Feeding, thermoregulation, and offspring viability in gravid garter snakes(Thamnophis sirtalis): What makes laboratory results believable?

Animals held in the unnatural surroundings of the laboratory sometimes may exhibit unusual behavior, making experimental results difficult to interpre t unless the natural history of the species is well understood, Some well-s tudied species, such as the garter snake Thamnophis sirtalis, which usually seem to adapt well. to captivity, are therefore commonly used in laborator y experiments and assumed to function normally. However, this assumption ma y sometimes be unfounded, In this study, captive gravid T. sirtalis showed reduced feeding behavior, similar to free-ranging gravid snakes from the sa me population but showed very different thermoregulatory behavior, choosing low temperatures instead of high, By contrast, gravid congeners, Thamnophi s elegans, showed similar feeding and thermoregulatory behavior in captivit y and in the field. Choice of lower temperature by gravid T.sirtalis appare ntly led to extended periods of parturition for individual females and a hi gh incidence of dead young in litters, other studies of T. sirtalis in capt ivity also have yielded fairly high proportions of dead offspring, suggesti ng that (1) this species has a relatively high background rate of natural s tillbirth; and/or (2) it is not always as suitable a species for behavioral /reproductive work in the laboratory as it seems to be. Whether or not the first proposition is true, I conclude that T. sirtalis in this study behave d differently from snakes in the field, exacerbating the rate of stillbirth . Thus, laboratory studies of behavior will be most fruitful if informed by field studies.