News in Science

What's that Skippy? You're left handed!

Leftie kangaroos Kangaroos prefer to use their left forelimb to do things, say researchers, who have reported the first ever discovery of human-like handedness in animals.

The study, published today in the journal Current Biology, found that wallabies and bettongs also had this trait, referred to by scientists as 'true' handedness.

"What we see in kangaroos is the same strength of handedness as we see in humans,", says lead author, Associate Professor Yegor Malashichev, a zoologist at Saint Petersburg State University in Russia.

"But the direction of this handedness is opposite to humans ... They use their left forelimb to wipe their snout, or to collect food and so on."

True handedness refers to a population-wide trend in which the majority of individuals prefer one hand over the other to carry out a number of tasks, says Malashichev.

He says most scientists have traditionally thought that such handedness was unique to humans.

"In the majority of cases, animals have only individual preferences. If you take one individual it can have a right or left preference, but another individual will have a different kind of preference, and the third one will have no preference."

However for the first time ever, Malashichev and colleagues have observed true handedness in non-human animals in the wild.

The research, carried out in Tasmania, involved observing over 100 kangaroos and wallabies going about their daily business.

Both kangaroos and wallabies were found to be strongly handed like humans, but their handedness differed.

While both preferred using their left hand to groom and hold food, only kangaroos preferred using their left hand to support their body.

While kangaroos eat grass, wallabies eat leaves from tree branches. This adaptation to different ecologies is likely the reason why wallabies prefer to use their right hand for some tasks, says Malashichev.

They use their right hand for supporting their body, and for grabbing on to branches, while using their left hand to rip off leaves and feed themselves, says Malashichev.

As well as collecting data on red kangaroos, eastern grey kangaroos and red-necked wallabies in the wild, the researchers also collected data on captive bettong, Goodfellow's tree kangaroo, sugar glider and grey short-tailed opossum.

True handedness was only seen in kangaroos, wallabies and bettongs (which were also left handed).

Malashichev says like humans, these bipedal marsupials stand on two feet, and this may explain why they have all developed true handedness.

"The significant difference between bipedal and quadrupedal macropods reinforces [an] evolutionary link between posture and handedness", says Australian team-member Janeane Ingram from the University of Tasmania.

The research was supported by a National Geographic Society Committee for Research and Exploration grant and the Russian Scientific Fund.