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A COMPARESGN OF THE ACTWQTlES OF
THE RWER DTTER {LUTRA CANADENSES)
EN TWO TYPES OF ECOLOGICAL EABITATS

Thesis for the Degree of M. S.
MICHIGAN STATE UNIVERSITY
RONALD J. FIELD
19°70

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A COMPARISON OF THE ACTIVITIES OF

THE RIVER OTTER (LUTRA CANADENSIS)

 

IN TWO TYPES OF ECOLOGICAL HABITATS

By

Ronald J; Field

A THESIS

Submit ted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE

Department of Zoology

1970

A C K N O W L E D G E M E N T S

I wish to express my gratitude to Dr. Rollin Baker for his assistance
and guidance in the research methods used in this paper, and to the other
members of my guidance committee, Drs. Eugene Roelofs and George A.
Petrides for their assistance.

I am further indebted to the United States Fish and Wildlife Service,
especially John E. Wilbrecht, Donald Elias, and the staff of the Seney
National Wildlife Refuge. Without their help this study would not have
been possible.

A great deal of gratitude also goes to the Michigan Department of
Natural Resources for its assistance in this project. Particular thanks
goes to Louis Verme, Elsworth Harger, John Ozoga, and David Arnold for
their cooperation and advice.

I wish to express my thanks here to the Michigan State University
Department of Fisheries and Wildlife for providing me the use of a snow-
mobile to facilitate this study. I am also deeply grateful to Dr. William
Cooper for his help with the statistical design of the project; to Mr.
Clair Ossian and Miss Elizabeth Butsch for their help in determining the
contents of the collected otter scats; and to the staff of the M.S.U.
Museum for their help and consideration. I also wish to thank my uncle,
Fred R. Field, for his assistance in collecting some of the data used
in this paper.

Finally, my greatest appreciation goes to my wife, Sandra. Without
her assistance in preparing this manuscript, and her tolerance of many

hours of work, this study would never have been completed.

ACKNOWLEDGEMENTS . . .

LIST OF TABLES . . . . . .

LIST OF FIGURES . . . .

INTRODUCTION . . . . . .

REVIEW OF THE LITERATURE .

STUDY AREA . . . . . . .

METHODS . . . . . . . . .

RESULTS . . . . . . . .

Locomotion in Snow

Activities -- Sector A

Sector B

TABLE OF

Interaction with Coyotes

Hunting . . . . . . .

Scavenging by Otters

Incentives for Overland Travel

Scat Analysis . . .

CONCLUSIONS . . . . . . .

REFERENCES CITED . . . .

ii

CONTENTS

ii

iv

11

11

13

14

14

,16

19

TABLE I.

TABLE II.

LIST OF TABLES

RELATIONSHIP OF OTTER GROUP SIZE TO STUDY SECTOR .

CONTENTS OF UNDIGESTIBLE MATERIALS IN COLLECTED OTTER
SCAT S O O O C O l C O O O O O O O O O O O O O O 0

iii

. 21

. 22

LIST OF FIGURES

Figure 1. TRAVELING DISTANCE OF OTHER GROUPS CORRELATED WITH FRESH
SNOW.ACCUMULATIONS . . . . . . . . . . . . . . . . . . . . 23

iv

I N T R O D U C T I O N

The American River Otter, Lutra canadensis Schreber, has long been

 

regarded in popular opinion, as the "gay blade" of the wild northland.

He has been described countless times in popular literature as a carefree
playboy spending most of the summer sliding down grassy banks to
disappear swiftly into deep crystal clear pools and emerge with a
dripping trout clenched in his jaws.

In winter, the animal also is reported to spend his time at play,
now chasing another otter or being chased in a playful game of tag, now
sliding swiftly across snow-covered slopes or across the frozen pools.
Again he is observed to dart quickly beneath the ice, and again he
emerges with a huge trout for his meal.

