Amphibian populations have been declining worldwide and they are part of the global biodiversity crisis. The growing human population increases the risk of habitat loss for amphibians, but the way that land is managed could mitigate these risks and even bolster local populations. We conducted frog call surveys for four species of summer-breeding frogs in an exurban landscape--semi-rural areas outside of the suburbs of a city. These species of amphibians (Blanchard’s cricket frog [Acris blanchardi], gray treefrogs [Hyla versicolor/chrysocelis], bullfrogs [Lithobates catesbianus], and green frogs [Lithobates clamitans]) occur across a habitat gradient from open to close canopy. Our central hypothesis was that land cover and management associated with exurban parcels influence amphibian presence and abundance more than other parcel- or landscape-level factors. We predicted that management that led to heterogeneous land cover will increase presence and abundance of amphibians. We used ArcGIS to select parcels between 1-20 acres with a pond in an unincorporated area in Butler County, Ohio. We classified the parcels by typology: open canopy (grass, pasture, mown lawn), mixed canopy (50% open, 50% closed), or closed canopy (forest). We randomly selected 96 parcels for frog call surveys to determine the presence and abundance in those particular sites. Using AICc model selection, we examined if other factors influenced the presence of frogs at a given site, including % land cover (forest, cultivation, pasture, recreational grasses, development) in a 1 km buffer, meters of roads or streams in a 1 km buffer, age of the house on the parcel, size of the pond, and property value, as well as parcel typology.
Results/Conclusions
We found that the presence and abundance of gray treefrogs and the abundance of American bullfrogs increased with forested land cover, the historic land cover in Ohio. Interestingly, cricket frogs, which are a species of concern in Ohio, were the most commonly encountered and most abundant species found in these ponds, suggesting that exurban ponds provide important habitat for this species. AICc model selection, however, indicated that size of the ponds and age of the homes provided the best models to explain amphibian presence. In conclusion, our study indicated that ponds in the exurban landscape provide important habitat for amphibians, that presence of forest increased the abundance and presence of some species, and that other factors like age and size of the pond may be more important than parcel habitat for summer breeding amphibians.