Dragon lizards fly by grabbing their fold-up wings with ‘hands’

Hold on tight

Maximilian Dehling

By Bob Holmes

The dragons in the Harry Potter movies fly using wings made from modified forelimbs, just as birds and bats do.

But real dragons — gliding lizards of the genus Draco — form their “wings” from flaps of skin stretched over elongated ribs and use their forelimbs for a different role: to help spread the wings and maybe even steer during flight.

Maximilian Dehling, a herpetologist at the University of Koblenz, Germany, photographed about 50 flights as Draco lizards glided from tree to tree in southern India.

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In every case, immediately after launching from its tree the lizard reached back with its forelimbs, grabbed the unfolding wing – known as a patagium – and spread it forward.

“This is a very rapid movement,” says Dehling. “It’s quite difficult to take photographs of the process.”

The lizard continued holding its patagium until the last moment of the flight, when it let go to use its forelimbs in landing.

Glide on

Maximilian Dehling

To grab its wings, the lizards need to rotate their wrists forward about 90 degrees. When Dehling examined museum specimens, he found that Draco lizards could do this, but other related lizards could not.

This suggests that their limbs have evolved for the task. Besides helping to spread the patagium, the lizard’s grip could also let the animal bend it to steer its flightpath, says Dehling.

If so, it would make the lizard unique among modern flying vertebrates in controlling flight with something other than the flight surface itself. Some fossil reptiles could have used a similar control method, he says.

Dehling isn’t the first to notice the lizards’ unusual mode of flight. “I’ve been well aware of this for years, but not certain that they always do it while gliding,” says Jim McGuire, a herpetologist at the University of California, Berkeley. Dehling’s study is the first to document this, he says.

However, he adds, Dehling hasn’t yet proven that the lizards also steer using their forelimbs. It could be that they arch the back to twist the patagium.

Journal reference: bioRxiv, DOI: 10.1101/086496