Supplementation of juvenile American alligators in Louisiana, USA

Summary

Louisiana's American alligator population, healthy and widely distributed enough to support commercial harvest, is managed through an egg-ranching program run by the Louisiana Department of Wildlife and Fisheries since 1986, in which biologists set annual egg-collection quotas on private wetlands based on aerial nest-count surveys, with 12% of eggs hatched required to be returned to the wild as juveniles to replace the wild mortality that egg collection prevents. Each spring through summer, a seven-person team travels statewide measuring, tail-notching, and toe-web-tagging 40,000 to 50,000 juvenile alligators before releasing them in suitable ponds with adequate cover, prey and permanent water, compensating for 350,000 to 400,000 eggs collected annually from over 2.5 million acres of wetlands. The program proved its value during 2005's Hurricanes Katrina and Rita and again during 2008's Gustav and Ike, when eggs that had already been collected for ranching avoided the high natural mortality that storm-flooded nests would otherwise have suffered. Recapture monitoring at harvest check stations over more than 20 years shows released alligators grow and survive as well as or better than wild counterparts, eat similar prey, show comparable stress hormone levels, and have documented successful nesting. Major difficulties included statistical models poorly suited to a long-lived species and ensuring juveniles are spread across enough separate release ponds to avoid crowding and cannibalism. The project rates itself Highly Successful, citing stable to rising statewide nesting-survey population trends alongside a strong economic incentive for landowners to maintain healthy wetlands.