It's not a scenario in which anyone would expect to find themselves, but one truck driver managed to avert tragedy when he took an extraordinary risk while on a trip to the zoo with his family.
When it comes to zoos, there are some animals whose escape is more of a mild inconvenience than a danger.
For example, if a capybara escapes, it seems more likely to get some pets than be a risk to safety.
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However, other animals are a different story.
Tigers, lions, bears are all obviously a risk to people, but one animal which could be terrifying for wholly different reasons is a chimpanzee.
But chimpanzees' reputation for unpredictability and aggression didn't stop Rick Swope from jumping into an enclosure when he saw that one chimp's life was at serious risk.
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The chimp in question was called Jo-Jo, and he lived at Detroit Zoo.
In 1990, Jo-Jo had gotten into a fight with another male in the enclosure. As a result of the scuffle, Jo-Jo had jumped into a deep moat surrounding the enclosure, which was there to keep him and the other chimps in.
While they are fantastic climbers, chimpanzees are not good swimmers.
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They can sink due to a low body fat and also have a very top heavy build with huge shoulders, making it difficult for them to keep their heads above the water.
All this meant that Jo-Jo was having difficulty staying afloat, prompting Swope to ignore the zookeeper's warnings and leaped in to rescue him.
Swope told the Chicago Tribune at the time: ''It was the most pitiful thing I ever saw.
''This chimp had his hands up and his head was sticking out of the water. He was looking at the crowd. It was like he wanted someone to rescue him.
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''I was really kind of hoping somebody else would do it. But when nobody did, I knew that if I didn't, I'd go home and kick myself in the butt.''
In the end, the truck driver managed to rescue Jo-Jo from the water, risking his own safety at the hands of the other chimpanzees in the process.
Swope also recalled how after he had got Jo-Jo back on land, he had 'got the hell out of there' when another chimp appeared with its teeth bared.
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At the time, the Tribune reported that he had been extremely unassuming and was even 'embarrassed' by the attention he received after rescuing the chimpanzee.
Swope said: ''It was no big deal, you know. It wasn't nothin' that hard. It didn't take an exceptional person to do it. If it did, I couldn't have done it.''
Kit Roberts