On waking sleeping bears

Three bears are sleeping in a den. Your camera trap is 10 feet from the entrance. How do you check it without waking them up? That's what Reverend Dick was wondering. I answered that bears sleep soundly.

But not as soundly as true hibernators like ground squirrels whose core body temperatures drop to a few degrees above freezing.

Winter-sleeping bears are rousable, though usually not instantly.

According to bear specialist Lynn Rogers, "black bears in the North hibernate so deeply that they may be jostled and prodded for several minutes in mid-winter before they awaken.”

This fact emboldened biologists to crawl into dens with sleeping bears in order to record their rectal temperatures. This is one of those punctuated achievements in field biology that begs the question, who tried it first, and was he sober?

Bears apparently don't roll over and look affectionately at the guy with the thermometer. Dr. Raymond Hock, a pioneering bear researcher in the 1950s observed, “When a hibernating bear is awakened, he tends to be cross as a bear.''

Hock however seduced slumbering black bears to cooperate with a bucket of maraschino cherries. When the sleeping bear smelled the cherries it briefly became wakeful and rose to its feet. Hock deftly inserted the probe and removed the cherries, and the bear went back to sleep.

This brings me to a mountain man and "grizz" story.

If bears didn't sleep soundly in the winter, I wonder if mountain man Joseph L. Meek would have lived to kill three denning grizzly bears in the 1830s. This is one of those mountain man stories that I suspect improved with re-telling. Writer Stanley Vestal did not annotate his references in his book about Joe Meek, as he did in other accounts of mountain men, so I can't go to the original sources.

Here's the story and my interpretation of it.

Meek found bear tracks in the snow leading into a cave in the Snake River country.

Meek, Claymore, and Hawkins entered the cave while a fourth mountain man, Doughty waited with loaded rifle at the entrance.

The cave "was about twenty feet square and high enough to stand up in." Sounds feasible.

"There the three men found three bears standing up to receive them." It seems unlikely the bears were standing, which would mean they were wakeful.

If so, they would have attacked the men. More likely the bears were sleeping or perhaps awakening in response to the disturbance, like dreamy bears smelling maraschino cherries. This is born out by the following statement.

"As soon as Meek was near enough, he whipped out his wiping stick and hit the big bear a smart blow over its sensitive nose."

There is no mention of the use of torches, and the description suggests it was not a particularly shallow cave. Unless the den was a rock fissure admitting some light, they must have used fire to see what they were doing.

"At once the big bear rushed out of the cave." . . . where it was shot by Doughty. The wounded bear "teared back into the cave growling and snarling" where the three men shot and killed it.

At this point Hawkins "started to sing and jump around and joined the others in striking the middle sized bear to make it run out".

Doughty despatched this one at the den opening.

"It did not take long to drive out the little bear", which was shot by three of the men.

Vestal refers to the bear as "he", but it was probably a female with cubs of the same litter, perhaps of differing size. It's less likely they were subadults of two different litters, separated in age by two or more years.

A great story, and one I would like to believe was based largely on fact.



References

Vestal, S. 1963. Joe Meek, the merry mountain man. University of Nebraska Press.

bearFacts

NY Times article on bear research

It's better to be fat

We named her meatloaf. She was rounded on top and squared off on the bottom edges. She looked solid. Actually, there were several meatloafs in the campground, all adult mantled ground squirrels.

There were also smaller ones, perhaps yearlings . . .



and certainly some of the most trim squirrels were young of the year.



I want to talk about fat squirrels. It's a relevant topic in light of the American addiction to junk food, rampant childhood obesity, and our obsession with dieting. They can teach us something. They have a good reason for getting fat, and they have a successful way of dieting.

First, a few words for those of you not familiar with this charming rodent.

Mantled ground squirrels inhabit the open coniferous forests of the Sierra Nevada and Rocky Mountains. These are great places to live in the summer when it's dry, sunny, and warm. In the spring the mountains offer nutritious fodder. Tender young plants are high in protein and fiber, so the squirrels don't gain much weight, and rest assured they have no complaints about "irregularity". As the forbs and herbs set seed and dry up, the mountains yield their gourmet luxuries. The squirrels then root about for hypogeous fungi, which we know as truffles. Still, they keep their mesomorphic physiques.

Then in late summer the conifers drop their cones, and our squirrels gorge on the protein and oil-packed manna from heaven. During the month of August they start to "plump out". By September, adults have three times the body fat they had in the summer. Juveniles on the other hand only gain about twice their summer fatness.

The seasons change. The dog days of August give way to freezing night-time temperatures, and then moisture-laden air from the Pacific drops a blanket of snow -- often as early as September. The mountains are a hard place to live when snow covers the countryside and temperatures are below freezing. Making it through the winter depends on getting enough food.

Squirrelly creatures have made two evolutionary choices: stay active and feed daily, or hole up and hibernate. Tree squirrels opted for an active athletic winter; they get bigger appetites, burn more energy, and tough it out. Chipmunks and mantled squirrels have opted for a restful comatose condition known as hibernation. Their appetite and metabolism shut down. They sleep and slowly burn fat. Chipmunks also have a lot of larders so they can snack periodically through the winter. Mantled squirrels tend not to hoard larders, and seem to rely almost entirely on their body fat.

Mantled squirrels undergo another mysterious change. As winter approaches their body water decreases. The point is this -- a critter whose body temperature hovers dangerously close to freezing may protect itself by lowering its own freezing point.

And what about the skinny mantled ground squirrels?

They have a problem, because without fat their bodies don't tell them it's time for winter sleep. Hunger drives them to continue their quest for food. With limited food they can't make a go of it. They are doomed.

We can draw only one conclusion: sometimes it's better to be fat.



References

Bartels, M.A. and D.P. Thompson. 1993. Spermophilus lateralis. Mammalian Species No 440:1-8.

Blake, B.H. 1972. The annual cycle and fat storage in two populations of golden-mantled ground squirrels. Journal of Mammalogy, 53(1):157-167.

Jameson, Jr. E.W. and R.A.Mead. 1964. Seasonal changes in body fat, water, and basic weight in Citellus lateralis, Eutamias speciosus and E. amoenus. Journal of Mammalogy, 45(3):359-365.

Jameson, Jr. E.W. 1964. Food consumption of hibernating and nonhibernating Citellus lateralis. Journal of Mammalogy, 46(4):634-640.

McKeever, S. 1964. The biology of the golden mantled ground squirrel, Citellus latralis. Ecological Monographs 34(4)383-401.

Pengelley, E.T. and K.C. Fisher. 1963. The effect of temperature and photoperiod on the yearly hibernating behavior of captive golden-mantled ground squirrels (Citellus lateralis tescorum). Canadian Journal of Zoology, 41:1103-1120.

Tevis, Jr., L. 1956. Observations on chipmunks and mantled squirrels in northeastern California. American Midland Naturalist 53(1):71-78.

Tevis, Jr., L. 1956. Invasion of a logged area by golden-mantled squirrels. Journal of Mammalogy 37(2):291-2.