Distribution Patterns and Factors Influencing Relative Abundance of the Alligator Snapping Turtle (Macrochelys temminckii) in Mississippi

Abstract - Macrochelys temminckii (Alligator Snapping Turtle) was recently proposed as a threatened species under the US Endangered Species Act due to current and projected future declining populations range wide. Despite a presumed statewide distribution in Mississippi, the Alligator Snapping Turtle had been documented in only 32 of 82 counties between 1857 and 2012, thus leaving a substantial gap in our knowledge of this species' distribution. Therefore, we collected credible records from museums, literature, and the general public, as well as directly assessed the current distribution and relative abundance of the Alligator Snapping Turtle in all major river systems (i.e., Pascagoula, Pearl, Tombigbee, and Mississippi river drainages) in Mississippi. From 2017 to 2021, we systematically trapped 77 sites across the state totaling 839 captures of 787 individual Alligator Snapping Turtles over the course of 4750 trap nights. State-wide catch per unit effort (CPUE) averaged 0.177, with the Big Black River (0.348) and Tombigbee River (0.028) drainages having the highest and lowest average CPUE, respectively. In Mississippi, CPUE was positively correlated with greater surrounding wetland area and river size, and negatively correlated with terrain ruggedness. This survey, along with the collaboration of other biologists and the public, verified an additional 189 locality records in 56 counties, with Alligator Snapping Turtle presence reconfirmed at 29 of 30 historical localities. Currently, it appears that there have been no local extirpations of the species in Mississippi, and state-wide CPUE was higher than those of the surrounding states.