I had my first experience with bats over 20 years ago in the tiny village of East Coker, in the southwest of England. Unfortunately, it wasn’t a very good one!
I had gone to East Coker in search of the burial place of T.S. Eliot, the American poet who made his home in England and immortalized this quaint village in “The Four Quartets.” I entered the deserted graveyard, walked up to the 12th century church of St. Michael, pushed the door open and screamed. A swarm of bats, dozens of them, screeched past me, flapping their wings and escaping into the warm summer evening. It was several minutes before I regained my composure, entered the church and found the burial plaque I was looking for.
Despite this unpleasant introduction, I later began wondering how these fascinating creatures — which are mammals, not birds — can muster the energy to take off and fly out so quickly. Indeed, it was both the unexpectedness of finding bats, as well as their rapid exit, which unnerved me.
Bats are the only mammals capable of free flight, able to launch into flight from a still position.
There are other types of gliding mammals, such as flying squirrels, flying lemurs and numerous varieties of gliders. But unlike bats, these creatures must launch from a high point in order to glide to a lower point. So they are really jumping animals.
So how do bats manage to take off and fly?
A team of biologists at Brown University recently decided to investigate exactly how bats manage to be the only mammals truly capable of sustained flight.
Using XROMM (X-ray Reconstruction of Moving Morphology), they took ultra high-speed X-ray videos of Seba’s short-tailed bats (i.e., fruit bats) as the creatures lifted themselves off the ground and discovered that their extra-stretchy biceps and triceps tendons are crucial for storing and releasing the energy needed for takeoff.
VIDEO: X-Ray of a Bat Taking Flight
Their analysis, which they presented on July 5 at a meeting of the Society for Experimental Biology, showed that the bats first stretch out the tendons that anchor their biceps and triceps muscles to their bones, and then compress the tendons to release energy and power their flight upward.
This finding was confirmed by another innovative method of studying the fruit bat’s anatomy in motion: a technology called fluoromicrometry, in which chemically labeled markers are injected into the animal’s muscles. These let the researchers directly measure changes in the length of the muscles during contraction and expansion as part of flight. Calculations showed that energy output associated with the changes in muscle length alone couldn’t provide enough power for flight, further pointing towards the role of stretchy tendons.
The discovery comes as something of a surprise to biologists, who previously believed that small mammals have tendons that are too stiff and thick to be stretched at all. But this capability, and their associated ability to fly, provides further evidence that bats are truly unique among their kind.
Bat wings are of course very different from bird wings. And now we know exactly how those bat arms, elbows and very long finger bones connected by two layers of thin skin operate. Bat thumbs, by the way, are separate little claws that help with climbing.
Of course, bats are great friends of farmers, since they eat insects that can destroy vegetable and fruit crops. A single brown bat can eat up to 1,000 mosquitoes an hour.
I suppose I didn’t need to worry on that summer night; any bat flying towards me was probably only interested in snacking on the mosquitoes or moths hovering around my head.
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