The consistent tendency for left sidedness across the individuals researched was unexpected
SLOTHS ARE SLOW FOR A REASON – TO minimise energy expenditure to survive on a diet of rough foliage. For the same reason, they also scrimp on muscle mass. But new research published in Journal of Zoology shows that they haven’t compromised on their grip strength. Melody Young and colleagues at the New York Institute of Technology have found that the grip of brown-throated three-toed sloths is, relative to their body mass, stronger than any arboreal primate.
“The flexor muscles in the arms and legs are the only compartments they haven’t cut muscle mass from,” says team member Edwin Dickinson.
While hanging suspended from branches is energy efficient, reserves of muscle power may be crucial when climbing up and down trees.
Tantalisingly, all five sloths tested were significantly stronger with their left arms than their right. “One possibility might be that they always hang from the same arm while doing things with the other hand,” says Dickinson.
“Our sloths were often hanging by only one arm and both legs,” says Young. “So it’s possible that’s what’s going on. But we didn’t quantify whether they were using their right or left arms.”
“All we can do for now is speculate recklessly,” says Dickinson.