Gordon has been conducting ant population studies in Stanford's Jasper Ridge Biological Preserve for 18 years, during which she has seen territory change hands as the invaders pushed into the preserve and displaced the winter ants. But several years ago, the winter ants began gaining the upper hand.
"It looks like the Argentine ants are getting pushed back tree by tree," Gordon said. The winter ants are showing up in trees where the Argentine ants had been.
"It seems the winter ants let the Argentine ants find the aphids and then they take over. Over time, the winter ants may be starving the Argentine ants out," she said.
The recent shift in the balance of power may be in part a result of cooler weather, which favors the winter ants, and low rainfall, which inhibits the Argentine ants, Gordon suggested.
So in a natural habitat, without warm buildings in which the Argentine ants can gather around the kitchen hearth, the winter ants can hold the invaders back. But continued development, which creates the disturbed ground and toasty homes that the Argentine ants favor, may well trump the winter ants' chemical weapon in the long run. Already, Gordon said, the Argentine ants in California far outnumber the native winter ants.
|Contact: Louis Bergeron|