOF‘ 90— 30L 8 70-— i; ‘U C o 60%- I- \ . . 250— § CIVolume’mc Induces U § V . g $ «0 .Frequency Induces u § 8. 0.40— a 2 § .- ‘~ 2! a m 73C)"' §§ U! u) § 3 3 \\ ‘+— ca ‘\ c: v) in § ‘- > >. 20'— s .2 E E g .\ 2 E > 2 ‘n a. § m 1:: 'z 3 g 10— 3 ‘L “- ‘3 -“-’ i; m § IE 2 m a: 6; \ § FE Q has 4s gm lime II. Graph showing the relative proportions of different genera of male identified in the stomachs of winter mink. VOLUMETRIC AND FREQUENCY INDICES OF DIFFERENT GENERA QF MAMMALS IDENTIFIED IN THE INTESTINES OF 101 WINTER MINK. Sorex Lepus Mus Rsttus Unidentified 100_ 90r- 80» 70- 60... +— 50% g DVolumetric lndices 5 ° IFrequency lndices u 2 m m 0 3‘ E40” 3 m E 2 g 30» 3: g t: -- >. 2 g a g 3 20‘- : E .g s. E’ 2 E 10% l m u I E IE IE rig figure 5. Graph showing the relative proportions of different genera of manuals identified in the intestines of winter mink. rule. Single occurrences of large, bulky items, such as the coot found in one of the staeache, often tend to place a disproportionate amount of emphasis upon the volmetric percents. when only a few items are repre- sented. Scott (19%) has concluded that the frequency of occurrence method in fecal analysis provided for the most reliable interpretation of the relative quantities of food consumed. nae findings reported here tend to support those of Scott although no really learned degree of dis- parity could be discerned between the two methods of representation. A further source of error is involved in the determination of vol- usetric percentages in the intestines. astb from that introduced when mking bulk estimation of the relative proportions when more than one item was presem. Ihen removing the contents of the intestine, a cer- tain .ount of the mucous lining of the intestine was unavoidably in- cluded with the intestinal contents. In an intestine which is chly partially fall this material would time tend to put a disproportionate mount of emphasis upon the bull: determination. lven though the mount of mucous lining remains as a more or less constant factor there is the possibility that those items occurring less frequently receive an undue amount of eqhaeie. A sipificantly greater nunber of crayfish were found in the in- testines as compared to the stanchs. Also a significantly greater usher of frogs were found in the stomachs as caspared to the intestines. It appears probable from these results that a differential rate of pes- eaae of different food items exists. Apparently the hard, indigestible pieces of food are passed rather quickly from stomach to intestine while fieshier material is retained in the stomach for a longer period of time. crayfish consisting largely of hard parts, and frogs consisting largely of soft parts migit then be expected to show the greatest difference in rate of passage. Items such as manuals, birds, and fish in shich the relative proportion of soft to hard parts approaches neither extrerne nigt well be expected to be passed along the digestive tract at a rate somwhere between that for frogs and crayfish. Dearborn (1932, pp. 11*- l5) has shown that evidence of a meal eaten by a mini: continued to ap- pear in its feces for three days after the meal was eaten. lrrington (1935, p. 197) has noted residue of indigestible material, such a. were feather butts, teeth and claws, coarse hair, etc., in stomachs and - throughout the length of the intestine of foxes which he seems are passed in from the stomach, bit by bit, over variable periods of time. It would seem however, that this resimal material would not be retain- ed in the stmach for a very long period of time even though such re- sistent particles from prey individuals 1111th be retained for several days in the intestine. he findings reported here tend to corroborate those of Dearborn and Hanilton in most respects. Birds and frogs were taken more freq- . uently then shown by either Dearboru or Hamilton, while fish were taken less frequently. his greatest discrepancy is found between these find- ings and those of Hamilton. Undoubtedly abundance and availability have affected the relative proportions in which prey items appear in the diet. This serves to emphasise the point that to gain a reasonably clear pic- . ture of the general food habits of an animal it is necessary to collect food habits material over its entire range and over a period of years. lonfood a! Included along the material falling into this category were unrecog- niseable amorphous mixtures of dirt and black protein waste, vegetation consisting of grasses and aquatic plants, and trap debris made up of such items as dirt, sticks, trap pads, and toes chewed off by the animal while in the trap. lost of the vegetable material showed relatively few effects of digestive action. he amorphous material, as is to be expected, was largely found in the intestine. . Inch of the abuse material is no doubt taken incidentally and is to be expected in the stomachs of predators which capture. and bolt small animals or feed off carcasses ell the noted. a certain amount of veget- able material midit conceivably be secondarily acquired from herbivorous animals which are captured as prey. It is problematical Ihether or not the animal would deliberately eat dirt or vegetation in an effort to relicve vitmin or mineral deficiencies although ingestion'of such mater- ial probably does have a definite nutritional importance. he occurrence of hair, toe nails, and toe pads of mink in the stem- achs and intestines of a number of the animals case as no surprise since it is well known that man species of mussels when trapped become infusb iated and chew off the imprisoned feet below the trap Jaws in an effort to escape. It is possible that ease of the mint fed upon other members of their kind caugtt in traps and subsequently were caught themselves. as presence of a considerable quantity of mink in the stomach and intes- tines of one animal would suggest that perhaps a dead mink was found and eaten. he mink my also not be averse to praying upon others of its own kind when they are in a helpless condition if the evidence can be eomtsued as such. Out of la} stomachs amorphous material and vegetation occurred in 13.01 percent and conprised 1.26 percent of the total volmee. In the ease stomachs milk totalled .73 percent by volune and 8.13 percent by 33 frequency. Out of 136 intestines amorphous material and vegetable debris occurred in 13.22 percent and made up inn} percent of the total voluee. link were represented in 12.5 percent of the intestines and nab up 7.53 percent of the total volume. ‘ lead pellets were found in tin stomachs of three mink: which had apparently been shot because the stanachs were perforated and evidences of mnshot wounds were visible on the carcasses thus ruling out the possibility that carrion had been eaten. 5 differences in 92$ 9332 It was thoudst worthwhile to consider the possibility of sex dif- ferences in the diet of the mink, not only cut of 1m. curiosity but also with the thought that such differences, if they existed, would con. tribute indirectly to the knowledge concerning the behavior of the two senses, particularly (hiring the trapping season. Discrimination by either sex as thind or sire of food items taken was looked for when examining the assembled data. luau-ice). representation of items and tabulation of percentages by. volume and occurrence are given for the two sense in i'ables 3, 1i, 5, and 6. he merical representations were com- pared statistically for significance (see tables 7 and 8). However, the percentages by values and occurrence are comparable by inspection 0317. he number of muskrats taken by males, as shown by both stomach and intestinal analysis, was greater than the number taken by females ' and when coupared statistically was shown to be highly significant. the fiber of small urinals found in the stomachs of females was significant- ly larger than the mnber occurring in the intestines of males. lo sig- nificant difference was found between the nunber of other items taken by Table 6. Parcentage by frequency and. by volume of the food items found in the intestines of 37 female mink. 19110-19’41. Huber of indivi- Percentage Percentage Item (lg; item; by volune occurrence unskrst 3 6.06 8.10 .Cottontail 5 5.62 13.51 scan Hmals 13 ' 33.30 35.13 Large Birds 2 2.16 5.10 3119.11 Birds 1 0.00 2.70 Snakes 0 0.00 0.00 has: 5 17.30 13.51 fish 10 23.79 27.02 Crayfish 8 11.77 21.62 Insects O 0.00 0.00 rotals.................... R7 100.00 126.99 39 Table 8. Tests of significance of the difference in rate of occurrence of prey items found in the intestines of 57 male as cornpared to 37 female mink.“ Number found in Number found in I? {tone 0 t f e stomachs Value m“ 20 3 10.20" Cottontail s 5 .09 Small Manuals 9 13 .76 Large Birds 5 2 .53 ““11 31"“ 0 1 3W“ 1 o frogs 1!» 5 .70 Fish 5 10 3.11. Crayfish a g .35 Wu“ 3 o Totals...... ..... ......... 