Grizzly bears in the Pacific Northwest prefer meals of freshly-caught salmon from freshwater streams. Each year, millions of salmon migrate from the Pacific Ocean to rivers, swimming upstream to spawn and then die, in an event known as the salmon run. The event creates a veritable “all-you-can-eat” buffet for these bears.

In addition to the bears and salmon, there are other organisms present at this dinner table.
Scavenger birds flock to the salmon spawning grounds, following bears wherever they go. Because the bears tend to be sloppy diners, the birds advantageously “swoop in” for scraps of salmon discarded by the bears.

Bacteria naturally inhabit bears’ intestines. The bacteria thrive by extracting nutrients from partially digested food, which in turn contributes to bears’ overall digestive health.

Bears often are infected with Trichinella, microscopic roundworms that reside in bears’ intestines. Adult Trichinella release larvae that can penetrate the intestinal wall, travel through the bloodstream, and then invade muscle tissues.