What’s in a somersault? A flap of the lip, a spit of water in the face? More than meets the eye, it seems. They may all be new ways of communicating that orangutans have come up with in captivity. This suggests that such gestural creativity may be ancestral in the great ape line, adding a new piece to the puzzle of language evolution.
Using new expressions to convey things – known as productivity in linguistics – is one of the fundamental building blocks of complex language, and it is rarely reported in the animal kingdom. Instead, most animals have a fixed set of messages, the meanings of which are determined by the context – such as the arrival of a predator. These signals seem to be innate rather than being learned, and have formed through a long process of natural selection.
Humans clearly show productivity, but whether other apes do is debated. To explore, Marlen Fröhlich at the University of Zurich in Switzerland and her colleagues looked at the question from a new angle, by exploring whether orangutans held in captivity in zoos have developed new ways to communicate not seen in their wild peers.
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Zoos offer orangutans a stable yet different ecological niche. Getting food is less of an issue, as is avoiding predators. In the wild, orangutans tend to live rather solitary lives. In zoos, they live in larger groups in close proximity to one another, with more social interaction. They spend more time on the ground, away from foliage that can disrupt their view of other orangutans. All of these factors may help establish an environment where productivity can flourish.
Fröhlich’s team suggests that zoo living really has made a difference. The group looked at information on more than 8000 examples of non-vocal orangutan communications by 30 individuals at five zoos, and 41 in wild populations in two forests – one in Sumatra and one in Borneo.
After identifying and categorising the full range of signals, the team focused on those seen exclusively either in wild or in captive populations. Seven signals were used only in zoos, whereas only one was exclusive to the wild. The zoo-only signals include a raised arm, and a repeated spit of water in the face.
The results suggest an increase of around 20 per cent in the gestures and facial signals of captive orangutans compared with those in the wild. Most of the zoo signals were used to invite play, or to get food, and were often repeated by an individual until they achieved the desired result.
Fröhlich and her colleagues declined to discuss the work before it has been fully peer reviewed.
“The study provides convincing evidence for innovation with regard to communicative signals in orangutans,” says Christine Sievers at York University in Toronto, Canada. She notes, however, that there may have been observational difficulties in the wild habitats, which could have influenced how much innovation was spotted there.
Simon Townsend at the University of Warwick, UK, says the study “adds to the growing body of data that indicates signalling in great apes may be more plastic than previously thought, with obvious implications for the evolution of human language, arguably the most productive and flexible communication system in the animal kingdom”.
Reference: bioRxiv,
