By Rose Eveleth
Posting in Technology
New research suggests that we might have overlooked a key part of how bats take off - many of them use their tails for thrust and lift.
There are a lot of untrue myths about bats. They’re not blind, they don’t suck your blood, and they very rarely get stuck in anybody’s hair. But there’s also a lot we don’t know about bats – including the details of how they fly. New research suggests that we might have missed a key part of their flight process: their tails.
In a paper published in PLoS ONE, researchers from the University of Northern Colorado analyzed the flight of five different bat species. What they found was that that bats tails were far more important in generating lift and thrust than anyone had previously thought. As they watched the high-speed videos, they saw the bats fanning their tails during down strokes, and collapsing them during upstrokes.
Here’s one view of what the researchers looked at.
You can see the bat using its tail – also called a uropatagium – to get itself up off the table and into the air. As the authors put in the paper, “the flapping kinematics of the tail-membrane is thus consistent with expectations for an airfoil.”
They also noticed that the timing of the tail thrust and the wing thrust during the down stroke was offset by about 50 percent. So while the wings were retracted, the tail provided thrust. This makes sense in the context of flying, where the goal is to minimize forces pushing downwards during the upstroke, and maximize the air-displacement during the down stroke.
Not all the bats in the study used their tails exactly the same way. The study looked at one particular family of bats, the vespertilionids. Vesper bats are also known as evening bats, or common bats, and are the largest family of bats around with over 300 species. They filmed 95 bats taking off from a stationary position on the platform you see in the video.
Some of these bats flapped their tails faster than their wings, others slower. The way the tail flapped in relation to the wings seemed to have something to do with the direction the bats tried to fly. Those that flew straight and those that tried to fly at a sharper upward angle, had somewhat haphazard patters (illustrated in the picture below) and those that flew at a modest angle had relatively regular tail to wing patterns.
These tail membranes aren’t just important for takeoff. Many bats use them for hunting and navigating. While taking off from this experiment’s flat surface might not seem realistic, many bats now live in and around buildings, and often encounter such level planes.
This paper is the first to document bats using their tails to fly. But understanding bat flight isn’t just for biologists. The military has been attempting to build bat-like flying machines for years. Perhaps with this new information, those little machines will be able to take flight.
Top photo from TeamZissou on Wikimedia Commons
All other photos and videos from PLoS ONE and author Rick A. Adams
Mar 1, 2012