From time to time my friend Mark Goldstein, a veterinarian, calls me to brainstorm about difficult animal-care decisions confronting him as director of the Los Angeles Zoo. This time he was faced with the dilemma of Nan, a teenage chimpanzee already saddled with a young son. The facility where they were housed was crowded, and it would be years before the new housing planned for them would be ready. Under the circumstances, the last thing that Nan needed was another infant, and she had been on contraceptives.
The contraceptives had evidently failed, because Nan now appeared to be nearing the end of her first trimester of pregnancy. Mark wondered about the wisdom of an abortion, which would have to be carried out soon if at all. What did I think?
My first reaction was: I’d hate to have your responsibility for deciding, but I think you’d better do it. Yes, a decision to abort is always agonizing. Nevertheless, of the last two pregnancies in that crowded facility, both of them also failures of contraception, one had ended in a stillbirth, the other in an infant that died within a week. With that track record, I reasoned, abortion would surely be the lesser of two evils.
Then Mark explained why he wasn’t so sure. No one had ever performed an abortion on a chimpanzee, so there’d be no way to be sure the operation would be safe. If Nan were to hemorrhage and die, we would lose a female of prime reproductive age from the small captive breeding population of a species endangered in the wild. Even assuming the procedure itself would cause Nan no harm, removing her from the cage where she lived with 12 other chimps would necessarily involve the risk of tranquilizing her; furthermore, her absence could trigger a war over social status among the remaining occupants. As for my suggestion that the pregnancy be allowed to run its course and room be found for the infant at another North American zoo, Mark’s answer was simple: all American zoo facilities have as many chimps as they can handle. Now what do you think? he asked.
I agonized for a while longer, and eventually I came down against an abortion. That was Mark’s decision also. To everyone’s relief, Nan went through an unremarkable pregnancy and birth, and both mother and infant are now doing fine. The long-term problem of a crowded chimp exhibit still exists, though, and will continue until the zoo can raise the millions of dollars necessary to build a much larger exhibit.
The dilemma posed by Nan’s pregnancy was typical of the challenges that zoo directors and their staffs face every day as a result of the enormous changes in the perceived function of zoos. Until recently zoos were viewed primarily as places to display animals to a curious public. These days their main function is to contribute to the well-being and future of their residents. The first and last question now asked when zoos face any decision about animals is: What is best for the animals? As Nan’s case illustrates, these choices raise difficult problems of science, conservation biology, scarce resource allocation, and ethics. In addressing such issues, zoos cannot ignore the constraints imposed by the human- dominated world in which animals are struggling for survival.
I got into this hornet’s nest of tough decisions when Mark asked me to serve on the Los Angeles Zoo’s Animal Management Advisory Committee. Our committee is very diverse, ranging from members of animal rights groups to veterinarians and lawyers. In going over my notes on the problems that we’ve discussed during the past two years, I find the following:
How should zoo personnel go about minimizing the dangers the animals face? Consider the case of Herman, an adult male Indian rhinoceros who had caught the scent of a female in estrus. Keepers were reluctant to bring her to his enclosure because the ground was slick with rain and they feared the pair would fall down and break their bones. In frustration, Herman injured his penis trying to copulate with a rock.
Should the Los Angeles Zoo feed live fish to some of its carnivorous animals so they can exercise their natural hunting behavior? If we feed live fish to bears, where do we draw the line? Would we also feed live rabbits or sheep to tigers?
Should the zoo be maintaining bull (adult male) elephants, which in captivity are a lethal danger to their keepers, to other elephants, and to themselves? Yet elephants are endangered in the wild, and their survival may come to depend on captive breeding, which requires captive adult males.
Should the zoo be maintaining macaques, which may soon be endangered in the wild, too, and will need captive breeding colonies? Macaques often harbor a herpes-B virus potentially fatal to humans, though relatively harmless to the monkeys themselves. In some macaque colonies almost all individuals harbor the virus. The risk of a monkey keeper becoming infected is very low, but once infected, a person stands a good chance of dying. Faced with those odds, some zoos have already gotten rid of their macaques, and others have refused to accept even highly endangered species.
Should we send animals for which we have no space to zoos in the developing world? If we refuse on the grounds that those zoos are not subject to rigorous U.S. standards of animal care, how can we expect citizens in those countries to support conservation of endangered local species that they have never seen?
Some of those questions we were able to answer: in June 1993, for instance, we decided not to maintain macaques. Other questions are still on the table. To see how gut-wrenching the ethical dilemmas facing zoos can get, let’s look at two of those questions: whether zoos should keep bull elephants, and whether they should feed live prey to carnivores.
