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Are ant invaders taking over San Diego?

ants November 26, 1997
Web posted at: 1:11 a.m. EST (0611 GMT)

SAN DIEGO (CNN) -- It may sound like the plot of a science-fiction movie. But scientists say swarms of ants are invading sunny Southern California.

Argentine ants hitched a ride to the United States from their native country in the late 1800s, most likely by stowing away with a shipment of coffee. By the early 1900s, biologists started seeing them take up residence in San Diego County.

Now scientists say they are overwhelming native ant species and threatening the food source of at least one other animal. One scientist fears they are even endangering the entire coastal ecosystem.

Scientists David Holway and Andy Suarez, who have been studying the Argentine ants for years, say the ants have proven adept at establishing themselves in the area at the expense of other ant species.

vxtreme CNN's Jack Hamann reports
video iconWatch the invasion of the Argentine ants.
1.5MB/42 sec./160x120

They will attack entire colonies of native ants.

But the scientists say Argentines are not the Arnold Schwarzeneggers of the ant kingdom. The individual ants are not superior to ants of other species. In fact they seem a little wimpy.

Their power comes in their numbers. Argentines live in incredibly large colonies that work as units to attack other species.

The Argentine ants also have other advantages:

  • They can move their nests quickly when they are disturbed.

  • Instead of just one queen, they have dozens -- which makes it easier for them to start new colonies.

  • Most important, one colony of Argentine ants will not fight with another.

Along with native ant species, the most obvious victim of the ant invasion is a creature called the horned lizard.

The lizard -- a prehistoric-looking creature that can fit in a person's hand -- eats the area's native ants, the species being killed off by the Argentine colonies.

Even animals that don't eat native ants may be in trouble. The Argentines have been observed devouring salamanders and baby birds.

People also are falling victim to them. Homeowners in San Diego now spend more money on pesticides to fight the invader ants than on rats, fleas and roaches combined.

But it may not be money well spent. If the ants are poisoned away from one yard, they will simply move on to another.

One scientist says people are actually the unwitting collaborators in the ants' occupation of San Diego County.

The Argentine ants are following development patterns. Each new home gives the ants a new water source and allows them to spread deeper into neighboring natural areas, said Dr. Ted Case, a professor at the University of California at San Diego.

Case fears much of San Diego's coastal ecosystem could collapse unless large tracts of native lands are kept off-limits to development, and by extension, to the ants.

"The Argentine ants would not be a problem in the absence of urban development," he said.

Ants may seem small, but scientists say they are an intricate part of the ecosystem.

Correspondent Jack Hamann contributed to this report.

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