Bears, like most wild animals, spend most of their waking hours looking for food. Much of the time that is left, they spend making nests. Sleep takes up a lot of each 24 hours, and hibernation can occupy much of the winter. That leaves a bit of time for seeking mates and seeing off rivals, and for females, quite a lot more for child rearing. It may not sound much, but it keeps them busy.
Bears in zoos – in the bad old days – spent most of the daylight hours begging. When they were not doing that they often took to pacing up and down. The polar bears seemed particularly addicted to this. They did not make nests, for the nests were made for them – though polar bears were presumed to prefer cold concrete to remind them of Arctic ice. They mated if the curator provided a compatible mate; a matter that was in his hands, and was decided largely on economic grounds.
There is, however, a new tradition in zoos. Most of the serious institutes now recognise that they have an important role to play in conservation by breeding animals in captivity. The descendants of the captive animals might well return to the wild, and to be fit to do so, their behaviour as well as their genes must be conserved. Zoos, too, acknowledge (as some of them did not seem to in the past) that animals are sentient beings, capable of being unhappy; that they are not simple machines, with reflexes routinely triggered by standardised stimulations. For their personal welfare, as well as their conservational value, captive animals should be kept in ways that respect their psychology.
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Nothing smaller than a national park could truly simulate the wild, but in zoos that must be smaller than that – even the ones where the animals each have several hectares – the buzz word now is ‘behavioural enrichment’; and the aim is to create an environment and a way of life that is at least an abstract of the wild. Among the pioneers in Britain are the Monkey Sanctuary in Looe, Cornwall, described in ¿ìè¶ÌÊÓƵ in April (‘More room for the woollies’, 21 April 1990); in Glasgow, where Graham Law is keeper of carnivores; and London, where David Shepherdson has been employed for three years specifically to enhance the lives of the residents.
We can trace the origins of behavioural enrichment back in several directions. At the turn of this century Carl Hagenbeck created Hamburg Zoo, with artfully designed landscapes that give the visitors the illusion of wilderness, and perhaps fool some of the animals some of the time. The American primatologist Robert Yerkes, interested primarily in the laboratory study of apes, wrote in 1925 that: ‘The greatest possibility for improvement in our provision for captive primates lies in the invention and installation of appartus which can be used for work and play.’ Note this friendly, ‘human’ concepts of ‘work and play’. This was written before Ivan Pavlov had done his seminal experiments on reflexes in dogs, and given rise to the mechanistic view of animals that prevailed for the following five decades.
But many feel that the true pioneer of behavioural enrichment is Hal Markowitz, who in the 1970s set out to improve the environments in Portland Zoo, Oregon. In those days these were ‘traditional’, which meant extremely barren. Markowitz began with the lar (white-handed) gibbons, a mother with her infant and two juveniles, who lived in a concrete box with bars, and were fed through a chute at floor level. Markowitz did not have the option of planting a forest for them, so he set out to devise games to bring out their wild behaviour. For starters, he and his colleagues created a machine that coughed up food on one side of the cage (near the top, for gibbons like to feed high up) when a lever was pulled on the other side, in response to a light.
By modern standards this has an ancient behaviourist laboratory feel to it, but it did allow the gibbons to exhibit a truly wondrous ingenuity and variety of behaviour. The oldest youngster, for example, nicknamed Harvey Wallbanger (because he banged the wall, why else?), was happy to work the machine so that his mother could pick up the titbit, but delighted in denying and teasing his sister.
From this beginning Markowitz and his followers devised a whole range of hardware and techniques, designed always to increase the complexity of the environment and its unpredictability: two elements that typify the wild and are singularly lacking in captivity. Monkeys learnt to work for poker chips, which they then cashed for food; and showed, along the way, a wonderful line in deception and sleight of hand. Servals leapt at flying targets, just as they leap for birds in the wild. Pumas chased the equivalents of the electric hares employed in greyhound racing. All animals showed they could outsmart the machines – even ostriches, traditional symbols of knuckleheadedness. All, more to the point, showed that they preferred to ‘work’ for at least some of their food even if they were given all they needed on a plate. All, as Markowitz puts it, liked to exercise ‘control’ over their environment, and were ‘proud’ of their achievements.
