... -.-‘. - .- ...,. . . ~ h ..._-.. -- ‘V ..... .....—.««. "u“..n. 5. mm at no um «n mu an 2 h — bll — _ ~ lip ~ h h — _ k am? <5 3. x— n o :3 m N 9 .3 H J W a -8 9 3 o l: 3 All‘ Figure 7. 24 Figure 8. Average time spent by females grooming themselves during 30 minutes of observation over 8 weeks (N=9) . 25 at we uh...— 2.9:...— no >_O.l) . If a female got wet or rolled in the wet food while trying to get to her kits when she was blocked from the nest box, she would lick herself much more and in two or three cases results were biased somewhat because of this. Just before parturition the females normally become rather aggressive and remain this way to varying degrees until the kits are weaned. This aggression was not measured quantitatively, but it did vary noticeably from the females that allowed themselves or their kits to be picked up to those that would savagely attack anything that lifted the lids of their cages. This aggression did dwindle as the kits became older, but the more aggressive ones were still biting when the kits were six weeks old. RETRIEVAL. Female ferrets are quick to retrieve their kits and seem to pay no attention whatsoever to which kit they pick up. Normally a female will enter the cage from the nest as soon as she is allowed, pick up the first kit she comes to (by the nape of the neck usually, but tiny kits are often almost completed enclosed in the mouth and are held by the back or belly), take it into the nest and deposit it, and then return almost immediately to get the next kit. After all of the kits are retrieved, she usually at least looks back into the cage as if looking for more as does Richardson's Ground Squirrel (Michener, 1971). Some females will reach as far as possible out of the nest without completely leaving it and grab as many young as they can. Only then will they go all the way into the cage to get any remaining kits. Some will deposit several kits at the door before entering the nest and pulling the kits in after them. Occasionally a female will spend a few seconds nuzzling or licking a newly retrieved kit, and very occasionally (usually during the first 31 few retrieval trials) will retrieve and curl up around two or three kits and forget the rest. As the kits get older, they will often return to the nest box on their own. Quite often after about four weeks of age the mother would go after the kits and herd them back rather than carry them. Females have been seen, however, actually carrying 6 1/2 - 7-week old kits, and it was common to see females with kits old enough to eat solid food trying desperately to keep them from leaving the nest. On the other hand, they often left kits that were in the process of defecating or eating in the cage either until they were done (and usually returned on their own), or at least for several seconds or even minutes before they would pull them away. Ferret kits do often vocalize (a squeaking noise), which sometimes does attract the female, at least initially. Often, however, the mother ignores the cries, but whether this is due to a disturbance by the observer, a "laziness" due to domestication, or something completely different is not known. GROWTH: Figure 10 and Table 2 show the increase in weight of ferrets from birth to 16 weeks and Figures 11-13 and Tables 3-6 show growth of body length, tail length, foot length and ear length, respectively. An F-test showed that males and females did not begin to differ in size until Week 7 for body weight, foot length and ear length and until Week 9 for body length and tail length (P<:.05). At this point the males grew faster and leveled off somewhat later than the females (two or three weeks later for ear, foot and tail 1ength--body length and weight were still increas- ing slightly at 16 weeks). Body weight increased steadily until 4-5 weeks of age (which coincides with the time the kits begin to eat solid food) 32 Figure 10. Body weight of male and female ferrets from birth to 16 weeks. P<:.05 at Week 7. 33 lllllillilllllT 012345618910111213141516 WEEK OF LITTER LIFE Figure 10. 34 me o. mva m. mam om.0H m~.mmh mm v.emoHIm.Nmm mm.mH mo.vmmH oH mo m. vva o. mom mm.m Hm.ooh mm m.~mMHIm.mvm mv.oH mm.mH~H mH me n. mmmIm. ovm om.m oe.mH> mm H.5mmHIb.bmm om.mH mH.~HHH eH mo m. mmmI m. «on vH.m ve.mmo mm o.omHHIo.Ohb hh.mH v~.o~0H mH mo H. vva m. hmv mo.m mo.o~o mm m.mm0HIH.hmo oo.vH mo.mom NH mo H. mth o. owe mm.m v~.hmm mm w.m>m Io.omm 0H.oH No.mom HH me e. vmoI H. mom hv.h mo.mem om m.mmm Io.mov o>.mH mm.vmo 0H me o. ova m. MhH mo.m mm.mvv mm 0.0mm IH.omm hH.MH we.Hmm m Hm H. movI v. mmH Ho.e mm.omm mm o.mmm Iv.mH~ mm.~H om.mmv m Hv o. no MIo. omH mn.h mo.mom we v.5me Iv.va oo.HH hm.ovm n mm H. FOMI m. HOH we.» mo.mom on m.mmm Im.mm Hm.0H vm.mm~ e on o. onI m. be mo.m mo.mvH Hm n.0vm Io.on m~.m om.omH m vv 0. moHI m. mm em.v No.m0H on m.hmH Iv.mm mo.m mm.0HH v mm o. oOHI N. no om.~ no.0m mm v.o~H Im.h¢ mo.~ oo.hm m No v. we Im.Hm mo.H mm.om mo «.mh Im.v~ ¢>.H om.mo m on v. on Io. mH om.o mo.m~ mm m.me Im.mH m~.H oo.Hm H em a. mH IH. m hv.o Hm.m on m.vH Im.m mv.o mm.m o z mozcm .m.m .m z mozmm .m.m m Mums m s .omo mo nxoo3 0H 0» muouuom onsom one oHoE How ouHm oHQEom one meson suH3 uouuo ouoocmum.H Roadway uanua zoom .N oHoma 35 Figure 11. Body length of male and female ferrets from birth to 16 weeks. P<.05 at Week 9. 36 N N LENGTH (MM) ~ IIIIIfl' 012345678910111213141516 WEEK OF llTTER LIFE Figure 11. 37 mo mhMImHm mo.H NH.mom mm ovambm Hm.m oo.vov oH we o>MImom Hm.H mH.ovm mm mNoImom ov.m 00.0mm mH me chMImHm mm.H No.omm mm mHeIoom oH.N vo.emm VH me oomIoom mm.H mm.mmm mm OHvamm mm.m mo.mom MH we OSMImmN Hm.~ Hm.o~m mm oooImom mm.m mo.bem NH we mmmIooN mo.m mm.oom mm chmIomN eo.m mm.mmm HH we mNMIooN Ho.m mm.om~ om osmImoN mo.m om.hom 0H me mOMImvm om.~ mm.mb~ mm QBMIMNN mb.m Hm.mm~ m Hm omNImmH mm.m mm.mom om mmNImom mo.m 5H.bem 0 Ho HoNIhmH mo.m em.mm~ co momIHhH vo.m om.Hmm 5 mm mNNIooH Hh.m oo.oo~ on ommIoMH Ho.v oo.mmH m on momImvH Nh.m bv.hhH Hm momIHMH om.m mo.th m vv thImNH vm.~ ow.hmH on mmHIbHH mo.~ mo.mmH e mm mmHIBHH ov.H so.