GRASSY KEY, Fla. -- Biologists say an unwelcome species of rat that grows as big as raccoons has turned up in the Keys.

Conservationists say the African Gambian pouch rat needs to be eradicated before it starts to harm native species in the Keys.

It's unclear how the rat was released on Grassy Key, but scientists say the omnivores are a threat because they eat almost anything.

The giant pouch rat can weigh up to 9 pounds. Biologists say it would compete for food with native species, carry diseases, and damage the bird population by eating eggs.

The fear is if the animals make it as far as Key Largo, they could threaten the Everglades.

In 2003, the Centers for Disease Control and Prevention and the Food and Drug Administration issued an order preventing the importation of the rodents following the first reported outbreak of monkeypox in the United States. Several African species are believed to carry the disease.

Biologist Randy Grau with the Florida Fish and Wildlife Conservation Commission said the Grassy Key pouch rats are the first documented breeding population in the United States.

Connie Faast, who lives on Grassy Key, had the giant rats living under her house. One night, she said, she heard loud screeches in the street. The rats were fighting.

"Two cats were on the side of the road just watching the rats," Faast said.

The male pouch rats are aggressive when they encounter one another.

But Chris Sutton, who lives on Grassy Key, said the rats are otherwise extremely friendly.

"They get along with everything," she said. "They're tame animals to start with, and they are not afraid of people."

Sutton says the rats eat out of the same dish as her cats and dogs, and her friend saw one of the rats eating out of a bird feeder.

Rumor has it that eight rats were let out five years ago. The rats have up to four litters every nine months with up to six offspring in litters, so there is no telling how many of the rats are living on Grassy Key now.

So far, there are no takers to eradicate the rat. Government agencies have not stepped up to fund a project to eliminate the pests.