Flying Lemurs With "Backpacks" Reveal Gliding Secrets

Ker Than
for National Geographic News

February 12, 2008

Gliding mammals equipped with high-tech "backpacks" chock full of sensors are giving scientists new insights into aerial maneuverability, a new study reports.

The study focused on the Malayan colugo, a cat-size animal commonly called a flying lemur—even though it is not a true lemur, nor does it technically fly.

(Related news: "Flying Lemurs Are Primates' Closest Kin" [November 1, 2007].)

Instead the animal coasts between trees using a skin membrane attached to its hands and feet called a patagium.

Colugos can glide for the length of two football fields (360 feet, or 110 meters), maneuver around obstacles, and execute 90-degree turns in midair.

To learn the secrets of the creatures' agility and how they can land safely after long glides, researchers glued small packages of sensors to several animals' backs.

The packs—each about the size of half a stick of gum—included motion-detection technology similar to that found in the remote control for the Nintendo Wii video-game console.

The findings shed new light on the biomechanics of gliding animals and could aid in the design of flexible-wing aircraft such as hang gliders, the study authors say.

"By studying how gliding animals control their membrane, we can learn more about how to control flexible wings," said study team member Greg Byrnes of the University of California, Berkeley.

Byrnes and colleagues describe their research in the online issue of the journal Proceedings of the Royal Society B.

Ace the Landing

The scientists caught adult colugos in the forests of the Singapore Zoological Garden as the nocturnal animals rested during the day. (Find out more about Singapore.)

Patches of fur were shaved off the animals' backs, and surgical glue was used to attach the electronic backpacks.

Included in each pack were a motion-sensitive accelerometer, a Flash hard drive to store data, and a radio receiver to allow the researchers to locate the devices after the glue wore off.

Data collected by the devices confirmed something scientists had long suspected but had never proven: Gliding mammals use their skin membranes like parachutes.

This means that—unlike leaping animals, which land harder the farther they jump—gliding mammals can achieve softer landings after longer glides.

Change Posture

The new study is the first to demonstrate this parachuting behavior in the wild, said Brigitte Demes, an expert in animal biomechanics at Stony Brook University in New York, who was not involved in the work.

"Prior lab studies did not find a reduction in landing forces with increased gliding distance, probably because the glides in the lab were too short," Demes said.

The new research showed that colugos make considerably softer landings for glides lasting longer than two seconds.

The study also revealed that the animals change their postures in a very precise way to slow down before landing.

In addition, they reorient their bodies so that all four limbs help absorb the impact.

"When they're gliding normally, they're pretty close to parallel to the ground," study author Byrnes said.

"But before they land, they pitch upward and use their patagiums like the parachute on the back of a race car to slow their momentum."

Patricia Wright is a primatologist also at Stony Brook University and a member of the National Geographic Society's Conservation Trust. (National Geographic News is part of the National Geographic Society.)

She had observed gliding colugos in the wild change their posture before landing, but she didn't think much of it at the time.

"I'd seen it, but I didn't know it was like a strategy," said Wright, who was not involved in the new study. "It was fun to find that out."

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