Bats lost the ability to run at least 60 million years ago, when their forelimbs became more adapted for flying. But a new study suggests that the Vampire bat (Desmodus rotundus) may have evolved afresh the ability to be a formidable bounder, to make it easier to obtain its next meal of blood.
Vampire bats were already known to be able to walk forwards, sideways and backwards. Naturalists had reported that they could hop, too. Now it seems that the bats can also break into a loping run on all fours, unlike other bats that merely flounder when not in flight.
Studies reveal that the vampire bat runs by a unique 'bounding gait', so both fore- and hind-limbs leave the ground, and reach a top speed of about six feet a second.
That gait, says the research, published in the journal Nature, is unlike any other seen in four-legged animals. The bats power their stride with long forearms, fingers bent so that the wrists touch the ground. They are walking on their wings, as it were.
Getting most of the push from their long forelimbs the bats run more like a gorilla than a comparable four-legged creature like a mouse. 'This is the first time that a bat has been shown to be able to run,' according to Dr Daniel Riskin and Dr John Hermanson of the Cornell University.
The team made the discovery in Trinidad while carrying out a video analysis of the vampire bats' gait inside a Plexiglas cage, where the bats could run on a custom-made treadmill. The researchers increased the treadmill speed and, at a certain point, the bats made the transition from walking to running. 'It was like, boom, all of a sudden they switched to this bounding gait,' Riskin said.
Although they walk with the same frequency of steps as a similar-sized creature such as a mouse, their galloping gait was at a lower frequency, reflecting how their long forearms allow them to take longer and fewer strides.
In the wild, the bats tend to sneak up on cattle along the ground. The ability to run not only helps the bat get its next meal but also allows it to take evasive action if it is about to be trodden on by its dinner, an animal that weighs 14,000 times more.
Riskin said the bats are more interesting than their usual gothic portrayal would suggest. 'They are very intelligent and social animals, which just happen to have a unique diet,' he said. 'How can an animal that takes only a tablespoon of blood from an animal the size of a cow be called ruthless'
They are smart, he explained: 'The treadmill in our experiments was powered by a drill. I could adjust the speed of the treadmill by squeezing the trigger on the drill. After three or four trials, the bats would see me reaching for the drill and immediately start walking in the direction the treadmill was about to move.
'After we put them in the cage they remembered where the door was, and when we reached to open the door, they would make a break for it ' before it even started opening.' He believes that the bats 'are smarter than dogs'.
Roger Highfield / The Daily Telegraph