Loss of Habitat Leads to Bigger Toads and Bigger Eggs: Natural Area Management Predictions for the Eastern American Toad, Anaxyrus americanus americanus (Holbrook, 1836)

Abstract

Reproductive characteristics of the Eastern American Toad (Anaxyrus americanus americanus) vary geographically across its broad eastern North American range. Northern populations are known to breed for a shorter period that begins later in the season (April and/or May) than southern populations that can begin in winter and last until April. Delayed maturity and larger minimum body size are also associated with northern populations. Specimens collected during two years of systematic trapping during 1982–1983 at the Powdermill Nature Reserve (PNR), Westmoreland County, Pennsylvania, were examined to test predictions of geographic patterns associated with reproduction and growth of a southwestern Pennsylvania population. The results indicate a short egg laying season in May, large adult body size, and delayed maturity. An apparent response to northern Allegheny climate, the reproductive-related patterns of this population were similar to those of other northern regions rather than populations at similar latitudes within Pennsylvania. Eastern American Toads collected from a breeding site at PNR in 2014 were larger in body size, clutch size, and egg size than those of the 1982–1983 study. Most notably, loss of open breeding habitat in the 30+ years between sampling periods resulted in fewer larger toads producing on average larger eggs and twice the clutch size than counterparts studied during earlier successional series of this study site. These differences quantify geographic and temporal variability in life history traits of an ecologically versatile and geographically widespread species and provide landscape-wide predictions of life history responses by the Eastern American Toad to natural or human-mediated changes to natural areas.