Diurnal and Nocturnal Habitat Use in Reticulate Collared Lizards (Croptaphytus Reticulatus)

Authors: Timothy B. Garrett, Wade A. Ryberg, Connor S. Adams, Tyler A. Campbell, and Toby J. Hibbitts

Patterns of habitat use in animals can vary over time and space in predictable ways. For ectotherms, behavioral cycles are tightly linked to varying temperatures in the environment such that microhabitat availability can constrain individual performance, fitness, and life history. A long history of research on diurnal microhabitat use in lizards exists; however, comparatively little is known about nocturnal microhabitat use that might also constrain individual lizard performance, fitness, and life history.

In this study, we compared diurnal and nocturnal microhabitat sites of the reticulate collared lizard (Crotaphytus reticulatus), a threatened species in Texas, to available microhabitat sites. We found significant differences between diurnal and nocturnal microhabitat characteristics, and both of these were significantly different from random microhabitat sites available. We observed that C. reticulatus used diurnal and nocturnal microhabitats with a gravel substrate and scattered boulders that were covered by a short overstory of woody and succulent plants rather than more heavily vegetated sites with dense grasses and forbs. We also observed that diurnal microhabitats were moderately open, shallow gravel slopes compared with nocturnal microhabitats that contained dense thickets of woody and succulent plants. The open, gravelly characteristics of diurnal microhabitats with occasional vegetative structure were more consistent with microhabitat descriptions of other Crotaphytids, which as a group are visual predators.

However, the daily shift to dense, thorny plant cover at night appears unique to C. reticulatus among Crotaphytids in general. This study suggests that private land stewardship across the C. reticulatus distribution in Texas has benefitted the species by maintaining habitat used by the lizard, and it suggests that future conservation actions for the species will be most successful with continued engagement with private landowners.

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