Do Siberian marmots influence toad-headed agama occupancy? Examining the influence of marmot colonies and three steppe habitats in Mongolia

Abstract

The Siberian marmot is a large, endangered rodent and often considered a keystone species because of its perceived effects on steppe ecosystems. However, few studies have examined the effects of marmots on other species. We examined the influence of marmots on toad-headed agama occupancy probability in an arid steppe region of Mongolia. We modeled the influence of marmot colonies and three habitats, including rocky outcrops, open plains, and shrubland using an occupancy modeling framework based on three surveys of 122 sites from June to August 2010. We detected agamas during 64% of surveys and at 85% of sites. Marmot colonies and their interactions with other habitats had little influence on occupancy probability at a given site. The amount of surrounding open plains and shrubland also showed little influence. Our results indicated toad-headed agama occupancy was inversely related to the amount of surrounding rocky outcrop. Rocky outcrop may be less suitable to agamas because of its sparse vegetation, lack of burrows, and heat-absorbing qualities. Although marmots affect the distribution of other species, our results suggest they exert little influence on toad-headed agamas. We also suggest that the creation of rocky habitat by mineral mining will negatively impact toad-headed agamas.