61% M7 (1. Seven intestines used in determining volunetric and frequency per- centages have been omitted because of lack of data as to sex. (2. Each item in the table has been coupared with the. number of all other items. ‘ five percent significance. In One percent significance. the two sexes. No widely dispr0portionate number of either one sex or the other occurred during any one year so that significant differences in mmbers of muskrats, small mammals, and fish taken by males and fem- else do not appear to be attributable to any particular year. Inspection of the percentage tabulation further reveals that the percentage by volume and by occurrence of frogs found in the stanachs of females seems to be considerably larger than for the males. Libe- wise the percentage occurrence and the percentage by volume of small manuals found in the intestines of females is noticeably greater than for the males. The percentage of frogs in the intestines of females likewise seems to be larger than those in the males. A definite selection as to size of prey items taken by males and females seems to be indicated from the data. Females apparently talus the .aller prey items more often than do the males. The reason for this is not readily perceptible. However, several factors may contri- bute. A marbed disparity in the size of the sexes is true of the min]: as well as a number of other mustelids. Some males may easily weigh twice as much as the average female. It seems probable that the smaller females might hesitate before attacking a large muskrat and might even come off second best in the ensueing struggle (cram, 1923). On the other hand the larger and more powerful males migt prefer to hunt for larger prey to satisfy their appetites most quickly since the min]: hunts largely for food and seldom indulges in such wanton destruction as is characteristic of the weasel (Seton, 1926, p. 553). mother factor to b. bonsidered is the cruising radius of the two sexes. Marshall (1936) has observed that the females tend to remain in a restricted area not ex- ceeding twenty acres while the males cover too large an area to he ’41 estimated acqirately. It is logical then to assure that the males which range over a more extensive territory will encounter more muskrats than the females. Hence, in areas where large concentrations of muskrats do not exist the proportion of muskrats taken by the males should tend to be larger. he females which do not travel so extensively mist then make up the bulk of their sustenance from the smaller items of prey. fhe fact that no significant difference existed in the whore or amount of cotton- tails taken w either sex might be attributed to the fact that the cotton- tdl is not as fonsidable an opponent to the femle min]: as is the musk- rat. An unbalanced sex ratio occurring during the trapping season could also be a contributing factor in determining sex food habits (see p. 63). During the period prior to the breeding season when an unbalanced sex ratio occurs the females appear to be more retiring or vary and are not caught in exposed situations as readily as are males. Ihe frequenting of less exposed situations by females at this time migit lead to more frequent encounters with cottontails and fewer with nuskrats which would inevitably be reflected in the diet. It might be said in passing that the above hypotheses concerning the reasons for sex. differences in food habits are conjectursl and are not to be accepted as fact. lhe suggestions are tentative and are offered in lieu of more definite information. mution In recent years there has been a great deal of controversy regard- ing the relationship of the nit to the muskrat. On one side is ranged a siseable group of trappers and fur-buyers who would prefer to have the mini: classed as a predator to be hunted the year around. This poup feels that the amber of mink they tabs during the trapping season does not nearly couponsate them for the destruction wrought moon the mushrat population by the mink. On the other side there is a more thoughtful group of trained and untrained individuals who would prefer to have the animal investigated thoroughly before deciding prematurely upon policies which might not produce the desired results. It is a known fact that the heaviest profition and greatest losses occur in areas where there are animal concentrations. Likewise can- plaints of mink predation on Illustrate appear to be more mnerous coming from those areas which normally produce the most mskrats. In areas where mushrat concentrations scour, then, the surplus must be trialled down either by trappers and predators or in other ways. he proportion of the surplus harvested by trappers and that captured by mini is not known. new efficiently the trappers would be able to remove the surplus in the absence of the mint is problematical. Certainly a considerable mnber ef muskrats would undoubtedly succumb to disease, exposure, intra- specific strife, and other factors before the trapper could harvest then. me net effect of predation upon populations may thus be minor in cm- parison to the effect of the controls which are inherent in the pepula- tion itself. As brington (1936, p. 252) has said, 'be “emulating evidence seems to suggest that new prey populations .1. constituted to withstand far more pressure from enemies than they ordinarily get: and within the restrictions imposed by their habitats, seem to be mainly self-limiting and. self-adjusting in numbers.“ In order then to be able to place a proper interpretation upon food habits data, with respect to predation, it is necessary to knew the abundance of the prey item con- cerned and some of the factors which operate to affect its availabdlity by making it more or less vulnerable to the predator. law of the factors which affect the availability of prey items are hard to evaluate because they act indirectly and hence are difficult to compare with direct observations. Data which may be used in interpreting food habits data are often incomplete and in some cases inaccurate. Hence, in lieu of actual field observations to supplement the data, only a very meagre amount of avail- able information applicable to the present study was found to be useable. Cmputed hills of fur-bearers which are based upon trappers' and hunters' reports returned to the Hichigan Department of Conservation (see Table 9) m serve as indices of population trends. The canputed kills indicated are not to be considered exact, however, because of several sources of error. lhe actual annual take of furs exceeds the catch reported by trappers. Trappers' caspulsory reports are not indicative of the total catch since they do not include fur-bearers taken by unlicensed trappers. Bayne (19%) found that unlicensed trappers took about twenty-five per- cent of the fare in 'illiemton township, Ingham county. Docause of a rather prevalent notion among nary trappers that reports of too great a catch will cause the Department of Conservation to shorten or close the season untruthful reports are sometimes suhnitted. Those are diffi- cult to appraise. The mnber of licensed trappers operating during each year sanctimes varies, dePending upon economic conditions and fur prices. naported kills might reasonably be expected to be affected by these variations. The computed hills of mush-ate, mink, and cottontails in the study area as indicated from trappers. and hunters' reports, are depicted graphically in figure 6. Iron the graph it would appear that the trends of both muskrat and cottontail pepulations during the winter Table 9. Computed kills of muskrats, cottontails, and min]: for 18 southern iiohigen counties. canpiled frun hunters' and trappers' reports for the period from 1938 to 1910.. mud kill w11.338 1939 1219 193:9, Computed muskrat m1" 385,735 235.2141 163,099 19mm Canputed cottontail k111"‘ 121515100 699:787 193-1“: 638 1916391”?! Computed mink: kill" 6.169 3.580 5.591 7.976 ‘ Countiesudllegan, Barry, Derrien, Branch, Calhoun, Cass, Clinton, Baton, Genesee, Hillsdale, Inghan, Ionia, Jackson, I818!- mazoo, Shiawassee, St. Joseph, Van Buren, Iashtenaw. ee Coupiled from trappers! reports. ”'" Compiled from hunters' reports. fable 10. Average precipitation in inches for the months of July, August, and September in zone III from 1938 to 191:1. gonth 1938 1939 ' 19340 1951____ July 2.8 1.5 1.3 2.5 August 3.5 3.2 8.0 3.3 September 1.5 2.0 1.} 3.]. ,__ ___ /‘r/__S— GOTTCIITAIL \ / '\ \\\ / \ e I \ \A . mam? P \ /' ‘\\. \(:£;f" V ' / . ...—- ' e \ . / . 1 1 L 1938 1939 19h0 lflhl Figure 6. Graph showing computed kills of muskrat, mink, and cottontails in the study area as indicated by travpers‘ and hunters' reports. months are relatively independent of the mink pepulation. It is true that the muskrat population appears to be lowest when the mink popula- tion seems to be high. Howefer, the decline in nunbers of muskrats be- an at the ease time as did that of the min]: and the harem in their mbers bean when the mink appeared to be most abundant which would seem to support the viewpoint that makrat populations are mainly self- limited and that predation by the mink plays a minor role in controlling them. Perhaps late smner droughts are indirectly more responsible in determining the population of mskrats going into the winter than any other factor since the drying up of habitats and the limiting of food eqaplies renders the population more vulnerable to predation by a mnber of predators including the mink. Intraspecific strife might also in- crease due to competition for food and the concentration of the popula— tion in the vicinity of the remaining water. Some data have been ac- quired concerning the average precipitation for the months of July, August, and September in Zone 111 (see Table 10). the month of July was arbitrarily chosen and the average precipitation during this month was graphed along with the computed kill of muskrats in the study area.