In what read like a scene from a Jurassic Park spin-off, visitors to London Zoo were told to seek safety in nearby buildings last night as police with guns descended on the facility in an effort to capture an escaped silverback gorilla named Kumbuka. He had fled the zoo's gorilla enclosure after its door was accidentally left open, and he was pursued by the marksmen before finally being tranquilised and returned to his cell.

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It's a relief that on this occasion, the incident ended without loss of life. There are far too many examples of animals who have been shot dead after attempting to escape from cages and the stress of captivity. But for Kumbuka – who, like any living being, longs to be free – being returned to a life behind bars is hardly a happy ending.

Humans share 98 per cent of our DNA with gorillas, so it should come as no surprise that a gorilla who's been locked up and displayed in a zoo for years reacted just as we would to an opportunity to escape: he seized it. The only surprise is that incidents like this one don't happen more often. The miserable circumstances that likely prompted Kumbuka to try to escape in the first place remain unchanged.

For him, today will be a lot like tomorrow and the day after that: he will be gawked at by a constant stream of visitors, and every aspect of his life will be controlled by humans, including where he can roam, when and what he can eat, and who he is allowed to socialise and mate with.

Animals in zoos frequently exhibit signs of extreme depression

It's no wonder that animals in zoos frequently exhibit signs of extreme depression and related psychological conditions, such as pacing, rocking, and eating their own vomit – all of which are unheard of in their wild counterparts. And – like humans who suffer from long-term stress – captive gorillas are also more prone to cardiac disease: in 2011, the Smithsonian Institution revealed that a whopping 30 of its gorillas were on heart medication.

While we know that so many of the animals incarcerated in zoos suffer from depression and frustration (clearly, even the gorillas in the supposedly state-of-the-art enclosure at London Zoo), these institutions are doing very little to help species survive in the wild. Almost no captive-born gorillas are ever released back into their natural jungle home, and when London Zoo spent £5.3 million on a new glorified prison for gorillas in 2007, Ian Redmond, the chief consultant to the UN Great Apes Survival Partnership, said, "£5m for three gorillas [seems a huge amount] when national parks are seeing [three gorillas] killed every day for want of some Land Rovers, trained men and anti-poaching patrols. It must be very frustrating for the warden of a national park to see".

And it's not just gorillas who are expensive to confine. It costs about 50 times as much to keep one African elephant in a zoo as it would to safeguard sufficient natural habitat to sustain that elephant and countless others. The same amount of money a zoo spends on buying or breeding and housing exotic animals could benefit so many more in the wild. Our exploitation of living beings for entertainment is expensive, unnecessary, and cruel to those involved.