Dracula's Most Recent Prey

By Sam Ofori
Inside Science News Service
October 30, 2007

(College Park, MD) -- In ancient times, the pursuit of the elusive Dracula proved to be a difficult task for that era’s investigators. Those chasing Dracula might have been more successful, however, if they’d had the tools of modern science – particularly a method recently developed by researchers in Germany that allows them to determine the identity of a bloodsucker’s last victim.

Scientists from the Leibniz Institute for Zoo and Wildlife Research, observed noticeable shifts in diet preference of vampire bats from Costa Rica by analyzing their breath. Various rain forest animals, as well as cattle, consume different species of vegetation that may be uniquely distinguished by the presence of numerical variance in their stable carbon isotopes. The plant life being used for food was grassland and pastures in the case of cattle, and shrubs in the case of rainforest mammals.  In view of the fact that these chemical signatures are present in the victims' blood system, the clue found in the bats breath fluctuates with their meals.

To confirm the hypothesis, an experiment was conducted. The outcome was found by analyzing the stable carbon isotope ratio of exhaled CO2 from captive bats. These caged vampires were fed with blood that was labeled with the stable (non-radioactive) isotope carbon-13 and then monitored for the time period between the blood meal, and the appearance of labeled carbon atoms in the exhaled breath. According to team member Dr. Christian Voigt of Leibniz Institute for Zoo and Wildlife Research : "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."

With the steady conversion of the rainforest ecological unit into farm animal producing land, the cattle are much more accessible to the vampires because they are enclosed in open pastures; whereas rainforest mammals such as peccaries, forest monkeys or even tapirs are free to roam in dense and thick vegetation. According to the recent studies carried out, the vampire bats' last victims were almost always cattle, rather than wild rainforest mammals which they were used to.

In light of the upcoming Halloween season all mammals, whether cattle or even human, should be vigilant because we might be all at risk of being the vampire’s next victim.

Inside Science News Service is produced under the auspices of the American Institute of Physics, publisher of several leading journals in the physical sciences.