Prey choice of the common vampire bat on introduced species in an Atlantic forest land-bridge island

The proliferation of native, alien, invasive and domestic species provide novel and abundant food resources for the common vampire bat (Desmodus rotundus) that could alter its prey preference. Based on the analysis of carbon and nitrogen stable isotopes, we report the prey choice of D. rotundus on introduced mammals in an tropical land-bridge island where the domestic animals were removed and 100 individuals of 15 mammal species were intentionally introduced. Our analysis shows that, D. rotundus on Anchieta Island were more likely to prey upon species from open habitats , i.e., animals with high C values characterized by the consumption of C4 resources. As expected for a top predator species, N values for D. rotundus were higher and overlapped the niche of the capybaras (Hydrochoerus hydrochaeris) from the Anchieta Island, while it was distant from coatis, and also from those potential prey from the preserved area in the mainland, including the capybaras, indicating that among all potential mammalian prey species, they fed exclusively on capybaras, the highest mammalian biomass on island. Based on previous information on human occupation, the domestic animals present on Anchieta island might be the main prey of D. rotundus and responsible for maintaining a viable population. As the capybaras were introduced only 36 years ago, this suggests a rapid prey shift due to anthropogenic disturbances, which has allowed common vampire bats to successfully exploit them. Literature records also show that common vampire bats were not captured in preserved areas of the mainland which are near Anchieta Island indicating that the percentage of capture of D. rotundus is usually low in natural forested habitats where potential prey are scattered. As three individuals of introduced capybaras were confirmed died from bat rabies viruses (RABV) in 2020, we suggest periodic monitoring of bat rabies viruses in common vampire bat populations on Anchieta Island and areas nearby, in order to quantify the magnitude of the outbreak area and develop strategies for controlling, especially considering that the island and areas nearby is frequently visited by tourists. We highlighted that this prey choice is context-dependent, and possibly influenced by the removal of domestic animals, the explosive population growth of introduced capybaras combined with their predictable foraging behavior.