Vervet monkeys in a KwaZulu-Natal reserve are the first wild primates to learn to use a touchscreen.
The breakthrough means scientists expect to be able to study intelligence in non-human primates without having to keep them in captivity.
But it brought a warning from the researchers at Mawana Game Reserve in northern KZN that using touchscreens to research monkeys who live in close proximity to humans could be risky.
“[There is a] risk of habituation to the touchscreen spilling over into increased attempts to interact with screens in other contexts,” they say in the Journal of Animal Ecology.
A team led by Erica van de Waal, who leads the iNkawu Vervet Project at Mawana, adapted touchscreen technology that has been widely used among captive primates.
“Some of the things we did to make the system work included reducing the size of the screens and changing the size of the symbols, finding the best possible location that was safe enough from predators, and finding a way to connect it to the internet,” says joint first author Tecla Mohr.
They built a 15kg box containing the screen, a battery and corn kernels, tied it to a tree and activated a web hotspot. Then they retreated at least 5 metres to control the screen and monitor the monkeys, which were visually identified from distinguishing physical features.
When small primates touched a blue square – first in a static position, then as it moved around the screen – they earned a few kernels of corn dispensed through a chute.
“The learner must understand and associate their gesture with the resulting ‘jackpot’,” says a statement from the ecology and evolution department at the University of Lausanne in Switzerland, where De Waal is an assistant professor.
“This proof of concept eliminates the need for animals to be held in captivity, thus expanding the potential for application to other species in their natural habitat.”
De Waal, Mohr and joint first author Rachel Harrison now plan to make their device lighter and to produce better recordings, and they are exploring face-recognition technology to identify monkeys who approach the screen.
“Individuals could also be trained to recognise a visual pattern on the screen indicating that it is their turn to interact with the task. This procedure could also be used to generate more balanced samples in terms of age and sex,” they say in their paper.
There are also plans for multisensory communication experiments, which would present the monkeys with the faces and cries of their group mates and observe their reactions, and even virtual reality games.
The iNkawu team performed the same experiments with four groups of captive vervets at the Wild Animals Trauma Centre & Haven in Vryheid, bringing the total number of animals involved in the tests to 240.
The sanctuary animals, which are provided with food and water, were much more likely to interact with the screen. “Wild individuals may have had less time to interact with the touchscreen due to the distraction of necessary activities such as foraging or being vigilant towards predators,” says the paper.
There was no difference in the performance of the two groups, but the scientists say that could have been because the task was simple. “It is possible that any captivity effect, or any other differences in performance between wild and captive populations, may become apparent only when using more challenging tests of cognition.”
Vervets’ complex social system is matriarchal, and the researchers say this could account for their finding that adult females and juvenile males were more likely to investigate the touchscreen.
“It is very likely that juveniles had to wait for the end of monopolisation by the high-ranking adult females before interacting with the experiment. Nonetheless, juvenile males were significantly more likely to participate than adult males.”
The likelihood of participation in one of the touchscreen sessions, which were held twice a week for more than two years, increased with the number of rewards a monkey received last time they took part.