(see fig. 7). Some degree of correspondence is evident from the graph which might indicate that the drought factor is inportant in regulating mskret populations. dvihla (1931) has estimated that an adult mink requires about 100 grams of rat per day while Stevens (1931) states that he has mink which till eat as much as a pound of food during the day. Smith andloosli (19%) have shown that food may traverse the alimentary tract of a mink in 15 hours or less. With these facts at ones disposal it becomes poss- GO! TUTZZD KI ~h00.,ooo #360,000 ”320,000 Gomputai 2-fusl:rat Kill '" — "’ "' Average Preciui tntion “-280.000 5.2183300 “330.000 ~160.ooo 1 1 i 1 1938 1939 19m 19? : Fig-airs 7. Graph showing computed makrat kill as compared to average July preciri tation. 2.55 A tan 3171 y W? .3. t A e 1 1 VF}. {AC}? “7 1+8 ible to make some use of food habits data in evaluating the muskrat item in the diet of the mink. a mink would normally require from one to tie average-sised muskrats per day to satisfy its appetite providing that it does not kill beyond its imediate needs. Available food habits studies show that during the winter months muskrat comprises not more than fifty percent of the mink's diet. a very liberal estimate would, then allow about thirty rate per month to an adult mink during the winter months. Since Dearborn and Hamilton have shown that the muskrat is not as important a constituent of the suner diet of the mink as the winter, the average number taken per month throughout the year would probably be considerably smaller. nix-ing the trapping seasons from 1938 to 19111 the ratio of mink to Mt in the study area varied from 1:66 in 1939 to ital: in 19%. fhis ratio is based on computed kills. it appears them that, during the winter months at least, the mink is an important natural predator of the muskrat. the relative percentages in which four maJor prey items appear in the stomachs of mink by volume (see i‘able 11) are indicated graphically in figure 8. he possibility that frogs and small manuals may serve in a buffering capacity against predation upon the mskrat is not to be overlooked and some indication of this is shown in the graph. Irrington (19%, p. 79) has observed masses of mink-piled frogs and fish in snow- drift tunnels along the Big 81cc river of South Dakota indicating that at tines such‘itans may constitute a large part of the mink's diet. Annotated 1.3.31 2f_ m 35;; he following list of item found in the winter diet of the mink is included in order that material not indicated in tabular form might be presented and for the value which it might have in life history stud- Rushers and percentages of four major food items found in the stomachs Table lle of 102 winter min]: from 1938 to 19%. item 1938 1939 19m 19's $232? 50.81 26.1% 30.30 15.70 m” 2:33.223 55.00 75.00 30.30 211.39 Ember ll 6 10 10 31.31112? UAR 0.00 23.11 13.28 0“th Percentage tail occurrence 20°00 0'00 21021 9075 {Ember ‘1 0 7 h Porcentage Headcw by volume 0'00 0'00 2050 15-32 “m“ 1:223:23: 0.00 0.00 6.06 1’4. 63 pnber O O 2 5 5:33:11? 12-65 52.99 2036 11.140 frog Percentage occurrence 25.00 57.1% 18.18 111.63 lumber 1 7 7 6 g a" 8; k)! C‘) J PERCENTAGE EY VCLUEE C 10 / armour :2. '2 iJ _ in) r— 1935 1939 19:40 yigure 8. Graph showing the percentage by volume 0? four major {,3 food items in the winter diet of the mink over four year period. 51 ies of parasites or in the study of food-chains of the various animals entering into the diet of the mink which is of basic ecological import- ance. me text also contains references to diagnostic items which were used to identify the various food items found in the stomachs and intes- tines. mums made up over fifty percent of the mink's diet whether rated by voluse or by frequency of occurrence (see rise. 2 and 3). t} mskrats, cottontails, and meadow mice comprised most of the mammals taken both by volume and by frequency (see Figs. h and 5). ltuskrats easily took first place in the diet (see Tables 1 and 2) while cotton- , tails and meadow mice were ef’lesser importance. It is interesting to note that meadow mice were not represented in the 1938 and 1939 stomachs (see fable 1).) possibly indicating lowpopulations in these years. he data for 1939 were limited since only 9 stomachs taken in that year were analysed. However, Blair (19%, p. 161) states that madow voles were very scarce in southern lichigan in the sumer of 1939 in ontrast with their abundance in 1938 and it seems reasonable to assume that the dec- imation of the 1938 population may have occurred during the winter of 1933. he remainder of the massalian food in the stmachs and intestines consisted of mice, shrews, noise, and. one snowshoe bare. At present the snowshoe hare is known to occur only in the 'thmb' region of lower Iichigan. Since the specimen in which the snowshoe here was found case from the northeastern part of the stw area which lies close to the 'thunb' it is presmed that the distribution of the snowshoe extends south frcm the “thumb“ at least as far as Genesee county. Items which were most useful in identifying the manual remains to genera were such things as hair, teeth, aid claws. Very few specimens contained bones or teeth which could be used for identification so that most of the identifications were based on cross sections, cuticular scale patterns, and medullary patterns of guard hairs. The character- istic shape and color of the claws were most useful for identifying mink in the stomachs and intestines. Meg-Birds were not found as often in the intestines as in the stomachs (see rigs. 1 and 2). Remains of pheasants were found in five stomachs and two intestines and domestic chickens were identified in two stomachs and two intestines. Whether rated by volme or by freq- uency pheasants and chickens formed the largest percentage of the birds eaten. Pheasants are evidently an important food of the mink (see Tables 1 and 2) although stomach and intestinal analyses are at variance in this respect. Danestic chicken does not rank as a very important food item as compared with other items in the diet. A cost made up the en- tire contents of one stomach. Since the migration of the coat occurs in the fall it is very likely that the bird was a cripple. Ruffed grouse feathers were found in one intestine. Host of the unidentified birds were small passerines. One of them appeared to represent the remains of a cardinal but could not be identified with certainty. Sine, shape, and color pattern of feathers proved to be most use- ful for identification purposes when compared with known specimens. BturgisQ breast feather key to the orders of birds north of Mexico (Vigit, 1939) was used to verify some of the identifications but could not always be used because of the action of digestive Juices on the feathers and because of accumulations of grease and gmm protein wastes which could not be satisfactorily removed from the feathers. Reptiles-«Snakes occurred rather infrequently in both stomachs and intestines. Genera or families could not be determined due to digestive 53 action upon the scales and because of the small sins of the pieces which were found in the digestive tract. gibians-om only amphibians which were found in the stomachs and intestines were frogs. host of those which could be identified were either leopard frogs or green frogs. Other species which were identified were bullfrogs and a spring peeper. be characteristic color pattern of the integument was the most a“ . in useful criterion for determining species, while bones, feet, and skin were used to identify those item which were listed merely as I'frogs". zi_s__h-1t was found practical to identify fish only as far as the f family because of the state of dissolution presented by most of the scales. Remains of smallmouth black bass and bluegills were recognise- able in a few cases and a miller's thmb was recognised by its character- istic otoliths, but otherwise no specific identifications were made. be family centrarchidae rated first in both stomachs and intestines with prrinidae and catastomidee next in order. Chagall—crayfish appeared more frequently in the intestines than in the stomachs. Specific identification was impossible because of the thoroughness with which most of them had been chewed. The character- istic orange color of the hard chitinous pieces of exoskeleton and the fragnents of the appendages made recognition easy. Insects—Remains of insects were found in three intestines but none were identified in the staunch material. llytra and appendages were most diagnostic. Under the binocular microscope the tarsal claws on the appendages were easily recognised. However, the