A new research has shown that Kangaroos prefer to use their left, not the right, hand for their everyday tasks – a finding that challenges the notion that handedness among mammals is unique to primates.
Published in Cell Press journal Current Biology, the research carried out on wild kangaroos found that there is a natural preference for left hands when performing particular actions, including grooming the nose, picking a leaf, or bending a tree branch. Researchers also found that left-handedness was particularly apparent in eastern grey and red kangaroos.
Further, red-necked wallabies prefer their left hand for some tasks and their right for others. Generally put, they use their left forelimb for tasks that involve fine manipulation and the right for tasks that require more physical strength. The researchers found less evidence for handedness in species that spend their days in the trees.
“According to a special-assessment scale of handedness adopted for primates, kangaroos pulled down the highest grades,” says Yegor Malashichev of Saint Petersburg State University in Russia. “We observed a remarkable consistency in responses across bipedal species in that they all prefer to use the left, not the right, hand.”
One reason true handedness wasn’t expected in kangaroos–or other marsupials, for that matter–is because, unlike other mammals, they lack the same neural circuit that bridges the left and right hemispheres of the brain. Studies of kangaroos living in captivity hadn’t yielded conclusive evidence either. In the study, to find out what wild kangaroos really do when left to their own devices, the researchers watched these iconic animals in Tasmania and continental Australia.
“What we observed in reality we did not initially expect,” Malashichev says. “But the more we observed, the more it became obvious that there is something really new and interesting in the wild.”
The findings should encourage more careful study of the marsupial brain, which differs from those of other mammals in many respects. Such studies might even yield important insight into neuropsychiatric conditions, including schizophrenia and autism, the researchers say, noting links between those disorders and handedness.
The researchers will continue to explore handedness in other species that stand upright regularly or from time to time. “This will give us a better resolution for the evolutionary interpretations,” Malashichev says.