Few institutions divide opinion quite like the zoo. For some, a visit to the zoo is a cherished childhood memory and a rare chance to see extraordinary animals up close. For others, the sight of a wild creature confined to an enclosure is deeply uncomfortable, even cruel. As our understanding of animals has grown, the question of whether zoos should exist at all has become increasingly difficult to answer.

Those who defend zoos argue that the best modern institutions are a world away from the grim animal prisons of the past. Good zoos, they say, play a vital role in conservation, running breeding programmes that have saved several species from extinction and later returned them to the wild. Zoos also fund scientific research and, perhaps most importantly, educate millions of visitors each year. A child who feels wonder at seeing a real elephant, the argument goes, may grow into an adult who cares about protecting it.

Critics remain unconvinced. They point out that many animals, particularly large and intelligent ones such as elephants, big cats and whales, suffer both physically and psychologically in captivity, however spacious their enclosures. No zoo, they argue, can truly recreate the vast territories these creatures roam in the wild. They also question the educational claims, suggesting that watching an animal pace back and forth behind glass teaches little about its natural behaviour, and may even send the message that it is acceptable to keep wild animals for our entertainment.

Between these positions lies a range of more moderate views. Some suggest that zoos should focus only on species that genuinely cope well in captivity and that clearly benefit from conservation efforts, while phasing out the keeping of animals for which captivity is plainly unsuitable. As with many ethical questions, there may be no perfect answer. What seems certain is that the standards we expect of zoos will continue to rise, and that any institution wishing to survive will need to prove, beyond doubt, that the animals in its care are there for their benefit as much as for ours.