When I took Jim Halfpenny’s tracking class last year, he gave me a small pamphlet entitled Bear Ecology. Yellowstone Ecosystem. The pamphlet consists of lots of charts, so I’ll try and digest a few for you, literally.
Since I’ve been watching bear evidence and their scats a lot lately, here are a few facts: About 80% of the nutritive value of Grizzly bear food comes from herbs. From this they get mostly protein. Less than 20& comes from animals, where they get fat and protein. The rest comes from shrubs and pine nuts.
Of the plants that Grizzlies in Yellowstone National Park consume: 78% or more of their plant diet comes from Sedges and grasses. A whopping 6% comes from Claytonia lanceolata or Spring Beauties. Further down in value importance are Cirsium (thistle), Clovers, Yampa, Biscuit root, onion grass, horsetail, and whitebark pine. But if you look at the nutritive values of food, the only two that provide fat as well as protein are animal and pine nuts. Therefore, they need these to increase their brown fat for winter hibernation.
On this chart, as far as animal foods, cutthroat trout are at the top of importance. After that comes gopher, voles and marmots, elk, deer, and bison. Below that are ants.
Another interesting chart is about the differences between Black Bear and Grizzly Bear den types.
Black Bears evenly split their types of dens between boulders, crevices, and outcrops. They only dig 13% of their dens.
Grizzlies, on the other hand, dig 86% of their dens and rarely use caves. Which might explain why in these charts, which are not that up to date, Black bears were denning almost a month earlier than Grizzlies. Grizzlies need to wait for more snow cover.
I’ve been intrigued with bear diet this year especially since I know that the White Bark Pine Crop is poor. I keep wondering how these bears, that are so huge and strong, survive on mostly vegetarian diets. These breakdowns help explain some of how they are able to use plants and convert them into useable proteins.
So far, living at 7000′, we’ve had no snow yet on the eastern side of the Absarokas. Today it rained some, October 17th. I wonder how global warming will affect the denning times of black and grizzlies. I wonder what plants they will find when its not cold enough to den but not warm enough, nor the days long enough, for good plant growth.
Mark Bruscino was on Wyoming PBS friday night. He said an interesting thing. He said that Grizzly bears are as intelligent as the Great Apes, making them the most intelligent wild animal in North America. Surely they are an animal worth protecting, and giving more room to move into habitat that supports their needs as we, and the bears, face new challenges ahead.