items were too fragnentary to allow a specific identification to be made. cher items—The remainder of the material recognised in stomachs and intestines was counposed of nonfood items. and other soft-bodied prey might be included in this category througi failure to recognize them as such among the stomach and intestinal con- tents. Bowever, until they can be identified in some way they met be omitted from the list of food items. Check list 3; food items fomd in stomachs and intestines Mammals Huskrat Cottontail Meadow louse Deer Mouse Pine House House House Brown Bat Short-tailed Shrew Long-tailed Shrew prairie Mole Star-nosed Hole Snowshoe Hare £2... Domestic Chicken Pheasant hffed Grouse Coot whims Green hog Leopard Frog m sibethica sibethica M floridauus mearnsii Hierotus 9. (probably Emszlvanicus) firggzscus n. m pinetoruls scalopsoides g2 musculus musculus m nerve‘icus Slarina brevicaude brevicsnda max. :2- M aflticus machrinus gonglura cristata cristata 1m emericanus americanus callus domesticus , MEN—WW9. Bonasa unbellus embellus E168 emericana mini-am Sana pipiene It is possible that clams Bans catesbeiana 52 1a crucifer Cubans no 55 56 “RABIES AND DISEASES from a wildlife management standpoint it is important to deter- mine the role which various destructive factors play in regulating populations. M is still relatively little known concerning some of the parasites and diseases affecting some of our wild animals. Until quite recently the approach to the problem has been largely taxonomic. However, if population trends and cyclic phenomena in populations are to be correctly interpreted, the proportion of the population infected and the severity of the infections from year to year should be known. food habits data will also shed valuable light upon the modes of infect- ion end transmission of parasites in the population. It is not to be expected that parasites infecting animals in the wild state can be ‘ls'ought under control to any great extent but a knowledge of their distribution, incidence, life cycles, and modes of transmission may serve to prevent them from becoming a menace to ranch-bred animals. An effort has been made in this study to determine the incidence of some of the more important parasites of the mink and to uncover evidence of a gross pathological nature which might indicate diseases occurring in wild mink. lo- doubt some parasites have been overlooked because of the techniques employed and preservation of the animals in formalin may have destroyed some of the pathological evidence. he incidence of microscopic parasites has not been determined because insufficient time did not allow for such close scrutiny of each specimen. A fecal sample was taken from about every tenth specimen and examined for ova and for mall helminth parasites. A saturated sugar solution was mixed with the centrifuged fecal material in order to fleet the ova to the top of the solution whence they were removed to a slide by means of a small 57 glass spatula. A gross inspection was made of all organs of the body for evidence of parasitism or disease. lite mink spends a good deal of its time in or near water and hence constitutestthe normal host for a number of parasites which pass their intermediate steps in aquatic animals eaten by the mink. Different species of crustaceans, frogs, and fish no doubt act as intermediate hosts for the large assortment of flukes and roundwoms which habit- hi ually infect the mink. In season with the muskrat, the mink has often I . been referred to as a virtual 'museum of parasites”. A fruitful field for parasitological research is open here, mch of it being relatively untouched. r he incidence of some of the more important parasites of the mink is presented. in Table 12. so significant difference. in the incidence from one year to the next was found for any of these parasites (see Table 13). Apparently then, the mm: may have been at the peek of its cycle, if it has a cycle, during these years since it is known that the incidence of parasitism shows an increase for some species when the population is declining. fhe sinus worm, Skrabimlus nasicola, appeared to be the most com- mon parasite of the mink. his wens occurs in the frontal sinuses of the animal and is frequently overlooked. In heavy infestations the frontal sinuses were noted to be inflated and discolored Iv the mass of worms within. In one mink ‘05 of these worms were recovered from the two sinuses although the usual mimber found more closely approximated a dozen. In one or two instances the worms had apparently bored through the wall of the sinus into the overlying muscle. Perhaps the high in- cidence of this parasite may account for the difference in temperament Table 12. Incidence of some helminth parasites found in trapped mink taken during the trapping seasons of 19% and 19,41. (1 Ember Average incidence for a Year infected ncidence the two ear riod 191m 32 100.00% krabEglus nasicola 19,41 116 92.06% ' 93.57% 19% 3 9-37$ Lnaroma. bronchialis 19,41 27 21.142; 18.98% 19140 2 6.257; Momma kellicotti 19,41 13 10.31% 9349* 19% o 0.00% 23211229218. .22- 19111 6 ”.76; 3.79% 19% 1 3.12% DioctngEe renale 19141 3 2.38% 2-535 (1. 32 mink were autopsied in 19140 and 126 were aut0psied in 19%. 59 Table 13. feats of significance of the difference in percentage of infestation with some helminth parasites of mink taken during the trapping season of 19m and 19141. (1 spec“. Eitigdmiiik para-(2 No. ofdmink pa! rte?3 flan. scrabingius nasicola 32 116 1.10 maroides bronchialis 3 27 2.111 mamas kellicotti 2 13 349 manure :2. l .06 o .... Dioctgphme renale (l. The number of parasitized individuals for each year has been com- pared with the number of unparasitized individuals. (2. 32 mink were autOpsied in 19%. (3. 126 mink were autOpeied in 19141. shown by wild and domesticated mink. i'he ferocity which is generally ascribed to the mink in the wild, as contrasted to the friendliness shown by domesticated mink, might well be attributed to the presence of these worms. It is unlikely that these worms would harm the mink as long as they were confined to the sinuses but their movements and. borings midit cause the mink excruciating pain and account in part for its supposedly diabolical nature. me sinus worm of the mink was origin- ally described as glaroides mustelarum but has recently been assigned a new species name and transferred to the genus Skrabinglus. No life history study has been made of this parasite as yet to the best of my knowledge. In view of its importance it would seem to offer a worth- while problem for parasitological research. Lungworms, lilaroides bronchialis, are perhaps the next most comon nematode parasites of the mink (see fig. 9). They occur as small, com- pact knots of closely intertwined worms lying below the mucosa of the trachea and bronchi and also occur on the surface of the pulmonary vein. hcause of the difficulty encountered in the removal and clearing of these worms a study of their morphology has not been attempted by any- one to date. As many as six cysts were found in the lungs of one mink. no incidence of this parasite my perhaps be smewhat higher than in- dicated since some very light infections may possibly have been over- looked. The lungfluke, Eagonimus kellicotti, which is an occasional para- site in the lungs of cats, dogs, and pigs finds its natural definative _ host in the mink. Various species of crayfish belonging to the genus Cambarus constitute the second intermediate host while the snail, Pomatiapsis 1521mm, 1. the first (Ameel, 193k). wanccc (1931) figure 9. Lungworms, rilaroides h-onchialis, in the lungs of a mint (courtesy of the Michigan Department of Conservation). reports snails of the genus Melania as constituting the first inter- mediate host. in incidence of 8.09 percent is reported by Wallace (1931) from 8“ carcasses received from fur farms in Minnesota. {Ehis compares closely with the incidence of infection found in wild mink but the mode of infection of the ranch-bred mink is obscure. rerhaps crayfish in the stomachs of raw fish fed to the ranch mink may have been the source of infection. Ova of this species were detected in a lumber of the fecal setuples. All of the specimens in which ova were detected also contained the adult flukes. The large cysts in which the flukes were located were easily recognised. As many as four cysts were found in the lungs of one mink with as many as six flukes to a cyst. However, the usual number of cysts found in the lungs was one. Larval and adult Esalgptera a. were found in the stomchs of six mink, the identification being furnished by Mr. J. '1'. Lucker of the Bureau of Animal Industry... is may as ten of these roundwoms were found in one stomach. In one of the animals which was heavily infected with this parasite the wall of the stomch had evidently under- gone hypertrophy and was very much thickened. The giant kidney worm, gioctom 2&2, (see fig. 10) was found in only four of the 158 mink which were autopsied. In one in- stance an atrophied and totally degenerated kidney suggested a possible former infection. mough not occurring as frequently as other para- ' sites this worm is probably more destructive in the wild because of the total damage which it inflicts upon the infected organ. a compensatory hypertroth of the uninfected kidney was noticed in some of the para- sitised animals. One of the kidney worms was found free in the abdom- inal cavity. a large urinary calculus was found in one kidney associ- figure 10. a mi& infected with the giant kidney worm, Dioctm renale. The infected kidney is opened to show the worm in place (courtesy of the Michigan Department of Conser- ‘t ion). 