Natural history of two iconic desert lizards (Dipsosaurus dorsalis and Gambelia wislizenii) in southern Arizona

Jones, Lawrence L.C.

Southwest Zoologists’ League

Tucson, Arizona

gilaman@comcast.net

Although there has been a fair amount of research on Dipsosaurus dorsalis and Gambelia wislizenii, these species have not been studied in detail in southern Arizona, an area that has a bimodal rainy season and unique biotic communities. From 2020-2023, I conducted radiotelemetry studies and surveys on these animals at two sites (one Arizona Upland, one Desert Grassland) near Tucson, Arizona. The overarching themes of the study were microhabitat use of this roadside lizard community, seasonality, and effects of climate change. This presentation is an overview, highlighting some of my findings. During telemetry, I obtained 2,475 fixes (locations) on 28 D. dorsalis and 23 G. wislizenii. I had a large enough sample to determine home range estimates for 17 Dipsosaurus and 17 Gambelia. The former typically had a small home range that was close to the road where captured, while the latter had a home range about three times larger but was mostly in the adjacent uplands, and was somewhat dynamic. One interesting attribute was the use of respite sites, where lizards were inactive. Dipsosaurus always slept in repeated-use burrows, while Gambelia slept in burrows or shrubs. Thermoregulatory maintenance and ambush sites will also be discussed. Feeding behavior was documented for both species. The results suggest that the Arizona Upland population of D. dorsalis, which emigrated from the Desert Grassland site, has a distinct advantage for survival, due to the presence of more food resources that are available for a longer period. Hunting behavior of G. wislizenii was intriguing, and these lizards toggled between active hunting and ambush modes. There were also fundamental differences in surface activity patterns of these two species. My research was conducted during a time when weather extremes consistent with climate change were rampant, affecting surface activity, and having other repercussions.