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Differences in resource availability and quality along environmental gradients are important influences contributing to intraspecific variation in body size, which influences numerous life-history traits. Here, we examined variation in body size and sexual size dimorphism (SSD) in relation to temperature, seasonality, and precipitation among 10 populations located throughout Arizona of the western diamond-backed rattlesnake (Crotalus atrox). Specifically, in our analyses we addressed the following questions: (i) Are adult males larger in cooler, wetter areas? (ii) Does female body size respond differently to environmental variation? (iii) Is seasonality a better predictor of body size variation? (iv) Is SSD positively...
Sympatric populations of Cophosaurus texanus and Callisaurus draconoides were periodically sampled from March 1973 through April 1974 at Burro Creek, Mohave County, Arizona. Callisaurus were also sampled at Rock Valley, Nye County, Nevada. Sex ratios were skewed in favor of males in the adult Cophosaurus but were equal in both adult populations of Callisaurus. Both species became sexually mature as yearlings. Mean clutch sizes were 3.55 (+/- 0.83) for Cophosaurus, and 4.25 (+/- 1.08) and 5.07 (+/- 1.33) for Callisaurus at Burro Creek and Rock Valley respectively. Evidence of multiple clutches was exhibited by both species. Egg weight/body weight ratios for both species and clutch weight/body weight ratios for Cophosaurus...
Desert tortoises, Gopherus agassizii, generally were active in the spring and fall. They often became active during and after infrequent showers and thunderstorms, and drank from temporary pools of standing water even when air temperatures were suboptimal (9-15 C). In several instances tortoises constructed shallow catchment basins which held water for as long as six h. Thus tortoises can obtain drinking water by modifying their environment. Following small amounts of rainfall (5.6 mm) in July 1976, six tortoises increased an average of 9.2% in body weight; this increase was due to ingestion of water. Drinking may be an important source of water for this species. Published in Herpetologica, volume 36, issue 4, on...
Accurately assessing free-ranging animals? patterns of surface activity and refuge use is critical, yet fundamentally challenging for biologists and wildlife managers. We evaluate the accuracy of an automated technique?temperature-based activity estimation (TBAE)?in estimating surface activity and refuge use patterns of two sympatric reptiles, the western diamond-backed rattlesnake (Crotalus atrox) and the Gila monster (Heloderma suspectum) in the Sonoran Desert. TBAE derived from a comparison of body temperature to shaded air temperature was effective in estimating the overall percent surface activity for both rattlesnakes (observed surface activity 51.8%, TBAE estimated surface activity 48.2%) and Gila monsters...
The geographic pattern of variation in Cnemidophorus tigris septentrionalis Burger was determined from 17 samples (664 specimens) drawn from populations distributed throughout its range. Principal components analysis and canonical variates analysis identified three groups of populations whose morphological differences coincide with three geographic areas: (A) north of the Colorado and Dolores rivers in northwestern Arizona, east-central Utah, and western Colorado; (B) south of the Colorado and San Juan rivers and east of the Little Colorado River in southeastern Utah, northwestern New Mexico, and northeastern Arizona; and (C) west of the Little Colorado River in northeastern Arizona. The latter population is of...
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