Always he is pictured in the beauty of the forest as a symbolic Pan,
Greek god of Nature. His prey is always the fleeting trout, a symbol
of the lithness, grace, and agility which are so much a part of his
image. How strange it seems that a member of the weasel tribe should
be so elevated while other members are often depicted as villainous and
insatiable murderers.

This inconsistancy immediately stimulates a question concerning
the accuracy of popular belief about the otter. This question, coupled
with the value of the animal as a furbearer and its esthetic value to

the general public, form the foundation for this research.

REVIEW OF THE LITERATURE

Literature concerning the ecology of the river otter is sparse.

By far, most published accounts have to do with the otter as a possible
predator on sport fishes. The results of examinations of the contents
of digestive tracts and/or scats have been published for otters in
North Carolina (Wilson, 1954), Montana (Greer, 1955), Massachusetts
(Sheldon and T011, 1964), Michigan (Lagler and Ostenson, 1942; Ryder,
1955), New York (Hamilton, 1961), and in Wisconsin, Minnesota, and
Michigan (Knudson and Hale, 1968). These investigations showed that
otter largely eat fish, lesser amounts of invertebrates (crayfish and
insects), some amphibians, and an occasional mammal. Most of these
workers concluded that otter, while being primarily a fish eater,
concentrated upon the species which was most abundant and most easily
obtainable.

An infrequent topic of discussion in the literature is the extent
of winter travel in which these animals participate. Emil Liers, in
his classic 1951 paper, states that the animals usually travel "fifty
to sixty miles of stream course in a year," but says that normally they
only travel some three to ten miles in one season. He also cites
instances where a male in breeding season traveled some three and six
miles on two separate occasions. He fails, however, to state the effect
of snow cover on travel.

Concerning travel in snow, Ognev (1962), Novikov (1956), and Seton
(1926), generally state that the animal is rather inept at travel in
snow, and therefore makes few overland movements during winter. Seton
further suggests that these mustelids seldom, if ever, come out of the

water in winter, but remain in underwater burrows and stay under the ice.

All of these works deal with some aspect of the classical
ecological concept of the niche of the otter. None of them, even in
combination with other works, comes any closer than a vague description
of the habits of this species during the winter season. From the
dietary studies previously described, a theory might be supported that
these animals are primarily Opportunistic feeders, but concentrate
mainly upon fish. This immediately raises the question concerning the
consequences of the severe winter in which all water bodies freeze
solidly. Is the otter frozen beneath the surface and relegated to a
diet of solely fish, or is he trapped above the ground and forced to
turn scavenger or to hunt terrestrial mammals and birds?

Secondly, the information available advances the theory that otters
are not exceptionally adept in traveling long distances in the snowy
conditions of a severe winter. This would necessarily restrict their
ability to hunt for food on land, or to travel between water courses.
Such limited mobility, if it does exist, would severly hamper a
carnivore which is primarily a resident of north temperate or boreal
climates.

The following study was pr0posed as an effort to describe the
winter activity patterns of these furbearers. Specific emphasis is
directed toward their ability to travel in snow, and the activities
engaged in during these periods of travel. Further, an attempt was
made to correlate the types of winter food consumed in two areas of

differing habitat types.

STUDY AREA
The study area in which this research was carried out is located in

the north-central part of Michigan's Upper Peninsula, within portions of

Alger and Schoolcraft counties. The northernmost region of the study
area was the Mosquito River approximately one-half mile south of Lake
Superior. The southernmost region was a small nameless creek, which for
convenience will be called Steuben Creek, just outside of the village of
Steuben. The west branch of Prairie Creek, slightly over one mile west
of Shingleton marked the western boundary of the area, and the eastern
limit was the M-77 state highway.

This overall area was subdivided into two sectors of dissimilar
habitats. Sector A consisted of several shallow pools which were
generally bordered by or partly covered with cattails (Typha‘gp.) and
sedges (Caggx‘_p.), and can be generally associated with Units I and II
of the Seney National Wildlife Refuge. These pools were all artificially
fashioned through the construction of earthen dykes to block the natural
flow of drainage. All are more than fifteen years old and have become a
part of the natural ecosystem. This sector is also interspersed with
several marshy areas containing clumps of red-oosier dogwood (Cornus

stolonifera), bog birch (Betula pumila), and tag alder (Alnus rugosa).

