Science Daily reports on research using stable isotope analysis to identify whether vampire bats are feeding on domestic cattle or wild mammals:
They fed captive vampires blood that was labelled with the stable (non-radioactive) isotope carbon-13 and then monitored the time period between the blood meal and the appearance of labelled carbon atoms in the exhaled breath. “Vampire bats used the freshly ingested blood very fast to fuel their metabolism; after less than an hour the stable carbon isotope signature of the vampires’ exhaled breath was similar to that of their latest diet” Dr Voigt states.
Then the researchers collected breath of free-ranging vampire bats in Costa Rica and analysed its stable carbon isotope signature. “The potential victims of vampires in Costa Rica are either cattle or rainforest mammals such as tapirs and peccaries. These two groups of animals feed on isotopically distinct plants which are grasses in the case of cattle and herbs or shrubs in the case of rainforest mammals. Therefore, we expected that the stable carbon isotope signature in bat breath would change according to their diet” Dr Voigt continues. The vampires’ breath clearly indicated that their last blood meal almost always originated from cattle, although rainforest mammals were also present.