~vH mm thImHH mh.H h~.mvH m we mvHImOH o¢.H mo.h~H me mvHIom mo.H oo.mmH m on mHHINm mo.H mo.mm mm MHHImm mo.H oo.00H H pm an Inn mm.o bo.oo em mm Ioo om.o no.0o o z moznm .m.m M 2 moznm .m.m m. Emu», no .omo mo axons oH on wuouuom THE—now one 0H9: now on? onfium one mono.» £53 £3.83 onnonoum H 2!: fimnoH Soon .m oHnmn. 38 Figure 12. Tail length of male and female ferrets from birth to 16 weeks. P<.05 at Week 9. 39 190 110 an E 150 .....€'ou. : ..w v no ,..' a: ’°' I— u x" {5 ,4 z j. u so -II " -l 10 E '- . 30 u 012345678910111213141516 WEEK or LITTER LIFE Figure 12. 4O we omHIOMH 0m.H mH.moH Hm oomIOMH oo.m mm.mnH oH mo owHIOMH m~.H wv.voH Hm oomummH mH.N om.HhH mH mo omHIOMH vv.H mm.voH Hm mmHImNH mH.~ mm.moH eH we mmHIomH mH.H oo.mMH Hm omHIomH om.H Hv.hmH MH mo omHIOHH mm.H mm.mmH om owHIvHH 0H.m wo.moH NH mo ooHIOOH hv.H 0H.va om ooHIBOH NN.N mm.va HH mo ovHIom mv.H mm.oHH we omHImm bH.N mH.HNH 0H me oNHIHh mm.H hm.m0H om moHIom mm.H om.noH m Hm oHHImo om.H m~.vm mm mHHImo mm.H 0H.hm m Ho mm Imm om.H mm.mh we OOHImv mo.m mm.mh 5 mm om IHv Ho.H mo.mo mm mm Imm 0H.m om.mo m on me Imm MH.H mm.mv on or Ion mm.m mH.mv m we mm Ion om.o hm.ov mm mm Imm h~.H oo.vv o om mo Ihm mm.o om.mm Hm mo INN mh.o Ho.mm m me on Imm no.0 mo.Hm mo mm Iom ov.o om.mm m on em Iom hm.o hm.- on mm IbH no.0 mm.mm H em on IvH mm.o mm.oH vm Hm IVH om.o Hh.oH o z moznm .m.m m. z mozmm .m.m mm Kama m «0 .omo mo mxoo3 oH ou muounom onfimm one on5 now oNHm onfiom one omnmn nuHs .nonno onmonoum H “EEO sumnoH HHoB .v oHooB 41 Figure 13. Hind foot length and ear length of male and female ferrets from birth to 16 weeks. P<.05 at Week 7. 42 Foot Length .....I.'..."".%.--. 0’... . Ear Length I I I I I I l l I Illa 4 56 78 910111213141516 1 2 :3 WEEK OF LITTER LIFE I I Figure 13. 43 mo memv vN.0 mm.mo mm voImm Hm.0 mH.00 0H mo hmImo mm.0 m0.0m mm voImm mm.0 hm.mm mH mo hthv om.0 mm.mv mm moImm Hm.0 mm.mm vH mo memv om.0 om.mv mm moIvm vm.0 Hm.mm MH mo NmIov 0m.0 v0.mv mm NmImm Hv.0 mo.hm NH we NmIov H~.0 00.0w mm HoImm 0e.0 No.0m HH we omIov vm.0 Hm.ho 0m mthv mv.0 mm.mm 0H mo 0mImm 0v.0 mm.oo mm mmIvo mv.0. hh.Hm m Hm 0mlmm mm.0 00.mv om vahm 0m.0 0m.mv 0 Ho moIHm 0v.0 mm.0o co 0mINm 05.0 em.me 5 mm 0vIo~ mm.0 mH.om 0m vavm om.0 hm.0m 0 on vMImm mm.0 mm.0m Hm hmImm mh.0 0H.Hm m we HMImH no.0 m~.om on mmImH mm.0 0m.0~ o mm mNImH om.0 mm.Hm mm othH m~.0 vv.mm m we 0mImH 0~.0 00.hH mo HNIvH mm.0 me.mH m on mHIoH .Hm.0 0m.mH mm bHIHH v~.0 Hm.MH H hm 0HIn oH.0 no.0 on 0HIm mH.0 mm.m 0 z moznm .m.m m. z moznm .m.m m. mums no .006 m0 mxo03 0H Qu muonuom oHoEom one onn Mom onHm onEom one munch nuH3 .Hounm ouoonnum H_AEEV numnoH uoom onHm .m mHoma 44 mw mNIwN NH.0 0H.oN Hm wmImN wH.0 Hw.0m 0H mw mNImN wH.0 mm.oN Hm NMImN wH.0 wH.0m mH mw mNIwN wH.0 mm.mN Nm NNImN wH.0 00.0m wH mw mNIwN wH.0 mN.oN Nm NNImN wH.0 mm.mN mH mw mNImN wH.0 mh.mN Nm NNImN HN.0 m0.mN NH mw mNImN wH.0 00.mN Nm HNImN mH.0 Nm.mN HH mw hNI0N wH.0 mm.wN 0m 0NIwN NN.0 00.hN 0H ow nNI0N wN.0 om.mN Nm mNIoN hN.0 Nw.mN m Hm oNImH NN.0 wN.NN wm leoN wN.0 wh.mN m Hw MNINH MN.0 Hm.0N ww mNIhH 0m.0 0m.HN n mm NNIwH 0m.0 mw.hH on NNINH mw.0 00.5H o wm oHIHH NN.0 hm.wH Hm mHIHH oN.0 mm.mH m ww mHIoH hH.0 wm.NH 0m oHIm mN.0 mN.mH w mm NHIm NH.0 mw.0H Nm NHIm hH.0 mm.0H m Nw 0HI> NH.0 mm.m mw 0HIh wH.0 ob.m N on b Im wH.0 mm.m mm h In HH.0 om.m H hN m IN o0.0 mH.N wN m IN m0.0 MN.N 0 z muzmm .m.m m. z muzmm .m.m m. Mum: m. In .omo mo de03 oH on mumnuom oHoaow one oHnE now oNHm onfinm one omnon nqu .Houno ouoonoum.H ABEL numnoH new .0 oHooa 45 when this increase became slightly sharper (Figures 14 and 15). Newborn kits weigh one per cent or less of the adult weight and have fine white hair all over their bodies. The pink skin is thin enough to see some of the dark outlines of the internal organs. The necks are quite long with a fat pad on the back of the neck and the kits stay slightly curled up most of the time. The young seem better able to use their front legs than their hind legs and, unlike rat pups, which are incapable of initiating suckling (Rosenblatt, 1970), they are able to pull themselves to the female remarkably well. By about the third day the hair is thicker and visibly gray (or white if albino), but the color is uniform. The hair is somewhat longer on the neck and head than elsewhere by about the end of the first week. This is also found in the ermine (Mustela erminea) which carries its young by the nape of the neck (Ewer, 1973) as does the ferret. Mustela nivalis and M} frenata. which have been seen picking up their young by the middle of the back, do not have this neck mane.r The fat pad on the back of the neck undoubtedly protects the kits when carried in this fashion. Characteristic dark markings begin to appear between the third and fourth weeks but are not really prominent until the kits are nearly five weeks old. Eyes and ears begin opening at approximately the same time--usually around 28 days. Occasionally the eyes begin opening a little earlier. Both eyes are normally open by Day 36 or 37. Females often "chuck" to their kits, but chucking was very seldom heard more than about a week before normal ear opening. The deciduous canines begin to appear about Day 14 and are normally completely through the gums by Day 18 or 19. The premolars begin to 46 Figure 14. Adult male (at top) and female ferrets showing difference in size. Figure 15. Ferret kits of different ages. (Top row, 1. to r.: 42 days, 36 days, 26 days of age. Bottom row, 1. to r.: 15 days, 11 days, 6 days, 4 days of age.) Figure 14. Figure 15. 