Scientists release Key Largo wood rats in first test of restocking experiment

On Tuesday, scientists lifted protective enclosures to release captive-bred Key Largo wood rats into Crocodile Lake National Wildlife Refuge -- the first test of a restocking experiment that might represent the last and best hope for an obscure rodent that ranks among Florida's rarest species.

So far, so good. Feral cats and Burmese pythons didn't immediately swallow any, and the lab rats -- products of a breeding program run by the U.S. Fish and Wildlife Service, Tampa's Lowry Park Zoo and Disney's Animal Kingdom -- showed some of the skills and instincts they'll need to survive.

For one, they've lived up to another name they sometimes go by: pack rat. They've busily added to nests -- distinctive mounds cobbled with everything from sticks to dung to the random bottle cap -- that were vacated by other members of their vanishing population.

"They've piled so much stuff over the nests it's incredible," said Sandra Sneckenberger, a Wildlife Service biologist.

The service started the breeding program in 2002 as a last-resort attempt to reverse the population decline in the rat's only known home, the tangled hardwood hammocks of the largest island in the Florida Keys chain. The estimated population has dwindled to no more than 300 -- down dramatically from about 6,500 before 1984, when the rat was added to the federal endangered species list.

Though they are rats, they are a different genus than the nasty, biting carriers of disease reviled by humans, said Christy Alligood, a research specialist at Disney's Animal Kingdom. The wood rat arises from a kinder, gentler rodent strain and wants nothing to do with homes or buildings. In nature and size, they're more akin to mice -- small at just four to nine inches, docile and shy.

Though handling the seven was kept to a minimum to help acclimate them to the wild, biologists and breeding teams grew attached enough to name them, Sneckenberger said. "They are very charismatic creatures."

The first group of seven -- Tweak, Ralph, Roxy, Frieda, Rosie, Fern and Garfunkle -- will be followed by seven others later this month. The rats, fitted with tiny radio collars, will be tracked for 60 days. If they survive, the hope is they'll breed.

It's not something they do all that frequently in the wild, which might partially account for the species' decline. Unlike prolific urban rats, wood rats breed only two to three times a year, producing about two "pups" each time, Alligood said. Otherwise, they tend to be solitary homebodies.

Getting them together in captivity proved one of the major challenges for the eight-year breeding program, she said. If they weren't in the mood, they might even attack each other. Researchers and technicians at the Animal Kingdom's Conservation Station learned to recognize the signs of a "receptive" wood rat, including a tell-tale, high-pitched raspy chirp.

Development, the most prevalent threat to wildlife in Florida, certainly played a role in reducing the rat's prime habitat, but its most recent rapid decline, starting around 1995, happened with much of its remaining habitat under state and federal protection.

The dire drop remains somewhat of a puzzle to scientists.

Tracking the lab rats also might help sort out threats, including diseases associated with a roundworm found in raccoon feces, as well as Key Largo's problematic population of feral cats and Burmese pythons.

Rat remains have been found in the guts of at least two captured snakes.

(c) 2010, The Miami Herald.
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