Backpacking flying lemurs reveal their gliding secrets

The development of a custom-designed three dimensional acceleration sensing 'backpack' has enabled scientists to examine the gliding and landing behaviour of a largely unknown nocturnal mammal in its natural habitat. The study, published today in the journal Proceedings of the Royal Society B, has provided important information which improves our understanding of the behaviour and biomechanics of gliding animals, and could aid in the design of flexible winged aircraft, like hang-gliders or micro-air vehicles.

Malayan colugos are incredible animals. They resemble very large flying squirrels, yet are a cousin to primates (adults measure around 30-40 cms long) with wings of skin between their hands and feet that are the size of a large doormat when extended.

“Despite being common throughout their natural range the Malayan colugo is quite poorly understood because it's hard to measure things about an animal that moves around at night, lives 30 metres up a tree, and can glide 100 metres away from you in an arbitrary direction in 10 seconds,” said Andrew Spence, RCUK research fellow in biomechanics at the Royal Veterinary College, who teamed up with colleagues Greg Byrnes and Norman Lim. “Our new sensing backpacks have given us an insight into the behaviour of these fascinating creatures and we can now use this new technology to learn more about other inaccessible and understudied animals in the future.”

The researchers were able to prove that the colugo can alter the aerodynamic forces acting upon it in flight, in order to reduce the effect of landing forces, and thus limit risk of injury. The creatures are able to glide at a steady speed and as they come in for landing they appear to be able to do a very precise manoevre that slows their speed and simultaneously orientates them correctly for spreading the impact of landing across all four limbs. The researchers were able to demonstrate a drastic reduction in landing forces for glides longer than about two seconds, where colugos are able to perform a parachute-like behaviour and re-orient themselves. This reduction in impact forces over long gliding distances has been predicted from aerodynamic theory, but until now scientists have not been able to demonstrate it conclusively in the wild.

By combining tiny microelectronic sensors and memory devices, such as the acceleration sensors that are used in automobile airbags and the Nintendo Wii controller, with memory chips founds in devices like the Ipod, the researchers were able to design miniature 'backpacks' that could be adhered to the colugo to register its movement. The researchers, working in the rainforests of Singapore and partly funded by the Singapore Zoological Gardens, were able to carefully catch the nocturnal adult colugos by hand whilst they were resting low on trees during the day. They shaved a small patch of fur off the animal, stuck the backback to its exposed skin using a surgical glue and released the animals back in the wild. Colugos, which can weigh up to 2 kg, were able to wear the sensors and glide uninhibited for several days before the adhesive naturally fails and the backpack falls to the ground. The backpacks were then recovered using a radio receiver.