53 ated with one of the kidney wome. Another urinary calculus was found in an unparasitised kidney. Bacent investigations have shown that vita- min a deficiencies, by creating improper elimination of various inorgan- ic elements such as lime, may be responsible for the formation of urin- ary calculi in ranch mink (Shillinger, 1937). Holmes, Tripp, and Better- field (1938) have shown, however, that the vitamin A reserve in wild mink is far above that of ranch-bred animals. It would seem then that mechanical obstructions by parasites are chiefly responsible for the occurrence of urinary calculi in wild mink. Knowledge of the giant kidney wens in the mink dates back for em. time. Seton (1926, p. 518) recounts the story of a liaise trapper who found two or three of these wens in the kidney of a small female mink. Little is yet known of the life cycle of this inportant parasite. Dr. Ioodhead, of the University of flichigan, who has been working on its life history for some time, has traced one of its intermediate stages into a small annelid worm which is parasitic on crayfish but has not yet succeeded in tracing the entire life cycle. Several other parasites have been recorded for the mink in this study. Some of these were of infrequent occurrence, and hence are prob- ably of little inportance while others which were detected through analysis of fecal samples may have been important although their num- bers and incidence were not ascertained. A tapeworm taken fru the intestine of one of the mink was identi- fied by Mr. Allen McIntosh of the Bureau of Animal Industry as lesseestoides 32. lggs of Miller-is 32. were frequently noted in the fecal samples along with larvae and adults. in adult female roundworm of this genus 65 was recovered from one of the stcmachs. Coccidia, Isospora bigmina, were also encountered quite frequently in the fecal samples. Coccidia are probably to be considered as important parasites of wild mink. Hoary infestations have often been noted to end in the death of ranch- bred animals and the some would probably hold true for wild mink. he greenish colored mucous which was noted in the intestines of several of the mink was probably an indication of coccidioeis. A possible symptom of infection with the gall bladder fluke, mtorehis canadensis, was indicated by the Jaundiced appearance of several of the mink examined. Heavy infestations of this parasite are often indicated by a Jaundiced appearance due to obstruction of the bile duct by the parasite (nan-on, 1933). Ben secondarily acquired parasites were also noted in stomachs and intestines. Immature Mabelbocolli, which is a frequent ecanthocephalan parasite of suckers, were ibntified in the intestines of one mink associated with sucker remains. About a doses of the para- sites were recovered. M ountocgphga, which is a fairly com- ln nematob parasite of frege was found in the stomach of one animal along with some partially digested frog remine. he specimens were recovered. A umber of other parasites occurring in the mink have been report- ed by various workers. Benbrook (19%) reports the occurrence of the guinea worm, Dracunculus medinensis, in a mink. Hanson (1933) states that trichinae are occasionally found in the mink and also reports spinyheaded worms, Gnathostoma ini rum, as occurring in wild mink. tinker (1932) reported Molineus 2319.922 fran a mink in Mississippi. The morpholog and life cycle of whelmis monorchis has been worked out by kneel (1938), while Iallace (1932) has worked out the life cycle of Ii‘roglotrema mustelae. Price (1929) has determined a new species of trematode mtorchis canadensis in the mink. Law and Kennedy (1932) report on a number of parasites which have been identified in the mink. Among these are Stromloides _e_p., Ascaris 52., Iilaria sp., zlgiorchis 221.922: Magus» W 2222: 11.1.2112 _____mtela°: and Mia 31. Shillinger (19%) has reported heavy losses in ranch mink from grube, Iohlfartia my Hanson (1933) mentions fleas, m- mllus Em, and lice, frichodectes retusus, as being found on wild as well as dunesticated mink. Very little evidence of a pathological nature was found in the milk emined. It seems very likely that mink suffering from diseases in the wild would seldom be caught unless the disease was in its incip- ient stages. Irho only evidence of a pathological sort was the Jaundiced Qpearance of several of the mink. As previously mentioned this Jmndice might be associated with the presence of the gall bladder flfie, EL? metorchis canadensis. There is a possibility that the Jaundice could have been caused by a paratyphoid infection which is often found in duestic mink. Failure to eliminate bile is often associated with this disease. A number of diseases affect ranch mink which say find their counter- part in wild mink. However, many of these diseases are the result of crowded conditions and improper sanitation so that the incidence in the wild would probably be much lower. Distemper and anthrax are cannon diseases among domesticated mm with which the rancher has to contend. Other diseases of rater occurrence are also found in domesticated stocks. Lewis (1929) reports a case of hemorrhagic septicemia while Hall and Stiles (1938) have reported the death of 1% out of 1’48 mink on a fur fam near Denver, Colorado from botulism. Law and Kennedy (193’4) have reported cases of nutritional anaemia in the mink which they attribute to lack of liver in the diet. 67 68 BREEDING lest authors are agreed that mating takes place during the latter part of rebruary and in “arch with the young being born from April to In. There are usually five to six young in the average litter al- though this number varies from three to ten. There is but one litter a year. he length of the oestrum which occurs but once a year is not definitely known although some information concerning this should be forthcoming from Hndsrs' work. Ihe gestation period generally extends for 15.50 days. Lohr (1937) has recorded a gestation period of 69 days. to evidence was uncovered in this study which might possibly re- fute any of the above statements. The reproductive tracts of all of the females examined appeared to be normal in every respect. That is there appeared to be no evident signs of breeding. Histological sec- tions of the testes of twelve mink taken in 1910 showed the presence of no mature spermatozoa although the testes ranged greatly in sine. It must be concluded from the above evidence that no breeding takes place during December althougi the approach or onset of the oestrum may possibly take place during this month. A difference in behavior of the males and fasales at this time was reflected both in food habits and. in sex ratio. A marked disparity in the sex ratio occurred during December 1940 and 19% as indicated from trapped mink collected «bring that month. This ratio is not necessarily an indication of an unbalanced ratio in the population itself but more likely it indicates a differential act- ivity of the two sexes during the trapping season. Of the total of 158 mink examined 62 were females and 96 were males or a ratio of 181.5”. Ithe disproportionate ration might be accounted for in several ways. 69 he most plausible theory would seem to be that the males having a center cruising radius (nutshell, 1936) would encounter and enter more traps than would the females. fee psychology of the two sexes might also enter in. Hales might conceivably be bolder and less wary than the females and hence would be cqngdt oftener. The unbalanced ratio might also indicate the onset of the oestrous cycle in the female. It is known that the females tend to be more retiring and wary and go into hiding at this time. Therefore one would expect fewer females than males to be trapped. Likewise male animals are known to range more widely previous to and during the breeding season, possibly in search of mates. Such a tendency would serve to upset the ratio further. Apparently then, for lack of information of a more definite sort, the unbalanced sex ratio must be attributed to a differential activity of the two sexes and a difference in behavior of the two sexes at this particular time of the year. the ovaries of 32 female mink were measured. The average width of these was 5.5 ms. and the average length was 8.9 m. Yolunetric measurements were inexact because the ovaries were two small to allow for an accurate measurement of the amount of water they displaced. These measurements of volume which were taken ranged from one to two milliliters. The testes of 68 males were measured and the voltne de- termined. The average volume was .88 m1., the average width was 10.3 mm, and the average length was 17.8 m. A frequency distribution of the testes volume is shown in figure 11. The marked skewness to the left would seem to indicate either that relatively few of the males were approaching breeding condition at this time or that a large nunber of young males which were not fully mature comprised a large proportion of 1°. ..., ... 