 

 

 

Sector B has no specific boundaries, but is restricted chiefly to
streams and the wooded or cut over land area on either side of or
separating them, as Opposed to open marshy areas and standing water of
any type. The streams included in this sector are: East Branch Fox
River, Pine Creek (Schoolcraft County), Driggs River, Marsh Creek,
Ducey Creek, Pine Creek (Alger County), Commencement Creek, Star Creek,
Prairie Creek, Hickey Creek, Stutts Creek, and Chapel Creek.

This part of Michigan commonly has rather heavy snow falls, often
measuring up to 64 inches per month from December through March. The

temperature frequently drops to less than -10°F during this period.

METHODS

This study has been designed to investigate the activity of river
otters in winter conditions, and travel is primarily emphasized. For
this reason, and because of the secretive habits and relative inaccess-
ability of these animals, direct observation of them was impossible.
Instead, the trails left in the snow as a result of their movements were
followed, and their actions were interpreted in a manner similar to the
methods used for other carnivores by Murie (1936), Arnold (1956), and
Ozoga and Phillips (1964). This tracking was accomplished between
December 12, 1968 and March 11, 1969. In total, trails were followed
for 73.7 miles, of which 31 miles were in sector A, and 42.7 miles were
in sector B.

In addition, all scats found along trails were collected for
analysis of content. The locations of these collections were recorded,
and special effort was made to interpret (from tracks, habitat, and
other signs) the activities of the animal responsible for each scat.

Finally, the temperature and snowfall for each day were obtained
from the weather station maintained at the headquarters of the Seney
National Wildlife Refuge. Since no accurate information could be
collected in any other part of the study area, these data from Seney
were generalized to include the entire area. It is certain that some
discrepancies exist, especially along the more northern streams of
sector B, since they are as much as forty miles from the weather station.
These weather data were also correlated with the recorded activities of
otters and with the contents of seats. This provided an estimate of the

effect of weather upon both diet and activity patterns of the otters.

RESULTS
Locomotion in Snow

The collection of data was accomplished by using a snowmobile to
gain access to the study areas to be investigated, and then following on
snowshoes any otter trail encountered. The trail was initially followed
in the same direction the otter was traveling, to its end. This
terminal point usually was at a place where the animal entered some
water course, but occasionally was merely the place where the wind and
snow had covered the tracks. At this point, the trail was retraced, and
then backtrailed to the point of its origin. The distance was measured
with a U.S. Army "tally-whacker", or manual event counter which recorded
the number of paces taken while following the trail. A previous
experiment determined that the investigator's pace length while on
snowshoes was approximately 1006 per mile. For the sake of convenience,
this was rounded off at 1000 paces per mile.

The continual trailing of these animals, coupled with four visual
observations, resulted in the recognition of a characteristic gait
utilized a majority of the time. Normally, while traveling on land, the
otters run in bounds of from 15 to 28 inches for 2 to 4 steps. This is
then followed by a 5 to 15 foot slide with the belly dragging and the
legs trailing backward. The pace of these animals is rather slow in
snow because of the short legs and low, dragging body. When frightened,
they are quite capable of outrunning a man on snowshoes rather handily,
at least for a short distance.

These are at least two modifications of this gait. The most common
of these occurs in group play. Here the otters simply leave their front

legs folded back beneath their bodies and prOpel themselves by pushing

with their hind legs. From visual observations, they are quite capable
of pushing themselves up at least 15 yards of a 20 to 25 degree grade in
this manner.

