Paris - Vampire bats are astonishingly good runners, thanks to an evolved
skill to help them sneak up on their prey, says a study published on Thursday in
the British science weekly Nature.
The blood-sucking species has long
intrigued scientists.
Bats are the only mammals that can fly but have
become so specialised at flight that, over the millennia, they have almost lost
the skill to move on the ground.
The big exception is the vampire bat
(Desmodus rotundus), which is well known for using terrestrial mobility to creep
up on a cow, horse or pig, leap on its back and feast on its
blood.
Whereas its cousins can only shuffle along awkwardly on the
ground, D. rotundus is the batty equivalent of a breakdancer, able to walk
forwards, sideways and backwards and then get flying with a single vertical
jump.
Eager to find out more, animal scientists Daniel Riskin and John
Hermanson at New York's Cornell University built a special treadmill inside a
plexiglass cage and put five adult male vampire bats through their paces, filmed
by a high-speed camera.
The animals used a walking gait at low treadmill
speeds of up to 0.56 metres per second.
They then broke into a loping
run, using the forelimbs of their folded-up wings, to propel themselves forward
when the treadmill was cranked up.
They zipped along at up to 1.14 metres
per second - warp-factor speeds by bat standards.
Even though vampire
bats demonstrably have the ability to run, they are rarely seen practising this
skill in the wild.
The reason, say the scientists: the advent of big
livestock herds in Central and Southern America, which has made food so
plentiful that the bats see no point in rushing if they fancy a
bite.