If you have lived in the Treasure Coast for any length of time, you’ve probably encountered quite a few gopher tortoises crossing the road, strolling across your lawn, or digging a burrow in the vacant lot next door.
But according to a research scientist and clinical veterinarian at the Harbor Branch Oceanographic Institute, populations of these gentle, charismatic reptiles are declining here and elsewhere in Florida – even though they are protected as a threatened species under state law.
“Tortoises in more urban and suburban habitats are fragmented by roadways,” said Dr. Annie Page-Karjian. “In a lot of these places, tortoises are not reproducing, probably due to stress.”
Page-Karjian, with help from veterinary student Kathleen Rafferty, has launched a comprehensive health assessment of a population of about 100 gopher tortoises living on the Harbor Branch campus in Fort Pierce.
The scientists are sampling blood and other body fluids and mapping burrows, combining those findings with a previous study Page-Karjian conducted with colleagues in Juno Beach.
Page-Karjian said the aim is to compare the reproductive success of the Juno Beach and Harbor Branch groups of tortoises and apply those findings to other groups that have been split up by roads and other human-created barriers and activities.
“Which groups of tortoises are reproducing and which are not?” she said. “And those that are not, why aren’t they? Just because there’s an adult gopher tortoise there, it doesn’t mean they are reproducing. It’s stressful being around cars and dogs and people.”
Gopher tortoises are considered a keystone species in Florida’s terrestrial ecosystem. Their burrows, dug mainly in longleaf pine forests, can run 30 feet long and harbor as many as 350 other species at various times, up to and including American alligators. But Page-Karjian says the animals’ sandy, scrubby habitat has been reduced to about 1 percent of its historic size, which has forced them into closer contact with people, where they get crushed by cars or succumb to diseases such as mycoplasma – a potentially lethal bacterial infection.
The reptiles’ threatened status affords them some protections: permits are required from the Florida Fish and Wildlife Conservation Commission in order to relocate them out of a development site to an approved recipient site. And the state policy of permitting developers to bury some of them alive, known as ‘entombment,’ was repealed in 2007.
But the animals are long-lived – more than 70 years – and they take 10 to 20 years to reach reproductive maturity, which is plenty of time for things to go wrong before they have a chance to mate.
Page-Karjian said the Juno tortoises appeared to be in pretty good shape, despite being hemmed in by the Atlantic Ocean on one side and concrete barriers on the other three. The animals seemed to be reproducing; some had antibodies for mycoplasma, but no active infections.
As for the Harbor Branch tortoises, Page-Karjian said, medical tests are incomplete. But she was heartened to discover a yearling recently among the 16 tortoises captured so far. Another interesting finding: a predatory bobcat has been seen poking its head into burrows at the same time one tortoise was found to be missing an eye and another missing a leg.
“Shows it’s a healthy ecosystem,” Page-Karjian said.
The researchers got a small amount of start-up money for the project, but recently launched a crowd-funding campaign online at experiment.com to raise $4,300 to complete it by mid-2020. So far they’ve received $1,665 in pledges and must raise the rest by the end of this month to go forward.
