Three mouse lemurs (Microcebus murinus) peer cautiously from their nesting tube at the sound of an approaching Duke Lemur Center technician who might just be carrying snacks. Credit: David Haring, Duke Lemur Center

Anyone who has ever owned a pet will tell you that it has a unique personality. Yet only in the last 10 years has the study of animal personality started to gain ground with behavioral ecologists, said Jennifer Verdolin of the National Evolutionary Synthesis Center, in Durham, NC.

She and a colleague have now found distinct personalities in the grey mouse lemur (Microcebus murinus), the tiny, saucer-eyed primate native to the African island of Madagascar.

In a study published in the journal Primates, Verdolin gave fourteen gray mouse lemurs living at the Duke Lemur Center a personality test.

Verdolin filmed the lemurs' reactions to a variety of familiar and unfamiliar objects—such as a tissue box, an egg carton, an orange ball, and a stuffed toy frog – which she placed one at a time into the animals' enclosures. She then measured how long it took each animal to work up the nerve to approach and investigate each object. Mouse lemurs that were quick to approach objects were considered "bold," whereas those that behaved more cautiously were considered "shy."

She also noted how agitated the lemurs got when handled by their human caretakers during routine weigh-ins and cleanings.

Verdolin found that those that hung back were also harder for their human caretakers to handle, meaning the lemurs' distinct personality traits held up across a range of situations.

The report that mouse lemurs have distinct personalities doesn't come as a shock to staff at the Duke Lemur Center. "[The mouse lemur named] Pesto is very chatty. Asparagus gets beat up by the girls. Wasabi is mean as sin, and her favorite flavor is human fingers," said Duke Lemur Center researcher Sarah Zehr, who was not an author of the study. Other scientists have also found evidence of personality differences among grey mouse lemurs living in the wild.

But for animals living in captivity, Verdolin hopes that personality studies like hers will help researchers determine which individuals are best candidates for breeding programs or for reintroduction back into the wild, as has been done with the North American swift fox, the giant panda, and the golden lion tamarin.

The next step, Verdolin says, is to determine the extent to which lemur personalities are influenced by the presence of other individuals, or whether behavioral training for some personality types could improve their chances of surviving in the wild.

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More information: "Are shy individuals less behaviorally variable? Insights from a captive population of mouse lemurs," Verdolin, J. and J. Harper. Primates, June 2013. "Are shy individuals less behaviorally variable? Insights from a captive population of mouse lemurs," Verdolin, J. and J. Harper. Primates, June 2013. dx.doi.org/10.1007/s10329-013-0360-8 . Study data available in the Dryad Digital Repository at dx.doi.org/10.5061/dryad.5m083