9.— 3" ’1 7? 6L av I w- L; END! 7 NMNNumoammmrseemoumrxe-ouzao O HdrzrzgdflflfleJNNNNNNN mammals : Pm 4;} ”U e e N“ figure 11. rrequenw distrihtion of testes volmse of 68 sink. 7O the population. Since known ages are lacking for all of the specimens, any suggestion relative to age ratios in the population must be regard.- ed as purely speculative. 71 72 HEIGHTS AND MEASUREMENTS here is very little published information on weights and measure- ments of the mink (Hustela 11393 31315). Average measurements as given by Dice (1927), Lyons (1936), and others are subject to inaccuracies because of the snnll number of animals involved. In order to furnish more information along this line measurements were taken on 157 mink of both sexes. fhe sumarised results of these measurements are given in Tables in and 15. The pessibility that a significant difference might occur in the body measurements of mink collected in 19% as compared to those coll- ected in 19,41, was investigated. A calculation based on the standard error of the difference between the means was used. A significant difference on a five pereent level (a difference which would be due to chanee in only about one out of twenty times) was found between the tail lengths of males collected in 19th and those collected in 19%. Since none of the other body measurements of either sex were signif- icantly different for the two years it seems probable that the dif- ference was due to an error in sampling. 'nie measurements for the two successive years can thus be safely averaged together since the character- istics of the population in regrd to measurements appear to have re- mained constant over the two year period. A highly significant dif- ference in the weights and measurements of males as compared to females is true of the min]: as well as of a number of other mustelids. Ho sipificant difference was found, however, between the ear measurements of male and female mink. All of the weights given in Table 1h are based on skinned specimens. A means of approximating the actual weigit of the animals was sought in 73 .do.:m oo.mm m mw.H on om.mm OH No.m on 0H.mm maoposwaawa oo.om 00.0N dfi nausea ham oo.mm 00.0N mempwe Hm ma.m on mH.om Hm aw.m on o~.mm needed an coca oo.mn oo.om one: do nemeoa oo.oma 00.0mm mm ma.m on mH.NmH mm we.ma on mm.oom nnnhoeaaaan oo.oeH oo.owH ca nuance Hana 00.0mm co.mmm mm mm.aa on we.mwn an mo.mm on mm.H~m onoeosaaaas ea 00.02: oo.mme apnoea Hence 00.0mm o.mmma om mm.mw on mm.mmn mm mo.maa on mo.emw mecca oo.:mm om.man on cannon demanded ..D 36mm cmmz deuzan >m 1D cursed Suez panacefimmmz «H o 0.25% .H m DESK mwflwfiwh mmflafi .nmmfisofix enogpfiom ed dopoomaoo Made Nma Mo mpmoaoadeoa pea mpgwwos one mo hamfifimm .na nanny wampoafiflafis a“ can menofioafimaea Had a cm.~H 0m.ma w: mm. 0» ma.ma m5 :H.H on wu.mH 30a nmflcsonmlagflcfi 00.xa 0m.HH nomad Mo Mummeq oo.mm oo.mm om am. on m~.~m m» mw.H on n~.Hm anemone adeaceno: oo.mm oo.mm ow.:H 0~.~H Om em. on :2.ma Na NH.H on :m.mH neon: oo.mH oo.ma Hmpfipnoampefl pmeon oo.Hm oo.m~ - om wfl.m on Na.mm Na mm.m on mw.nm nemeoa oo.xm o~.:m mmmpoahwmoo cMMmpmba lb omumm neoE cdmwnwaw ab muedm and: puosmefimmmz Manama empfidm mmaafimm mmamx a.:¢m.xowa chompdom ca pmpoofiaoo Mafia mmH mo mpeogmesmmma HHSMm one mo hemfififim 4 a .5 eBay 51/ 7 mocmofimHuw Hm penance m>4m s mw.m1 nm.mm‘ aw H;oa oaoz on.a m:.n m .mm me once needed mampofifiaawa a“ apnoea hood ceam mH.m mH.Om m Heme one; om. am.m mm.me ma onma neocoa HH.:H ofl.Hcm ma Heme once“ ca. Ha.ma ma.mma we came cannon mgmpmcta .IH ..Ew on he one Hans 0:.m :n.woa m: Heme oats mm.a we.» on.mma ma came cannon m~.mm mm.nmm mm flame cane .mH.N am. me m~.wmm wH came needed whomeH. H H ME ea humane Hence mm.ae m~.mm: m: Han name we. mn.ma om.mw: me oema neocom Hm.mma mmnmmw ma Heme neon on. mm.o~a Ha.on an came cannon macaw a“ vegans mm.m~ mm.Hm: m: Heme one: mi. em.m:‘ Ha.om: we came or and @Dflwb I.“ “mm?” m PCmEmeH.:.mmmF .fimww Kmm pmmfioefifimmwz mo aonfifin magma omega 0» vmemmnoo mm Gama ca cmpodaaoo Mafia mo mpnmawafiamen hmop a“ ooeonommfiw .Hnmn ea eoeooaaoo on» mo ocemoHchmflw a0 mpmme 76 order to make comparison with actual weights possible. An Opportunity was obtained to weigh fifteen specimens before they were skinned. The loss in weight was then determined by subtracting the weight of the preserved specimen from the actual weight. A slight but not appreci- able gain in weidit was observed for two specimens which were weighed fresh before being put into fonnalin so that for all practical purposes the less in weight as determined by subtracting the preserved weith from the actual weight represents the actual loss in weight. A pre- dicting equation based on linear regression was used to determine the weight loss due to skinning (see Table 17). Using the regression equation, I: a e bu), the values of (a) and (b) were determined by the normal equations: (1) 2(1) - In e 112(1) (11) an): sax) . bar?) Solving for the equations the regression coefficient (b) was found to be .268 and the correction factor (a) was found to be -6!&. The theoretical loss in weight m then be determined by substituting the values of (a) and (b) into the formula, Ilsa e b(X). The standard error of estimate which is the measure of variation about the line of regression was determined by using the formula, By,‘l£(d2) I e Solving for 9y the value of ’48.7 was obtained. The corrected formula for theoretical loss in weight is then, 1.: a e b(x):i=1ts.7 gr. Entification 2_f_ 22 by measurements Harshall (1936) has proposed a census technique for determining mink populations which is based on measurements of tracks of the hind feet. in fresh snow. This involves the assumption that the lengths d the hind feet of the males and females fall into two distinct groups Table 17. The determination of the predicting equation for weight loss due to “innings. Actual loss of Height after Theoretical Deviation of weight due to skinning loss of weight actual values skinning due to skinning $2121: the- r w x to ad“) d2 122.0 10100 ‘ 218. 6 -96.6 9331.56 1511.0 923. 188.9 -30.9 991.81 56.0 1112 142.3 13.6 181+.96 63.0 589 91.7 ~28.7 823.69 85.5 #59 553+ 30.1 906.01 156.0 1132 2&3.2 -87.2 7603.31; 221.0 953 193.3 27.7 767.29 163.0 813 1511.2 8.8 77.1411 115.0 727 130.2 -15.2 231.01. 85.0 516 n.” 13.6 1811.96 1hi.o 750 136.7 11.3 18.39 333-5 1116 238.8 9%? 8968.09 15.0 R57 5% -9.9 98.01 136.5 802 151.2 -5.7 32Je 303.5 1061 223.“ 80.1 7 916.01 2189.0 11750 36598.69 2cm = 1.952. 839: ix?- =10,191,992 ' Heights are in grams. 7? 78 which are clearly separhble upon the basis of mamements. Since the population estimate is based upon the female territories found in a unit area it is essential that the tracks of males and females be dist- inguishable from each other to render the census technique valid. In order to test the validity of Harshallis method the frequency distributions of the hind foot measurements of 15”: minke of both sexes were graphed (see fig. 12). It is true, as Harshall has stated, that these is a significant difference in the means of the two groups but he ignores the distinct overlap which occurs in the distribution of hind foot measurements of the two sexes. 21.5 percent of the males measured overlapped into the distribution of the females while 57.5 percent of the females measured overlapped into the distribution of the males. In the area of overlap the measurement can not be definitely assigned to either sex althoudl the probability of its being one or the other can be demonstrated. The comparative chances which a given measurement of the hind foot has of being either a male or a femle is shown graphi- cally in figure 13. The ordinates of the (t) values for the normal curves of the male and female distributions have been converted to per- centages on the graph for a more ready comparison. The number of ani- mals which can be determined as males with some degree of certainty is seen to be greater than that of the females. Since the census tech- nique which Harshall his propoud is based largely upon the accurate determination of female tracks in the field it appears that the method is subject to a considerable margin of error. Any measurement which falls into the area of overlapping distributions of the two sexes could very easily be misidentified in the field. Hence it seass that the census technique as preposed by Marshall is unreliable. In any 79 it-.. . .-.. .\. t} n or... .. \ . J a. - :1... ... . o ...v . . I . a . ....e... mm. .. m0 ...E off.» 5 he manoeekzega age we: no :....«f5«.3uad Emmflwmmh .min 0.9.2“; mfi....fi................3m.h E gab...“ H.854 Emu a... n) a}. 9 n: 02. a? 9 0.. n) n.) 9 ...) Q... In r4 .5 (J .3 Ch r: ...... rm rd .3 4... ...”... h. .3. «.... .«w «In ...... ..... ...c. .... ..