Alligator snapping turtle population simulation model developed in support of the Species Status Assessment

This software release contains six R scripts that comprise a population viability analysis for the alligator snapping turtle (Macrochelys temminckii). To predict numbers of M. temminckii in the future, we constructed a female-only, stage-structured matrix projection model. We incorporated multiple types of uncertainty into the simulation model, including parametric uncertainty and temporal variation. We used expert elicitation to generate modified survival rates in the presence of specific anthropogenic threats, for which empirical estimates were unavailable. We constructed a set of simulation scenarios to evaluate the sensitivity of model predictions to the expert elicited model parameters. We also conduced additional sensitivity analyses aimed at describing the effect on model outcome of a subset of expert elicited parameter values, for which there was high disagreement among experts. The results of this future projection model are presented in the M. temminckii Species Status Assessment (SSA) versions 1.2 (USFWS 2021) and 1.3 (USFWS 2024/in press). The accompanying research article can be found in Christensen et al. 2024.