Naturally, unlike other wildlife, gorillas do not need to drink water from lakes or streams as they get all the moisture they need from their food and morning dew.

In fact, in one of Dian Fossey’s journals the famous scientist, who lived among mountain gorillas for nearly two decades, wrote that mountain gorillas had an “obvious dislike of rain, and they seem to dislike water in general, usually trying to cross streams without getting wet.”

However, one day during a rainy season in 2013, Rwandan researcher Jean Felix Kinani saw a gorilla drinking water in the Virunga massif.

“I visited the Hirwa group on April 16, 2013 for a routine health check,” the veterinary doctor recalls. “I found silverback Munyinya and several other individuals drinking water using the back of their hand, a rare observation in mountain gorillas as they are known to get the majority of their fluid intake from the vegetation that they eat.”

Dr Kinani found the group in the Rwebeya stream, which runs through the Volcanoes National Park, which is located in northern Rwanda, and swells to a sizable river during the rainy season, often destroying houses in neighbouring areas.

The scientist’s observation was surprising since the primates were not known to drink water — until that day.

Ian Redmond, a British tropical field biologist and conservationist who regularly visits the park, commented on the discovery: “Most of the play I’ve seen in streams has been in the dry season, when they are a little more than pools linked by a trickle, and so there is no danger of an infant being washed away.

“This is fascinating.”

According to Dr Kinani, it is usually infant gorillas that like to play with water, especially during the dry season.

“They enjoy looking at their reflections in the water, thinking that there are other gorillas down there,” Dr Kinani explained. “Sometimes they can be seen making gestures or trying to touch their own reflections.”

Dr Kinani intends to publish his findings soon in an international journal that he is not willing to reveal yet.

This will be his second report on new behaviours in mountain gorillas following Tool Use for Food Acquisition in a Wild Mountain Gorilla, which was published last year in the American Journal of Primatology when he became the first person to see wild gorillas using implements to eat with.

Critically endangered, the world’s remaining mountain gorillas can only be found in two locations: The Virunga Massif, a chain of volcanic mountains that straddle Rwanda, the Democratic Republic of Congo and Uganda, as well as the Bwindi Impenetrable Forest in Uganda.