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Prehistoric bats learned to fly before they could "see"
2/13/2008 11:38:00 AM - Dragana Kovacevic

We all know the adage "you have to learn to walk before you run". But what about learning to see before you fly?

It seems like a logical progression, but it's not the way things happened for bats, a recent study co-authored by the Royal Ontario Museum suggests.

Going 'batty' 52 million years ago

The 2003 unearthing of the most-primitive known bat species turns a previous notion of bat evolution on its head: the fossil of Onychonycteris finneyi suggests that bats learned to fly before they knew how to echolocate - the primary method of "seeing" for modern bats.

Yet it's not clear whether the remarkably well-preserved bat from Wyoming didn't "see" at all, or whether it would have relied on some other sense - perhaps actual eye-sight - to get around.

It's also not clear whether the bat would have spent most of its day awake or whether it was nocturnal, like the bats we're familiar with today, says Dr. Kevin Seymour, a Royal Ontario Museum (ROM) assistant curator of Vertebrate Palaeontology and a co-author of the study.

"We can't say how the bat got around, but we can say how it didn't," Dr. Seymour told DiscoveryChannel.ca. "We need to find more fossils to figure out the first part."

The researchers also couldn't determine whether the preserved bat was male or female.

The team realized Onychonycteris finneyi was different when they noticed the species lacked the ear and throat features present in all living, echolocating bats today, and even other ancient species.

A different way of flying

The bats of 52 million years ago flew differently than the bats of today and looked vastly different.

Onychonycteris had claws on all five of its fingers, whereas modern bats have - at most - claws for only two digits on each hand. It also had longer hind legs, and shorter forearms, similar to those of climbing mammals that hang under branches (such as sloths or gibbons).

This palm-sized critter had broad, short wings that suggest the prehistoric bat couldn't fly as fast or as far as those that evolved later. Instead of flapping its wings continuously while flying it would likely have alternated flapping and gliding while in the air.

The physiology suggests that this species also didn't fly as much as modern bats do - perhaps just to get from tree to tree, spending most of their waking day just climbing or hanging.

"There has been much debate about how bats evolved, because there were no specimens to address this issue" says Dr. Seymour. "Now, the combination of features seen in this species finally gives us an answer: flying evolved first and echolocation must have evolved later."

Echolocation 101

Echolocation - also known as biosonar - is used by animals to navigate their environment and to search of food, among other things. It involves emitting high-pitched squeaks and then listening for the sound bouncing back, once it ricochets off an object.

This ability is one of the defining features of bats, but other animals (such as whales) are known to use it too.

The study is featured in the most recent issue of the journal Nature.