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Gophers- Acorn Challenge Number One
If
you have ever had a grass lawn in suburban California, you will soon find
that gophers will find it, and burrow in it. Each day, one gopher can
excavate enough soil, and carry it above ground to form loose piles about
six inches deep that can cover several square feet. At Hastings, we find
that from 30% to 50% of the soil surface is covered each year with these
piles of gopher diggings, or tunnel tailings.
Think about this for a minute. It is like the soil is boiling! If the gophers cover 30% of the soil in one year, (about 3" deep) this means they bury everything in 3 years. In 100 years, they can bury the same area something 30 times over, or about 8 feet deep! Although we don’t see it in our fast lives, an oak tree that lives up to 400 years will effectively be floating on a boiling surface of soil. Archeologists in California have observed this effect for a long time and have a name for it- "faunal turbation". For an archeologist, this means that if a person dropped a stone tool 400 years ago, it could be found now anywhere from the surface to 8 feet deep. "Faunal" refers to animals, (gophers) and "turbation" means mixing or stirring up.
Why are there so many gophers? Is there something wrong with this picture? Maybe. We do know that the non-native grasslands, as studied at Hastings, have a density of gophers only exceeded in some alfalfa fields. There can be as many as 2,000 gophers per acre. Gophers relish the non-native annual grasses as food, and the non-native grasses have a 3:1 advantage over native grasses in growing on the freshly tilled, bare soil provided by gophers. Gophers may have stumbled across the very successful technique of farming annual grasses by providing an annual abundance of tilled soil, just as we farm by tilling the soil and planting an annual grass- wheat. By "farming" non-native, annual grasses, gophers (like people) are probably supporting much higher populations than otherwise possible. Predators on gophers (hawks, weasels, badgers, bears) have been all but eliminated from the scene by humans. Such predators may not have been that important anyway in "controlling" the number of gophers - very often predator numbers only rise after the number of their prey rise. In turn, prey animals are typically held in check by their (plant) food supply. If the food supply (plants) goes down, the gopher numbers drop, and then the predator numbers decrease. In any event, gopher numbers remain impressive. And as long as they are so abundant, few acorns make it past this part of the gauntlet. But wait. There is more! Read about th annual weeds.