The second modification occurs in the deliberate hunting of small
mammals. On two occasions, tracks were observed where an otter stopped
the bounding and sliding gait and stalked clumps of grass. The feet
were moved in steps of about five inches, either one at a time, or else
one hind and one fore leg worked simultaneously. At a distance of about
two feet from the clump of grass the otter jumped on it, probably in
much the same manner as a fox catching mice, and in at least one case a
mouse was captured as evidenced by the blood stains remaining on the
snow.

One playful movement pOpularly attributed to these animals was
encountered only once in more than 73 miles of trails followed during
this 3 month period. This was an otter "slide" on Hickey Creek, and
involved two otters who slid down a 20 foot bank into water at least
three times each. In contrast, on each of four other occasions, groups
of from one to five animals chose to walk down steep banks rather than
slide recklessly into the open water. On several occasions the tracks
indicated that they often slide down a slope while engaged in overland
travel. Apparently this action is routine in traveling and is not
really play behavior.

There was also evidence that these animals will follow packed
trails in the snow made by other animals, especially deer and snowshoe
hares. Due to their short legs, otter undoubtedly are able to travel
more easily on packed snow than on the fluffy powder. They also travel

single file when there are more than one traveling together. The first

animal ”breaks trail" for the others in the troupe, with the others
simply following in his tracks. The trails also show that they switch
positions occasionally, so that each takes his turn at going first.
Otters make their trips on land most frequently alone, but
occasionally in groups of from two to five animals (see Table I). There
does appear to be a significant difference in group size between sectors
A and B (t is significant at .05). The animals in sector A, which is
primarily covered with cattail marshes, seem more prone to travel singly
than in groups, while in the stream area (sector B) otters appear more
prone to travel in pairs. In total, by far the majority of overland
traveling was done either by single animals, or by pairs. In 38
observations there were 16 single and 14 pairs of animals trailed.
These made.up 42 and 37 per cent of the total respectively. These
animals traveled distances of from about .13 miles to about 3.2 miles
overland. The average distance traveled was .83 miles for single
animals, 1.14 miles for pairs, 1.3 for trios (two observations), 1.03
for groups of four, and .97 for groups of five animals. These are,

however, not significantly different statistically.

Activities -- Sector A

During their normal movements, the otters in sector A tended to
travel at random from pool to pool, but usually went through cattail
marshes which separated most of the pools. In most cases they kept
within 400 yards of a pool, even though during the colder stages of
winter, these were usually frozen over.

The cattail marshes through which the otters traveled were nearly
always open to some extent, and had from 2 to 15 inches of water in

them. These were kept open both by spring action, and apparently by the

otters themselves. Dozens of places were found where they had dug and
chewed through up to 6 inches of ice both in the marshes and on the pool
surfaces, probably in search of food. In several instances the animals
went through clumps or swales of tag alder while traveling between
pools, and in some cases, they entered a large area covered primarily by
bog birch and red-oosier dogwood. Again, these areas were never more

than some 400 yards from one of the pools.

Sector B

The animals in sector B, on the other hand, ventured further from
water. There was an instance when one pair traveled overland through
hardwoods, pine, and frozen sedge marshes for 3.2 miles between the
Driggs River and Pine Creek. Another pair went from Walsh Creek
primarily through spruce and pine stands to Ducey Creek marsh for some
2 miles, and a third instance when 5 animals migrated from Chapel Creek
to the Mosquito River for one mile through a white-cedar (Thgja

occidentalis) swamp. On still another occasion, 5 animals followed a

 

large circular path through red pine and spruce stands for .9 miles
while leaving and returning to Pine Creek.

In following a stream, however, otters almost invariably either
swam in the Open water or under the ice, or else they walked on the ice.
Only in two cases was evidence found showing that otters had followed
the bank parallel to the stream, and both of these were for distances of
less than 200 yards. In addition, they never strayed more than 20 yards
from the stream bank.

By far, the most common occurence was for the animals to swim
beneath the ice and come up at breathing holes from 50 to 300 yards

apart along the stream course.

