Forest harvesting generates attractive breeding habitat for male Eastern Gray Treefrogs (Dryophytes versicolor) at their poleward range edge

Abstract

Climate change and anthropogenic disturbance are changing many species' ranges. Anthropogenic habitat modification typically restricts species ranges, but at poleward range edges it could create warmer microclimates that offset marginal climatic conditions. I hypothesized that clearcutting is creating warmer, more favourable breeding habitat at the expanding, poleward range edge of the Eastern Gray Treefrog (Dryophytes versicolor). Using an autodetection tool and passive acoustic monitoring, I found higher calling activity at recently clearcut ponds compared to forested ponds. Structural equation modelling revealed significant direct effects of warmer air and pond surface temperatures on calling activity. Reduced canopy cover, leading to higher pond surface temperatures, were the key mediators between harvesting and increased calling activity. Clearcut ponds were 1.9±0.5 degrees warmer than forested ponds during the breeding season, which could facilitate faster tadpole development. However, I found no difference in tadpole food resources (periphyton production) between clearcut and forested ponds. These findings demonstrate how microclimate and anthropogenic disturbance influence breeding habitat at a poleward range edge. However, we still require crucial information on pond preference of females, tadpole development, and juvenile survival as a measure of fitness, and to determine whether anthropogenic habitat modification is facilitating this range expansion.