But it appears that the grizzly would like more meat than is generally available. This I infer from the quantity he eats when he finds a carcass and from the avidity with which bears of all kinds seek spawning fish when available. The only animal that the grizzly consistently hunts in the park is the ground squirrel, but a squirrel contributes only a mouthful and its capture usually requires excessive time and energy. Sometimes a squirrel is surprised and captured before it can disappear in a burrow. But generally a squirrel is secured only after extensive excavating which may involve as much as half an hour, and not infrequently the bear, after much digging, fails to unearth his intended victim. In years when meadow mice and lemmings are especially abundant, bears may make their capture a project which contributes at least a tasty diversion. Caribou and moose calves may occasionally be captured when very young, but the season for this food is short. Occasionally tidings come to a bear’s keen nose that carrion lies upwind, and the lucky bear keeps gorging until only a few bones and patches of hide remain.
After feeding on a carcass the bear often covers it with sod and vegetation. One fall at Stony Creek I watched a bear at a cache which showed up as a dark mound surrounded by a dark circular area from which the sod had been torn loose. For an hour the bear kept methodically raking the surrounding area beyond.
Grizzly bears digging for ground squirrels.
He was scraping the loose vegetation toward the cache, working leisurely with one paw at a time. The loosened material was pushed toward the cache as the work progressed. When I examined the area later, I noted a circular patch, extending out 20 feet from all sides of the carcass, that had been combed clean of loose vegetation. The bear finally lay down on the cache to wait for digestion to create more space for this rich fare.
North of Wonder Lake a grizzly had similarly covered a caribou that a hunter had left lying in the field. The bear was not at the cache, but since most of the carcass was still intact, he probably was not far away. I found some carcasses that were not covered with sod. A mother and two yearlings at Polychrome Pass left a caribou carcass without covering it and retired to some steep cliffs overlooking the area. The following day they rested near the carcass, but still no effort was made to cover it.
Mating takes place in May, June and early July, and a pair remains together for two or three weeks. I suspect that a male might look for a second marriage following the termination of the first. One large crippled male was successfully consorting with two females at the same time, neither female objecting to the presence of the other—in fact, both probably preferred it that way.
The cubs are born in the hibernating den in midwinter, are 8 or 9 inches long, and weigh less than 2 pounds at birth. The number of cubs in a litter ordinarily varies from one to three, two being the most frequent.
The cubs not only nurse throughout the first summer but to about the same extent during their second summer abroad, when they are robust yearlings. I had been surprised to find yearlings regularly nursing, but it was a greater surprise to observe mother grizzlies nursing cubs over 2 years old, in their third summer abroad. The protracted nursing period indicates a breeding interval of females with cubs, of three or more years, since females followed by nursing yearlings have not been seen consorting with a male.
The dens used for hibernation are excavated by the grizzly if natural caves are not available. A den is usually dug on a rather steep slope. The entrance to one I examined was about 2 feet wide and a little less than 2½ feet high. A tunnel 6 feet long led to the chamber which was roughly 4 feet in diameter. Cinquefoil brush and grass had been used for the bed. This den was still usable six years after it was dug. But another den dug in October caved in the following summer. It lacked the firm protective sod roof of the more durable den.