10

There was no dominant type of vegetation through which the animals
traveled in sector B. They simply entered and traversed any area they
came upon in their overland jaunts, including stands of jack or red
pines. However, in sector A, the major habitats through which the otters

traveled were covered with the conspicuous cattail.

Effects of Temperature and Snowfall

The temperature and amount of snow seemed to have no effect upon
either the frequency of overland movements or the distances traveled by
the otters. One animal was followed between two pools for .9 miles on
January 10, 1969. He was going diagonally into a 15 mile per hour wind
during the height of a snowstorm which deposited 15 1/2 inches of snow
in 24 hours. The temperature at the time was about 15°F and there was
at least a foot of fresh snow, but he completely disregarded the shelter
of dense pine and spruce stands, merely crossing through them as he
encountered them. He continued on his way across completely unsheltered
sedge and cattail marshes which were almost buried beneath the snow.
The time of this journey was between 11:00 A.M. and 1:00 P.M. On two
other occasions nearly identical movements were recorded during similar
storms. One of these, on January 17, was in mid-morning, the other, on
February 1, occured during the preceeding night. From these observations,
it would seem that neither the weather nor the time of day have a
significant effect upon the movements of this species. A trend toward
decrease in the average distance traveled by animals may be indicated
when compared with snowfall (Figure l and Table I), but an insufficient
number of observations were recorded to demonstrate any significant

difference (t not significant at .05).

11

Interactions with Coyotes
Occasionally in their travels, otters apparently have interactions

with coyotes (Canis latrans). For example, on February 7, 1969, three

 

coyotes were observed to follow the trail of three otters as they went
overland between Pine and Commencement Creeks, and again as they
traveled on the ice of Commencement Creek. The coyotes trailed the
otters for about .75 miles in total, during which time they chewed up a
scat pile deposited by the otters. From the evidence left in tracks,

the two groups never came within sight of each other.

Hunting

Deliberate foraging behavior was observed several times from the
tracks followed within sector A. Several areas were found in cattail
marshes where otters had dug through the snow and ice, then down into
the bottom sediments. The animals obviously rooted around in the mud,
probably digging out and devouring crayfish, frogs, and an occasional
large aquatic beetle or belostomatid. The eating of these foods was
later verified by scat analysis.

On February 21, 1969, a lone female otter was observed while
fishing through the ice on one of the pools on the Seney Refuge. She
dived several times through a hole in the ice and in times ranging from
one minute 8 seconds to 4 minutes 23 seconds she re-emerged with small
fishes. These were promptly swallowed whole. She was then observed to
enter an adjacent cattail marsh where she began to dig in the mud as
described above. Here she caught a crayfish which she chewed and
swallowed with much loud smacking and crunching.

In addition to this digging in the mud, several instances were

recorded where otters deliberately stalked clumps of grass and pounced

12

upon them to attempt capture of a mouse or vole. On several other
occasions there was evidence to demonstrate that the otters had dug into

the grass tunnels of the meadow vole, Microtus pennsylvanicus, and on

 

at least two of these occasions, one or two drops of blood remained to
verify that a capture (presumably of a meadow vole, see Hamilton, 1961)
by the otter had resulted. Seven scats also contained traces of small

microtine rodents, either Microtus or Cleithrionomys gapperi.

 

On February 17, 1969, the trail of a pair of otters was followed
into a marshy area which contained several small clumps of red-oosier
dogwood and bog birch. This marsh which encompasses approximately three
acres, was marked by the trails of at least a dozen otters, and along
each trail were a series of holes dug in the snow. The pair of animals
which was being followed at the time dug into the snow at the bases of
birch and dogwood clumps 25 times within a distance of 300 yards. .About.
five minutes later one of these animals was surprised while digging one
of the holes and immediately ran for safety. Scats collected in that

area later revealed skeletal parts of both Microtus and Clethrionomys,

 

along with the exoskeletons of some insects.

