Hoagland is a biologist at Westfield State University in Massachusetts who has been studying the animals on St. Croix since the '80s. He gave a talk on his research Monday at the University of the Virgin Islands' St. Croix campus.
First brought to the island in the 1880s in an ill-advised attempt to control rats, every single mongoose comes from a few pairs brought in from Jamaica - which itself became populated by just nine individual mongooses in 1872, Hoagland said. They are originally native to Asia, Africa and Southern Europe.
Curiously, although they look very similar to ferrets and weasels, they are actually more closely related to cats, while ferrets are more closely related to dogs, he said.
With no natural predators and a wide and varied diet, the animals have thrived, eating everything from carrion to fruit to baby birds, he said. But insects make a large part of the diet of those he's studied around Sandy Point National Wildlife Refuge.
They will dig up sea turtle nests, if they are shallow enough, and so are a threat to endangered hawksbill and green turtles, he said. Protecting those turtle nests, as well as birds, lizards and other local fauna, is the goal of the U.S. Fish and Wildlife Service, which runs the refuge.
When he and student volunteers trapped some individual mongooses, dusted them with fluorescent powder and released them. The trail of powder left behind by the freed mongooses showed they systematically hunted out plants they knew had millipedes, rather than randomly foraging. So as long as there are gungaloos on the island, the mongooses will have one of their preferred foods. They also go for katydids and any other good-sized insects, including cockroaches, he said.
Ironically, the animals are even healthier here than they would be in their native environment. When the first ones arrived, they had their own parasites. But those parasites generally have a part of their life cycle outside their host and could not reproduce when they got here.
"We have looked for internal parasites and have not found any," he said. "By and large these animals are very healthy."
There have been eradication efforts here and elsewhere, sometimes by paying for each dead mongoose, but to little avail, he said.
"The fact is, human beings have been moving plants and animals around for hundreds of years now, and some of them are just incredibly obnoxious," he said. "The end result is we just have to learn to live with them."
While the island as a whole may not have any hope of eradicating them, Sandy Point's particular geography may make it possible to clear just that area and keep it clear, he said. Because the point juts out into the sea and St. Croix's West End Salt Pond covers much of the width of the spit of land on the island side, much of the park is somewhat cut off from the rest of the island, making the task more manageable.
One possibility might be to remove them on an ongoing basis by setting traps near turtle-nesting beaches. But that is a labor-intensive approach and therefore expensive. Hoagland suggested a fence or physical barrier on the narrowest strips of land where the salt pond is widest
"Mongoose don't swim," he said. "They have no underfur, their fat is near their tail, so they cool off very quickly in water." So a barrier might work, so long as they can't climb it, and there are no trees close enough to allow mongoose to make it over, he said.
Hoagland teaches in Massachusetts and comes to St. Croix several weeks each winter to study the animals with the help of student volunteers. Information about the study, including data and photographs, can be seen at the project website.