Fine scale analysis of intraspecific and interspecific interactions in two varanid lizard populations adjacent to a sea turtle nesting beach

Abstract

Differential space use is one of the strategies used by species with similar niche requirements to avoid direct competition while in sympatry. Here, we used Global Positioning System devices to investigate - two sympatric species of monitor lizards in a coastal habitat adjacent to a sea turtle nesting beach. Adults of yellow-spotted goannas Varanus panoptes and lace monitors V. varius were tracked throughout the summer sea turtle nesting season to explore their space use and investigate how often individuals were close enough to each other that direct interspecific and intraspecific interactions could occur. The two species utilized different habitat at this site. Yellow-spotted goannas spent a greater proportion of their time in the beach-front dune habitat where sea turtles nest, while lace monitors spent most of their time in the woodland habitat behind the beach-front dunes, and as a consequence, encountered fewer sea turtle nests compared to yellow-spotted goannas. Yellow-spotted goannas and lace monitors rarely came closer than 15 m of each other, both intra- and interspecifically, although their home ranges overlapped.