Measuring snake activity patterns: The influence of habitat heterogeneity on catchability

Activity patterns for two populations of the Concho water snake (Nerodia harteri paucimaculata) were studied in a large lake system in central Texas, USA, and compared to a river population. Trap data suggested different activity patterns for the two geographically proximate lake populations. Testing of the trap data using the program CAPTURE revealed differences in catchability rather than activity cycles. Based on these results, the apparent activity patterns for one of the lake sites was considered erroneous; and the differences in catchability were ascribed to habitat differences. It is suggested that future studies should incorporate a test of equal catchability when making interpopulational comparisons.