Temperature and snowfall fluctuations seem to have no more limiting
effects upon the hunting procedures than on travel of the otters. On
almost every day, fresh diggings were found in the marshes, and in early
December, an otter was trailed while stalking mice during a three inch
snowfall. On a number of occasions throughout the winter, holes were
found extending through at least two feet of snow to intercept rodent.
tunnels in subsnow grass.

The otters in sector B showed different movement patterns. Since
their tracks were not often seen in marshes, they were never observed to

dig for frogs or stalk small rodents. Scat analysis showed crayfish

 

 

13

present only 60 per cent of the time as opposed to 84 per cent of the
time in scats taken in sector A. Frogs were not found in the scats from
sector B. This shows a significant difference in diet of otters in
these areas, which is almost certainly the result of the greater

availability of both crayfish and rodents in sector A.

Perhaps in place of Microtus in sector B, the otters frequently

tracked snowshoe hares (Lepus americanus). On nearly all of the over-

 

land travels by either single animals or groups, the trails would lead
beneath brush piles, windfalls, snowcovered lower branches of spruce and
pine trees, and similar places frequented by snowshoe hares and usually
containing their tracks. On two occasions otters were found, from track
evidence, to give chase to hares which they came upon suddenly. On
February 28, conclusive evidence in the form of tracks, blood stains,
and hair was found to substantiate the capture of a hare by a pair of
otters. The carcass was completely devoured, and nothing remained but

tufts of hair.

Scavenging by Otters

It has been hypothesized (Elsworth Harger and John Ozoga, personal
communication) that otters may act as scavengers on deer carcasses. In
order to determine the extent to which this might occur, two road-killed

whitetailed deer (Odocoileus virginianus), autopsied previously and

 

Opened up to afford a maximum amount of scent from the fresh venison,
were placed in the field.

The carcass of a juvenile male was deposited in sector A on January
31, beside an open water ditch which was frequented by otters. It was

not molested by otters on February 1, 6, 9, 16, 17, and 21; although on

14

February 17, fresh tracks showed that two otters had passed within 25
feet of the carcass, but in passing had not detoured either toward or
away from it.

A second carcass which had been similarly treated was placed on the
bank Of Stutts Creek in sector B. On February 18, after a week during
which otters were not attracted, the carcass was discovered and devoured

by ravens.

Incentives for Overland Travel

There are several possible reasons for overland travel by otters,
but this study has shown only one to be important. This is for the
purpose of hunting terrestrial foods -- chiefly small mammals. A great
deal of the overland travel which is recorded here was in the form of
short trips (a few hundred yards), presumably in search of food.
Increased movements resulting from the mating urge in late winter and
early spring, as stated by Liers (1951), was not in evidence in the
present study. There was no significant increase in length of trails or

frequency of movements in late winter, at least through March 3.

Scat Analysis

Each scat collected was crumbled and qualitatively examined under a
stereomicrOSCOpe to determine the content and relative undigestible
proportions of each species of animal remains. The scats collected in
sector A (see Table II) contained primarily forage fish, with the species
Umbra limi being.dominant in quantity as well as frequency. Several
game fish, mostly Lepomis sp., were also present. Nearly all fish were
less than six inches in length. There was also a high frequency of

crayfish occuring in the scats from this area. Frogs and mammals also

l 1 I 1| ‘ll! 1 l I i I. l l. I‘

15

appeared several times, thus offering evidence that otter diggings in
marshes were not without success.

In contrast, the seats taken from the stream area (sector B) have a
similar incidence of forage fish and game fish, but a much lower rate of
crayfish, amphibians, and especially mammals (see Table II). The fish
taken are about the same as those in sector A. The only noticeable
difference in the frequency recorded for various species is a slight
increase of Lepomis _p. in streams and the slight decrease of cyprinids
and U, limi in the stream area as compared with the pool area of sector
A.