48 emerge by this time. No deciduous incisors were seen, but these were not watched as closely as they might have been and their presence may have been temporary. However, permanent canines appear before the deciduous canines fall out and are visible by 47-52 days; the deciduous ones fall out between 56-70 days. The kits begin to eat solid food fairly regularly by 4 1/2-5 weeks of age, although one litter was observed in the cage eating from the food plate as early as 18 days on a very warm.sunny day. Some kits were seen lying in their cage (which is much more Open and airy than the nest box) on very hot days when they were only 14 days old, but no eating was observed. The mothers were first observed taking food into the nest boxes when the kits were about 23 days old, but food was seen in the nests five or six days before this a couple of times. The kits begin to defecate without stimulation from the females about the time they begin eating solid food. They definitely are able to do this by the time they are four weeks old and two kits were observed defecating in the nests at 23 days. Up until this time, the mother licks the anal region to stimulate defecation and urination. EXPERIENCE EFFECTS: Using a two-way univariate analysis of variance (with experience of the female and fostering as the two variables), it was found there were no significant differences (P).05) between primiparous and multiparous ferrets in time spent in the nest, nursing, licking or grooming (see Figures 16-19). There was a difference, however, in latency of retrieval and time to retrieve kits (.01.05) for either group. The statistical tests showed no interactions in any of the measures. FOSTERING EFFECTS: Fostering had no effect (P:>.05) on how the ferrets treated their entire litters for any of the six variables studied according to a two- way univariate analysis of variance (see Figures 22-27). Differences in amount of time spent licking and nursing and rate of retrieval of the kits that belonged to the females with mixed litters and those that were foster- ed were also tested. No significant differences (PI>.05) in these para- meters were found. A split-plot factorial analysis of variance also showed that there were no differences in growth rates of fostered or nonfostered kits. Retrieval times for two females with young kits were also tested with other kits of different ages. Retrieval was nearly immediate except in one case where the alien kit was six weeks old and one female's own young were one week old. In this case, the female reached out and bit the un- related kit. One female that was pregnant for the first time was l o ' . Bin-T cranium-Tm we 6m Figure 16. 50 Average time spent by multiparous (N=9) and primiparous (N=10) females in the nest. 51 u...=._ gut... .._0 >5. Ho MM NM 0N MN 9N NH ‘0 fi .............. b. coo o’caan’ oooooo o... v ( oooooo (no 0000 o ’ no... no. . one. u so ‘ 4ll-I‘ I on: 5.38:: ....... tonne-goals, ...... 0 acid eazouonuxs_ IIIII ooosetzxseu-rlllno w— I. .00._mmmm .mw_mmm a... W... an s _: m pale Figure 16. 52 Figure 17. Average time spent by multiparous (N=9) and primiparous (N=10) females nursing each kit. S3 2 l P... Hapefw 210 Wm sum n: y g ----- o "Wished ....... Lgast SquIfOS Flt 190 3110 I 9- O .‘A‘ we \a G . 2 III I (n ‘I: 11’ = z 9 w E — 70 l- 9 3o 1 9 I "'"'2‘ 10 1'4 1 2'0 2'3 2'6 zlsr 3'2 3E 35 4i DAY OF LITTER LIFE N- Figure 17. .§nlflfll h~wnuivm . Ii“. Figure 18. 54 Average time spent by multiparous (N=9) and primiparous (N=10) females licking each kit. 55 HExporlenced — Regression Line 6 O ------ ONonexperloncod A --------- Regression Llno o '. ‘i-v X 40 2. z 2 ------- - 3 ........ :: ~- - ‘ .0"... ..... d 20 , ..... .....o. s ’ ..H'. . s. 00'... ..... .. m O‘RW‘O. 2 m ............. - 'II fl . 14 17 38 41 20 23 26 29 32 35. DAY OF LITTER LIFE Figure 18. S6 Figure 19. Average time spent by multiparous (N=9) and primiparous (N=10) females grooming themselves. 57 HEW — Regression Una .- ------ ONonoxperloncod 7° . -------- Regression Line A ' ‘ 8 so u a, ....... . {’3 so .9 ‘2’ 4o ' ......... g 30 .' .giuuoossssssssol".....-.. a. c ............ g 2.. lull E 1 I- 14 1 7 20 23 26 29 32 35 38 41 DAY OF LITTER LIF Figure 19. 58 Figure 20. Average latency to retrieve the first kit of multiparous (N=9) and primiparous (N=10) females. uh...- zuhh: “3 >5— : v» 3 nu ma «a an 3 3 a . .3 w ........ o I ........ 14.31% I .............. 13:23....302 0...... v I I .0 I I I n (3033) AONJIVT 'IVIISIIIHII 9 . . .- . “9. k: . . .7 2 ‘ 9 . - “ht—I- 60 Figure 21. Average time to retrieve each kit by multiparous (N=9) and primiparous (N=10) females. 61 A 8 40- ‘9 C—OExperlenced a 0- ----- . Nonexpsrlenced \o I“ 30— E I- : 20- > I! E II— 10" III E I>< I I I 10 13 16 19 22 25 26 1 DAY OF LITTER LIFE Figure 21 . 62 Figure 22. Average time spent in the nest by females with their own litters (N=9) and females with mixed litters (N=10). 63 e-—o Own Litter —- Regression Lhe o-u-efllxed Litter ----- Regression Llne A 8 60° ......... .“n‘ " "" ~ -' 550°— "..9. ....... u ........... z __ :5 ~ I“ 400- _ .. I— — ' I l I i l i 1 l T 14 17 23 26 29 35 38 41 20 32 DAY OF LITTER LIFE Figure 22 . 64 Figure 23. Average time spent nursing each kit by females with their own litters (N=9) and females with mixed litters (N=10). 65 HM Litter — Least Squares Fit 0 ----- oMIXed Litter . """""" Least Squares Flt 14 11 3 26 29 32 3 36 1 20 2 DAY OF LITTER LIFE Figure 23 . 66 Figure 24. Average time spent licking each kit by females with their own litters (N=9) and females with mixed litters (N=10). 67 3 an an 2.... 5.389.. ....... 83... 3559...... 2.... 5.3933. I .83... e OI um... cut...— Nn mu .3 >< mu 2 v— e d 8 3 S 8 (sass) amen 3m )_(, Figure 24. 68 Figure 25. Average time spent grooming themselves by females with their own litters (N=9) and females with mixed litters (N=10). 69 Hawn Litter _ Regression Line . ..... oMIxed Litter ........ Regression Line :: ........... ‘- I’ I I l I 14 17 20 23 26 29 32 35 38 41 DAY OF LITTER LIFE Figure 25. 70 Figure 26. Average latency to retrieve the first kit of females with their own litters (N=9) and females with mixed litters (N=10). Before Day 14 all females have their own kits. 71 uh...— zut: .3 >5. mu m— an as «N a. on “WIJflmmuHUHHHLH. uuuuuuuuuuuuuuu .. .33... .35.... ..... .- sgzfi.:§5.0lllo em ~F~ 6 F‘ E: (9035) AONJLV'I TVAJIIIIJII fir 6 G3 3‘ Figure 26. 72 Figure 27. Average time to retrieve each kit by females with their own litters (N=9) and females with mixed litters (N=10) . Before Day 14 all females have their own kits. 73 O—oOwn Litter _ I'm-oflixed Litter s. 7’ yo ? N ? y.- 8’ i I \ I I I T fi‘l 1 4 7 lo 13 16 19 22 25% DAY OF LITTER LIFE )1 RETRIEVAL TIME (SECS) Figure 27. 