Insects are especially important here and black bears favor ants, wasps and bees. In some areas, the bears like tent caterpillars and are among the very few animals that will eat them. Along the north Pacific coastal areas, salmon is the most important food for both black bears and grizzlies. In the northern woods of Canada, plant foods are limited with short growth seasons and the bears tend to be much more predatory. In the tundra of Northern Labrador, a group of black bears has recently migrated north of the tree-line, but they have become almost as carnivorous as polar bears in the process.
Grizzlies show similar variation.
In fact, the bears of Glacier appear significantly more carnivorous and predatory than those of Yellowstone. Two important food sources for grizzlies in the High Rockies are white pine nuts and codling moths. White pine nuts are important to grizzlies because they are so rich in fat and protein, and they get the bears in condition for winter. Authorities are worried that these trees are under increasing attack by pests and disease. The codling moths are a recent discovery.