The public goes ape for elephants, but for zoo directors, elephants are a big pain in the neck. Both literally and figuratively, they eat up a disproportionate amount of the budget. They require their own full-time keepers, mammoth enclosures with strong barriers, and lots of lunch. They are dangerous to each other, to visitors, and to their handlers, killing on the average two keepers per year in North American zoos, circuses, and private elephant facilities. Bull elephants, which become increasingly difficult to handle as they grow older, pose the greatest hazards.
All zoo committees blanch at the prospect of dealing with bull elephants, but at the Los Angeles Zoo we have reason to blanch paler. The worst disaster in our recent history involved a wild-caught male African elephant named Hannibal. We made the mistake of acquiring him when he was a small and tractable four-year-old, in March 1980, although we lacked the specialized facilities required to contain and manage a big bull elephant. By the early 1990s Hannibal had taken to ripping his barn’s 20-by-10-foot- wide, two-inch-thick steel door off its hinges. That left only one barrier between him and the public, his keepers, and the other elephants.
Rebuilding our elephant facilities to manage even adult females properly, let alone bulls, would have required at least a year, but we could not risk another year with Hannibal in our existing facility. We had to move him fast, before he injured or killed someone. Arrangements were made to transfer him to a zoo equipped to handle bull elephants. Tranquilizing and moving a big, stubborn animal, however, is a tricky business. During the attempted move on March 20, 1992, Hannibal lay down, refused to get up, and eventually died; we still don’t know why. Animal rights groups blasted our zoo and drew an onslaught of angry newspaper and TV coverage. Even the California state legislature got into the act and considered a bill that would micromanage zoos’ handling of elephants.
Hannibal’s history hit the fan again at the first meeting of our newly formed Animal Management Advisory Committee in February 1993. Our elephant facility was scheduled to be rebuilt at last, with massive hydraulic doors, remote door controls, and other devices for separating animals from their keepers and companions. But our elephants had to be transferred somewhere else during the yearlong construction, lest they get it in their heads to make hamburger out of the construction workers. While moving the young animals and adult females was not so worrisome, a potential Hannibal situation loomed, in the form of a ten-year-old Asian elephant named Billy.
Billy was not dangerous yet, but he was likely to become so before long. There was no way to get around the problem of moving him once, so that our facility could be rebuilt. We did, however, have a choice about what to do with Billy after a year. Should we plan to transfer him permanently or to bring him back to the Los Angeles Zoo?
My first response was: Get Billy out of here fast, and make sure he never comes back. It would take only one more accident, one well- intentioned miscalculation with an unpredictable animal, for the media to start screaming Hannibal! again. How could we risk damaging our entire operation, which involved so many animals, for the sake of maintaining one individual?
Suppose we did abrogate our responsibility for bull elephants, and other zoos did so for the same reasons that swayed us? Both in Africa and in Asia, elephant numbers are crashing in the wild because of habitat destruction, legalized shooting, and poaching, even in supposedly protected game parks. If developments continue at the present rate, eventually there may be no more African or Asian elephants left in the wild. The only ones in existence would be those in zoos and other captive facilities, and the continuation of tens of millions of years of elephant history would depend on captive breeding.
There are already many species that survive only because self- sustaining captive populations were established before the animals became extinct in the wild. Those species include our own California condor, our black-footed ferret, and our Guam rail, as well as the Arabian oryx, the Przewalski’s horse, and the Père David’s deer. Their survival in captivity has bought time during which conservation biologists can try to find, improve, and protect suitable habitat for the species to reestablish a wild population.
The Arabian oryx, the California condor, and the Przewalski’s horse have already been reintroduced to the wild, and the Guam rail is on its way. Reintroductions are being planned for many other endangered species, as soon as sufficient numbers have been bred in captivity and sufficient wild habitat can be secured. But think of all those other remarkable species that became extinct before captive breeding programs could be established--think of the passenger pigeon, the Carolina parakeet, the Tasmanian wolf, and that symbol of extinction, the dodo. Every such failure to establish a captive breeding program is an inexcusable crime of humans against animals.
At least two important general lessons have been learned from the captive breeding programs already undertaken, such as that for the California condor now under way at the Los Angeles and San Diego zoos. The first lesson is, simply, to start with enough breeding male and female animals. When all surviving individuals of a species are descendants of only a few fathers or mothers, they are likely to be each other’s siblings or cousins. Such inbreeding often leads to infertility, poor survival, and other genetic problems that have plagued recovery programs. To minimize those risks, the California condor program, which started with only 27 birds--including the entire surviving wild population--has to use elaborate computer-based calculations to figure out which male should mate each year with which female.
The condor program also shows how important it is to start captive breeding programs early, long before the wild population is down to its last few individuals. When a species has reached the verge of extinction, recovery programs become awful, expensive cliff-hangers. Many animals besides condors and elephants are difficult to maintain and breed in captivity, and last-minute programs can’t profit from years of experience in overcoming those problems. Whenever an infant dies or a pair mate without results, the species strides closer to extinction. Every capture of a wild individual to increase the diversity of the captive population then represents a big reduction in the dwindling wild population. The time to start serious captive breeding programs is when the warning signs are already clear but long before the wild population is in imminent danger of extinction.