Shepherdson came to London from the University of Sussex in 1987 with a PhD in badger behaviour, and was keen to emulate the work of Markowitz. By that time, though, Markowitz had come under quite a bit of fire – albeit largely unfairly – because people felt that the behaviour he was tending to stimulate could be just as abnormal as the behaviour he was seeking to replace. Incessant pacing and other sterotyped behaviour (‘stereotypy’) seems bad, but animals hooked on games like children on fruit machines were hardly an improvement. In the wild, for example, carnivores are singularly idle; but a puma in one zoo was seen to ‘hunt’ his electric prairie dog 200 times in a day. This was ‘natural’ behaviour perhaps, but there was far too much of it.
There arose in the 1980s a different and ‘softer’ approach. Armand Chamove and his colleagues, then at the University of Stirling, showed that primates benefited enormously from nothing more than a floor covering of woodchips. Each chip was a potential toy; and the animals spent hours looking for food tucked among them, just as they would forage in the wild among leaves and leaf litter. Such an innovation is more radical than it seems, for the concrete floors and ceramic walls of previous decades had not been introduced to give the animals a bad time, but for hygiene. The woodchips represented a shift in philosophy, reflecting growing veterinary confidence in the control of disease, and greater reliance on the natural behaviour of animals in keeping themselves clean.
Shepherdson’s approach can be seen to owe much both to Markowitz and to Chamove – while the individual ideas, he stresses, usually come from keepers, who know the animals best. Simplicity is his watchword: creating devices that others can copy for irreducible expense. Markowitz has also been keen to ensure that his machines were cheap, for even the richest zoos have many pressures on funds, so his early gibbon lever-pressing game was built largely from bits of an ancient coffee grinder.
But some of Markowitz’s followers were less thrifty. Antwerp Zoo, for example, had a locust dispenser built like a Gatling gun that fired live insects in among the fennec foxes. Great fun for the foxes (if not for the locusts) but as Shepherdson points out: ‘Each locust had to be loaded individually into its chamber – which took an enormous amount of the keeper’s time.’
Shepherdson has built a variation on the theme that consists merely of a tube with holes in the sides. The tube is stuffed with newspaper, with crickets lurking among the folds, and is tied to the roof of some cricket-lover’s den. Every so often, one of the insects falls through one of the holes. Thus the animals find a sizable supply of crickets at irregular intervals, just as they would do in the wild; and thus (they quickly learn) it pays them to forage, as they would do in the wild. The meerkats at London have such a tube stuffed with sawdust, from which mealworms fall from time to time.
Primates, of course, with their lively minds, have always been favourite targets for behavioural enrichment. They have also been studied in the wild more than most mammals, so there is plenty of wild behaviour to act as a model. One of Jane Goodall’s early observations during her studies in Tanzania (in what is now the Gombe National Park) was that chimpanzees ‘fish’ for termites, by poking twigs into the insects’ nests. They also modify the twigs by tearing the leaves off – the first evidence that non-human animals may not only be tool-users, but tool-makers as well. Every zoo that has chimps now seems to have an artificial termite mound, where the animals fish for honey or what you will.
London also has a simplified variation: a plastic drainpipe fixed on the outside of the enclosure. The pipe has holes in the sides, and inside there are pieces of fruit. The chimps push the fruit along by poking twigs through the holes, until the pieces fall out of the end and can be grabbed. Gorillas and orang-utans have not been observed to probe for termites in the wild, but they too enjoy the termite-fishing game. Orangs, indeed, take to it better than chimps because in general they are less excitable, and concentrate better.
Nuclear families fail
For any social animal, the best behavioral enrichment is the presence of their fellows – provided, of course, that the group has the kind of structure that it would have in the wild. Cornwall’s Monkey Sanctuary succeeded in breeding woolley monkeys in the early 1960s when most other zoos were failing miserably, largely because its founder, Leonard Williams, recognised that wild woollies live in troops with one dominant male and several subordinates, plus females, juveniles and infants. Keep them in pairs, as zoos commonly did, and the male simply bullied the female unmercifully, and sometimes, literally, to death.
