Marmosets in the wild can learn new behaviours from strangers — monkeys of the same species but who are not part of their social group — as this video shows. Such a feat had so far only been seen in laboratory conditions.
Tina Gunhold, a cognitive biologist at the University of Vienna, and her collaborators got wild marmosets (Callithrix jacchus) from the Pernambuco region of Brazil to learn how to open a box (and get a reward) from watching videos of other marmosets.
The researchers first trained two captured marmosets to get their treat out of the box in two different ways, either by popping open a lid or by pulling a drawer, and shot videos of the two monkeys' acquired behaviour so that they could serve as unwitting instructors. The team then took the same type of box to the forest and placed it on a tree branch, together with a laptop screen on which they showed either of the two instructional videos. Twelve groups of marmosets — 108 animals in all — got to watch either video or, to serve as controls, a still image showing the instructor next to the box.
Many of the animals failed the class. But some found the video useful: of 12 marmosets that were able to open the box, 11 had watched either video, while only one had figured out the trick by himself. And most of the successful animals used the same technique they had seen in their video. Gunhold and her colleagues report their results in Biology Letters1.
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