For the first time, a wild gorilla is seen using a tool to eat food
It’s a scene that would grace the opening of any Planet of the Apes movie. But rather than being fiction, this is fact, and one that is new to science. For the first time, a gorilla in the wild has been seen using a tool to acquire and eat food.
The young female gorilla watched another older male attempt to collect ants from a hole in the ground, only to see the ants bite his arm, scaring him away. The female gorilla tried to put her own arm in the hole, and she too was bitten. But instead of giving up, the young ape then had her very own ‘eureka’ moment. She looked around for a suitable implement, and selected a piece of wood approximately 20 cm long, tapering from 2 cm wide at one end to 1 cm long at the other. She then inserted the stick into the hole, withdrew it, and licked off ants clambering over it, avoiding being stung.
Other great apes have been seen to use tools in the wild, and captive gorillas have been known to fashion and use a range of tools in their enclosures. But the incident is surprising because wild gorillas were, until now, rarely known to have created and used tools.
The only known examples are when a western lowland gorilla was documented using a stick to gauge the depth of water before crossing a waterway.
It was not until 2005 that the first observations of tool use in wild gorillas were made, when a female was spotted using a branch as a depth gauge before attempting to cross a pool of water. However, unlike other ape species, wild gorillas had never been seen using tools to eat prior to these latest observations.
This report documents for the first time, an observation of tool use in a free-ranging mountain gorilla.
But until now wild gorillas have never been seen using implements to eat with.
Lisanga, a very clever ape
The use of the stick was witnessed by Dr Jean-Felix Kinani, the head veterinarian with Gorilla Doctors, an organisation of vets that works with wildlife authorities to monitor the health of wild gorillas. He and colleagues were observing one of eight mountain gorilla groups habituated to humans in the Volcanoes National Park, in Rwanda.
Within the group live 23 gorillas, including three silverback males, a younger male, and seven adult females, as well as juvenile gorillas and infants.
The veterinarians saw a gorilla named Kigoma, the second ranking silverback in the group, insert his left hand in to a hole in the ground, attempting to catch driver ants to eat.
He quickly withdrew it, and ran from the hole, shaking his arm, presumably remove the biting ants, report Dr Felix and colleague Dr Dawn Zimmerman, who are both affiliated to the University of California, US.
All the time, a younger female, Lisanga, watched his actions, they report in the American Journal of Primatology.
She approached the hole and for approximately two minutes watched the ants enter and leave it. She then put her own hand in the hole, suffering Kigoma’s fate.
Undeterred however, she found her tool, a broken branch lying some 2 m from the hole, and preceded to use it to dine on the ants.
Chimpanzees are well known to use tools in the wild, with different groups using different implements; some use sticks to dig out termites or to fish or dip for ants. They have even been seen using spears to hunt monkeys.
Wild orang-utans in Asia have spontaneously created hammers, probes and scrapers made of sticks. And in captivity, gorillas have been seen using sticks as weapons, using coconut fibres as sponges, and logs as ladders. Which begs the question, why don’t they in the wild?
One answer is that they do, but it goes unnoticed. Another is that gorillas are observed more in captivity, making it more likely that scientists spot novel behaviours. But it could also be that captive gorillas have less to do than their wild counterparts, so are more inclined to experiment to fill the time, Mike Cranfield, Director of Gorilla Doctors told BBC Earth.
Captive gorillas often have new objects placed in their enclosures to enrich their environments, providing more opportunity for them to be turned into tools.
“Lisanga is a curious gorilla,” explained Dr Kinani. “She is known to have an investigative personality.”
For example, one anecdotal report details her showing more than casual interest in a researcher’s bag, quietly approaching behind the researcher and attempting to take the bag away.
“This looks to be an idiosyncratic behaviour,” he adds, referring to her use of the stick to catch and eat ants.
No other gorillas witnessed Lisanga’s actions, so it is unlikely that they too will learn the same trick, developing a culture of stick use.
This time, at least.
Dr. Antoine Mudakikwa, Head of Veterinary Unit, Research and Monitoring at the Rwanda Development Board hailed Kinani’s findings as a credible reference for primatologists around the world: “Naturally as a primatologist it was a really good surprise because it is the first time such an observation is being documented. In the past people used to speculate and talk about tool use by gorillas in the wild, now we have seen it – a wild mountain gorilla adopting tool use for food acquisition,” he explained, adding that the development would lay ground for further primatological research.
“It has revealed that we still don’t know enough about animals we’ve monitored for thousands of years. We need to find out more, and with more research you discover more,” he explained, adding: “Dr Jean Felix Kinani first observation is important because it helps us understand the urgent need for more time and resources to be dedicated to more research.”
He added that it would enhance the value of gorilla tourism, a key foreign exchange earner for the country: “People have always liked and adored them (gorillas), and now that their intelligence is being put in the public domain for everybody to appreciate, we can only expect a boom in gorilla tourism in the country.