HIBERNATION OF BEARS
by William E. Kearns, Assistant Naturalist
Not long ago, I read an article in the Saturday Evening Post by J.
Frank Dobie on "The Last of the Grizzly Hunters." The statement that
bears "lay up and suck their paws," (hibernate) from "November for four
months," caused me to do a bit of investigating of the "theories" for
bears hibernating.
Here in Yellowstone, the beginning is largely determined by the
weather, but the majority of both grizzly (Ursus horribilis imperator)
and black (Euarctos americanus cinnamomum) bears go into hibernation in
October and November. The earlier the snows come and the colder the
weather, the sooner the bear seeks out his den. When seasonal conditions
are more favorable, some of the bears may remain out as late as
December. The period spent in hibernation will vary from four to five
months, and here again, weather plays an important role, and is often
the deciding factor. A few bears may appear in February, but it is
usually mid-March or even the first of April before the majority
appear.
Few actual observations have been made of wild bears in hibernation,
and in the time of my father and other old timers, supposition and
conjecture took the place of fact. With some, the belief was rampant
that all bears gorged themselves on pine needles immediately before
going into their dens for the "all-winter sleep," assuming that these
needles would form a lining in the bear's stomach and keep him from
getting hungry before the weather moderated and he could again find
food. Still another, as suggested by Mr. Dobie, was that the animal
would suck his paws; until by spring they were too sore for the bear to
more than hobble about.
With the majority, the belief is still current that an animal in
hibernation loses all consciousness, and that bodily processes slow down
to a point where the heart scarcely beats and the blood barely flows.
With the Marmot (Marmota flaviventris hosophora) and the Picket Pin
(Citellus armatus) this is true, but not so for either the grizzly or
black bear found in Yellowstone. Observations made in specially
constructed dens indicate that the bear is not absolutely in a state of
coma, but rather, the opposite. Upon the approach of the observer, the
bear would move, sometimes growl, and open-eyed, would repel the annoyer
if too aggravated. While on a ski trip around the grand loop during the
winter of 1935, I went to visit the den of a black bear in the hope of
getting pictures. His winter quarters were beneath the floor of the
kitchen of the lodge at Old Faithful and near a trap door. Lifting this
door, I lowered my camera and the necessary paraphernalia to the ground
some four feet beneath, intending to follow. Fortunately, I looked first
with the aid of a flashlight and saw a large black bear moving toward me
as rapidly as the floor joists would permit. Hastily retrieving my
outfit, I just had time to lower the door, closing it almost in the
bear's face.
Usually the bears select some spot not so accessible for man, and
authentic pictures of bears in hibernation are rare. Dens beneath
buildings are often used, natural caves, wind-falls in dense timber
offer quarters, and the big animals often dig their own den. Strange as
it may seem, the site is usually on the north slope of a hill. It would
seem reasonable that a den dug in the warmer south slope, which is freed
from snow at an earlier date, would be the preference, but not so with
bruin. Here again, the bear is wise for the prevailing winds are from
the southwest and the snow piles deeply on the north slopes, covering
the dens with a thick, warm blanket which helps to keep out the bitter
cold of winter.
On January 1, 1937, Junior Naturalist Oberhansley led a party of
fifteen people on a ski trip to visit the den of a black bear which was
hibernating on the northern slope of a hill to the north of Mammoth.
Although the party proceeded as quietly as possible on nearing the den,
the bear was wide awake and came to with in 4-1/2 feet of the entrance.
The opening of this den was about 1-1/2 feet across, and had been dug
into the hillside in the midst of a small stand of cedar trees. This
bear came out of hibernation on March 7. He did not eat the heavily
crusted snow, contrary to other observations when bears had eaten
quantities of the icy substance, and after basking in the sun for a
short time, this bear retired to his den for another nap.
This last summer, road crews at Fishing Bridge constructed a
heavily-oiled surfaced road in front of the operator's buildings.
Beneath the Haynes Picture Shop was a den which a black bear had used
for several winters. When Mr. Bear returned late in October to look over
his winter apartment, he found the entrance entirely blocked with a
thick section of roadway. Undaunted, he tore away the hard, almost
rock-like surface in huge chunks, and proceeded with preparations of his
winter bed.
Mrs. Pierson called me on the phone the other day to tell me that
while her husband, Dave Pierson, with Tom Phillips and Rudy Schmidt,
were out feeding hay to the buffalo at the Buffalo Ranch on January 22,
they observed a small black bear, probably a two year old, come from the
direction of Druid Peak and disappear up the slopes of Specimen Ridge.
He was very thin, and one of the boys suggested that he might be
sick.
