Flying mammals are a big waste of energy

Bats are the only mammals that can technically fly, but a lot of other creatures do a pretty good impression of flight by gliding down from the tops of tall trees. But there's a problem: this behavior makes no sense.

Lots of small mammals have perfected the art of gliding, using folds of skin to maintain lift over long distances, sometimes as much as a hundred feet across the rainforest canopy. The weird thing is that, according to new research from UC Berkeley and UC Davis, it would be a much better use of energy for the creatures to simply run across the floor of the rainforest as any other creature would. Gliding may look like a leisurely way to get around, but it's actually very taxing on these critters.

The researchers attached motion sensors to the backs of four colugos, a type of lemur found in southeast Asia and the Philippines. They found that it consistently took 1.5 times the amount of energy for these colugos to glide over a given distance than it would for them to travel that far on foot.

It's not just a question of why the colugos would bother gliding when it's so energy-intensive - more to the point, why did it and other gliding species evolve that ability at all if it's such an inefficient adaptation? The researchers believe that simple survival may have trumped energy concerns for these mammals - being able to glide over dangerous terrain would have protected them from predators, and the ability to glide would give them a built-in safety net if they fell off a branch while trying to eat from leaves in the canopy.

Journal of Experimental Biology via ScienceNOW. Image via.