The area occupied by sagebrush ecosystems has declined throughout western North America. This trend is predicted to continue with increased energy development, reducing habitat availability and threatening diverse flora and fauna that are dependent on sagebrush ecosystems. For some species, the structural characteristics of sagebrush shrubs themselves may be critical habitat features. For example, in many parts of their ranges, horned lizards (Phrynosoma spp.) burrow under loose soil to maintain preferred body temperatures. However, horned lizard populations also occur in environments where clay-rich soils prevent burrowing and other habitat features, such as sagebrush plants, may help lizards to thermoregulate. We measured environmental temperatures, operative temperatures of models, and body temperatures of the greater short-horned lizard (Phrynosoma hernandesi) in a sagebrush ecosystem and evaluated the importance of sagebrush for thermoregulation in this lizard.
Results/Conclusions
Over 12-hour periods, lizard body temperatures initially rose parallel to operative temperatures and then flattened out to fluctuate around a body temperature of ~35°C, within the range of their known preferred body temperature. Lizards maintained their preferred body temperature by first moving under sagebrush and then, as environmental temperatures peaked, climbing up into sagebrush. Lizards remained perched in sagebrush until environmental temperatures dropped below 35°C. This pattern was without exception among the lizards we observed. Where hard soils prevent burrowing, sagebrush shrubs may be a critical habitat feature allowing horned lizards to increase convective cooling during the hottest part of the day. While greater short-horned lizards inhabit a variety of ecosystems in the southern and central parts of their rage, sagebrush dominates the northern portion of their range. Protecting this ecosystem is, therefore, a priority for conserving horned lizard populations in this region.