COMPARATIVE ECOLOGY OF THE MOTTLED ROCK RATTLESNAKE, CROTALUS-LEPIDUS, IN BIG-BEND-NATIONAL-PARK

Environmental factors that influence geographic variation in life hist ory have both direct and indirect effects on time-energy budgets of in dividuals. The exact relationships between environmental factors and t ime-energy budgets of snakes remain relatively unexplored. I studied t wo populations (Boquillas: area B, and Grapevine Hills: area G) of the mottled rock rattlesnake (Crotalus lepidus) in Big Bend National Park , Texas. Area B is hotter, drier, and less productive than area G. I u sed mark-recapture and radio telemetry to study age specific size, rep roduction, surface use, movements, diet, and body temperatures of snak es from these sites. Adult snakes from area B had smaller age specific body masses and snout-vent lengths, lower frequency of surface use, h igher average body temperature, and lower probability of defecation th an snakes from area G. These observations suggest that resources for g rowth may be limited to a greater extent at area B. High environmental temperatures at area B may limit foraging time (therefore energy harv esting) and increase body temperatures (which influence maintenance me tabolism) to a greater degree than al area G. Ongoing tests of these h ypotheses may clarify relationships between environmental factors, tim e-energy budgets, and life history traits of snakes in these populatio ns.