棕熊季節性揀飲擇食

If you see bears only eating the skin, brains, and eggs of a salmon, they are practicing good energy economics...As a bear fills up on salmon, it can “afford” to not eat certain parts of the fish. This behavior has been nicknamed “high-grading.” Like miners looking for high-grade ore, bears try to consume high grade fat.

Salmon are a high calorie meal for a bear. A sockeye salmon (red salmon) contains about 4500 calories, but the fattiest parts of the fish contain the most calories proportionally. Bears know this and prefer to eat the skin, brain, and eggs—the fattiest parts of a salmon—when fish are in abundance. This is an ephemeral (短暫的) behavior, however. When salmon are not abundant or hard to catch then bears will not be as selective and will most often eat the whole fish.

https://www.nps.gov/katm/learn/photosmultimedia/brown-bear-frequently-asked-questions.htm