Potential for the American toad ( Anaxyrus americanus ) to contribute to biological control in a vegetable agroecosystem

Abstract The American toad ( Anaxyrus americanus ) is a native insectivorous amphibian common in agricultural fields in eastern North America. Past research on this and related species suggests potential for positive or negative effects on pest populations, depending on the prevalence of intraguild predation. We investigated the ecological role of the American toad in a vegetable agroecosystem in Pennsylvania, USA, by (1) characterizing stomach contents of field‐collected individuals in relation to prey availability, (2) identifying drivers of toad foraging behavior through a laboratory experiment, and (3) assessing the net impact of toads on the arthropod community and kale productivity in a preliminary field mesocosm experiment. In toad stomach samples collected across the growing season, rove beetles, ants, ground beetles, and spiders accounted for >80% of the prey consumed. The prevalence of prey taxa in toad stomachs was moderately correlated to field availability after tiny invertebrates were removed ( R 2 = 0.37–0.63). In the laboratory, prey size and movement were more important than prey trophic group in predicting toad foraging behaviors; toads were most likely to attack prey that were >4 mm and actively moving. In field mesocosms, toads significantly reduced the activity‐density of ants and ground beetles yet did not increase pest damage or decrease kale productivity. Our results suggest that the American toad is likely neutral in relation to kale production but deserves further study in a wider range of crop species, owing to the contingency of its effects on traits of crop, pest, and predatory taxa that vary across cropping systems.