Demographic forecasting of Sistrurus rattlesnakes using Integral Projection Modeling

Dreslik, Michael J.

dreslik@illinois.edu

Kessler, Ethan J.

LaGrange, Seth M.

Illinois Natural History Survey

University of Illinois Urbana-Champaign

Champaign, Illinois USA

Farrell, Terence M.

Department of Biology

Stetson University

DeLand, Florida USA

Baker, Sarah J.

Department of Biology

McNeese State University

Lake Charles, Louisiana USA

Understanding an organisms’ biology necessitates deep knowledge of its life history patterns and how those traits interact. Although we have a rapidly growing body of knowledge on the life history of pit-vipers, many species remain data deficient in one or more parameters or are represented by single estimates. Full demographies are known for few species, likely because of the relatively reclusive nature of snakes. Thus, obtaining sufficient sample sizes is difficult, and approaches to studying pit-viper demographics necessitate long-term commitments. In addition, traditional demographic analyses focus on stage- or age-based vital rate estimates, neither of which best represents maturity in reptiles. Newer methods such as Integral Projection Modeling (IPM) use continuous, size-based estimates of vital rates and are likely more appropriate for ectotherms. We compare the demography of two Sistrurus species, S. catenatus and S. miliarius, from long-term data sets using Bayesian survival and regression methods within an IPM framework. Although sister taxa, both species have different range extents, across vastly different habitats, and likely have adaptational differences in survival, fecundity, and maturity. Our data will also provide insight into the diversity and plasticity of pitviper life history strategies.