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A trapping survey targeting head-started alligator snapping turtles in southwest Louisiana

August 1, 2020

The alligator snapping turtle Macrochelys temminckii is the largest freshwater turtle in North America and is sought after as a food source, primarily in Louisiana. Decades of intensive commercial harvest of alligator snapping turtles has been implicated in population declines. The Louisiana Department of Wildlife and Fisheries initiated a head-start program for alligator snapping turtles and released 53 head-started juveniles at seven sites along an approximately 5.7-km stretch of Bundick Creek in southwest Louisiana between November 2015 and October 2016. Before release, all alligator snapping turtles were measured, weighed, and marked with both an internal passive integrated transponder tag and a numbered external tag. In 2018, the U.S. Geological Survey initiated a turtle trapping survey at those seven release sites targeting the head-started alligator snapping turtles. In one week of trapping effort at each site, we recorded 69 turtle captures comprising seven species, including 15 alligator snapping turtles (representing 12 individuals). Of those 12 individuals, 8 were head-started juveniles and 4 were native to the creek. An additional head-started juvenile alligator snapping turtle was captured by a landowner during our trapping and measurements were taken before release. A minimum of 17% of head-started alligator snapping turtles survived since release, and most captured head-started individuals were trapped near their release site and exhibited growth consistent with other studies, indicating acclimatization to their new environment. Three head-started alligator snapping turtles had their external tags entangled in the net mesh, and two of these turtles drowned. An additional two head-started individuals lost their external tags in the natural environment prior to their capture in this study. The use of external tags was discontinued by the Louisiana Department of Wildlife and Fisheries based on our findings, as they were detrimental to the health of head-started turtles.