A Historical Resurvey of Flatland Lizards in the Mojave Desert

Historical resurveys are uniquely valuable for the information that they provide regarding population responses to environmental changes. As anthropogenic impacts on the environment proceed, such efforts are becoming increasingly important for developing a historical baseline and for understanding how contemporary populations respond. We undertook a >50-year historical resurvey of the Mojave Desert flatland lizard community by pairing data from the 1960s and today, which provided a repeatable benchmark for future monitoring. We found few changes in distribution, with at least 9 of 11 species continuing to occur where they were previously detected. However, we found marked declines in abundance for the widespread and highly detectable Side-blotched Lizard (Uta stansburiana), one of three species where data were sufficient to robustly estimate abundance. Both our work and other recent works highlight the difficulty of estimating abundance for wild lizard populations and, should we wish to understand declines before they turn into extirpations, call for the continued development of methods for efficient and robust tracking of desert reptile populations.