Bears of the Pleistocene

[brotherbear]

In the Shadow of the Sabertooth by Doug Peacock.

Grizzlies colonize new habitats slowly. A useful way to think about grizzly society is to see it as an "Amazon" culture. The last grizzlies to survive in a fading bear ecosystem seem to be older females, mothers with daughters. Of course, there has to be a male somewhere. Similarly, female grizzlies dominate biological expansion into new territories.
Grizzly bears expand their range into new habitat one female home range at a time. Sows with cubs have small ranges compared to males: twenty to thirty square miles while a boar might range over a hundred square miles or more. The quality of the habitat can shrink or inflate these numbers, less home range necessary along a productive salmon stream as compared to grizzlies on the tundra requiring greater foraging ranges. Typically a daughter sets up her own range adjacent to her mother's. A rough measure of brown bear colonization of suitable habitat unoccupied by grizzlies would be in the range of 20 to 40 miles every five years or so.
Brown bears were in Beringia by about 60,000 years ago and around 30,000 years ago they came down an ice-free route to the lower states, probably via an ice-free region as opposed to a corridor between ice sheets. That means that a pre-LGM route was also available to humans for millennia. It was probably open for many thousands of years before the glaciers advancing slammed the route shut around 20,000 or 22,000 years ago. It was an easy route with all kinds of plants and animals. Reply