The Eastern American Toad, Anaxyrus americanus americanus (Holbrook, 1836) is an ubiquitous and geographically wide-ranging subspecies of eastern North America. As such, it also varies geographically in several of its life history traits. A statewide examination of its gonadal cycles and body size-age relationships in Pennsylvania revealed a conformity to contemporary latitudinal patterns associated with these life history traits. Likewise, these very responses to spatial differences in climate, we proffer, predispose the Eastern American Toad to climate-change related shifts in timing of reproduction in Pennsylvania. Such a change, depending upon the reproductive response to climate change by Fowler's Toad, Anaxyrus fowleri (Hinckley, 1882), could result in an increased likelihood of hybridization, a phenomenon with significant evolutionary implications.