Of the 47 scats obtained, only 10 (21 per cent) were taken along
the 42.7 miles of trackways followed in sector B, or one for every 4.3
miles, whereas, 37 (79 per cent) were picked up along the 31 miles in
sector A or one for every .8 miles. The reason for this difference in
scat finds in the two sectors is unclear; in fact, more trails in sector
B were made by two or more otters than in sector A. Even so, more
droppings were deposited in sector A and these also averaged larger
(7.6 + 3.6 grams as compared with 4.2 t 1.6 grams with 66% C.L. for
those taken in sector B).

These data indicate that otters in sector B, as compared with those
in sector A, moved around in larger groups and produced fewer and
smaller scats. This can probably be interpreted to indicate that the
type of food ingested in stream habitats had a higher coefficient of
digestibility than that captured in marshes. This is exemplified by
comparing the residue left after the digestion of a fish with that

remaining after digesting a crayfish.

16

CONCLUS IONS

From the results of these observations, several conclusions can be
drawn about the habitats of otter in this region.

Much of the popular Opinion regarding both the food habits and the
playful antics of these animals either stems from isolated occurences or
is primarily myth. There appears to be very little evidence, at least
from this study, that any more than a minute percentage of their time is
taken up with repetitive sliding, tag, or similar playful activities.

On the contrary, the majority of their time appears to involve such
necessities as hunting for food or in traveling between water bodies,
perhaps in search of a better supply of food.

This collection of data also points toward the idea.that.otters may
work together in pairs or small groups more efficiently than singly to
capture food. The specific factors contributing to this conclusion are
the facts that otters in the predominently Open marsh area tend to hunt
and travel alone, while those in isolated stream areas tend to work more
frequently in groups. This, coupled with the fact that frogs, crayfish,
and small mammals such as Microtus are more abundant and consequently
more easily captured in the marshes, would lead one to believe that
hunting is more successful in these open areas. Also, fish are probably
more easily captured in shallow pools with essentially smooth bottoms
than in the turbulent waters of a trout stream. For these reasons, it
may well be that otters have developed the method of working as a team.

to catch fish and mammals such as the snowshoe hare captured on February

28, 1969.

17

Another aspect of travel which is illuminated by this research is
the mobility of these animals in fresh, deep snow. Although their move-
ments seemed slow, they did not hesitate to strike out overland under
extremely adverse conditions, as evidenced especially by the observations
on January 10, January 17, and February 1. In short, there seems to be
no correlation between the amount of fresh snowfall and the movements of
these animals.

It has been demonstrated, however, that given a choice, otters seem
to take the easier route of travel, Eafi- it appeared that they would
rather swim in Open water or under the ice on frozen streams than walk
along the stream bank in deep snow. In addition, if they are traveling
overland in deep snow, they seemed to take advantage of any well-packed
areas such as deer trails, snowshoe hare runs, or the packed-down tracks
of their cohorts in the traveling troupe. These findings also complement
the Observations of Formozov (1946).

This ability to travel in snow, which somewhat contradicts the
reports of Seton, Ognev, and Novikov, is probably of survival value to
otters. It enables especially those living in wooded stream areas to
travel between separated water courses in search of food. As further
evidence that winter food for otter in wooded stream areas (as in sector
B) may be in short supply is the fact that otter (more commonly in
groups) moved around a great deal and deposited only a few, small scats
as compared with the otter in Open marshes of sector A.

In summation, it is the conclusion of the author that the river
otter is not accurately described when he is conceptually regarded as a
"carefree clown" of the northland. The majority of his time, at least

in winter, seems to be spent in gathering food. Although on occasion

18

there is evidence of "playful" behavior, it is probably in the context
of learning between young animals, or between young animals and their
parents. From the data presented here, however, it must be concluded
that this behavior occurs little during the severe winter season, when
groups of otters apparently become efficient teams of hunters, and
probably do not have either the time or presumably the desire to engage
in idle play.

On the basis of this research, it can also be concluded that otters
which winter in wooded stream areas probably have less food available to
them than those which winter in Open marshland. Therefore residents of
the former travel more frequently and for greater distances, and also

occasionally work as hunting teams.

