Trapping Survey Results for the Alligator Snapping Turtle (Macrochelys temminckii) in Southeastern Louisiana, with Comments on Exploitation

Abstract

Two hundred alligator snapping turtles were trapped at an average rate of 0.057 turtles per trap-night in all but 1 of 33 sites in southeastern Louisiana. Trap rate varied between sites, by harvest pressure levels at sites, and by season, but not by hydrology. Perceived trap rate differences under different harvest regimes appeared to be a function of seasonal differences in trap rate. No differences in sex ratio or percentage of immature turtles were detected between sites, harvest regimes, seasons, or water-body types. Turtle weight varied between harvest regimes and hydrology. Weight–length relations for turtles was highly correlated and similar between sexes, except that males continued to grow to larger sizes than females (males averaged 150% female weight and 118% female carapace length). Sex ratio was 1:1, and immature turtles made up 48% of the total. Average sizes of turtles were very similar between Louisiana and turtles from surveys in several other states. Population structure differed between surveys, with Louisiana having a higher percentage of immature turtles and lower trap rate than elsewhere. Population differences could not entirely be explained by differences in harvest regimes between states. Large-scale turtle butchering operations in southern Louisiana have closed, as has commercial harvest. Anecdotal reports that alligator snappers were nearly extirpated from a heavily harvested site proved erroneous. Resurvey of sites to determine current population trends is recommended.