Gibbons, though, have an unusual social life. They live in monogamous pairs (which is not particularly unusual) but they also ‘sing’ loud and long, to tell other pairs in neighbouring territories that they are indeed in residence and that the neighbours can forget any territorial ambitions they may have. London has one pair of lar gibbons, which is the correct grouping, but these were denied the natural choruses of neighbours. So Shepherdson rigged up a 30-watt loudspeaker 50 metres away from the gibbon enclosure, 10 metres from the ground, and blasted a recording of wild gibbons twice a day, at 11 in the morning and 4 in the afternoon. This was on an endless 60-second cassette which, he says, ‘contained several sequences of alternating male and female calls of increasing intensity climaxing in a long screeching call from the female, the great call, and a warbling reply from the male’. Just like the wild.
London’s gibbons undoubtedly responded to this, climbing to the top of their enclosure and swinging across it by their arms, and they did not grow bored with the recording. After several months, they were still responding. Of course, such stimulation could in principle be negative; it could simply frighten the resident pair. But observation in the wild suggests that the neighbours’ calls strengthen pair-bonding, and the response of London’s gibbons certainly did not seem negative.
Carnivores are a special challenge because in the wild they hunt, and very few zoos care to offer live prey. Among carnivores, bears are commonly regarded as the biggest challenge because they are in general more active than cats, less social than dogs and particularly prone to stereotypy. Doubts have been raised whether polar bears in particular should be kept at all. But it’s the carnivores that are the special interest of Graham Law at Glasgow. The first of his innovations (one emphasised also at nearby Edinburgh) was to give the animals a good view. The value of this first dawned at Glasgow when the cheetahs showed slightly bizarre behaviour when fed. The keepers threw their meat over the fence of their enclosure, and the animals would leap to catch it. But if the cheetahs missed, and the meat fell to the ground, they would return plaintively to the fence perhaps tripping over their dinner as they came. But then, says Law, in the wild they are daytime hunters who catch their prey with a long sprint. They do not have an outstanding sense of smell, and neither do they look at things that are under their noses. But they do have excellent long vision and they like looking at the world from afar.
So Glasgow built a large platform, from which the cheetahs have a clear view over the elephant house, onto the motorway beyond. In the wild, cheetahs climb to the top of termite mounds, to look around and to defecate. Glasgow’s cheetahs now spend much of their time on the lookout. The tigers, too, were given a large platform; and they look over the river to the riding school beyond. Theoretically, such a view could be frustrating. But the animals seem content to watch. Edinburgh has also modified many of its cat enclosures to give the residents a distant view from the zoo’s natural hills.
Changes in feeding regime have been Glasgow’s second major innovation for the cats. Meat for the leopards and smaller cats is hung from the ceiling on the end of pickaxe handles and in a different spot each day; the animals have to be ingenious to get at it. A favourite trick for awkward spots is to leap from the ground to set the pole a-swing, and then climb onto a branch to catch the meal at the end of its swing. Sometimes, Law admits, he has tested the animals too much. For the ocelots he introduced hanging poles which they had to climb to reach the meat at the top. To make it difficult, the pole was attached to the wire roof by a swivel. But the climbing cats then ‘whirled round and round at 100 miles an hour, and the more they tried to save themselves the faster they went’. When the dazed animals finally picked themselves up from the floor the keepers changed the arrangement to a simple swing.
But the bears at Glasgow – polar bears and Himalayan bears – have experienced the most radical changes. The polar bear enclosure was inherited from the 1960s, when it was considered rather good: an acre (0.4 hectares) of space, with concrete hills and a large pool, initially intended for six animals. Big it was, by the standards of the day, but it was still fundamentally a bear ‘pit’: a large hole in the ground.
Pits for keeping polar bears have advantages: they are secure, as bear enclosures need to be, and they are cheap. Disadvantages for keepers and animals alike include the problems of cleanliness. Litter blows into pits. More to the point, the bears themselves are reluctant to move from the enclosure at large into their dens, because they do not like being locked up; and if they cannot be locked up, the keepers cannot get in to clean the enclosures. If there is more than one bear, they cannot be lured into their dens even by putting their food inside, because they go in to get it one at a time and then bring it out again. One solution has been to reduce the potential mess by feeding meat as small fillets, so that at least there are no smelly bones left lying round. The result is a meal that the animals can bolt down in five minutes flat.
