Date of Award
2025-08-01
Degree Name
Doctor of Philosophy
Department
Biological Sciences
Advisor(s)
Jerry D. Johnson
Second Advisor
Elizabeth A. LaRue
Abstract
To understand how animals coexist on the landscape, the individual aspects of a species life history must first be understood. Animals need to find locations that provide the resources they need to survive. Movement, microhabitats, and temperature can alter such areas where animals occur. Understanding animal movements provide important information on space use and microhabitats on the landscape. Ectothermic animals must acquiesce to ambient temperatures or use behavioral modifications to alter their body temperature. The ability to maintain suitable body temperature is essential for physiological function, reproduction, and ability to avoid predation. Research on the variation in a species ecology can be especially helpful to identify the dynamics of closely related sympatric species that occupy similar ecological niches. In Chapter 1, I used Very High Frequency (VHF) radio telemetry to study the spatial ecology of the Western Diamond-backed Rattlesnake (Crotalus atrox), Rock Rattlesnake (C. lepidus), and Eastern Black-tailed Rattlesnake (C. ornatus) at the Indio Mountains Research Station (IMRS) in West Texas. The large-bodied Eastern Black-tailed Rattlesnakes was predicted to have the largest home ranges and use elevational changes more than the smaller Rock Rattlesnakes and the habitat generalist Western Diamond-backed Rattlesnakes. Traditional two-dimensional home ranges and core use areas were estimated and then clipped to a digital elevation map to give a three-dimensional spatial estimate. Daily movement estimates between all species were significantly different, but daily elevation changes were not. The Western Diamond-backed Rattlesnakes had the largest estimates across all metrics, and the Rock Rattlesnakes had the smallest, with the Eastern Black-tailed Rattlesnakes consistently falling in between them. In Chapter 2, I compared the winter thermal ecology of three rattlesnake species, specifically looking at winter emergence from hibernacula. I collected body temperature data in 22 free-ranging rattlesnakes, 11 C. atrox, 6 C. lepidus, and 5 C. ornatus at IMRS. Winter basking events were estimated for 14 individuals for which winter temperature data were collected, with C. ornatus most frequently coming out to bask during December, January, and February; with C. atrox egressing the least and C. lepidus nested between C. ornatus and C. atrox. Male C. atrox emerged from hibernacula more frequently than female C. atrox. These data provide important insights into the variation in winter activity of these secretive organisms, which are commonly thought to be non-active during this season. In Chapter 3, I used location data from C. atrox, C. lepidus, and C. ornatus implanted with VHF radio transmitters and tracked for up to one year in the Northern Chihuahuan Desert of West Texas. Gradient surface of elevational metrics and environmental factors for 708 locations from 22 rattlesnakes of these three species were used. A random forest model showed that ground temperature and humidity were the most important explanatory variables to predict body temperature of individuals outside of temporal metrics. Two generalized linear mixed-effects models (GLMMs) were used, one with body temperature as the response variable and one with ground temperature as the response variable. Ground temperature and pressure were the most explanatory variables in the body temperature GLMM, and body temperature and mean elevation were the most explanatory variable in the ground temperature model. Geodiversity metrics outside of mean elevation were not explanatory in my GLMMs. These three species of rattlesnake appear to not be strongly tied to gradient surface metrics but more associated with temperature in this arid, montane landscape of West Texas.
Language
en
Provenance
Received from ProQuest
Copyright Date
2025-08
File Size
106 p.
File Format
application/pdf
Rights Holder
Joshua James Mead
Recommended Citation
Mead, Joshua James, "Spatial And Thermal Aspects Of The Ecology Of Three Sympatric Rattlesnakes In The Montane Northern Chihuahuan Desert" (2025). Open Access Theses & Dissertations. 4410.
https://scholarworks.utep.edu/open_etd/4410