07/01/2015 12:37 GMT | Updated 09/03/2015 05:59 GMT

Let's Weigh in on the Cruelty in Zoos

People don't often contemplate how a particular tradition got started, but we should certainly think about it when it's time for tradition to make way for progress. The annual zoo "weigh-in" is a great place to start.

Many zoos use this gimmick to attract visitors and garner free publicity. What picture editor could resist a photo of a lemur propped against a weighing scale or a gorilla standing next to a giant ruler? But for the captive animals, it's just another day - no different from all those before it and all those ahead. In zoos across the UK, animals wait for relief that will never come.

Animals kept in zoos are denied everything that gives their lives meaning. Being confined to one cramped place for our entire lives is inconceivable to us. We take for granted our liberties, such as being able to come and go as we please, to decide when and what to eat, to spend time with people we like and avoid those we don't, to choose and court our mates and to decide whether or not to have children. Denial of these fundamental rights is used as punishment for the criminals in our society. Yet animals in zoos, who have committed no crimes, are denied all these important choices.

Oxford University researchers have concluded that animals who are wide-ranging by nature experience physical and mental anguish in captivity and should be phased out of zoos altogether. Big cats such as lions and tigers - who should be roaming vast territories - are often driven insane by the deprivation they experience in zoos. They know they aren't where they belong. Last year, visitors to Edinburgh Zoo raised the alarm when a seven-year-old Amur leopard called Skodje was seen constantly pacing an enclosure measuring only 20 feet wide and 30 feet deep, which isn't much larger than a one-car garage.

Nevertheless, zoos continue to breed animals to produce crowd-pleasing babies and to bolster their inventories. Zoo breeding programmes do nothing to help wild populations of endangered species since none of the captive-bred animals whose species face extinction in the wild - including elephants, polar bears, gorillas, tigers and chimpanzees - will ever be able to be released into their natural environments.

Furthermore, breeding programmes inevitably result in a surplus of less crowd-pleasing adult animals. There's never enough space for them all, so zoos routinely trade, loan, sell, barter and warehouse adult animals they no longer want. Others - such as the young giraffe Marius, who was infamously killed at Copenhagen Zoo last year - are deemed too extraneous to live. The European Association for Zoos and Aquaria admitted that between 3,000 and 5,000 animals are "management-euthanised" in European zoos in any given year. Of course, that doesn't make for a good photo op.

Zoos readily sacrifice individuals for the supposed eventual good of the species. Species survival plans would be better titled "individual death plans". In the wake of Marius' undignified slaughter - which was performed with a shot to the head instead of a painless euthanasia injection so that his corpse could be fed to lions - the chief executive of Longleat Safari Park admitted that his zoo churned out lion cubs to "bring in more people", and a whistleblower reported the killing of four cubs because of inbreeding.

Zoos are based on the menageries of old and harken back to a time when Europeans used to pillage other continents and steal their treasures. Zookeepers today must recognise that their business model is dying and stop pretending that zoos make meaningful contributions to conservation. They should be at the forefront of the movement to target the root causes of extinction and endangerment of animals all over the world: habitat destruction, poaching and the exotic-animal trade.

In 2007, when the Zoological Society of London spent £5.3million on a new gorilla enclosure, Ian Redmond, the chief consultant to the UN's Great Apes Survival Partnership, lamented: "£5million pounds for three gorillas when national parks are seeing that number 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." The large sums of money spent on captive-breeding programmes and keeping animals in cages could instead be used for direct aid aimed at increasing the number of artificially created watering holes, developing community-based wildlife conservation programmes to increase the benefits of tourism, protecting vulnerable areas by erecting and maintaining fences and implementing other non-lethal conflict deterrents.

The fundamental causes of species endangerment must be addressed and remedied. All the cages in the world won't save animals from extinction.