Reproduction of the Plains Garter Snake,Thamnophis radix, Near Its Northern Range Limit: More Evidence for a “Fast” Life History

Abstract

Do high-latitude environments constrain life histories of ectotherms? One expectation is that shorter and cooler active seasons at high latitudes limit opportunities for maintenance of optimum body temperature and restrict time for foraging and therefore for growth and reproduction. Thus, under this hypothesis, individuals in high-latitude populations of wide-ranging species would be predicted to grow more slowly, have lower reproductive output, and perhaps reproduce less frequently than lower-latitude conspecifics. However, at Miquelon Lake in central Alberta, the Plains Garter Snake (Thamnophis radix) grows as fast annually as more southerly conspecifics and reaches sexual maturity at the same age. Here, we make a comparable test of latitudinal variation in reproductive traits. Both litter size and offspring size were larger in the Miquelon Lake population than at lower latitudes. Moreover, female snakes could reproduce annually, although the frequency of annual reproduction remains unknown. Litter size...