74 tested for retrieval of different-aged kits. In the first test, with a three-week old kit she smelled and licked the kit and after about 30 seconds picked it up and began carrying it around the cage befbre taking it into the nest. All this happened within about 75 seconds after she first noticed the kit. When tested again a few days later with a 6-week old kit she immediately retrieved it. Several females either pregnant or with young were observed to respond to the cries of the kits that were put in neighboring cages for retrieval. One female was given four 2-week old kits the same day her own kits were to be weaned. She retrieved them immediately, but her older kits attacked the younger ones. When the older kits were removed, the female licked the new kits, especially one that had been injured and 45 minutes later they were all nursing. She appeared to treat them as well as she did her first litter, but the kits never grew much and about 10 days later began to die. This could pose a very interesting problem for future research. MALE-KIT INTERACTIONS: The data Obtained (Table 7) indicated that. on the average. the males spent much more time with kits that were over four weeks old than with younger. less mobile kits. Most males spent some time smelling the anal region of the younger (0-3 weeks) kits and would often turn the kit over on its back. but would then usually walk away and ignore it unless it cried or happened to catch his eye again, or he stepped on it. Two of the males did a little licking, and one actually carried a kit to the food plate, licked it, and ‘Uhen carried it into the nest box. However, it was being rather rough. and it could not be determined if he was being somewhat aggressive or 7S N.NmH h.HmH m.h¢H m.om o.m¢ N.Hh m.om m mm mm vb me an cm Hm Holmo OhH MwH mm hm ha mg mm HVIhU mNN mmd me mv 0N mg ma Hmimm mom mew won me ms Mb mm mHImU 09H CNN mad mm 0H 00H 05 Himm mum NmH mva VA ONH OMH hw mlhm nxmo3 m mxoo3 m mxooz o axons m mxoo3 N x003 H when N LT mung no man .Amccooom oom «Andaman. mufix an“: ucomm moans Amocooon. new» no unsoad .h manna 76 just overexuberant. One male (the only albino) was consistently aggressive and would immediately approach a kit and bite it. After he had killed a few kits, I was careful to remove the kit from him as soon as he started getting rough, and for this reason he was not included in the averages. At four weeks the kits were able to maneuver somewhat by themselves, although they still cannot see. The males seemed more interested in these young that were more mobile. Several males carried their kits around the cage or into the nest box, and more licking was observed at this age. The males commonly "danced" around the kits as if trying to get them to play. Again, the albino male was extremely aggressive (my interpretation--someone else might call it over-protective) and it was difficult to take his kit away from him. By the fifth week the kits were able to see, and a couple of times actually tried to follow a male. Some males acted frustrated at this and retreated. Several males carried their kits around or pulled them in and out of the nest boxes. This time the albino male was much less aggressive. His kit was a female and he actually appeared to be trying to mate with her. He spent over three of the allotted five minutes with her, and she never showed any signs of being hurt or even frightened. Six~week old kits are quite playful as well as mobile and able to see well. The males "danced" around and the kits often ran after them as if to play. Several kits followed the adults into and out of nests, but there was less actual carrying than with five-week old kits. 77 MALE -FEMALE-KIT INTERACTIONS : On September 20, 1974, sixzyoung were born to one pair of ferrets that was left together after mating, but four were dead. On that day the male and female were found sleeping closely together and the two remaining kits were beside the male. The next day only one kit remained and it was dead, crushed under the two adults who were curled up together. The other pair had seven young on September 21. Both the male and female were in the nest, but the female was curled up around six of the kits and the other was by the male which was curled up an inch or so away from the female. This family was left together for six weeks, until the young were weaned, with no mishaps. MINK X FERRET KITS: When the ferret kit and the two mink kits were cross-fostered to respective mothers, the female ferret immediately savagely bit the 6-day old mink kits so that I was forced to remove them quickly. However, these kits died soon after. The mink female, on the other hand, never harmed the two-day old ferret kit, but after about seven days she removed it from the nest. At that time I returned the kit to its original mother, who readily accepted it, and found that it was appreciably smaller than any of the other kits in the ferret litter. This probably indicated that the kit had suckled very little from the mink. PREDATION: In the predation study, the ferrets seldom noticed the prey unless the mouse moved or they touched it in some way. Even though the barrel was quite small, the ferret would normally chase the mouse around it for some time. The mouse was often caught by the tail or rear a few times, at WhiCh point the mouse would usually turn around and bite the 78 ferret, before the ferret eventually delivered a well-placed bite to the back of the neck or the skull. Sometimes the ferret would hold the mouse under its front paws for a few seconds and then the mouse would often get away for another chase. If the ferret was unable to catch the mouse within five minutes, it generally lost interest. All adult ferrets, both male and female, were able to kill mice within five minutes (normally less than three minutes) except for one lactating female who showed litte interest. The most adept killer was a lactating female that had sustained an injury to her abdomen not long before. She was always able to kill her mouse within 1 1/2 minutes, and was the only adult that showed any desire to eat her prey. The youngest kit that was able to make a kill was a nine-week old female that caught her prey about two minutes after she took interest in it. A male of the same age lost interest in his mouse after about five minutes, however, and there were some lO-week old kits that were not yet able to make a kill. Six S-week old