Spatial and Temporal Ecology of a Highly Specialized Reptile: Regal Horned Lizards (Phrynosoma solare)

From 2015 through 2020, we used radiotelemetry to investigate spatial and behavioral ecology of Regal Horned Lizards (Phrynosoma solare) at Cave Buttes in the Sonoran Desert near Phoenix, Arizona, USA. Our results reveal dramatic variation in space use and behavior by season and sex over the course of an annual activity period centered around the summer monsoon (June through August). Brumation at the base of shrubs occurred from early fall (late September and October) through late spring (April and May) for males (∼195 d); females were inactive for a significantly shorter period (∼180 d) but still relatively longer than expected for a desert dwelling ectotherm. A postbrumation period (April and May) was characterized by relatively little movement and a postbrumation ecdysis event prior to a mating period (June and July). Males moved significantly more than females during the mating period and mated with up to four females. A nesting period (August) was characterized by increasingly diminished movement by males, who began brumation as early as 24 September, and nesting and nest guarding by females. A prebrumation period (September and October) followed the nesting period and included a second ecdysis event. Both of our home range size estimator methods, 95% kernel density estimator (KDE) and minimum convex polygon (MCP), showed annual male home ranges (KDE: X=16.40 ha, n=14; MCP: X=8.44 ha, n=14) almost four times greater than female home ranges (KDE: X=3.32 ha, n=18; MCP: X=1.90 ha, n=18). Home range overlap within and between sexes was relatively low (30–40%) for lifetime home ranges.