Seasonal shifts in shelter and microhabitat use of drymarchon couperi (eastern indigo snake) in Georgia

Drymarchon couperi (Eastern Indigo Snake), a threatened species of the southeastern Coastal Plain of the United States, has experienced population declines because of extensive habitat loss and degradation across its range. In Georgia and northern Florida, the species is associated with longleaf pine habitats that support Gopherus polyphemus (Gopher Tortoise) populations, the burrows of which D. couperi uses for shelter. The extent that D. couperi uses these burrows, in addition to the use of other underground shelters and the microhabitat features associated with these structures is largely unknown. From 2003 through 2004, we conducted a radiotelemetry study of D. couperi (n = 32) to examine use of shelters and microhabitat in Georgia. We used repeated measures regression on a candidate set of models created from a priori hypotheses using principal component scores, derived from analysis of microhabitat data to examine microhabitat use at underground shelters. Proportion of locations recorded underground did not differ seasonally or between sexes. In winter, we recorded >0.90 of underground locations at tortoise burrows. Use of these burrows was less pronounced in spring for males. Females used abandoned tortoise burrows more frequently than males year-round and used them on approximately 0.60 of their underground locations during spring. Microhabitat use at underground shelters was most influenced by season compared to sex, site, or body size. Females in spring and summer used more open microhabitat compared to males, potentially in response to gestation. Our results suggest that the availability of suitable underground shelters, especially G. polyphemus burrows, may be a limiting factor in the northern range of D. couperi, with important implications for its conservation. ?? 2009 by the American Society of Ichthyologists and Herpetologists.