-. ...J .. ... h. r... .... T. T. C re 3 1L I. «.../r- .n. (L .1 .3 T. .e {a (u G. IL 0JC.C.. 0 I O O O I O 0 I O 0 O O O O O O O O O O O O O O O 0 O O O 0 O O .1. a... ...t... .... ..n\ w. ...... we 3 ..l c1 9 0 P... n... 3 S 0 a h... 9 3 0 3 ...n. 9 3 O a “99.0 r/ q _ — — . Jr .1 J l . 4 L. l l «mg eedéeh 1 mm hmufifi isnmbmm ffiNHO 0H NH L? 1:.” In." LWH S 1w." t: o g as '3 e :52 h E: .\\\\\‘ J 0'001[7 00' O'OOI[ 00' 0'oot[_‘ 00. O'OOII . 00. 0'001[f 00‘ 53'66 [' 7 hI' {‘3 9“ ll‘f fig QL'ag [ SB'II’EQENSXSSSQQQEXXSQ§S§§§L SL‘GI ‘ 831:3 \ \ \ S x LX 8PM“ 83°96 EShxQyQO6AAXX9QQQ6hRQQOdXXKSYS90dococQDCQAXYQOSXX§§SK§\\ 99 ' I 8 f ' 2 5 t\\\\\\\\\\\\\\\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ . ' LI'I {3.36 \ xx “A X 5w 1 l l J l l l 53 SR E3 51 £8 E? 5% 53 53 H xgxtzsvucxa mxraxxd 66 65 70 6h 62 he 50 n5 us 0 “fl BRIGTII CF IIIIID FOOT III figure 13. graph showing the comparative chances which an animal at a given measurement lo. up; u. male or form J has of be event a great deal of caution must be used in interpreting the results of the method if it is followed. m 2.: an 2222: heliable age criteria are of definite value in evaluating breeding pepulations and in analysing the hill of trapped animals. Criteria which are most useful for determining age are these which are based on external measurements or superficial appearances, e.g. the condition of the teeth, wary glands, or external genitalia. lvidences denoting breeding are often used to separate adults fran Juveniles but since the trapping season on mink occurs prior to the breeding season indications of this sort are meagre. m separation of the population into age groups must then be based upon body measurements. 30 references per- taining to growth rates of min]: (with the exception of Svihls (1931) who has given weights for the first 50 days growth) could be found in the literature so that no correlations of observed measurements with known ages could be made. fherefore any age criteria and age group- ings proposed here must be considered as tentative in view of the ob- vie. lack of infomation on growth of the mink. The frequency distributions of body measurements and skull measure- ments were graphed to see if any of the measurements would fall into natural age grouping. All of the body and skull measurements, however. seemed to follow a normal distribution. A small degree of skewness in some of the distributions suggested that the measurements may have been affected by age. Burt (1936. p. we) and Bprague (1939, p. l$95) have consented on the noticeable age variation which is apparent in the heels of mice of the genera Peroflthus, 2M, and m. we possibility suggested itself that this might also hold true for the mink. Measurements were taken on the bacula of a number of min]: and these data are sumarized in Table 18. It was noted that the proximal ends of some of the bacula were incmnpletely ossified and appeared to be less bulbous than others. 'mese bacula presumably belonged to young animals. leasurements of the base of the heels when graphed showed a bimodal type of distribution. This was more pronounced for the measure- ment of the lateral diameter of the base than for the done-ventral diameter. The frequency distribution of the measurements of the lateral diameter of the base of the bacula is shown in Figure in. A similar grouping was found when the frequencies or the weights of the bacula were grade (see fig. 15). A scatter diagram of the lateral diameter of the bacula when platted against the weight showed a clese correlation between the two measurements. The linear measurement then some as a good index to the weight which is really the more accurate measurement of the two. Two overlapping age groups seem to be indicated by the frequency distributions of baculum measurements. i'he largest group shows a definitely skewed distribution and therefore is probably composed of one and two year old animals while the smaller youp may represent ani- mals which are older than two years. Most of the measurements of the lateral diameters of the bacula in the first gasp lie within a fairly narrow range of from 2.0 m. to about 2.7 me. n... measurements pre- sumably represent the young of the year that have grown rather rapidly and at about the same rate. The ratio of the presumed one and two year olds to those which are probably older is about 1m. Those in the first group which are presumably young of the year are in the ratio of about 3:2 to the other individuals in that group so that apparently the young Summary of baculnm measurements of 80 mink Michigan. Table 18'. collected in southern Nina‘s er Measurement Mean Range averaged 110.0 . Weight in grams 212.MO to 77.11 76 1.61m 35-5 Length in millimeters M0.78 to 2.39 80 h6.o Dorso-ventral diameter 2.7 of base in millimeters “.03 to .93 7? é.h Lateral diameter of 2.0 base in millimeters 2.97 to .85 77 5 . b. Dorso-ventrel diameter 2.0 of shaf in millimeters 2.33 to .SH 77 3.1 Lateral diameter of shaft in millimeters 2.92 2.5 .20 77 to 0“. 81+ 2.... .535 2 Mo «grown. mo vamp exp mo aheamfixav Hmampn H 0.0 we c:H»—puhuwHw bucmrvmhh .nH mhdem FUELHHHH; . : “59.5%.... he was «C m Amanda 4......“ 39.3 r4r.d.....-.. 1.4%-...13.‘ nlfitflnxlfillf..L/\L.ZL ..lr...L Lula newsman,» Buy—dang 01. O O O O O O O O «.--/i J T. .5?» 37.1.“), .3 h\/.i 3 .l “.06 09...). 0.4/3 hwrl 375 Numb Maw}. muJ/b wan/.... a .L .nU E H; .. '"i" ’ ‘Je' L 5.- R'VP‘FM \ .t u.:" l r0 rd h' to IHIQUEHCY *‘ <3 P N H.31' \fl ax -l on \D O 155 8.3 Figure 15. O N Fl [.0 mon mom m momom mo 2§aee§ses§a§sse3s§r§ ILOULUM WEIGHT IR HILLIGRLMS Frequency distribution of the weights of the bacula of 76 mink. 36 of the year constitute about half of the entire papulation. 1'his large ratio might account for the rapid increases in the pepulation from year to year as indicated by records of the comlmted kill curing the trapping season. On the basis of the above evidence it appears that at present measurements of the bacula of considerable numbers of individual mink provide the best criterion for age detemination of animals taken out of the breeding season. Some confirmation of age can also be obtained by examining the teeth for signs of wear due to age. 1. 2. 3. SW! Imals constituted well over half of the contents of both stomachs and intestines of winter mink whether rated by bulk or by frequency percentages. m6 relative percentages by volume and by frequency of other classes of animals varied in the stomachs and intestines. lush-at was the most inportant individual prey item represented in both stomachs and intestines with cottontail being the second choice. Mice, birds, frogs, fish, and crayfish were also important constit- uents of the winter diet. lonfood items included in the diet were morphous mixtures of dirt and black protein waste, vegetation, and trap debris. A differential rate of passage of hard and soft parts of prey items was indicated. Bard parts appeared to be passed into the intestines more rapidly than soft parts as shown by a significantly greater occurrence of hard parts in the intestines as compared to the stomachs and a significantly greater occurrence of soft parts in the stomachs as chared to the intestines. 89: differences in selection of prey items were apparent. Males took a significantly greater amber of muskrats than did females while females took a significantly greater number of smaller food items than did males. rectors which may effect these differences such as the size disparity of the two sexes, greater cruising radius of the males, unbalanced sex ratio, and approach of the heading season base been considered. The mini: appears to be an important natural predator of the mskrat. Ilink-muskrat relations are considered. frogs and small manuals seen to act as buffers against predation by the min]: upon the mush-at. 7. 9. 11. 12. 88 The incidence of a number of parasites of the min]: was detemined. the sinus wom, Slcrabinglus nasicola, appeared to be the most cannon parasite and lungworms, l'ilaroides bronchialis, lungflukes, gar—agonime hellicotti, and the giant kidney worm, Dioctm renalel also appeared to be of considerable inportance. Little evidence of disease in wild min]: was found. A Jaundiced appearance of several of those which were autopsied may indicate paratyphoid infection but is also an indication of the presence of the gall bladder fluke, {gmtorchis canadensi_s. An unbalanced sex ratio of trapped mink occurred during the trapping month of December. Differential activity of the two sexes at this time may account for the unbalanced ratio. No evidence of breeding in either sex was found. I‘eigits and measurements were taken of mink collected in 19140 and 1941. he measurements for 1910 as compared to 1931 showed no significant differences with the exception of tail length. The significant difference in tail lengths of males is thought to be due to an error in sampling. W11. census technique based on measurements of tracks of males and females has been found to be invalid. Baculum measurements appear to offer the best criterion of age of mink trapped out of the breeding season. Tentative age groupings are proposed on the basis of these measurements. 