kits were put in the barrel together and given one mouse, but they showed little interest in it except as a play object when it moved. However, when their mother was added, and she killed the mouse, the kits were immediately interested and fought over the dead animal. The mouse was ripped apart and eaten by the kits (the female took no part) and they were very possessive of their pieces. STIMULI: Table 8 indicates the different stimuli tested and the responses obtained. Note the rather high frequency sounds are better than others in eliciting responses. The dropping of the can which made a loud clanging noise got much more consistent responses than the dull thud Table 8. Stimuli used on the ferrets. STIMULUS RESPONSE Odor: Ben Gay shakes head Vicks Vapo-Rub shakes head Food becomes active, climbs cage; 5-9 wk. kits go to feed pan Sound: Hand clap jumps or activity stops Drop weight sometimes looks around Drop can activity stops, looks around Dog whistle sometimes stops activity as if listening Other: Puff air shakes head if directly in face Running wheel Another ferret plays on it see text 80 of a dropped weight or even a hand clap. The ferrets would often jump or look around at the first clap, but would pay no attention the second time. A running wheel might be twilized quite well, especially by young ones (adults sleep a lot). In this study, however, a wheel was made available to a whole litter and they all tended to play on it at the same time, which meant two could be trying to turn it in different directions. These animals are inquisitive and therefore usually tend to approach other ferrets. But the stimulus elicits a much more consistent response if it is a kit attracting a female (especially if it is vocal) or a female in estrous attracting a male (or possibly just the odor of the female in estrous). DISCUSSION As with most mammals, the female ferret must spend much time with her young for the first few weeks of life to insure their survival. The kits are quite helpless and rather immobile until they are almost four weeks old at which time they are able to eat solid food to some extent and to wobble around the cage. Within a few days after this, the eyes and ears begin to open and development occurs rather quickly from that point on. Within less than two weeks after this, the young can depend entirely on solid food and are very active. The mother's behavior toward her young through the suckling and weaning periods is closely geared to the behavioral capacities of the young at different stages of their physical development. Therefore, the gradual changes that occur in the relationship between mother and young must always be kept in mind. The female ferret normally spends at least 90 per cent of her time in the nest with the kits during the first four weeks. After this, she spends progressively more time out of the nest, but so do the kits, so they are still together much of the time. Adults, however, normally spend a good deal of their time in their nest boxes, sleeping, and the time the mother spends in the cage after the first four weeks could actually be more than when she is alone. The female spends most of the time in her nest during these first four weeks nursing her kits. Individual kits do not necessarily suckle constantly, but a combination of at least one or two kits is usually nursing most of the time. It is not too surpriSing that licking of the kits does not change ranch over time, but there was some indication that the direction of the 81 82 licking changed. Ferret kite; need the stimulus of the mother's licking to defecate and urinate, as i4; true of many other mammals, particularly altricial species (Ewer, 1968) . so it is reasonable that most of the licking should be directed.tc>'the ano-genital region until the young are able to defecate on their own. After this point, licking becomes more general with more face and ear washing especially. Contact seems to be very important for young ferrets. As soon as the female leaves the nest, the kits immediately crawl into a pile and sleep that way until the mother returns. Ewer (1973) reports that most young carnivores have this tendency to come to rest only when in contact with a littermate's body. Undoubtedly, this contact is for warmth since their thermoregulatory mechanisms probably are not refined for some time after birth. But even six- or eight-week old kits were usually seen sleeping piled on top of each other (and their mother when she was in the nest) even if there were 10 or 12 in the litter. The ambient temperature had to be 85-900F to make them distribute themselves more widely or for them to sleep in the cage. Adult male ferrets are significantly larger than adult females, but the kits grow at the same rate until they are 7-9 weeks old. At this point the growth of the females slows down some and tapers off two or three weeks sooner than that of the males. As should be expected, the body weight is much more variable than the length measurements, which increase from week to week regardless of the nutrition they are receiving. Some kits actually lose weight during certain weeks. This is probably due to nutritional inadequacies of the milk, since generally if one member of a litter is underweight, they all are. Normally if small kits are able to survive until they can consume solid food, they will survive to maturity 83 and will probably even attair: the normal weight before they are fully grown. The physical developmend: of these kits agrees fairly well with the information supplied by Herter (1953) and Pitt (1921). They each had only one litter, but their data for eye opening and other factors fit within the ranges noted in this study. Although observations on tooth development were quite sketchy, there have been several detailed analyses of the growth and replacement of teeth in ferrets by others (Berkovitz, 1968, 1969, 1973: Berkovitz and Thompson, 1973a, 1973b; Berkovitz and Silverstone, 1969; Ruprecht, 1965). Although deciduous incisors were not observed in this study, Berkovitz (1968) explains that ferrets have four of these on each side (only three permanent incisors), but all that is ever visible is the