November 2009


My previous post about acorns reminded me of a bear, Green 52, who provides a good example of how far bears will go to get acorns.

Green 52 was a black-colored bear (fairly rare in the Sierra) who appeared one spring and was often seen grazing in the meadows. He caused frequent and long-lasting bear jams, which allowed him to slowly get habituated to people (as he got comfortable as people ventured closer and closer to him). Despite becoming habituated, he didn’t seem to get much (if any) human food. One day, he passed through Curry Village, and followed his nose to a tent cabin (illegally) containing quite a bit of food.

He was never quite the same.

We started seeing him more and more in campgrounds and other developed areas.  He even broke into the Village Store (a grocery store) via an open window. (Later in summer, apple trees have lots of apples in Yosemite Valley, so it’s somewhat amusing that the first food he went for once inside the grocery store was… apples. He later found his way to the pastries.) What goes through a bear’s mind when it finds itself inside a grocery store?

Black bear up a snag, eating acorns

Green 52 picking acorns out of the snag. (NPS photo by Kate McCurdy)

Even the most food-conditioned bears seek out their natural foods, and Green 52 was no exception. With the arrival of fall, he tried to eat as many acorns as possible, although he may have been a bit more ingenious doing this than other bears. One day, the wildlife crew found Green 52 up a snag near their office. It turns out that acorn woodpeckers had converted the snag into a granary (as they do to many snags in Yosemite Valley), where they had stored hundreds of acorns. Green 52 had climbed the tree and was painstakingly removing the acorns from each hole the woodpeckers had pecked and filled with an acorn.

It just goes to show you that bears will leave no stone unturned as they search for food, particularly in the fall, when they’re hyperphagic (very hungry, consuming 10,000 to 20,000 calories per day).

As for Green 52, I don’t remember all the details, but we relocated him north of Yosemite Valley. After that, he left the park and began getting into trouble in areas outside the park near Highway 108. As a result California Fish & Game trapped and killed him.

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At this time of year, a black bear could eat 10,000 to 20,000 calories per day as it bulks up in preparation for its winter hibernation (during which time it won’t eat, drink, urinate, or defecate). The typical person eats about 2,000 calories per day. So, if you were to eat as much as a bear, you would need to eat breakfast, lunch, and dinner five to 10 times, each. Every day.

Acorns

Black oak acorns. (Photo by Steve Ryan)

What kind of tree can feed a bear this much?

The black oak. And, at this time of year, it provides most calories bears in Yosemite are getting.  A bear eating only acorns would have to eat over 1,600 acorns every day!

Aside from feeding bears, black oaks also feed deer, acorn woodpeckers, squirrels, jays, and probably some others I’m forgetting. Before 1851, acorns were the staple of the diet of the people living in Yosemite Valley (and, I imagine, throughout much of California).

Why do people, bears, deer, birds, and squirrels rely so much on acorns? They are incredibly nutritious, being rich in fat, protein, and carbohydrates, and containing a wide variety of vitamins and minerals.

So, aside from entertaining us with its yellow leaves in fall and sheltering us with its shade in the summer, the black oak truly is the tree of life.