Determining the phenology and predictors of spring emergence for the Timber Rattlesnake (Crotalus horridus) in Illinois using in-field cameras

Jesper, Andrew C. ajesper2@illinois.edu

Dreslik, Michael J.

Illinois Natural History Survey

University of Illinois Urbana-Champaign

Champaign, Illinois USA

Eckert, Scott A.

Department of Biology and Natural Resources

Principia College

Elsah, Illinois USA

Ballard, Scott R.

Illinois Department of Natural Resources

Carterville, Illinois USA

Bielema, Brian J.

21491 Lake Rd

Morrison, Illinois USA

Many ectotherms are particularly vulnerable during spring egress when thermoregulating individuals congregate near communal refugia for several weeks. Consequently, entire congregations are susceptible to potential threats such as management activities (e.g., prescribed burning, logging), poaching, and wanton killing. The Timber Rattlesnake (C. horridus) is a species of conservation concern which relies on subterranean refugia to survive temperate winters. As a slow maturing and long-lived reptile, C. horridus lacks the demographic plasticity to recover from population declines rapidly, and even limited mortality events can be detrimental to population viability. Thus, information regarding the timing and predictors of spring emergence in C. horridus is required to inform conservation and land management. Here, we describe the phenology of spring emergence for two populations of C. horridus in Illinois and build a predictive model of phenology across the latitudinal gradient of Illinois using in-field cameras. Our results suggest C. horridus have substantial variability in the timing of emergence across the latitudinal gradient, which should be considered when conducting conservation and management activities near the species’ refugia.