One fifth of all mammals are bats. Here's why.

Bats are everywhere, and they eat everything from fruit to blood. What keeps these small, furry fliers winning the natural selection game? A group of researchers tried to answer this question by studying the evolution of a particularly diverse group of bats. They discovered that the success of bats is all about body modification.

Photo by Leyo.

Specifically, the North American leaf-nosed bats these researchers studied had evolved new skull shapes quite quickly. Animals with the slightly-different skulls were able to bite harder than their predecessors, and started chomping on hard fruit as well as soft. Once they'd mastered the art of crunching, these bats could move into new environments, and new species of leaf-nosed bat evolved. Body changes — the result of evolutionary mutations — preceded their ability to colonize new areas.

Write the authors:

The evolution of diet was associated with skull morphology, and morphology was tightly coupled with biting performance, linking phenotype to new niches through performance. Following the increase in speciation rate, the rate of morphological evolution slowed, while the rate of evolution in diet increased. This pattern suggests that morphology stabilized, and niches within the new adaptive zone of frugivory were filled rapidly, after the evolution of a new cranial phenotype that resulted in a certain level of mechanical efficiency.

Video by Dan Riskin

So why do bats represent such a large number of mammals? Based on this study, published today in Proceedings of the Royal Society B, the researchers would argue it has to do with the animals' ability to diversify quickly in new environments — and that a big part of that is bats' extremely varied diets. Bat species range from nectar-sippers to insect-eaters and blood-munchers, and this allows them to spread into new territories.

A result of this success is that bats vary tremendously from species to species. Some are the size of insects, while others are more like small dogs. Bats can live anywhere, but most individual bat species have evolved to thrive in a specific region.

Several science fiction authors have dealt with the idea that humans will have to diversify like bats if they want to adapt to environments in space. In The Quiet War, Paul McAuley writes about a conflict between the body-modding, environment-hacking settlers on the outer planets, and the people who stay on Earth where human body evolved. Perhaps one day humans will look as dissimilar as bat species do — because some of us modify our DNA to thrive in the methane-saturated atmosphere of Titan, while others change themselves to suit environments even more unimaginable.

Further reading:

"Morphological innovation, diversification and invasion of a new adaptive zone," via Royal Society B

Dan Riskin's Bat Photos