outermost tip of the fourth one (a supernumerary incisor). The time and order of eruption of deciduous and permanent canines and permanent incisors appear to be very similar to that of mink (Aulerich and Swindler, 1968), although the ferret's teeth seem to begin erupting two or three days earlier than those of the mink. The time of eruption of the first teeth (14-19 days of age) also coincides with the first consumption of solid food which occurs, as with most carnivores (Ewer, 1973), before the eyes Open. Although in the laboratory kit ferrets can be removed from the mother at six or seven weeks of age, this does not mean the same would pertain to either them or their relatives, the polecats, in a natural situation. King (1963) and King g£_31, (1963) used the earliest age at which the young could be kept from their mothers for 24 hours without a weight loss as the criterion for weaning Peromyscus. It was found that ferrets can gain weight away from their mothers several says before their 84 eyes are open. But they obviously would not be able to survive in the wild at such an age. There vmas little indication that the mothers made any effort to disperse their kits even at eight or nine weeks of age. Like most carnivores that are highly skilled predators (EMer, 1968, 1973), kit ferrets probably stay with their mother for some time after being able to eat solid food in order to gain experience in finding and killing prey, etc. Novikov (1956) reported that wild polecat kits become independent at about two months of age, but remain together until the fall of their first year. The sparse data collected here on prey-killing behavior indicate that a ferret is capable of killing a mouse by the time it is 9-10 weeks old. However, in a natural situation where the mouse has a chance to escape, a ferret of this age may not be agile enough to capture a fleeing mouse. Mustela nivalis are able to kill mice by the time they are 42-45 days of age (Heidt, 1970), but their development is faster than that of the ferret. These data also agree with Eibl-Eibesfeldt's (1957, 1970) observations on the killing techniques of polecats. He stated that in- experienced animals chase and kill fleeing rats, but only after grabbing the rats several times by different parts of the body so the rat often turns and defends itself. Experience is important for the specific killing technique of immediately grabbing the rat at the back of the neck. Heidt g£_al. (1968) observed N, nivalis mothers training 40-day old kits in killing, which does appear to quicken the process, and Goethe (1940) has reported that captive mother polecats will carry a piece of meat into the nest, pull it out again and leave it so that their onetmonth old kits will follow the scent trail and find the food. This could be a form of predator training in an artificial environment. 85 This was never observed in the ferrets, but kits less than a month old orient toward meat quite readily. The method used by the ferret to kill seams to be similar to other weasels which grab prey by the nape of the neck and then bite through the base of the skull and/or throat area (Heidt, 1970: Allen, 1938: Glover, 1943; Hamilton, 1933). It is interesting to note that neither experience nor fostering appear to have much, if any, effect on the maternal behavior of ferrets. Primiparous ferrets nurse and lick their kits in the same'way multiparous females do. Inexperienced females do, however, retrieve their kits significantly more slowly on the first test day then do the experienced females, but this difference disappears by the second trial period three days later for both latency of retrieval and mean retrieval time for each kit. Even the multiparous females retrieve their kits more slowly for the first couple of trials, but for both groups, this retrieval rate and the latency decrease during the first three trial periods. These results agree with those of Carlier and Noirot (1965) for rats. Evidently a minimum of practice induces long-term changes. These changes carry over to the next litter a year later, but even then some practice is needed to gain "ideal" speed. Fostering appears to have even less effect on the behavior of the female toward her young than does experience. 'The tests showed there were no behavioral differences between females with their own kits and those with mixed litters. Also, the females did not treat individuals that were fostered any differently from those that were not fostered, although immediately after fostering some females appeared to manipulate and lick the new kits more. It should be pointed out, however, that since the average number of young in a litter of ferrets is seven or eight. 86 there is a possibility that reducing the number of kits to four could have induced the females to react more maternally toward anything, including alien young. This seems unlikely, though, since young have been fostered into litters already containing seven or eight young with no obvious change in the maternal behavior. Rabbits also adopt strange young readily (Sorenson e£_al,, 1972). as do mice, rats (Beach and Jaynes, 1956a) and cats (Schneirla et_al,. 1963). But cats show somewhat different responses than do ferrets. Nursing cats will readily accept one strange kitten and encircle it immediately, but the addition of three strange kittens distrubs them and they will sometimes even attack. Kittens are also able to distinguish their own mother soon after birth (Schneirla et 31,, 1963), so an initial hesitancy to suckle a strange female is not too surprising. Rats will retrieve alien young as do ferrets, but they do so more slowly then they retrieve their own, which indicates they recognize their own young at retrieval (Beach and Jaynes, 1956a). A ferret, on the other hand, seems to take no notice of which kit is being retrieved, and picks up the first one she comes to. Also, the mortality rate of fostered young increases and the body weight of survivors decreases in rats as the number of days the foster mother has been lactating increases (Denenberg et_al,, 1963). But the age of the young seems to have no effect on the ferret mothers since in these tests