The question of whether you are a righty or a lefty no longer applies just to humans and great apes. It turns out that kangaroos prefer one hand over the other as well.
Most kangaroos prefer to use their left hand to pick up leaves, move food into their mouths, and groom their bodies, according to a study published Thursday in Current Biology.
The finding suggests that "true handedness" may be more widespread across the animal kingdom than was previously thought.
The research was led by Yegor Malashichev of Saint Petersburg State University in Russia. His previous work had shown subtle preferences for one hand over another among marsupials that walk on all four legs like the gray short tailed opossum and the sugar glider, but no one had ever studied whether that also applied to kangaroos living in the wild.
Observing kangaroos in captivity did not reveal any conclusive findings, so the research team went to Tasmania and continental Australia to see red-necked wallabies, red kangaroos, eastern gray kangaroos and Goodfellow's tree kangaroos in their natural environment.
After documenting the habits of more than 70 individual animals, the researchers found that forelimb preferences in kangaroos are actually comparable in strength with human handedness. This was especially true among eastern gray and red kangaroos, who spend most of their lives standing on their hind legs.
"According to a special-assessment scale of handedness adopted for primates, kangaroos pulled down the highest grades," Malashichev said in a statement.
The researchers were also surprised to find that across bipedal species, the kangaroos prefer to use the left, rather than the right hand.
Malashichev and his team report that red kangaroos and eastern gray kangaroos preferentially use their left hands for nearly all tasks. However, among red-necked wallabies, who prefer to use a four-legged gait, the one-handedness was less pronounced. These animals generally used left forelimb for tasks that required fine motor skills, and their right forelimb for those that required more strength.
From these observations the researchers conclude that one-handedness may be more linked to posture than heredity.
One reason the finding is surprising is because forelimb preferences were thought to be tied up with differences between the two hemispheres of the brain seen in placental mammals. However, the researchers write that those differences have not been seen in marsupials.
They write that more work should be done to study the neurobiology of one-handedness in marsupials.