Bi-seasonal stress biomarkers in two species of sympatric rattlesnakes (Crotalus atrox and Crotalus ornatus) in Far West Texas

Rocha, Arturo

Mata-Silva, Vicente

Ecology and Evolutionary Program

Department of Biological Sciences

The University of Texas at El Paso

El Paso, Texas USA

There are relatively few studies in the measurement of stress biomarkers free-ranging snake populations; including chronic, or elevated stressed rattlesnakes. The utilization of implants filled crystalline corticosterone (CORT) have been used as a proxy for elevating CORT in terrestrial animals, given the difficulty of assessing chronic stressors in field studies. Plasma CORT and leukocyte profiles (heterophils: lymphocytes) are common, and efficient methods in determining stress profiles in vertebrate ectotherms. Herein, we present an overview in determining seasonal baseline, acute reactivity, and elevated-stress levels effects in body conditions and other spatial variables in monitored, free-ranging Western Diamond-backed (Crotalus atrox) and Eastern Black-tailed Rattlesnakes (Crotalus ornatus) in Chihuahuan Desert scrub habitats (Indio Mountains Research Station, UTEP). The use of corticosterone implants in snakes will be categorized in two experimental groups: a treatment (CORT implants) and a control group (blank implants). For each species (C. atrox and C. ornatus), half of the snakes will be randomly selected for treatment of crystalline CORT implantation (while the other half will receive blank implants). Snakes will be monitored via radio-tracking, and blood will be drawn for plasma CORT and leukocyte profiles (blood smears) during two periods (pre-monsoon and post-monsoon months). Seasonal spatial (e.g. movements) and fitness effects (body conditions) will be determined from the changes in CORT at baseline, acute stress reactivity tests, and blood smears will be stained (Wright-Giemsa) to determine the changes in leukocyte profiles in different experimental groups and seasons.