Preliminary information on the microhabitat use of the rock rattlesnake (Crotalus lepidus) from Hudspeth County, Texas

Background/Question/Methods Radio-telemetry has proven a useful technique for studying different aspects of snakes in their natural environment including habitat and microhabitat selection. Obtaining detailed information of the habitat and microhabitats selected by rattlesnakes is important for enhancing conservation strategies of species that might become threatened by human related activities and that live in fragile environments as the Chihuahuan Desert. The main questions of this study are the following: A) what is the preferred habitat and microhabitats of C. lepidus? B) Does the microhabitat selection change throughout the year? C) Do sexes prefer different microhabitats? And D) what is the preferred substrate in the study area? Crotalus lepidus is a small rattlesnake whose habitat is chiefly found in mountainous areas of the Chihuahuan Desert. We present initial data of the snakes’ active season, from mid-July to mid-November 2007, and from mid-April to November 2008 from four individual (three males and one female) C. lepidus at Indio Mountains Research Station (IMRS); a 39,000 acre station located in Hudspeth County, Texas, and administrated by UTEP. The vegetation is a Chihuahuan Desert landscape with different shrub associations mainly on conglomerate slopes and alluvial flats located at an average elevation of 1200 m above sea level. Snakes were collected in the study area, and taken to the stattion’s laboratory for morphological measurements and then implanted with a 5 g  transmitters. Snakes were relocated and radio-tracked at different times for three to four days a week using an antenna and a R-1000 telemetry receiver. Field data such as: date, time, microhabitat, main element providing shelter, plant species and frequency, percentage of rock, gravel, sand, soil, litter and vegetation in a square meter was recorded.

Results/Conclusions Until now, we have observed the three males and the female 405 times. When the main element providing shelter to the snake was analyzed, snakes were observed 242 times (60%) under vegetation and 163 times (40%) under shelters other than vegetation. When shelters other than vegetation were subdivided, we found the snakes 73 times under rocks (18%), 40 times (10%) under litter or yucca logs, 11 times (3%) underground, and only 39 times (9%) were observed in the open with no shelter at all. When we analyzed the vegetation, the snakes were mainly found 99 times (41%) in shrubs, 42 times (17%) in grasses, 38 times (16%) under yuccas. Future acquisition of more data will strengthen or refute the tentative results presented herein.