UF Researchers: Development Promotes Disease Among Gopher Tortoises

February 3, 1998

GAINESVILLE —Urban development in Florida is forcing the threatened gopher tortoise into closer and closer quarters, increasing the likelihood of them spreading a disease that could help speed their demise, according to new findings by University of Florida researchers.

Mary Brown, a UF associate professor of pathobiology and a primary investigator in the research, said as land is developed, the decreasing habitat increases contact among tortoises and creates a greater chance of spreading Upper Respiratory Tract Disease, which destroys the respiratory tract and olfactory senses.

“This is an ideal situation for the spread of most infectious diseases,” she said.

Paul Klein, a UF professor of pathology, immunology and laboratory medicine and a primary investigator, said the disease is not treatable in the wild.

Klein said the loss of smell interferes with the tortoises’ ability to find food, which may lead to malnutrition and starvation. He said the damaged respiratory tract can lead to secondary infections that would not have occurred with a healthy respiratory tract.

The researchers developed a brochure to help field workers identify ill tortoises, which may show signs of a runny nose, ocular discharge and swollen eyes. However, he said, some tortoises can be infected and show no outward signs of the disease.

Sanibel Island and Indian River are considered hot spots for the disease, Brown said. Because Sanibel is an island, she said, “animals are more likely to come in contact with each other, especially as habitat shrinks due to development.” Brown said researchers are not sure why Indian River has a lot of animals indicating exposure to the disease.

Conservation of the gopher tortoise is important, Brown said, because the burrows they create provide homes for small animals and are important in sustaining the ecosystem. She said the burrows provide homes for about 60 vertebrates — from snakes to birds — and more than 300 invertebrates, including spiders, crickets and beetles.

“Tortoises can act to spread seeds of plants and also to aerate the soil via their digging action,” Brown said.

Researchers discovered the disease is caused by the same bacteria that decimated the desert tortoise in the American Southwest. The disease has been seen in captive tortoises since the 1950s. The organism that causes it, Mycoplasma agassizii, was isolated seven years ago. “The disease is one factor that can contribute to population decline,” said Brown.

Klein, Brown and Elliot Jacobson, also a primary investigator and a professor of small animal clinical sciences, presented the findings last month at a mini-symposium at Walt Disney World’s Animal Kingdom theme park. The four-year study was sponsored by Walt Disney Co.

Brown said the symposium created an exchange of ideas to help fish and game authorities, water management personnel and the state Department of Agriculture identify the disease and successfully save the gopher tortoise without disrupting land development. Among the issues discussed at the symposium were relocation, restocking and land mitigation banking.

“Relocation involves moving a tortoise from one site to another,” she said. “While this makes people feel good, it is not very effective and risks spreading the disease.

“Restocking involves moving healthy animals to an area which was once tortoise habitat but is now devoid of tortoises,” she said. “This would re-establish new populations, but … it would require a long-term commitment.”

Brown said mitigation banking is the most effective conservation tool but is more expensive. It uses fees from developers to purchase and protect critical habitat.