Know Your Primate: Cebus libidinosus

Order: Primates
Suborder: Haplorrhini
Family: Cebidae
Subfamily: Cebinae
Genus: Cebus
Species: Cebus libidinosus
Common Name: Black-striped capuchin
The genus Cebus is, currently, composed of eight species. I was not able to find out much about the black-striped capuchin – other than that it lives in Argentina, Brazil, and Paraguay. I have chosen it in place of it’s more widely known cogeners because of one unique trait.


Capuchin.jpg
Black-striped capuchins use tools in the wild:

“We confirmed that the monkeys were wild. We surveyed the area for lithic (stone) artifacts showing evidence of the nut-cracking activity,” said Fragaszy. From a blind built 15-20 meters from one of the nut-cracking sites frequented by the capuchins, Fragaszy and the team observed a group of wild capuchin monkeys (Cebus libidinosus). The area seemed to offer scarce food resources, especially in a dry season. It contained natural vegetation and, scattered across the site, boulders and exposed rocks that the capuchins used as anvils.
“We surveyed the area and measured the weight of the hammer stones. Our original estimate was 470 grams (16.6 ounces), but on our next trip, funded by National Geographic Society and the L.S.B. Foundation, we found that they were actually over a kilo. Adult capuchin monkeys weigh 3-4 kilos (6.6-8.8 pounds), so they are lifting a third and sometimes a half of their body weight!”

One of the more interesting things about capuchin tool use is that because of the size and strength needed to crack the nuts juveniles are unable to do this, so there is little in the way of teaching (unlike in chimps). As the above linked article puts it:
Capuchin%201.jpg

There is, however, one notable difference in the research on capuchin monkeys, according to Fragaszy. “There is no evidence of teaching. The juvenile monkeys share the propensity to explore objects in a percussive fashion, as children do. They explore, but they are not effective,” she said.
“The effective behavior only appears in mature capuchins. The juveniles are interested in the activity, they play lifting stones and pounding things, they try to crack one nut with another, but they are not strong enough to crack the nuts with the stones.”

There are a number of articles on capuchin tool use available should you wish to learn more
Note added later: Cebus libidinosus is also referred to as a bearded capuchin, I suspect this is the correct common name rather than black-striped capuchin…

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3 Responses

  1. I don’t know if you can say there is direct “teaching” in chimpanzees (or maybe I’ve just missed the lit)? But anyway, the juveniles in Brazil do learn nutcracking, even though they are understandably not as skilled as adults. Think less in terms of teaching or no teaching, and more in terms of social facilitation of learning: the juveniles hang around the skilled adults, and even if they don’t imitate the exact skill after just watching, they learn which objects to play with and in roughly what fashion (some sort of picking up and smashing down). They just tend to smash nuts into each other or use too-small hammer-rocks. I work in Dr. Fragaszy’s lab, and even though the wild tool use is not my own area of study, my peers/friends have been studying just this area — the juveniles’ picking up of the skill over time. Right now, longitudinal studies are going that’ll give us more data.

  2. Ahh, that explains what Dr. Fragaszy was getting at in the last quote. I can think of one – maybe two – papers that address direct teaching, of juveniles, in chimps. Most focus on observational learning by peers (I’m thinking of the research performed by the group at the University of St. Andrews, such as this). One question, normally I like to provide more information on diet, behavior, group size, etc but most of the sources I normally use for this series had no information on Cebus libidinosus

  3. Monkeys have long been known to be imitative. They will try activities they see others doing. Most often others in the troop, but they will also imitate humans. Which gives rise to this question; why are they so dang fascinated with us?

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