89 GONGLUSIONS Since the nature of this study has limited its scope somewhat the picture which is presented may appear one-sided in some respects. Ideally, field observations should supplement those made in the lab- oratory in so far as possible in investigations of this kind. The evidence as found may then be evaluated and interpreted on a broader basis. However, in spite of the limitations imposed, some knowledge has been gained which may be useful in determining management policies and in deciding upon the economic status of the mink. A reasonably clear conception of the winter food habits of the mink has been obtained. The mink appears to be an inportant predator upon the muskrat and a more thorough study of minkth relationships would be in order. no economic value which the mini: possesses both from the standpoint of fur value and its effect on small mama). popula- tions should also be appraised more cornpletely. Some indication of the role which parasites and diseases may play in wild mink has been gained from this study. However, a continued study over a period of years should be made in order to detemine the part which these factors play in regulating the population. Very meagre data regarding breeding were obtained in this study. A more adequate knowledge of this is needed for the mink. me writer does not know how far along Enders of Swarthmore is with his investiga- tions at the present tine but the paucity of accurate information in the literature attests to the necessity for this type of research. in. growth of the mink should be studied. In order to properly determine age groups and age ratios in a population growth data is essential. At present measurements can not be chared directly with known ages and hence any infomation along this line must be deduced by analysis of the measurements themselves which may lead in some instances to some tangible errors. In some respects the evidence in this study has been rather inconclusive but enmigh information has been gained from it to point out further avenms of investigation which appear to be worthwhile. me present study, which has been somewhat preliminary in nature, suggests that before any sound management policies can be put into effect additional studies of this Mutant fur-bearer must be made. 91 MODS heel, Donald J. 1931‘. garaggnimus. its life history and distribution in lorth America and its 13mm. Amer. Jour. mg. 19(2) 2279- 317. _. 1938. me morphology and life cycle of when“ monorchis n. sp. (armada) from the mink. Jour. Parasit. 2N3):219—22h. Bailey, Vernon. 1926. A biological survey of North Dakota. 0. 8. Dept. Agru an. 3101., Survey, North American Fauna ban-:26. Denbrook, D. 1. 19,40. The occurrence of the guinea worm, Eacunculus medinensis, in a dog and in a sit, with a review of this pare- sitisII. Jour. mar. Vet. sea. Assoc. 96(755):261—263. 31.11:, s. Drank. 19140. Home ranges and pepulations of the meadow vole in southern Michigan. Jour. sue. sgmt. Manila-161. Burt, v. s. 1936. n study of the baculum in the genera [onetime mnigoms. Jom'. flannel. 17(2):).15-156. (Bones, 3. 1877. fur-bearing animals-«A. monograph of North American lustelidae. Dept. Int.. U. 3. 0601. Survey of the territories, Hisc. Pub. No. 8. Gran, I. I. 1923. The tussle on tide water creek. Jour. Hamel. Mines-26. Dearborn, led. 1932. foods of some predatory fur-bearing animals in Iichigan. Univ. of Rich. School of Forestry and Conservation Dull. 1:1-52. ______. 1939. Sections aid in identifying hair. Jour. Dismal. 20(3): 31*6-318. Dice, 1.. n. 1927. A manual of the recent wild mamals of lichigan. Univ. Rich. rum. Handbook Ser. 221-62. 92 lrrington, Paul L. 1935. food habits of mid-west foxes. Jour. Hamel. 16(3):192-200. _____. 1936. that is the meaning of predation? Smith. Instit., Iash. n. 0., saith. nept. for 1936, pp. 2H3.252.' _____. 1939. Reactions of makrat papulations to drought. Beoloy 20(2) 2168-186. _. 19141. Versatility in feeding and population maintenance of the mskrat. dour. Iild. light. 5(1):68-89. 3811. Iran 8. and George I. Stiles. 1938. An outbreak of botulisn in captive milk on a for farm in Colorado. dour. Bact. 36(3) 2282. milton, I. J. Jr. 1936. Food habits of the mink in New York. Jour. m1. 17(2):169. ’ _____. 19,40. The sun-her food of minke and racoons on the Iontesusa earth, Hes York. Jonr. Iild. unit. taboo-sh. Benson, Karl 3. 1933. Parasites of mini: and their control. Am. rur Breeder. 50085-7. Hardy. J. I. and There It. Plitt. 19140. An improved method for reveal- ing the surface structure of fur fibers. U. 8. Dopt. of Int" fish and Wild. Bel-7.. lild. Giro. 7. Kayne, D. 1. 19:1. llichigan trappers. Mich. State coll. Lgr. kpte Sta., Special Bull. 307. Ms, Arthur 1)., Tripp, rrancis, and Setterfield. G. H. 1938. The vitamin A.reserve of fur-hearing animals. Amr. Jour. Physiol. 123:693-700. Law. Ronald G. and Arnold 3. Kennedy. 1932. Parasites of fur-bearing animals. Ontario Dept. of Game and Fish, Bull. 1:31.29. . 19314. Nutritional anaemia in mink. The Called. l'ield Nat. hemtlw-hg. 93 Levis, Henry Y. 1929. Mrrhagic septicemia in a mink. Jour. Amer. Yet. lied. Assoc. 28(6):771-773. Lehr, Lester. 1937. How long is the mink‘s gestation period! Am. J‘ur Breeder. 10(1):28. ' Lyons, II. In Jr. 1936. Manuals of Indiana. file Am. Midl. Nat. l7(l):1-38u. nerahall, I. x. 1936. A study of the winter activities of the mink. Jour. Hammad. 170053-392. Mathiak, Harold A. 1938. A rapid method of cross-sectioning mamalian hairs. ’ Jour. wild. last. 2(3):l62-16h. _. 1938. A key to heirs of the manuals of southern nichigen. Jour. Iild. Ignt. 2w) :251-268. ~ Deleon, B. I. 1918. haller male of Uorth Amcrica. lat. Geog. Hag. 33:371-“93. Price, hot I. 1929. Two new species of trematodes of the genus {ametorchis from fur-hearing animals. Proc. U. S. lat. Hue. 76(12):1-5. Scott, Thee. G. 1911. Methods and computation in fecal analysis with reference to the red fox. Iowa State 0011. Jour. lc. 15(3):279- 285. - Seton, 1:. r. 1926. Lives of game animals. Doubleday Doran and 06.. Garden City, New York. ’4 701m, 22518-560. Shillinger, J. I. 1937. Diseases of fur animals. U. 8. Dept. Agru farmers Dull. No. 1777. 19110. Grays in minke. U. 8. Dept. Int., Fish and-Ind. Sal-v" Iild. Leaflet 167. kinker, I. 8. 1932. Molineus 251.53g reported fran the mink. Proc. Helm. Soc. Iash., Jour. Parasit. 19(1):91. Smith, 8. I. and J. I. 100811. 19140. Some nutritional studies with mink. rat. rur News. 12(11):} 11+. Suedecor, a. w. 19%. statistical methods. The lows. State College Press. Ames, Iowa. pp. 1.192. Sprague, James M. 1939. A preliminary study of the baculum of Perflscus leucOEus and 1° maniculatus in Kansas. Trans. Kane. Acad. Sc. ‘Ezh95-1‘97. Stevens, Howard. 1931. link relish glandular substances. Am. Fur Breeder. 3(7) :28. Svihla, Arthur. 1931. Habits of Louisiana mink (metela £1.93 vulgvafl). Jour. Manual. 1290666668. Wallace, 1'. G. 1931. Lung flukes of the genus {organimus in American mink. Jour. Amer. Vet. Med. Assoc. 31(2) 929.2314. _____. 1931. Lung flukes of the genus {argonimus in mink. Am. Fur Breeder. 3(12):2ll—25. ____. 1932. The life history of Troglotrema mustelae n. sp. Jour. Parasit. 19(2):l6h. Vigit, 3. II. 1939. J'ield and laboratory technic in wildlife manage- ment. Univ. Mich. rrtu. Ann Arbor. pp 1-107. Uilliems, 00611 S. 1938. Aids to the identification of mole and shrew hairs with general comments on hair structure and hair determination. Jour. Iild. ngnt. 2(n):239-250. APPENDIX SPECIMEN RECORD Cat. Ho.......... Coll. Ho......... mtaOOOOOOOOOOOOOOOOOO meie.OooeoosooeoooeeeeeeeeeeeesseeseeeeoeoMte callectedcoeeeoeeeoeeoeeesee __found dead shot trapped-trail set bait. Collector. . . . . . . . . . . MityOOOOOOOOOOOOOOO000e0O.o...OOOOTOCOOLOOOSOOOOcmtyQQ.OOOOOOStatOOOOO Habitat t Ueather: Ecological Notes: Spec. hem:__wild_dead_captive__a1ive_entire__partia1. Specimen 30......" 8a.....Ad_Juv_, determined by..... night".........1ive_degd_preserved__, dondition.......................... Bodymeasurements............................................................ m1 mummnt..000000000......OOCOOOOOO0.0....OOOOOOO......OOOOOOOOOOOOOQ Condition of teeth Testes: Velma.................measurements....................condition.... Penis: Condition...u.................hacul\mmeasurements"................ Mva................Cop. pluguamnae. Yagina...... ...... ...wag. smear.................Uterus....................... MMOIZ HooeeeeeeeeenO HornoeeoOL. Homeseee81”: MoeoooeooeowuooOOeoo Ovaries: Volune".............measurements...............condition.......... Pathol 0g lctoparasitee: Location.... .....................Ro......_attached__free. spe1°.......0000000000000OOOOOOOOOOOOOOOOOOOO0.0.0.0..........CO...OOO...... lndoparasitee: Location , m Dunbar Pelee! General Notes 11 FOOD HABITS Dat°OOOOOCOOOOOOOOOOOOO meie.Oooeeeeeee eeeeeeeeeeeeeeeeeeeeeeeeee eCOlle Ecoooeeeoeeeeeeseouxooooolo LocalitYOooeeee eeeeeeeee e eeeeeeeeeeee eeeeeoOcOIIOCtorees eeeeeeeeee eee eeeeeeee lo 701 .ft Remarks Wt“ General lotes iii . ‘0 1.- e. .. Ave W. .i ... . «.61. _0 at ,. l ‘ f . W r. u .4... m Li HICHIGRN STQTE UNIV. LIBRRRIES Ill?9 016”le l7|l| l3! ll