Non‐native stinging ant interactions with native anurans

Abstract

AbstractNative predators may ignore or avoid non‐native prey because they do not recognize the novel organisms as food, or the invasive prey may bring antipredatory defences against which the native predators have not co‐evolved a sufficient attack. Non‐native ants successfully invade novel habitats worldwide and, in eastern North America, several invasive ant species bring venomous stings in quantities that far exceed that of native ant species. Ants make up a considerable portion of anuran diets, and we investigated how several native anurans reacted to the invasion of the non‐native European fire ant (Myrmica rubra). Myrmica rubra has a venomous sting, and it occurs in aggressive swarms that can deliver multiple stings. Despite these defences, based on field observations, we expected that leopard frogs (Lithobates pipiens) might consume the abundant ants. We also predicted that habitat niche differences from the moisture‐dependent ants would limit consumption by the more terrestrial American toads (Anaxyrus americanus) and more aquatic green frogs (Lithobates clamitans). Our results suggested that none of the anuran species make use of the M. rubra swarms. The anurans, particularly A. americanus, consumed ample native ants in the field, but not M. rubra ants. In the laboratory, A. americanus ate several M. rubra ants, and L. pipiens a few, but experienced anuran individuals collected from M. rubra‐invaded habitat were less likely to eat the ants in laboratory. Hence, at best, M. rubra invasion appears to supplant rather than supplement anuran food resources.