19

REFERENCES CITED

Arnold, David A. 1956, Red Foxes of Michigan, Mich. Dep't of Conservation
Pub., Lansing, Mich. 48 pp.

Formozov, A. N., 1946, Snow Cover as an Integral Factor of the
Environment and its Importance in the Ecology of Mammals and Birds,
translated in Occasional Paper No. 1, Boreal Institute, Univ. of
Alberta, Edmonton, Alberta, Canada.

Greer, K. R., 1955, Yearly Food Habits of the River Otter in the
Thompson Lakes Region, Northwestern Montana, as Indicated by Scat
Analysis, Am. Mid. Nat. 54(2): 299-313.

Hamilton, W. J. Jr., 1961, Late Fall, Winter, and Early Spring Foods of
141 Otters from New York, N.Y. Fish and Game Journal, 8(2): 106-109.

Knudson, G. J. and J. B. Hale, 1968, Food Habits of Otters in the Great
Lakes Region, J. Wildl. Mgt., 32(1): 89-93.

Lagler, K. F. and B. T. Ostenson, 1942, Early Spring Food of the Otter
in Michigan, J. Wildl. Mgt. 6(3): 244-254.

Liers, E., 1951, Notes on the River Otter (Lutra canadensis), J. Mamm.
32(1): 1-9.

 

Murie, A., 1936, Following Fox Trails, Univ. of Mich. Museum of Zoology
Pub. No. 32, U. of Mich. Press, 45 pp.

Novikov, G. G., 1962, Carnivorous Mammals of the Fauna of the USSR, Eng.
trans. A. Berron and Z. S. Cole, Israel Prog. Sci. Trans.,

Jerusalem. 293 pp.

Ognev, S., 1962, Mammals of Eastern Europe and Northern Asia, translated,
Jerusalem.

Ozoga, J. J. and C. J. Phillips, 1964, Mammals of Beaver Island, Mich.,
Pub. of the Museum 2(6): 307-347, Mich. State Univ.

Ryder, R. A., 1955, Fish Predation by Otters in Michigan, J. Wildl.
Mgt. 19(4): 497-498.

Seton, E. T., 1926, The Lives of Game Animals, Boston, Vol. 2, 671 pp.

Sheldon, W. G., and W. G. T011, 1964, Feeding Habits of the River Otter
in a Reservoir in Central Massachusetts, J. Mamm. 45(3): 449-455.

20

Wilson, K. A., 1954, Mink and Otter as Muskrat Predators, J. Wildl. Mgt.
18(2): 199~207.

21

TABLE 1

RELATIONSHIP OF OTTER GROUP SIZE TO STUDY SECTOR

 

 

GROUP OCCURENCES
SIZE SECTOR A SECTOR B
1 11 5
2 6 8
3 O 2
4 2 2
5 O 2
TOTAL
OBS. 19 19
MEAN OF 1.6 2.4
ANIMALS

PER GRP.

22

 

OTHER

streus

sqoasuI

 

FROGS

 

MAMMALS

anozorw

 

sAmouoranan

 

CRAYFISH

 

GAME FISH

 

suaosaAEI; 9919a
aepruomtes
srlandoxorw

srmodaq

 

1’

TABLE II

CONTENTS OF UNDIGESTIBLE MATERIALS IN COLLECTED OTTER SCATS
FORAGE FISH

aeprmoqsonag
aspruaeros
aeprnnoo
aeprlntenol

BEPIBImv

aeproxad
aeprurldfio

aspransoxanses

aepIJan

 

N0.
of
SCATS

 

MONTH

 

SECTOR

 

 

 

11

26

10 6 1 7

1 6

23 9 25 24 9 20 -
6 6 6

26

DEC.
JAN.
FEB.
JAN.
FEB.

 

 

 

 

o.

mmmmm EH3 ogjgoo mmaomo awake mo mozamHn UZHAEZEH

.— Maseru.

7

 

3mm NI gamma asuvmsm

Semi-logarithmic
3 We]. 3 ID to the inch

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