Variables influencing vocalization and breeding effort in the Fowler's toad, Bufo fowleri, in southern New England, United States of America

Extensive mortality and local extirpations of Fowler's toad ( Bufo fowleri) have recently been observed in the northeastern United States and Canada. Monitoring population fluctuations via standardized calling anuran surveys (CAS) and protecting habitats critical to B. fowleri are useful in preventing further population declines in this species. To increase precision of long-term monitoring and to facilitate better protection and management of B. fowleri in New England, the optimal CAS sampling regime for detecting this species was determined and key habitat features that influence breeding effort this species at Cape Cod National Seashore (CACO) were identified. Sixty-six percent of choruses were documented within two hrs of sunset and most calls were heard when surface water and air temperatures were >17.85C° and 20.75C°, respectively. Surface water temperature and Julian date were important predictors of calling, June was identified as the optimal survey window, and three-minute CAS were ample for detecting B. fowleri. Breeding aggregations of B. fowleri were documented more often at permanent wetlands (64%) than at semi-permanent (23.1%) or temporary wetlands (34.5%) and breeding was not influenced by the presence of predaceous fishes or R. catesbeiana . Sites that supported breeding had shallower shores, less emergent vegetation and canopy cover, and were less acidic, clearer and warmer, than sites without breeding. Woody emergent vegetation had the largest effect on breeding effort in B. fowleri, with breeding aggregations typically occurring in wetlands containing < ∼24-33% woody emergent vegetation. High percentages of woody emergent vegetation present in wetlands were structural barrier to oviposition and likely reduced the thermal and chemical suitability of wetlands for successful reproduction in this species. Because the landscape at CACO is well-protected and is uniformly heterogeneous, we were unable to identify landscape features that significantly influenced breeding effort in this species. Thus, in areas where B. fowleri are present, open-canopy, freshwater wetlands with little or no woody emergent vegetation within an undeveloped landscape are likely suitable breeding habitats.