Should zoos exist?

At half past seven, before the gates open, a keeper at a mid-sized European zoo is scattering food across the red panda enclosure so that the animals have to search for it. She has worked with animals for nineteen years, and she dislikes the word "exhibit". "People think we're here to put animals on show," she says. "The good days are when visitors barely see them, because they're busy being red pandas." Her zoo, like many others, now describes itself as a centre for conservation and education rather than entertainment.

That is a long way from where zoos began. Rulers kept lions and elephants as symbols of power, and the public zoos of the nineteenth century displayed animals in bare cages, like stamps in a collection. The case for modern zoos rests largely on a handful of real successes. The Arabian oryx had disappeared from the wild by the early 1970s, but animals bred in captivity were later returned to Oman and other countries in the region. The California condor was down to twenty-seven birds in 1987, when every one of them was taken into captivity. Breeding programmes have since brought its numbers back into the hundreds.

Critics reply that such stories are far from typical. Most animals in zoos, they argue, belong to species that are not endangered and are kept because visitors like them. Baby animals reliably draw crowds, which gives zoos a commercial reason to keep breeding whatever sells tickets. Large, wide-ranging animals pose a particular problem. Elephants, polar bears and orcas cover huge distances in the wild, and in captivity they often show signs of stress, such as pacing or swaying for hours. Some zoos have stopped keeping elephants altogether.

Even the oryx story is less tidy than it sounds. Poaching cut Oman's wild herd sharply, and after the government shrank the protected area by around ninety per cent, UNESCO removed the sanctuary from its World Heritage list in 2007. On education, the evidence is mixed. Some surveys find that visitors leave knowing more about wildlife, while others suggest the effect is small and fades within weeks. The keeper is frank about this. "A bored animal behind glass teaches children the wrong lesson," she says. "I'd rather they saw fewer animals doing more."

Few critics would close every zoo tomorrow, not least because thousands of animals born in captivity could not survive on their own. The more realistic debate is about which zoos deserve to continue. Those that focus on species they can genuinely help, give animals far more space and stop keeping the ones that clearly suffer have a reasonable claim. Those that keep elephants in concrete enclosures to sell tickets do not. Fewer animals, larger enclosures and smaller profits would follow, a trade-off the keeper says she would accept without hesitation.