Tigers' Keepers

A real-life fairy tale in which the wild beasts are hunted, the jungle is a plantation, and the knight in shining armor hails from Apple Valley.

Not that it matters much: These days, Tilson's work has more to do with databases, international meeting rooms, and high-tech research equipment than with animals in the flesh. He is the founder and head of the Tiger Global Conservation Strategy, an umbrella program that coordinates all the scientific tiger-management efforts in the world. He also supervises the Sumatran Tiger Project, an endeavor uniting the Minnesota Zoo and Indonesian conservationists to save an entire subspecies of tigers. Finally, he heads the tiger portion of the Global Animal Survival Plan, an international strategy that coordinates zoo programs with nonzoo activities. The man has a résumé that reads like the phone book, representing a lifetime of work for and with tigers.

Tilson came to the great cats by way of a long-term love affair with Southeast Asia. In the '60s he served a stint as a Peace Corps volunteer in Malaysia; later he worked as a field biologist studying gibbons on the remote Indonesian island of Siberut. (He still sports the gibbon tattoo he acquired to convince the island's residents that he was serious about his work.)

In 1984 Tilson came to the Minnesota Zoo to work with Ulysses S. Seal, one of the zoo's founders and an international authority on the management of endangered wildlife. When Seal stepped down eight years ago, Tilson assumed his mantle as the world's foremost zoo-based tiger conservationist. Today he spends half his time in the field in Indonesia, raises funds all over the globe, and finds that tigers are "all-consuming. I do nothing but tigers. If I could clone myself, I would."

To get a sense of Tilson's stature in the tiger-conservation movement, consider this: No zoo tigers in the world mate without his go-ahead. And that's bad news for Zara, a Siberian female at the Minnesota Zoo. In the throes of estrus (heat) recently, Zara was madly, desperately friendly. She rubbed her face on the bars of the cage where she was being kept away from the males, a submissive house-cat look in her eyes. She swung her big head around like a drunk woman with a glamorous shock of hair. She made the quiet chuffing noises tigers use as an amicable greeting to anyone who walked by. She rolled around on the ground like someone with a saturating itch.

Zara, mother of two litters, won't mate this year because there isn't room in North American zoos for more tigers. Only about eight or nine cubs are needed every year to replenish the captive population, so most fertile tigers are kept alone or on birth control. But Zara is lucky: Unlike most zoo tigers she will mate several times in her lifetime, constituting as she does a precious contribution to the captive-tiger gene pool. As early as next year, zookeepers plan to join her with her Minnesota Zoo neighbor and fellow Russian émigré Globus.

To tiger breeders, Zara and Globus are a match made in heaven because both were born in the tundra, among the 400-some wild Siberian tigers left in the world. Zara's mother was killed by poachers when she and her brother were cubs; since they lacked the resources to survive on their own, researchers installed them in Russian zoos, which sent them--via Calgary, where Zara's brother lives--to Minnesota. Globus's mother lost her own mother to poachers before she could teach her how to care for a cub; Globus was taken from her after it became clear that he was suffering severe malnutrition. (Poaching is one of the greatest threats to wild tigers: By some estimates a tiger a day is killed to end up as an ingredient in traditional medicines. TRAFFIC, the World Wildlife Fund's wildlife trade monitoring program, recently found that tiger parts were readily available in pharmacies throughout the U.S. and Asia.)

Zara and Globus's wild origins mean that they are probably not related to any of the tigers in the Siberian Tiger Studbook, a database maintained by Kathy Traylor-Holzer, a research biologist at the Minnesota Zoo. When zookeepers at one of the world's scientifically managed institutions want to mate one of their tigers, they send a request to Tilson and Traylor-Holzer, who run the numbers through a complex mathematical formula to calculate how closely related the animal is to all other managed tigers. A committee headed by Tilson and composed of members elected from zoos with tiger programs then tempers the results with a dose of pragmatism: It is hard for tigers to switch climates or travel great distances, so a Boston tiger will be more likely to receive a partner from Philadelphia than one from Miami.

On the worldwide ranking system used to measure which tigers are least related to any other captive tigers (and thus most likely to be bred), Globus is number 1 out of 61 Siberian males. Zara is number 8 of 48 females. Once their cubs are born, all the rankings will be recalculated to reflect the new kin.

The tiger studbook is part of a series of international efforts to scientifically manage the captive populations of rare and endangered species. Many of the programs are based in Minnesota, including the International Species Information System, a database coordinating the genetic future of some 6,000 rare species at 500 zoological institutions around the world, which is housed in the same building where Traylor-Holzer and Tilson work.

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