UF/IFAS Scientists: Fire Ants May Further Threaten Endangered Species
October 17, 1996
GAINESVILLE—While fire ants may be just a nuisance to homeowners, some University of Florida scientists think they could be a nightmare for endangered wildlife.
Researchers from UF’s Institute of Food and Agricultural Sciences (UF/IFAS) have begun a 2-year study on the red imported fire ant and its effects on a variety of animals in the Florida Keys, including endangered species like the Lower Keys marsh rabbit, the Stock Island tree snail and nesting sea turtles.
Craig Allen, a UF/IFAS wildlife biologist, said scientists need to know if the imported fire ants present an additional challenge to species already under siege since the ants can be controlled in some settings.
“The impact of the red imported fire ant is somewhat chronic, both because their populations build slowly and because their impact on native species is difficult to assess,” Allen said. “Even if we just look at invertebrate communities, fire ants cause major changes which are likely to move up the food chain and affect ecological structure and processes.”
Tom Wilmers, a fish and wildlife biologist with the National Key Deer Refuge, said endangered species are in a different league than almost any other kind of wildlife management since each individual creature can be vital when populations are very low.
“For some of these species, if you lose a few individuals from different places where they’re very rare, over a period of time it can erode your breeding potential,” Wilmers said. “The fire ants’ aerial breeding habits are such that it’s going to be a perpetual fight. You don’t just wipe out fire ants one time.”
Elizabeth Forys, an environmental scientist at Eckerd College, first noticed large increases in fire ant populations in the natural habitats of the Florida Keys, and saw the ants as an additional threat to endangered species, particularly the Lower Keys marsh rabbit.
Because rabbits nest on the ground, their young are especially susceptible to fire ants, Forys said. When they are born, young rabbits can’t move, are barely furred and are covered in mucous that fire ants can sense. Mother rabbits can’t pick up the babies by the scruff of the neck and move them away. So as the ants move in, they attack and eventually eat the young rabbits.
“As we get to greater densities of fire ants in the marsh rabbit’s habitat, there could be some fairly severe impacts, at least with multiple queen fire ants at high densities,” Allen said, adding that a fire ant invasion appears to be ongoing in the Keys since the ants haven’t filled in all the habitats yet. Studies have found the fire ants in habitats that have been disturbed or altered, as the scientists expected, as well as in the interior of pristine, undisturbed hammocks.
The researchers are studying fire ants both on the ground and in the trees of the Florida Keys to determine their effects on other endangered species like the Stock Island tree snail. The snails spend most of their life in trees, but when they come down to nest in the soil, they are widely prone to fire ant predators because they can’t get away quickly, Forys said. In other laboratory studies, scientists are using surrogate non-endangered species of the Schaus Swallowtail butterfly to see if fire ants are also attracted to it for food.
Wilmers found fire ants in the nests of sea turtles while conducting studies on Marquesas Key. Since the female ants can fly several miles, Wilmers said, no island in the Florida Keys is safe from fire ant invasion.
“I found a nest of endangered green sea turtles and a swarm of fire ants just covering the babies that were coming out of the eggs. We saved some of those babies, but some of them perished,” Wilmers said. “Since we only have four female breeding green turtles in the entire refuge, there is cause for concern.”
Daniel Wojcik, an adjunct UF/IFAS scientist and a research entomologist with the USDA’s Agricultural Research Service, said fire ants are very adaptable and do well in both sandy and mild soils, and in the mucks of the Everglades. They are often found along beaches which surprises many people, Wojcik said.
“People will have to learn to deal with fire ants over the longterm. The days of massive chemical treatments, I think, are pretty much over,” Wojcik said. “We are working on introducing a number of organisms from South America to provide biological control for fire ants, maybe some diseases of the ant, some parasites, and probably eventually some predators. But none of those things are going to be the golden bullet.”