Hong Kong claims the mantle of Asia's world city - a position that necessitates us aspiring to and upholding the highest standards. But to look at the orangutan enclosure at the Zoological and Botanical Gardens is to get a very different impression. Modern zoo-keeping practices have been all but ignored in housing the one male and three females of the endangered species, leading animal welfare campaigners to worry about their physical and psychological well-being. For the sake of the animals - and our city's image and reputation - international standards that we have signed up to must be implemented. The keeping of animals in cages for the amusement of people has long been a moot point. But there is no doubting the worth of zoos for research and education and ensuring the survival of endangered species through breeding programmes. Our zoo, although small, exists for these objectives. High veterinary and hygiene standards are maintained, although the enclosures and cages - especially those of the orangutans - are wanting; some people call them depressing and a disgrace to our city. A movement has long been under way to ensure that zoos recreate, as much as possible, the exhibited animals' natural environment. This is enshrined in the codes of the World Association of Zoos and Aquariums, of which the Hong Kong gardens is a member. Its provisions state that exhibits must be big enough and contain sufficient material to allow animals to express natural behaviour. This is clearly not the case with the orangutans - they are kept in a 270-square-metre, five-metre-high cage that bears no resemblance to the rainforest of their Borneo relatives. Orangutans are the only great apes that live in trees. They are falling towards extinction because their forest habitats are being burned down to make way for palm oil plantations. The Hong Kong zoo enclosure does not contain a single tree, blade of grass or other sign of vegetation: the only concession to nature is that the concrete floor is painted green. The enclosing metal bars and reinforced glass panels house a climbing structure, artificial boulder, cement-paved pond and a night shelter with a concrete sleeping platform. There is no reason why Hong Kong can't have a small zoo in the heart of the city. If we are going to have one, though, animals should be kept under internationally sanctioned conditions. Our zoo does not do this, even for our most popular exhibits.