Gus, the eight-year-old polar bear in Central Park Zoo, is in pyschotherapy. He has been spending every waking hour swimming up and down his pool. This so-called "stereotypic behaviour" indicates serious mental instability and depression. An animal behaviour expert has been brought in at a cost of รบ16,000 to cure his boredom and paranoia. Gus's neurotic state is the result not of living in New York, but living in a zoo where thousands have turned up to stare at him.
Gawping at mental patients is nothing new. Throughout the 17th and 18th centuries, a trip to the lunatic asylum, Bedlam, was considered a pleasant diversion. Pepys, Boswell, Johnson, all saw nothing wrong with such entertainment. Only the anonymous author of "The World", a journal of 1753, dissented: "I found a hundred people at least who, having paid their tuppence a piece, were suffered unattended to run rioting up and down the wards, making sport of the miserable inhabitants." The day trip to Bedlam is now regarded as the barbaric practice of an unenlightened age and, as the parallels with zoos become ever more marked, it seems as if we could soon regard visits to them in a similar light.
There is growing evidence that Gus is not alone in his plight. As well as the repetitive pacing of big cats and polar bears, psychologists also point to the relentless swaying of elephants from side to side and the reingestion by gorillas over and over again of their own vomit as evidence of mental disturbance. Dr Phil Murphy, an expert in stereotypic behaviour in animals and people, believes both are driven to it by an inability to understand their circumstances or to see any way out. "Despite the enormous differences between people and animals, we share some needs in common, and these are just not met by life in an institution," he says. "You cannot artificially generate a natural environment in a setting like an institution."
Not far from Brussels is an animal Alcatraz called De Limburgse. The inmates include a blind wolf and a group of Himalayan bears in danger of being made lame by grossly overgrown toenails. David Taylor, a leading British vet who specialises in zoo animals, has called De Limburgse a living museum. "The only difference between them and stuffed specimens is that their blood circulates," he said.
While the animals display more and more symptoms of lunacy, zoo visitors are displaying the same attitudes as the Bedlam day-trippers. An opinion poll last year revealed that although 62 per cent of visitors said they felt the animals they saw suffered physically or psychologically, 88 per cent still gave the main reason for a visit as "entertainment".
Bedlam did not survive the 19th century. Increasingly it looks as if the traditional urban zoo will not survive the present one. Attendances have fallen drastically, and seven zoos have closed in Britain in the last three years. Others have received bad publicity in even the most auspicious circumstances. A royal visit to London Zoo was accompanied by stories about the decapitation of surplus animals for experimental purposes. No sooner had the Queen left Dudley Zoo last month than two peacocks inadvertently landed in the lions' den and were promptly despatched. Nevertheless, 17m people a year still visit a zoo in the country that saw the first one founded in Regent's Park in 1828, and that now has more of them than any country in the world except America.
Many directors of the world's 10,000 zoos are now wondering whether they should continue primarily to display a wide variety of species for our interest and entertainment on family days out; or whether they should pursue the loftier ideal of conservation more vigorously to justify their existence to an increasingly sceptical public and ensure their own long-term survival.
A growing number may be declaring conservation their priority, but, just as the idea of holding the mentally ill under lock and key came in for scrutiny, so zoos face similar difficult questions: how much can really be done for the dwindling wildlife of Africa and Asia by urban zoos in Europe and North America? And are the benefits enough to justify the perceived cost to animals in captivity?
In answer to these questions, the animal behaviouralists employed by zoos have become much more sophisticated. As recently as the 1960s, they believed that food, water and shelter were enough to ensure any creature's well-being. These days, they recognise that a bear that spends much of its day foraging for food in the wild should have the opportunity to do so in a zoo. Meat is hung up for leopards accustomed to leaping for their prey; even the behavioural needs of lizards are considered: special guns make it possible to fire locusts through the air towards them to be caught.
The so-called "enviromental enrichment" in recent years of progressive zoos has extended to the replacement of cramped cages with more spacious and natural enclosures. The changes have not only improved the lot of the animals, but also, at some zoos, helped to prepare them for release to replenish depleted populations in the wild.
This is the new zoology, the zoos' much-trumpeted answer to their opponents. Captive breeding, say the zoo directors, could be the last chance on earth for the most ruthlessly hunted species such as tiger and rhino, both of which could otherwise be almost entirely lost within a decade.