Everyone who has seen newsreels of rotting elephant carcasses and ravaged tropical habitats knows that the time has already arrived for elephants. Yes, Billy will get harder and harder to manage as he gets older. That’s why modern elephant pens at zoos are so expensive, and why so few American zoos are still willing to maintain bull elephants. However, there are only 17 sexually mature Asian bull elephants in accredited North American zoos, which leaves an uncomfortably narrow genetic base to guard against inbreeding. If even the Los Angeles Zoo, one of America’s leading large zoos, is unwilling to maintain an Asian bull elephant, where then do we think that the necessary males are going to live instead?
On September 23, 1993, Billy was moved for one year to a specialized elephant-care facility near Los Angeles, which caters mostly to non-zoo elephants. The facility could not house him for much more than a year, but that would at least give our zoo time to reconstruct its own elephant facility. The move caused planning nightmares and received close scrutiny from the press, the city government, and the federal government. So did Billy’s return, on July 20, 1994. Fortunately for Billy, for our zoo, and for elephants of tomorrow, both moves proceeded smoothly. Clearly my initial gut reaction--transfer Billy elsewhere!--was wrong.
What about feeding live prey animals to our zoo carnivores? Nearly two years ago a zoo staff member proposed this practice to us, suggesting that we offer live fish as food. She explained that many other accredited American zoos provide live goldfish or trout fingerlings to carnivores such as foxes, raccoons, bears, and tigers. The public, she assured us, has no objection and even enjoys watching the carnivores’ behavior.
Our committee felt uncomfortable at the suggestion, though, and spent three meetings discussing it. Some members objected on ethical grounds. It is already debatable that we humans have the moral right to raise prey animals for food, regardless of whether we plan to eat them ourselves or let carnivores do the devouring. At least the prey animals can be killed quickly and painlessly if they are to be consumed dead. But humaneness tends not to be a big issue with carnivores, who may wound and play with a prey animal before finally killing it.
Others of our committee members were worried about the effect on our staff and on the public. Some of our zoo volunteers had already protested when they learned that their duties would include feeding live mealworms to insectivorous animals. Surely, we thought, more volunteers would fret over live goldfish than over live mealworms. We began to extrapolate. Once we started with goldfish, where would it stop? Will we offer live rabbits to our tigers? Will the next step be to offer them live deer? Just imagine how the Bambi-loving public will go for that!
At that image, I thought: My God, enough of this discussion. Fish-based cat food out of a can is as nutritious as live goldfish anyway. Why do we have to go out of our way to invite trouble?
After further debate, however, I wasn’t so sure. Anyone who has ever visited an old-fashioned zoo knows that many captive animals spend most of their time sleeping or doing nothing. When they’re not sleeping, they’re likely to be pacing back and forth, back and forth, along a single line. If they’re not doing that, they’re probably practicing unnatural behavior, such as vomiting and reswallowing their food (as captive gorillas often do), eating their feces, being abnormally aggressive, or grooming themselves far more than any wild animal would.
In the wild, animals spend most of their time on food: searching for it, capturing it, processing it, and eating it, often in many small amounts at many different places. Mountain gorillas, for example, spend half their time foraging; black bears, in autumn, spend up to 18 hours a day combing the woods for things to eat. In zoos, though, food traditionally consists of prepared chow that requires no capturing or processing, placed on the floor in a pan that requires no finding, and provided once a day. The animal gobbles down the chow in 5 minutes, leaving it 23 hours and 55 minutes a day to be bored.
It’s not just the food that’s dull for zoo animals. Even many natural exhibits consist of little more than an irregular gunite mound surrounded by a moat, with a few logs, waterfalls, and cane-grass patches added as a naturalistic sop. Lacking are all the sounds, smells, and spatial complexity of the outdoors.
These days we take it for granted that we must provide for the physical and nutritional well-being of captive animals. Government and zoo- association inspectors regularly scrutinize zoos, and any institution that repeatedly let its animals starve or become injured would be closed down. Now, at last, the U.S. Department of Agriculture and zoo professionals also expect zoos to provide for animals’ psychological well-being. The key term is behavioral enrichment. That is, zoos are obligated to enrich an animal’s environment in ways that permit it to engage in a variety of natural activities.
Behavioral enrichment assumes many forms to which nobody could possibly take offense. A few droplets of animal or plant scent essences can be placed around an otherwise monotonous exhibit to liven it up for its residents. Cats will rub against a scented object until they replace the foreign smell with their own. Bears like to shred raw cowhide, while big cats chew it, drag it around, roll on it, and try to bury it. Playing cassettes of natural sounds, including prey sounds, similarly elicits natural behavior.
