04 December 2011

"Predator satiation"

It's how oak trees outwit squirrels and mice - by varying the output of fruit (acorns) to overwhelm, and then starve, the scavengers.  Excerpts from the New York Times:
While last fall set a recorded high for acorn production, at roughly 250 pounds per tree, this year is seeing a recorded low, with a typical tree shedding less than half a pound of its seeds, said Mark Ashton, a forest ecologist at Yale University. On average, oaks produce about 25 to 30 pounds of acorns a year...

Coming on the heels of an acorn glut, the dearth this year will probably have a cascade of effects on the forest ecosystem, culling the populations of squirrels, field mice and ground-nesting birds. And because the now-overgrown field mouse population will crash, legions of ticks — some infected with Lyme disease — will be aggressively pursuing new hosts, like humans...

One theory for why oak trees vary their acorn yield is the so-called predator satiation hypothesis. Under this theory, during bumper years, the trees litter the forest floor with seeds so completely that squirrels, jays, deer and bears cannot possibly eat them all. Then, in off years, the trees ramp down production to keep the predator populations from growing too large to be satiated. 
More at the link.   The same hypothesis has been applied to the cyclic populations of cicadas.


  1. Great. MORE ticks. We live in an area already imfested with them!

  2. Bamboo does the same thing. That why parts of the Orient get ravaged with black rats. There is so much fruit that they reproduce until the food supply is exhausted, then hit the rice fields.


  3. Is M. Night Shama-lama-ding-dong going to make a film about this???


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