AboutZoos, Since 2008


Great apes that swim and dive, first doc­u­mented report

pub­lished 14 August 2013 | mod­i­fied 28 June 2014

Two researchers have pro­vided the first video-​based obser­va­tion of swim­ming and div­ing apes. Instead of the usual dog-​paddle stroke used by most ter­res­trial mam­mals, these ani­mals use a kind of breast­stroke. The swim­ming strokes pecu­liar to humans and apes might be the result of an ear­lier adap­ta­tion to an arbo­real life.

Cooper chimp swimmingFor many years, zoos have used water moats to con­fine chim­panzees, goril­las and orang­utans. When apes ven­tured into deep water, they often drowned. Some argued that this indi­cated a defin­i­tive dif­fer­ence between humans and apes: peo­ple enjoy the water and are able to learn to swim, while apes pre­fer to stay on dry land.

But it turns out that this dis­tinc­tion is not absolute. Renato Ben­der, who is work­ing on a PhD in human evo­lu­tion at the School of Anatom­i­cal Sci­ences at the Uni­ver­sity of the Wit­wa­ter­srand (Wits Uni­ver­sity), and Nicole Ben­der, who works as an evo­lu­tion­ary physi­cian and epi­demi­ol­o­gist at the Insti­tute of Social and Pre­ven­tive Med­i­cine at the Uni­ver­sity of Bern, have stud­ied a chim­panzee and an orang­utan in the US. These pri­mates were raised and cared for by humans and have learnt to swim and to dive. Their find­ings have been pub­lished online on 30 July in The Amer­i­can Jour­nal of Phys­i­cal Anthropology.

Per­haps this abil­ity to learn to like water and learn to swim, requires zoos to recon­sider the com­mon approach to con­fine these Great Apes in out­door enclo­sures by water-​filled moats. Although, until now goril­las in zoos broke out of their enclo­sure by jump­ing the sur­round­ing — appar­ently too small — water-​filled moats, but swim­ming across the moat to escape has not been doc­u­mented yet. With his escape in 2007, Bok­ito the male gorilla in Rot­ter­dam Zoo, became big news. He jumped the water-​filled moat around the rather new out­door enclo­sure and injured a woman so bad she had to be hos­pi­talised for weeks. Imme­di­ately after the inci­dent the out­door gorilla enclo­sure was closed for refur­bish­ment and a wall appeared where the moat used to be.

Watch a com­pi­la­tion of the events that took place as a result of Bokito’s escape:


We were extremely sur­prised when the chimp Cooper dived repeat­edly into a swim­ming pool in Mis­souri and seemed to feel very comfortable

Renato Ben­der, lead author, School of Anatom­i­cal Sci­ences, Wits Uni­ver­sity, South Africa »

To pre­vent the chimp from drown­ing, the researchers stretched two ropes over the deep­est part of the pool. Cooper became imme­di­ately inter­ested in the ropes and, after a few min­utes, he started div­ing into the two-​meter-​deep water to pick up objects on the bot­tom of the pool. ‘It was very sur­pris­ing behav­iour for an ani­mal that is thought to be very afraid of water,’ said Renato Ben­der. Some weeks later, Cooper began to swim on the sur­face of the water.

The orang­utan Suryia, who was filmed in a pri­vate zoo in South Car­olina, also pos­sesses this rare swim­ming and div­ing abil­ity. Suryia can swim freely up to twelve meters.

Watch Cooper the chimp repeat­edly made full sub­mer­sions in deep water hold­ing on to one or two ropes, often try­ing to grasp with one foot or one hand objects placed 2 m deep on the floor of the pool. He also is cov­er­ing his eyes dur­ing the dives. He does that every time he sub­merges, which can be seen in the other videos where he goes under:

Suryia the orang­utan swims with his limbs alter­nately for­wards and back­wards. Like Cooper, these move­ments are highly diver­gent from swim­ming move­ments known from other primates:

Both ani­mals use a leg move­ment sim­i­lar to the human breast­stroke ‘frog kick’. While Cooper moves the hind legs syn­chro­nous, Suryia moves them alter­na­tively. The researchers believe that this swim­ming style might be due to an ancient adap­ta­tion to an arbo­real life. Most mam­mals use the so-​called dog-​paddle, a mode of loco­mo­tion that they employ instinc­tively. Humans and apes, on the other hand, must learn to swim. The tree-​dwelling ances­tors of apes had less oppor­tu­nity to move on the ground. They thus devel­oped alter­na­tive strate­gies to cross small rivers, wad­ing in an upright posi­tion or using nat­ural bridges. They lost the instinct to swim. Humans, who are closely related to the apes, also do not swim instinc­tively. But unlike apes, humans are attracted to water and can learn to swim and to dive.

The behav­iour of the great apes in water has been largely neglected in anthro­pol­ogy. That’s one of the rea­sons why swim­ming in apes was never before sci­en­tif­i­cally described, although these ani­mals have oth­er­wise been stud­ied very thor­oughly. We did find other well-​documented cases of swim­ming and div­ing apes, but Cooper and Suryia are the only ones we were able to film. We still do not know when the ances­tors of humans began to swim and dive reg­u­larly,’ said Nicole Ben­der. ‘This issue is becom­ing more and more the focus of research. There is still much to explore,’ said Renato Bender.

Cooper could not wade on all fours in the shal­low part of the pool. Watch how relaxed he is while adopt­ing an upright posi­tion to keep his head above the water:

(Source: Wits Uni­ver­sity media release, 14.08.2013)

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