Photo showing an orangutan engaged in the TUBE task. Photo used with permission of the researcher William Hopkins.
Mmm, love that peanut butter
Apes are right-handed or left-handed, just like us. Not a big surprise, since they're our closest evolutionary relatives. A research team led by William Hopkins of Agnes Scott College recently tested 777 captive apes - orangutans, gorillas, chimpanzees, and bonobos. Each ape was given a PVC tube 15 cm in length and 2.5 cm in diameter, with peanut butter smeared in both ends. The peanut butter was too far inside to reach with their mouths. The apes had to hold the tube with one hand and reach inside with a finger of the other hand. The researchers recorded which hand the apes used to reach inside for the peanut butter. Each ape was tested on 2 to 4 occasions, in solitude if possible.
Only the orangs were left-handed
Orangutans turned out to be the only southpaws. The majority of gorillas and chimps are right-handed, as are 90% of humans. Bonobos showed no significant handedness at the population level. Hopkins believes that handedness at the population level in apes may be a result of ecological adaptations associated with posture and locomotion (personal communication with Hopkins). He plans further research to try to understand why orangutans are left-handed, while other apes and humans are right-handed in general. It may be somehow related to the fact that orangutans are the most arboreal of the apes.
Hopkins' research will soon be published: Journal of Human Evolution 60 (2011) 605-611.
Orangutans at a sanctuary on Borneo, drinking milk. Note that they're holding hands! Photo: Sally Kneidel
Handedness in crows too
Apes are not the only nonhumans to display handedness. In 2007 I wrote this post about research by Gavin Hunt of the University of Auckland, who documented handedness and tool-making in New Caledonia crows.
Post by Sally Kneidel, PhD
For further reading on primate conservation and behavior, and my observations of wild orangutans on Borneo and Sumatra, check out some of my earlier primate posts:
Some of my earlier primate posts:
Trade a major threat to primate survival. March 21, 2011
We are family: new evidence of our close link to chimps Feb 16, 2011
Is males' attraction to trucks and balls genetically based? Jan 14, 2011
Hunting may threaten orangutans even more than habitat loss Dec 6, 2010
Wildlife trade rivals drug trade in profits September 20, 2010
Laws flaunted: flourishing pet trade threatens orangutans' survival August 23, 2010
My search for a wild orangutan in Borneo and Sumatra August 16, 2010
Orangutans dwindle as Borneo, Sumatra converted to palm-oil plantations August 3, 2010
The great apes are losing ground March, 2010
The U.S. imports 20,000 primates per year. February, 2010
Baboons are Africa's most widespread primate. Females rule! December 30, 2009
Mama monkeys give in to tantrums....when others are watching. April 23, 2009
Angry chimp reveals a "uniquely human" ability. March 21, 2009
Monkeys and parrots pouring from the jungle. September, 2008
Chimps' short-term memory is better than humans' April 2, 2008
Chimps share human trait of altruism August 3, 2007
Keywords: orangutans chimps gorillas apes handedness William Hopkins