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The programs, and the philosophy underlying them, are the legacy of Tilson's mentor, Seal. When he began his work some 20 years ago, zoos frequently bred tigers and other rare species indiscriminately, to preserve a popular animal's legacy or simply for the babies' crowd appeal. Seal, concerned that this was leading to inbreeding and health problems, devised a scientific method designed to maximize genetic difference among animals. As a result, notes Tilson, some captive populations today are more genetically diverse than their wild counterparts. "[Seal] was the architect of the philosophy that is now used in every zoo in the world," he says, "and it was all done with tigers, and it all started here."
Up to now the work of breeding specialists has essentially been that of a matchmaking service--setting up animals for blind dates. But that could change thanks to the efforts of Traylor-Holzer and others working on the next level of rare-species reproduction. For eight years, Traylor-Holzer has been climbing into tiger cages all over the world to collect tiger semen--a process that involves getting uncomfortably close to a sedated male, inserting an electrode-studded probe into his anus and pulsing low voltage so that he eventually ejaculates. (You can see a picture of Traylor-Holzer doing this on the Tiger Information Center, a massive Web site started by Tilson, at www.5tigers.org)
"Here you have a dangerous animal who is sedated, but you're providing a good reason for it to wake up," Traylor-Holzer explains. "It's quite an experience. They extend their legs, vocalize and growl a little. By the time you get into it you're very watchful. You don't want to become nonchalant about their welfare and for your own welfare."
Once collected, the semen, along with tissue samples and blood serum, is frozen in a liquid nitrogen tank and flown to the National Zoo in Washington, where it becomes part of a collection called the "Tiger Genome Resource Bank." Ultimately, researchers hope to use the material for artificial insemination and in-vitro fertilization. The techniques are more difficult to use in tigers than in people or cattle, since females only release ova after several days of mating or hormonal stimulation. But both procedures have succeeded in experiments at the Henry Doorly Zoo in Omaha, and Traylor-Holzer is enthusiastic about their future.
"If you want to get real idealistic about it," she says, "not only can you exchange [genetic material] between Minnesota and Miami, theoretically you could exchange material between captive and wild populations." Right now, mating a wild female with a captive male would mean holding her for one week to three months--the period it takes for tigers to conceive--and during that time she could lose her hard-won land to a rival, Traylor-Holzer explains. "But if we can inseminate her with captive-tiger material, then she would only need to be held for about two or three days, and she won't lose her territory or have any problems."
But if the goal is to add to the wild-tiger population, you might ask, why not just release young tigers, like they did with the lion in Born Free? One reason is that the last thing tiger advocates want is to send ferocious animals who see humans as the bearers of food--or, for that matter, as food--wandering around the landscape. Another reason becomes evident once you spend a few hours at the Minnesota Zoo's tiger barn.
The barn, where the tigers spend their unexhibited time, is essentially a wet jail--a series of 10-by-12-foot concrete-floored cages with spartan sleeping platforms, bright lights, an animal scent like clean, wet dogs, and tiger threats telegraphed from cage to cage with looks, huffs, growls, and snarls. The signals are evidence that domestication hasn't changed the tigers' fundamental preferences: In the wild, these are among the most solitary of animals, requiring enormous private ranges of between 10 and 120 square miles each. Even at the zoo, most adult tigers want nothing so much as to chase the other tigers from what they consider their personal territory. Imagine keeping a dozen medieval warriors, with knives and clubs attached to their bodies, and you'll get an idea of what it's like to keep tigers. Siberian tiger males grow to around 10 feet long and can weigh up to 675 pounds; their jaw muscles are as powerful as our thigh muscles, and their canines are the size of human fingers.
"We really have to be very careful," says zookeeper Taylor. "The other side of the bars is as close as we come." A few years ago, he recalls, two Minnesota Zoo subadults who had been exhibited together finally decided they were adults and had had enough of sharing territory. Since fences prevented the loser from running away, the bigger tiger bit clear through the smaller one's trachea.
But while zoo tigers retain many of their wild instincts, they have lost the vast majority of their "culturally transmitted" information--the sophisticated survival skills developed over hundreds of years and transmitted among wild tigers from generation to generation. Captive tigers don't know how to butcher animals by removing the colon first, so that the meat will keep better; how to chase jaguars out of their territory or keep crocodiles from eating their food; how to recognize poisonous or dangerous animals; how to pluck birds (tigers don't eat big feathers); and so on. When an unlucky peafowl or woodchuck strays into the Apple Valley exhibit, says Taylor, the tigers will jump it out of instinct. But instead of eating their prey, they'll carry it around like a rag doll or effetely deposit it in a corner. In short, chances are they would not last long in the wild.