ROBERT THOMAS ALLEN,Brian D. JohnsonDecember131982
A helping hand for an altered love life
The Metro Toronto Zoo has nine gorillas, and their keepers would be delighted to enlarge the tribe. But that is proving to be an extremely elusive goal. It has been more than two years since the births of Tabitha and Natasha, daughters of Josephine and Samantha, respectively —a rare achievement for captive gorillas. Since then, however, the two males at the zoo, Charlie and Barney, have remained aloof from the females. Zoo officials cannot tell whether one fathered both youngsters or each sired one, but their immediate concern is to determine the reason for the gorillas’ failure to mate again. There is also a possibility that one or both of the gorillas may have since become sterile, a phenomenon that has been detected in captive gorillas in other zoos around the world.
But sterility is just one of the problems confronting zoo officials. Overpopulation of animals not in great demand for breeding often forces zoo population-management experts to devise birth control methods. Still, whether the problem is the failure of valuable animals to mate or the overbreeding of some species, zoo officials may look to ISIS, the Minnesota-based computermating bank, to solve their problem.
Named after the ancient Egyptian fertility goddess, the International Species Inventory System provides a link with 145 other zoos in North America. All 2,000 mammals and birds in the Metro Toronto Zoo are registered with
ISIS, and the reptiles will be listed next.
For less than $1.70 per animal, ISIS enables a zoo to register its population and have instant access to information on animals in other zoos. Founded in 1973 by zoo officials in Minnesota, ISIS is run by a group representing zoo associations and veterinarians and it is supported by subscription fees and grants. “The idea behind it,” says John Carnio, a curator and trainer whose special interest is population management at the Metro Toronto Zoo, “is that all the animals in captivity be part of one population. This keeps the gene pool flowing among zoos and cuts down on inbreeding.”
Zoo incest is already a major problem. North America’s 226 Siberian tigers, for example, are descendants of only 17 original imports. Such inbreeding often results in a loss of fertility, a greater incidence of stillbirths and a reduced resistance to environmental and climatic change. ISIS enables a participating zoo to mate animals of different lineage and counteract the tendency of a single family’s traits to overrun the species.
The continuing ISIS census helps warn zoo officials about overpopulation in certain species, a problem that zoos only wish they had with their gorillas. Various forms of population control are used in the case of animals that zookeepers do not want to breed. Planned parenthood for lions, for example, consists of the insertion of a silicone implant containing experimental hormones in a small incision behind the shoulder of each lioness. Released gradually over a period of two years, the hormones have the same effect as a long-lasting birth control pill.
Whether research is focused on family planning or the problem of infertility, it is equally exhaustive. Before a decision is taken to enlist the help of ISIS to find new gorilla mates for Samantha and Josephine, for instance, Kay Mehren, head of veterinary services at the metro zoo, is trying to pinpoint the reasons for the gorillas’ failure to produce more offspring in the past two years. Says Mehren: “You may find sperm count low with an individual, but climate, nutrition, compatibility with cage mates and the time of year may all be contributing factors, and I’m sure there are others we don’t know anything about.” Theories abound. It has even been suggested that heated floors have an effect on gorillas’ testicles.
The decreasing number of animals in their natural habitats throughout the world underscores the importance of zoo breeding programs. In the case of gorillas, it is estimated that there are now only about 11,500 left in their natural habitat. Only 3,000 of these are in conservation areas, where largely ineffectual efforts are made to protect them from hunters. As Toby Styles, the overseer of the African and American displays at the metro zoo, says, “We can send a man to the moon but we can’t create a gorilla.” Indeed, zoos and their breeding programs may not only be the gorilla’s last hope but also that of many of the gorilla’s four-legged friends, such as the gazelle and the rhinoceros.
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