Vampire bats that live in Latin America have switched to blood meals from cattle instead of from rainforest mammals, ecological physiologists report. They say that the conversion of rainforests ecosystems into livestock producing farmland resulted in the expansion of vampire bat populations in Latin America.

Farmers are observing vampire bats satisfying their need for blood by attacking cattle instead of wild mammals. To document this change in behaviour, Dr Christian Voigt and colleagues analysed the stable carbon isotope ratio of exhaled CO2 in vampire bats.

The authors argue that the vampire bats do not necessarily prefer cattle blood, but that cattle are much easier to find for vampires than rainforest mammals. Cattle are held fenced-in on open pastures, whereas rainforest mammals roam in dense vegetation.

Very thoughtful of ranchers to provide fly-in snacks.