Lemurs have identifiable personality traits that are consistent from situation to situation, and those tendencies may have evolutionary implications, according to a new study conducted at the Duke Lemur Center.
She placed items such as a tiny chair, a wooden ladybug, and a stuffed toy frog, as well as new foods such as mango and papaya, into the animals’ enclosures. After classifying individual lemurs’ reactions, she monitored how agitated they became during routine handling for cage cleaning and health measurements.
Bolder lemurs—those who spent more time interacting with the new objects—were less likely to urinate, defecate, bite, or otherwise protest when handled, compared with their counterparts who had avoided the unfamiliar objects. (The study didn’t find a measurable difference in their reactions to the new foods, perhaps a sign that the lemurs did not perceive them as unusual.)
Verdolin explained that these protest reactions likely reflect fear, and that the bolder lemurs responded with more confidence in the stressful situations. Bold lemurs may be more likely than shy ones to adapt to uncertain or changing environmental conditions, and boldness and shyness may run in families.
“There’s actually evidence of heritability in these traits,” Verdolin explained, which would have implications for the evolution of the species.
“Of course natural selection can’t work on something that’s not heritable,” said Verdolin.
Since the time of her study, the lemurs have had offspring.
Up next? Verdolin says she would love to return to explore whether the traits have been passed down.
“If you have a bold mother, are you going to be bold too?” she asked.
The idea of studying animal personalities has experienced a bit of a boom in the last decade, countering the prevailing tendency by animal researchers to treat individual variation in animals as statistical noise. Some work in the early 20th century with chimpanzees explored the idea of animal personalities, but research has really taken off since an influential paper on the subject was published in 2004.
Many scientists still shy away from even using the term personality when talking about animals, favoring the less anthropomorphizing term “behavioral syndromes.” But both terms refer to individual animals reacting in the same way under different circumstances. “I personally don’t have a problem with using the term personality,” Verdolin said.
Verdolin sees the recognition of animal personalities as key to our understanding of species. “We have to remember we can’t just blankly categorize an entire species as being one way,” she said.
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