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Border wars among neighbors
are focus of research on fire ants
May 3, 1999
heir name screams it all: fire ants. Thousands of people in the southern United States have learned about them the hard way. Being repeatedly stung by an angry horde of fire ants is an unforgettably painful experience.
To Eldridge Adams, associate professor of ecology and evolutionary biology, however, the multi-stings of fire ants are as familiar as handshakes. He's been stung hundreds of times, fire ants being the major subject of his field studies.
Native to South America, fire ants were ferried unwittingly to the U.S. on a cargo ship from Brazil, when a breeding colony jumped ship in Mobile, Ala., around 1920. Once established, the ants adapted exceptionally well to the southern U.S., spreading like the plague they are now into a belt that reaches from Virginia to southern California. Although there are several other species of fire ant, this single species of imported fire ants, Solenopsis invicta, is now the most serious pest species of ants in the U.S.
Adams's two major areas of study are the population ecology and behavior of social insects. Originally from Los Angeles, he began his study of ants as an undergraduate at Harvard in the 1970s. "As long as I can remember, I was always interested in behavior and ecology and when I was in college I had the opportunity to participate in a research project on social insects," he says.
"Fire ants are excellent subjects for studies on social cooperation and competition and the effects of behavior on population dynamics," he says. They're also convenient because, Adams explains, fire ant colonies grow quickly and their mosaics of abutting territories allow abundant opportunities for studying interactions among colonies.
Adams, who came to UConn in 1997, keeps about 100 thriving colonies of fire ants on hand in the Torrey Life Sciences building, safely out of the way behind a double door.
Aggressive, omnivorous, and producing high population densities, fire ants feed on insects and related creatures, dead vertebrate animals, and seeds. They build their underground castles in fields, roadsides, and lawns.
Currently, with a three-year, $178,000 grant from the National Science Foundation, Adams is researching how adjacent fire ant colonies struggle for control of space and how colony sizes change through time.
"I'm studying border wars between neighboring colonies," he explains, "and how neighboring colonies of different sizes divide up the space that's available to them."
Adams is developing a model to predict where boundaries will be established by territorial animals or colonies. "The model assumes that territorial residents push aggressively at neighbors along the borders."
Using field data and experiments to measure how hard neighbors will push and how that shapes their territories, he is seeking to understand how competing neighbors establish a boundary. He expects his findings to apply to other territorial animals, including birds.
Adams's studies have added significantly to knowledge of fire ant behavior and that of communal animals in general.
He has demonstrated, for example, that the populations of mature colonies are regulated by competition among colonies for foraging space. Adams has produced a mathematical model of territory size and shape, based on his research, that predicts much of what researchers see in field studies.
He is now testing this prediction model and extending it. "What I want to be able to do is to see how changes in the environment - especially food supplies - affect the behavior of colonies," he says, "and then in turn how that drives their population dynamics."
Adams says studying fire ant behavior has wider applications. "Many of the specific things we're studying in fire ants are instances of broader themes that ecologists study. Behavioral ecologists are very interested in the mix of cooperation and competition that occurs within social groups.
"What we find happening in fire ant populations in one sense tells us something very specific about what a particular species does, but part of the point of this work is that this is a species within which it's very easy to do experimental work on this mix of cooperation and competition, and to see how it affects the fates of individuals and groups. This information can be used to test theories that have broader applicability to social animals."