Microhabitat selection of adult female eastern diamondback rattlesnakes (Crotalus adamanteus) in the Carolinas

Reptiles rely on environmental conditions to regulate body temperature using behavioral strategies to meet basic life history needs. Viviparous squamates use thermoregulatory behaviors to meet energetic requirements for vitellogenesis and gestation, which carry considerable energetic costs and must balance with maintenance and survival. Embryonic development is often optimized in a narrower temperature range than the mother’s preferred temperature, creating an intergenerational conflict that should be addressed with maternal microhabitat selection. Field-based studies are needed to understand the link between the thermal biology of reptiles, their reproduction, and implications for population viability. With a use-availability logistic regression framework, I examined thermal and structural predictors of adult female gestation and overwintering microhabitat selection for the declining eastern diamondback rattlesnake (Crotalus adamanteus; EDB) in the Carolinas. I expected reproductive females (vitellogenic females overwinter, gravid females during gestation) would select microhabitats with cooler or more stable temperatures, denser vegetative cover, and wetter soils to alleviate energetic costs associated with reproduction in a subtropical climate. Habitat models indicated female EDBs required access to a wide range of thermal microhabitat conditions (i.e., cool surface temperatures and warm soil temperatures during gestation, warm surface temperatures and cool soil temperatures while overwintering), suggesting female EDBs employ active thermoregulation most likely to alleviate metabolic effects of opposing seasonal thermal extremes. Overwintering females selected sites with greater coarse woody debris log cover, but other microhabitat structural predictors received little or no support. This work supports EDB conservation strategies incorporating life-history and emphasizes the importance of suitable thermal microhabitats for adult females, especially in context with climate change.