The most formidable and flamboyant exponent of such thinking is John Aspinall, whose multi-million-pound personal fortune funds the operation of two zoos in Kent. The most important primates there are not the visitors but the monkeys and apes. "Most zoos are forced to placate humans," said Aspinall. "Humans dominate them totally. They always have to refer back to what the public like, and they love entertainment, pets' corners and recreation grounds. None of this is zoology. It's hominology - that's looking after humans. We're lucky to be liberated from that."
Aspinall's gorillas - 48 at the last count - romp on straw rotted for two years, just like the vegetation on the floor of their natural habitat, the African rainforest. His zoos aim to establish five breeding families of gorillas so that one group can be sent every year or two to West Africa, where their territory has been shrunk by poaching and deforestation.
There are similar ambitions for tigers, now falling so fast to poachers' guns that they are in imminent danger of disappearing from all but the most highly protected reserves. Aspinall acknowledges that the perils they face would make any release as desperate a gamble as any in his long experience of casinos. "But you have to take these risks to give them a chance of recovering some of the ancient lands which belong to them."
Not all of Aspinall's views are shared by zoo owners with an interest in conservation. Those without private funds to sustain them say such operations could never be commercially viable. Some zoo directors dislike the idea of "playing God". Others say releases into the wild can achieve only limited success at enormous expense.
In America, a $17m project was launched to save the California condor when its wild population dropped to nine. The difficulty of boosting numbers was demonstrated by the latest release of captive-bred birds. Half died when they flew into power lines.
Doctor William Conway, the president of the Wildlife Conservation Society, which has renamed New York's Bronx zoo a "wildlife conservation park", calculates that zoos may ultimately be able to help only 500 species in all, compared with an estimated 10,000 that become extinct each year. The task will become harder in an ever-more-crowded world. "We are on an enormous breeding binge," said Conway. "Last year, the world's human population increased by about 97m people. They are people who, in order to live, will take space away from nature, from wildlife.
"Most biologists think the human population will peak some time between 2015 and 2115. If it's 2015, there may be enough habitat left to survive in some recognisable form. But we're losing species with land, and last year we lost about 16 million hectares - a piece of land the size of Florida."
Cincinnati Zoo looks beyond the time of worthwhile releases of endangered species to the day when they run out of the wilderness they need to survive. Betsy Dresser, its director of research, is creating the world's first "frozen embryo zoo", a refrigerator full of test-tube cubs, calves and chicks that could enable man to bring birds and animals back from extinction one day.
"I think that what we can do here is comparable with what Noah did. We're trying to prepare for the flood," she said. "If predictions hold true, we'll be losing a species a second by the year 2115. I think the reality is that by then we won't have a wild anymore. There will be large animal parks, zoos, institutions that hold animals and we'll have the frozen zoo as a supplement."
Some may question the point of an Ark that could never discharge its animals. If 500 species were somehow saved by zoos, however, there would be few objectors, especially if the animals included those such as gorillas and tigers, whose loss we would feel most keenly.
The animal protection lobby claims that even this would not be enough to justify confining large wild animals to small spaces in inner cities. Will Travers, son of the late Bill Travers and now head of the Born Free Foundation, suggests that traditional urban zoos should be replaced by electronic worldlife centres. Here visitors could stroll through virtual reality rainforests and savannahs: they would be linked by satellite to wildlife parks in the animals' native land and could see them in minute detail on giant screens.
"Go to a normal zoo and what do you see? Animals behaving unnaturally or perhaps not doing anything at all," says Travers. "Does that inspire you about wildlife? In the virtual world, animals will react to you; you'll react to them. You'll be exploring creation with them. Six hundred million people go to zoos around the world and only a tiny number get turned on by what they see. I want everybody to get turned on to wildlife."
Zoo directors reject the motion that there could be any substitute for seeing animals in the flesh and smelling their fur. The intimacy of close contact with an elephant or rhino at the zoo, they say, will be more effective than any electronic image in encouraging support for their conservation from children who will never be able to afford a trip to Africa.
Zoos will strengthen their own support if they radically improve the conditions of their animals and the relevance of their activities to the survival of species. Many could do worse than to try and emulate Gerald Durrell's Jersey zoo, which he set up in 1959. Its emblem, a dodo, serves as a constant reminder of Durrell's aim of saving species from extinction. He even has a satellite zoo in Mauritius, where the dodo died out in 1620. So far, he has prevented the last 24 Mauritius pink pigeons and the last four Mauritius kestrels in the wild from following it into natural history.
Durrell's aim for his zoo is for it to go the way of Bedlam: "What I would ultimately like to see is for it to be closed down because there would be no further use for it. But we've got a long way to go before we get there."
