Kangaroos are southpaws, showing left-hand preference 95% of time, says study

Kangaroos are left-handed, according to a new study.

The finding challenges a prior assumption that the consistent favouring of one hand over the other is a characteristic unique to humans and certain primates.

Wildlife ecologist Janeane Ingram said it was the first time a marsupial population had been shown to have such a strong preference for one hand, with the observed kangaroos showing a left-handed preference 95% of the time.

The joint study was conducted by the University of Tasmania and University of New South Wales, along with researchers Andrey Giljov, Karina Karenina and associate professor Yegor Malashichev from Saint Petersburg State University, who had first observed the trait in red-necked wallabies kept in Russian zoos.

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Follow-up research into wild red-necked wallabies and eastern grey kangaroos at Maria Island national park and Mount William national park in Tasmania, and red kangaroos at the UNSW arid zone research station at Fowlers Gap, New South Wales, was conducted in 2012 and 2013.

Only kangaroos observed doing the same manual movement (such as grooming) at least 15 times were included. Researchers used special photo-recognition software to keep track of the kangaroos. Thousands of photos were taken.

In 38 observed eastern grey kangaroos, all consistently used their left paw when grooming, bringing objects to their mouth and leaning on one paw while grazing or stepping first on one paw while moving forward.

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The red-necked wallaby also showed a strong preference for the left paw, with one interesting exception.

Ingram said there was a common presumption that kangaroos only graze, and do not pick things up. “But at both national parks we saw red-necked wallabies always used their right paw for strength work, like pulling a branch down, but always brought the leaves to their mouth using their left paw,” she said.

Studies into laterality, or the preference for one side of their body over the other, in animal species is a relatively new field. Laterality has been observed in animals such as jumping frogs, killer whales and four-legged marsupials such as gray short-tailed opossums and sugar gliders.

However, such a consistently strong preference for one or the other as seen with humans, in which 90% of the population have a bias towards their right hand and 10% have bias towards their left, is relatively uncommon.

The discovery marks the first two-legged animal other than humans or great apes – both of which tend to be right-handed – that has exhibited such a strong preference for one hand.

Significantly, a study of the four-limbed Goodfellow’s tree kangaroo at Taronga zoo and several German zoos found no preference for either left or right paw. Ingram said this strengthened the link between posture and handedness.

The finding could contribute to a greater understanding of how the left and right brain hemispheres control laterality, and lead to the discovery of new brain pathways in marsupials.