The next morning, the feeders frightened him from the haystack where
he had dug-in and the bear ran toward a distant stack. He was not
observed eating hay. Monday morning about 9:30 A.M., the little fellow
was again seen, headed for a near by stack. From all appearances, the
coyotes had pre-empted his bed of the night before. The bear was seen
almost daily and his condition was so pitiful that the men fed him
scraps nearly every morning. A week after he was first observed, he
spent the night sleeping on top of the hay and although the thermometer
registered 37 degrees below zero, he was up and ready for breakfast
Sunday morning. As suddenly as he had appeared, the bear vanished,
probably in a newly acquired den in one of the numerous haystacks.
Several days later, the Piersons reported that a second two-year old
black bear was in the vicinity, and that he had moved in to dine on the
contents of the garbage cans at the Ranch House. This second bear was in
much better condition than number one, and was marked quite differently
so that there was no doubt as to his identity. Mrs. Pierson stated that
"he seems to hear alright, but from the half-baked way in which he acts,
his eyesight must not be right." When a person approached, the bear
would jump, raise his head, and finally seem to smell-out the source of
the disturbance. It has been suggested that he may have been suffering
from snow-blindness.
The second arrival wasn't satisfied with the scanty fare afforded at
the garbage cans, and moved in on the Piersons' porch where he helped
himself to bacon and butter, and later made-up his bed on their back
porch. The latest report (February 14) is that this bear is still at the
Ranch and eating from the garbage cans.
Wondering how many instances of this sort had been recorded, I
perused back issues of Nature Notes with the following results: in the
issue of February 28, 1926, this item concerning bears is noted:
"On the 6th of January, a large black bear and three cubs were
outside at the rear of the Lake Hotel. The old bear is seen nearly every
day. In coming out they are very careful to keep in the same tracks on
paths made on previous trips and do not exert themselves very much.
These bears have taken for their winter abode the cook's quarters of the
hotel. The place left open is not large and underneath the floor makes a
good den for them. Even after the snow was on they spent many hours
pulling coarse slough grass and dragging it in for a bed. It seems
possible now that the old bear will be out almost every day during the
winter, if fed."
Ranger "Ben" Arnold who was at Lake the winter of 1925-1926 as
winterkeeper for the lodge, relates the incident of two big black bears,
"Nicodemus and Nebuchadnezzar," coming out from their hibernation den
under the hotel building after the trails were well packed, and states
that they remained out more or less all winter. On one occasion, they
"stole" a pair of pants belonging to Ed Admunsen, hotel winterkeeper,
from the clothes line and took them to the den, supposedly for lining.
(Al was a big fellow, and they were an immense pair of pants!) On an
other escapade they visited the Laundry room of the hotel and removed a
heavy fabric belt from one of the machines. Dragging it to their den,
they chewed it until it was ruined for further use. These two bears
visited the garbage cans of the rangers and winterkeepers, but did not
venture from the beaten trails at any time.
A further reference in Nature Notes is found in the issue of February
28, 1927, as follows:
"A large black bear that has been hibernating under the hotel at
Yellowstone Lake appeared on the trails in the vicinity of the buildings
on the 19th of February. He was out during an interval of two days. His
activities consisted in part, of the theft of a ham from the winter
keeper and after finding nothing further of interest he returned to his
den. This is the first and only activity of bears reported since late
last fall, with the exception of the captive bear, Juno, at headquarters
station. Frequent visits have been made to his den during the past two
months and we find that he is easily aroused but is very sluggish in his
movements. He accepts very little food and rarely emerges from the den.
His disposition is harmless and gentle."
Mrs. Marguerite L. Arnold informs me that several years ago, former
Park Naturalist Edmund Sawyer attempted to feed Juno, the chained pet,
while, he was in hibernation, but she states, "the bear just wasn't
interested."
On Christmas day, Ranger David Condon saw a black bear running across
the firing-line just north of the Park, and on January 8, Junior
Naturalist F. R. Oberhansley viewed the carcass of a bear in the same
vicinity. These men surmise that this animal might have been literally
bombarded out of his den by the heavy firing of the hunters massed in
the area, and that the bear was unable to make good his escape.
Bears have been observed outside their dens in winter at various
times through the years, usually after unseasonally warm days, but with
the exceptions noted (with others unrecorded and unknown), the bears did
not go more than a step or two from the entrance of their dens.
From actual observations of bears in hibernation, we know then, that
they sleep for indefinite periods, are restless at times, even to
leaving their dens, and that when on such foraging expeditions they may
eat. However, as far as I've been able to ascertain, the bear in
hibernation will not eat. Ranger Frank Childs offered bacon and sweets
to several bears while they were hibernating, but without exception,
they refused the proffered food.