Movement, Home Range Size, and Habitat Use of Eastern Black-Tailed Rattlesnakes (Crotalus ornatus) in the Northern Chihuahuan Desert

Abstract: Despite its wide distribution throughout the northern Chihuahuan Desert, extraordinarily little is known about the ecology or behavior of Eastern Black-tailed Rattlesnakes (Crotalus ornatus). The primary literature for Black-tailed Rattlesnakes was largely based on research conducted on the former conspecific (C. molossus); thus, the revalidation of C. ornatus widened the void in our understanding of the species. The aim of this study was to elucidate movement patterns, home range size, and habitat use by C. ornatus in the northern Chihuahuan Desert of far West Texas. Radiotelemetry was used to monitor individual snakes for at least one active season (March–October) from May 2015 through August 2018. Mean (±1 SE) home range size for all individuals was 22.84 ± 4.49 ha and mean daily distance moved was 9.28 ± 0.93 m/d. Male snakes had larger home range sizes, larger core use areas, and greater daily distance moved than did female snakes. On a monthly basis, male movement peaked in August and female movement was statistically similar throughout the active season. Multinomial logit models were used to analyze habitat use patterns of C. ornatus, while controlling for snake, habitat availability, and season. Despite limited availability within snake home ranges, most observations of snakes occurred in arroyos or on rocky slopes. Microhabitat was also used nonrandomly, with snakes seeking cover in rocky refugia or under dense vegetation, rather than in areas containing high proportions of gravel or plant litter. This study presents the first detailed information about habitat and microhabitat use, along with patterns of movement and home range size for the recently revalidated C. ornatus.