With a concrete environment, no view, and perfunctory meals it seems no wonder that polar bears have been among the most notorious stereotypers; and Glasgow’s bears were stereotyping too, when Law took over.
The first innovation was to feed in the morning instead of the evening, so that the bears at least spent the morning in post-prandial comfort, instead of growing hunger. This brought immediate improvement: more sunbathing and swimming, and less rocking and head-tossing. The second was to feed several times a day, and the improvement was compounded.
But the biggest and most fundamental change has been to stop treating the polar bears as if they were seals, committed to a life on the marine ice. After all, despite appearances, polar bears evolved from brown bears only recently: perhaps only 70,000 years or so ago. For many millions of years before that their ancestors were terrestrial omnivores, and polar bears retain many of the basic ursine instincts.
With this in mind, Law and his colleagues put straw in the polar bears’ dens. Of course, they have no straw in the wild, but they do have snow, which they do shape into ‘nests’. With straw to sleep on and to shape to their needs, the bears were less reluctant to go into their dens in the evening. This meant that their enclosures could be cleaned in safety. So instead of buckets of chopped meat they could be given entire legs of beef, whole small animals, fish to dive for and live crabs; an altogether more challenging and occupying diet. Neither are polar bears as carnivorous as they seem, even though they are the most carnivorous of the bears. In the wild they may dive for kelp. In captivity (as many zoos now appreciate) they like branches to play with and to chew; especially willow. They also like chunks of vegetable, especially if frozen into ice to provide yet another challenge.
Polar bears also like toys, especially things that float. One of their favourite tricks is to bring a big plastic container ashore and thump on it with the full weight of their front feet: a memory, it seems, of the days when they thumped open the ice dens of seals. In the wild, small polar bears, lacking weight, do handstands onto the seals’ mini-igloos to break them open.
Ideally, though, Law would like to take the ‘polar bears are bears’ philosophy to its logical conclusion, and give them fields with grass to roam in, earth to dig, trees to climb and places to get out of the public gaze, as well as the traditional rocks and water. Such an environment may not resemble the high Arctic in detail; but in spirit, in its variety and challenges, it would be far closer to the wild than the unyielding concrete that usually substitutes for ice.
It is with the Himalyan bears that Glasgow has come closet to realising its own ideals. The four bears have some three acres (about 1.4 hectares) of which two-thirds is natural wooded hillside; and on the flat field at the top of the field they have yet another tall Glasgow-style platform, for the view. Much of the day they spend searching for raisins and other titbits scatterd around their enclosure, as they could do in the wild, or climbing for meat, carefully hung by their keepers on the struts of the platform. To encourage them to use the whole enclosure, the keepers tie small pieces of meat to a string and trail them into the corners. The bears, who have an excellent sense of smell, can follow the trails many hours later. Sometimes the meat is left for them at the end and sometimes not. After all, hunting in the wild does not always (or even usually) end in success. When the Himalayan bears are not feeding or resting, they are making nests. These have proved to be so elaborate that visiting biologists have sometimes accused the keepers of building them. Not so; a bear builds as dextrously and assiduously as a gorilla.
As Shepherdson emphasises, we cannot just assume tht anything done in the name of behavioural enrichment is good. Animals may indeed become addicted to particular playthings. The recorded gibbon songs could have upset London’s resident gibbons (thought it seems fairly clear that they did not). It is not enough simply to guess that stereotypy has been reduced. The amount of packing or bobbing must be measured before and after the changes are made, using the kind of observation patterns that given statistically valid results, just as with field observations in the wild.
The evidence so far, however, is that behavioural enrichment certainly can do an enormous amount of good, and indeed can produce daily routines that in their general content – the amount of time spent resting, foraging, nest building and socialising – come very close to the wild. What is needed are resources, the application of scientific rigour so that progress is properly monitored and, above all, ingenuity on the part of keepers. Of course, all these innovations take plenty of the keepers’ time. But then, says Law, ‘this can hardly be grudged as the animals have themselves given all their time to the zoo, and to the zoo-going public’.
Colin Tudge is now writing a book on captive breeding called Last Animals at the Zoo, to be published by Century Hutchinson.
