Factors Influencing Anuran Wetland Occupancy in an Agricultural Landscape

Abstract/Summary

Habitat disturbance is an important cause of global amphibian declines, with especially strong effects in areas of high agricultural use. Determining the influence of site characteristics on amphibian presence and success is vital to developing effective conservation strategies. We used occupancy analysis to estimate presence of four anuran species at wetlands in northern Iowa as a function of eight environmental covariates hypothesized to affect occupancy: fish abundance, salamander abundance, invertebrate density, aquatic vegetative cover, wetland area, atrazine concentration in water, surrounding crop land use, and an overall wetland health score. We surveyed 27 wetlands in 2015 and 2016. Wetland site occupancy for all species in our study ranged from https://0.23 (Hyla spp. tadpoles) to https://0.95 (L. pipiens adults), indicating agricultural wetlands can provide refuge or habitat for amphibians. Detection probabilities ranged from https://0.13 (P. maculata adults) to https://0.61 (A. americanus adults). Fish abundance, percent of surrounding cropland within 500 m of the wetland, and salamander abundance were among the variables best supported in our model sets although their estimated effects were weak. The direction of predicted effects varied by species and life stage.Although we did not find strong evidence that the environmental factors we measured influenced amphibian populations in our study, we provide insight for managers and researchers on how amphibians use a landscape modified by agriculture.