Fawn survival rates increase or decrease with the size of the acorn crop.

On average, acorn crops are produced in 3 out of 10 years.

Especially mule deer and western gray squirrel, who rely so much on the acorn crop that a poorly producing year can limit their populations.

They can eat or damage a high percentage of the acorn crop in most years and essentially all of it in poor seed years.

Good acorn crops are frequent, occurring at 1- or 2-year intervals, with light crops in intervening years.

The acorn crop on the trees this fall has been heavy.

"That may have to do with the acorn crop," another favorite mouse food, Dr. Elkinton said.

And why do acorn crops fluctuate?

He determined that the "migration" was a result of a rise in squirrel births which happened to coincide with a poor acorn crop, causing them to seek food in unfamiliar territories.

The volume of the acorn crop may vary wildly, creating great abundance or great stress on the many animals dependent on acorns and the predators of those animals.