An equally uncontroversial measure is to provide captive animals with the usual dead food but to make them use natural behavior to find it. The world’s many small species of wild cats are considered unappealing zoo animals because they spend most of their time sleeping. Yet many small feline species are endangered in the wild and urgently need to be bred in zoos. An experiment on leopard cats, a species from India and southeastern Asia kept in the National Zoological Park in Washington, D.C., showed how easy it is to enrich these animals’ lives.
Instead of leaving a pan of food once a day in the center of the exhibit, keepers divided the same food into four meals, which they brought at unpredictable times and hid around the display. With these simple changes in feeding procedures, the leopard cats spent less than half as much time at stereotyped pacing as they had before, interrupted their pacing bouts more often, and increased the time they spent exploring their exhibit threefold. They continued nosing around all day, even after they’d eaten the last bite, in hopes that there was still hidden food to be found.
Many other species respond well to similar gustatory challenges. Chimpanzees and bears, for example, love to pry or lick out raisins, blackberries, honey, or peanut butter stuffed into crannies or into holes drilled in logs; the chimps even use twigs to extract these treats, as they would in the wild. The caracal, an Asian and African cat that in the wild often leaps as high as 15 feet in the air to catch its prey, is happy to jump for its dinner when keepers hang food high in its exhibit.
Things get a bit more problematic when it comes to feeding whole carcasses to animals rather than merely hiding or suspending prepared food for them. One might reasonably expect that this means of behavioral enrichment could make the zoo-going public uncomfortable. Yet for our captive-bred California condors destined to be released into the wild, we have no choice but to give them sheep carcasses, since the birds are carrion eaters and need to practice their scavenging skills. These gastronomic rehearsals take place behind the scenes. But carnivores such as bears and tigers also appreciate the challenge of dismembering and consuming dead animals. And as it turns out, perhaps surprisingly, in those zoos where it’s been tried, visitors have liked watching bears working on a chicken carcass.
Potentially more touchy for the public, but also more enriching for the animals concerned, is to offer them live prey. When the fishing cat, an Asian species that habitually fishes in the wild, was fed with the traditional modified cat food at the Metro Washington Park Zoo of Portland, its life was as boring to the people who came to see it as to the cat itself. It spent two-thirds of its time sleeping in a corner, another quarter resting in the same corner, and only 8 percent doing anything active or interesting. However, when keepers put just one or two live goldfish or trout fingerlings into a pool in the predator’s exhibit, it exchanged its love of sleep for a battery of natural hunting activities. It entered the pool, even ducking its head underwater. It put its paw under rocks to look for fish in hiding and pounced on its prey with both paws. The cat evidently loved the challenge, for it spent up to five hours trying to catch especially evasive fish and would occasionally release one for the pleasure of catching it again. The beneficial effect of live feeding persisted: eight days after receiving the last goldfish, the cat was still spending less time sleeping or resting and more time hunting.
Live goldfish induced the Allen’s swamp monkeys at the San Diego Zoo to practice not only natural feeding behavior but also natural social learning. When the fish were introduced, a wild-caught adult male monkey captured them using a technique he had probably learned in the wild. He threw hay on the surface of the pool, waited for the fish to seek shelter under the shadow, then reached his paw through the hay to grab a fish. The monkey’s offspring in the same enclosure learned his fishing method by watching him, and the technique spread to a troop in a second enclosure when one of the straw fishers was transferred there. Gradually, over the course of the past nine years, the monkeys have developed other fishing methods and have applied them to catching crayfish as well.
If swamp monkeys and fishing cats have had such positive experiences with mere goldfish, should we throw live rabbits or deer into the tigers’ exhibit? In defense of that modest proposal, one might point out that we sell hamburgers and hot dogs to the zoo-going public. It seems hypocritical to grind up cows and pigs that have been killed out of public sight and offer their meat to humans who exercise no hunting behavior, while denying our captive carnivores an opportunity to practice a natural skill important to their well-being. Nevertheless, I don’t expect to see a live deer put into the tigers’ exhibit within my lifetime. The line needs to be drawn somewhere.
But where, exactly? After all, of the many scientific and ethical questions that arise daily at zoos, merely keeping animals captive poses the biggest dilemma of them all. In an ideal world, these problems wouldn’t exist--nor would zoos. No animal would be threatened with extinction. All people would live near vast, untrammeled tracts of natural habitats and have daily opportunities to observe and learn to appreciate animals.
Alas, we live in the real world, where habitats are being trammeled at a horrifying rate. The only places where most of us can see most animal species are zoos. People who haven’t seen and come to appreciate animals aren’t going to vote for (and contribute dollars to) protecting natural habitats. Until all of the world’s animal species face a secure future, we shall continue to need and value zoos--and to grapple with questions we’d probably rather not ask.