the kits were not fostered until two weeks of age. At another time a kit as old as five or six weeks was fostered to a female, and the new female's kits showed more interest in the alien than did the female herself. Ewer (1968) suggests that altricial species with their own nests, such as the ferret or the polecat. are generally more ready to adopt strange young than are precocial species 87 since there has been little need for selection fOr recognition of young. The fact that these ferrets did not show any differences in the maternal behavior parameters studied, regardless of experience or fostering, could be very important to future researchers. It is difficult to get a large sample size with an animal like the ferret which takes up quite a bit of room and eats a rather expensive diet. When the age of the animal has to be considered also, even more problems are created. For future maternal behavior studies, any adult female, whether she has 9 had young or not, can be used. Since fostering is so easily done, ferrets would be good models for studies on the effects of different-sized litters, which can be created when necessary by fostering. When survival of as many kits as possible is important, kits can also be fostered when a female dies or is incapable of nourishing her young adequately. MINK X FERRET KITS: These results were surprising since ferret females do so readily accept alien kits of the same species, and mink very sel- dom do (Aulerich, 1975). Bahlcke (1939) has even reported using ferrets as foster mothers to mink when the mink litters are too large. Of course, since only one mother ferret and one mother mink were used, this could simply have been a quirk. But there must be some pre-planning to carry out an experiment such as this since the reproductive season of the ferrets in this area begins just about the time that of the mink is ending and it is sometimes difficult to find litters of each species coming at approximately the same time. Better success might have been Obtained if all kits had been dusted with baby powder or some such thing to mask the new odors for a time. The odor of the mink kits is much stronger than that of the ferret kits, so these mothers must surely be able to detect a difference. Perhaps the odor of the mink kits was 88 strong enough to mask that of the ferret pup from the mink mother for a time, but was so overwhelming and strange to the ferret mother that she attacked them as aliens. Perhaps the females’ responses would have been different if they had been allowed to retrieve the alien young along with their own. Ewer (1968) discovered that if foreign young were placed outside the nest of Cricetomys, the young were retrieved, whereas if they were placed inside the nest, these young were immediately killed. Lorenz (1956) described how dogs and other animals sometimes appear interested in foreign young but lick them as if trying to remove the fetal membranes, and since these membranes do not exist, the skin gets out and the young eventually eaten. However, these mink pups were bitten so quickly by the female ferret that this does not appear to have been the probable cause. If this fostering could be effected successfully, many new lines of research would be opened. Not only could we foster mink to ferrets when the mother dies or is unable to raise her kits, but such things as the effect of maternal behavior on aggression would be better studied since the mink is by nature a very unfriendly and unsocial animal. Studies of aggressive strains of mice raised with rats have shown con- flicting results (Denenberg gt_al., 1964; Hudgens e£_al,, 1967; Rosenberg gtflal., 1970), but there is some indication that the aggressiveness of the mice is reduced. It would be a great boon to the mink industry if mink could be made more passive by fostering them to ferrets when very young. MALE-FEMALE-KIT INTERACTIONS: Although some mustelid males do take a part in caring for the young (Mustela frenata, g, vison, g. erminea, Taxidea taxUS). according to Palmer (1957) polecats do not. The results 89 of this study, however, do seem to indicate that they would be compatible. In situations where cage room is a problem, males could be left with females after the last breeding with little fear of losing the kits as a result. The interactions of males and kits could be better discerned in this situation also. It appears that most males show very little antagonism toward kits at any age, and actually play with older kits, and occasionally retrieve and lick younger kits. Perhaps this is a result of domestication since male polecats are not known to stay with their families. Since so many other mustelid males stay with their families, it is more likely that this desertion is due to some factor other than his aggression toward the young causing the female to drive him away to protect the kits. Although relaxation of care of the young is often inadvertently selected for during domestication by bottle-raising young that the mother either cannot or will not take care of,this does not seem to have happened with the ferret. Perhaps this is because ferrets were usually not considered as real pets, so cute and cuddly that one could not bear to see a baby die. They were a work animal, used to catch vermin, and probably were not always cared for as well as dogs or cats. The young are also too small to be able to bottle-feed easily, so most kits born of mothers either behaviorally or nutritionally deficient would not live to reproduce. Furthermore, since litters can be quite large, the breeders presumably were not overconcerned. It is, however, quite conceivable that aggression and protection of the kits have been selected against since these animals have been pro- tected from the elements of nature for so long. Some of these mothers were somewhat aggressive. but not to the extent found in mink mothers. 