Effects of Differential Use of a Resource Hotspot and the Mating System on Season and Sex

DeSantis, Dominic L.

Mata-Silva, Vicente

Johnson, Jerry D.

Department of Biological Sciences

University of Texas at El Paso

El Paso, TX USA

Patterns of animal movement and space use reflect individual responses to spatiotemporal variation in the distribution of critical resources (e.g., food, water, shelter sites, mating partners) in the environment. In this context, habitat heterogeneity and patterns of habitat use are important considerations, as variation in habitat characteristics can directly affect local resource arrangement and abundance. We are investigating the effects of differential habitat use, season, and sex on variation in movement strategies by Crotalus atrox in an arid Chihuahuan Desert landscape. On our study site, ephemeral cattle tanks or ponds have created discrete resource hotspots that contain an abundance of shelter (i.e., vegetation), prey (i.e., rodents and lagomorphs), and water relative to surrounding native habitats, and, as a result, might influence movement and spatial strategies of snakes using these features. Through radio telemetry we have monitored movement and space use by 24 C. atrox (12 males and 12 females) and are also using tri-axial accelerometry to continuously measure activity for selected males. Preliminary data indicate that, in general, C. atrox at our site display season and sex-specific patterns of movement expected under the polygamous mating system, with males increasing movement during mating seasons in mate-searching efforts and females showing no significant seasonal differences. However, relative to snakes in native habitats, those using tank habitats display lower measures of movement and smaller home range sizes across seasons, possibly due to the spatial clustering of conspecifics around these resource hotspots. Remote and continuous measures of activity obtained with internally implanted accelerometers in male C. atrox will supplement data collected with radio telemetry. Validating this method in wild-ranging snakes could facilitate improved testing of proximate and ultimate mechanisms driving the timing, duration, and frequency of movements.

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