Grizzly Bears That Dine on Salmon Grow Larger
The amount of salmon a grizzly eats varies from region to region and among individual bears.
The greater proportion of salmon in a grizzly bear's diet, the bigger the bear grows. Among grizzlies in British Columbia, those on the north coast eat the most salmon, which forms over two-thirds of their diet.
In Owikeno Sound, where salmon returns have undergone major declines, salmon consumption is lowest for BC's coastal bears, comprising less than 30 percent of their diet.
Bears living inland rarely feed on salmon, even where large runs occur, except in the Quesnel Lake and Wells Gray Park areas. In central BC, kokanee salmon contribute 3 to 26 percent of the food supply for grizzlies, and is particularly important for younger bears.
Where ungulates are plentiful, these replace salmon on the menu for some interior bear populations. In the Muskwa region, for instance, moose comprises nearly half of a grizzly's diet. But the link between the amount of terrestrial meat consumed and the size of bears is inconclusive. At the other extreme, bears in the southern Selkirk and Columbia mountains feed exclusively on plants.
When meat forms less than one-third of the diet, males dominate the scarce resource and eat more meat than do females. Where salmon is plentiful, it becomes an increasing component of the male grizzly's diet as he grows older.
Garth Mowat and Douglas C. Heard. 2006. Major components of grizzly bear diet across North America. Canadian Journal of Zoology. 84(3): 473-489.