<p>Brown bears are almost always hungry during the summer, but when the fishing is good, they are selective eaters. 
</p><p>If you see bears only eating the skin, brains, and eggs of a salmon, they are practicing good energy economics. At these times, a bear’s profit margin in calories is so high that it can ignore some excess fish. 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.
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Salmon are a high calorie meal for a bear. A sockeye 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 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.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/99350217@N03">Katmai National Park and Preserve</a>
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/katmainps/11123704376/">218 Ugly high-grading salmon (July 2013)</a>