Accessibility and surface area drive desert toad presence at artificial water sites in the Great Basin and Mojave...

Artificial Water Sites (AWS) are human-made or modified water sources constructed or maintained for livestock, select wildlife game species, or other management purposes in arid environments. However, non-target species such as desert toads have been documented utilizing AWS. Because the reproductive ecology of desert toads relies on water, understanding factors explaining their presence at AWS can inform conservation practices. To address this lack of information, we examined how AWS design, spatial isolation, local terrain, and surrounding vegetation influenced toad presence in the Great Basin and Mojave Deserts. From May to June 2011, we surveyed 68 AWS for species presence of toads and quantified AWS design features and environmental variables. We detected Great Basin spadefoot toads (Spea intermontana) at 61% of Great Basin AWS and red-spotted toads (Anaxyrus punctatus) at 38% of Mojave AWS. We used generalized mixed-effects models and AIC model selection to identify the most informative variables. Top performing predictors resulted in the final model 'access height (lowest distance between water edge and ground surface) + surface area (surface area coverage of water)', which accounted for 86% of model weight. The predictor 'access height' had a significant negative association with toad presence whereas 'surface area' had a significant positive association. Spatial isolation, terrain, and vegetation predictors were not found to influence toad occurrence. Our results indicate that AWS design, specifically lower access height and increased surface area, enhances desert toad use, potentially improving amphibian habitat suitability and persistence.