New UGA research suggests moving threatened animals to protected habitats may not always be an effective conservation technique if the breeding patterns of the species are influenced by a social hierarchy.
Research, published in the early online edition of Biological Conservation, found an initial group of gopher tortoises released on St. Catherine’s Island were three times more likely to produce offspring than a later-introduced group, although the initial group had a much smaller proportion of reproduction-aged males.
“There definitely appeared to be an advantage to the order that the tortoises were released,” said lead author Tracey Tuberville, an assistant research scientist at UGA’s Savannah River Ecology Laboratory. “The earlier the males were released, the more likely they were to be successful fathering offspring for the next generation.”
Moving multiple groups of gopher tortoises at different times may disrupt their social structure, said Tuberville, resulting in differential success in reproduction among potential breeders. Introducing a specific number of males to reach a target population size may not achieve the desired results if all of the males are not reproducing.
“We found that females released later were not excluded from reproduction,” she said. “If you need to augment a population, you might consider targeting females as opposed to males or introducing more females than males, because females produce the eggs, and they also seem to be incorporated into the breeding and social structure faster than males.”
Gopher tortoises are federally listed as a threatened species in the western part of their range, though not in Georgia and Florida, where much of the destruction of their habitat has occurred.
They prefer open-canopied longleaf pine forests, which now cover only 2 percent of their historic range.