90 Pitt (1921) and Poole (1972) stated that polecats are quite nervous and untamable, but ferrets are indeed very tractable animals. Poole (1972) continued to develop the hypothesis that since the ferret has been kept as a pest-destroyer, selection has been toward an easily handled animal that is not too quick or nervous so they are not too difficult to recapture. In his first chapter on the adaptations of domestic animals, Hafez (1968) states that domestic animals must be adapted to their environment and that "well-adapted animals are characterized by....high reproductive rate..." This is certainly true of the ferret which can have 10-12 young or even more at a time, although they may not all survive. Perhaps the fact that mink usually have three or four and that they sometimes have trouble raising them indicates that this animal is not yet fully adapted to its caged environment. Actually, it is somewhat Surprising that the ferret has ever been domesticated at all. Most authors (Zeuner, 1955: Ucko and Dimbleby, 1969; Scott, 1954) agree that animals which have social relations with members of their own species to begin with are more ready to form the same kind of relationship with another species--namely man. This is one reason why so many bovids have been domesticated so successfully. In addition, most people are familiar with the highly social life of wolves and most other canids to which our domestic dog is so closely related. 'But polecats are supposed to be rather secretive animals. The only social tie they appear to have besides at mating is between mother and offspring. So why would this animal ever be chosen? Nobody seems to have an answer. However, our present-day ferrets are at least sociable animals. if not actually social, so perhaps the polecat ancestor did have some 91 propensities toward a certain amount of socialization. Perhaps polecats would be more social if there were large enough numbers of them to allow them to come into contact with each other more often. Of course, it is not impossible for domestication of a solitary animal to have occurred, even 2000 years ago. The domestic cat is certainly not from a social group and there is great individual variation in animals, so som --- the ones "chosen for domestication---could have been quite social even though others may be more secretive. Acceptance of young other than their own facilitates successful domestication by allowing transfer of young and adoption of wild young by tamed mothers (Kretchmer and Fox, 1975). Since ferrets do so readily accept foster young, this could have had a large bearing on the domestication of this animal. Perhaps the fact that mdnk do not so readily accept foster young could account in part for the difficulty breeders have in taming this species. Since so little has been done to investigate the maternal behavior of the other wild mustelids, few comparisons can be made and any con- clusions as to changes in this behavior that could be due to domestication are almost impossible to make. Much more research needs to be done in this area on the mustelids and the other carnivores to find answers to a few of our questions. SUMMARY AND CONCLUSIONS Maternal behavior was observed over an eight-week period for a total of 30 minutes every third day for each of nine female ferrets. It was found that they gradually spent less time in the nests as the kits got older. Time spent nursing remained fairly constant until about Day 19 and then decreased rapidly until there was essentially no nursing by 7 1/2 weeks. Licking of the kits and grooming remained at a constant low level throughout the eight weeks. Growth and development of kits were also studied over 16 weeks. Males and females grew at similar rates until they were 7-9 weeks of age at which time males began to diverge rapidly from the females. Experience and fostering effects on maternal behavior were studied with 19 females divided into the following groups when the kits were 14 days of age: (I) Multiparous with own kits; (II) Primiparous with own kits: (III) Multiparous with two fostered kits.and.two own kits: (IV) Primiparous with two fostered and two own kits. The experience had no effect on maternal behavior as measured by time spent in the nest, nursing the kits, licking the kits, grooming themselves, rate of retrieval and latency to begin retrieval. Fostering had no effect on any of the measures except rate of retrieval and latency to begin retrieval on the first test day. There was no difference in the behavior of the females toward their own kits and the fostered kits, nor were any subtle differen- ces shown in growth rates. Various parameters of this maternal behavior are discussed in terms of the evolution of the ferret as a domesticated animal and maintenance of this animal for research purposes. 92 93 The following conclusions could be made as a result of this study: 1. The experience of previously having raised kits has little effect on the maternal behavior of the ferret. Those differences that are due to experience are very short-lived. 2. Fostering has no effect on the maternal behavior of the ferret. However, if the female's own kits are three to four weeks older than the fostered kits, the older kits could injure the younger ones. 3. Ferrets would be good models for the study of maternal behavior for the following reasons: (a) Ferrets are quite docile and are usually quite calm while being observed. (b) They are smaller than dogs, so eat less and take up less room. (a) Ferrets often have large litters, and since they can be easily fostered, many different-sized litters can be obtained to study differences in maternal behavior due to litter size. (d) Ferrets can have two litters per year under normal photoperiod, but this is more than many other carnivores. (e) Since previous experience has little effect on maternal behavior of the ferret, studies can begin as soon as the animal reaches reproductive age. (f) Since this is a carnivore, it could be used to study the role the mother plays, if any, in teaching the young to hunt. 4. This is a beginning to the study of maternal behavior of mustelids, and more complete studies should be made on the other mustelids, especially mink and weasels. 5. Although aggression and protection of the young may have been selected against during the process of domestication, actual care of the young 94 has probably been affected little. 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