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Gory Details

The bizarre side of science
Erika Engelhaupt

Gory Details

Why was Marius, the euthanized giraffe, ever born?

Many European zoos allow captive animals such as giraffes to breed as they would in the wild, while American zoos generally use contraceptives to prevent pregnancies outside of breeding programs.

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Marius the giraffe was a surplus animal, from the Copenhagen Zoo’s perspective. His genes were common within the facility’s breeding program, so he could not be allowed to mate with females because of the risk of inbreeding. He died February 9 from a shot to the head with a bolt gun.

A furor erupted after Marius was killed, necropsied and fed to lions. Whatever you think about the case of Marius or how the zoo handled it, his death brings to light a different way of thinking in U.S. versus European zoos about what constitutes a “natural” life for a zoo animal. And one of the biggest decisions zoos make is one that few zoogoers think about: birth control for animals.

In Europe, zoos generally do not use contraceptives to prevent unwanted animal pregnancies, a common practice in the United States. Zoos that belong to the European Association of Zoos and Aquariums subscribe to the idea that contraceptives disrupt an animal’s natural behavior. “In Copenhagen Zoo we let the animals breed naturally,” reads a statement from the zoo. “Parental care is a big part of an animal’s behavior. It is a 24-hour job in longer periods of their lives and we believe that they should still be able to carry out this type of behavior also in captivity.” The zoo also said that contraceptives can have “unwanted side effectson the internal organs” of animals.

This argument boils down in large part to what humans consider natural or desirable for a captive animal. Since captive animals live such constrained lives already, there’s an argument for letting them have babies so they can have at least one part of their lives that (we humans think) is deeply satisfying for them.

The problem comes when the babies grow up and, like Marius, become surplus. The European solution is to euthanize some of these extra adults once the parents have raised them. Marius’ case got public attention, but similar euthanasias happen regularly. Another giraffe, also named Marius, was considered for euthanasia in Denmark shortly after the first Marius uproar, and six lions were recently put down at an English safari park after a spate of pregnancies. In 2012, the Copenhagen Zoo’s conservation director Bengt Holst told the New York Times that the zoo was putting down 20 to 30 exotic animals per year, including hippos and even occasionally chimps.

But in the United States, contraception for non-breeding populations is the norm. The Saint Louis Zoo maintains a wildlife contraceptive center that does research on zoo animal contraception and advises zoos on contraceptive methods. They also track the safety of contraceptives. Various birth control methods have been used in more than 600 species, the program reports, in mammals and in some birds, reptiles and fish. There are contraceptives for females, including some of the same hormones used in human birth control and even IUDs, and contraceptive methods for males, including vasectomies and castration. As in humans, hormone contraception can have side effects, though the Saint Louis Zoo program argues they are used safely in many zoos, where they allow animals to live in natural social groups instead of being segregated to avoid mating.

Birth control for female giraffes includes a synthetic progestin hormone called MGA added to their feed or Depo-Provera injections. For a variety of male mammals, vasectomy (sometimes reversible) and castration are the most common contraceptive methods, though there has been success in some species with hormone suppressors called GnRH agonists. Those suppressors have not been effective in male giraffes, but vasectomies have been performed in giraffes.

That circles us back around to the fundamental problem presented by Marius’ birth. Once born, a zoo animal takes resources to maintain, and maintaining genetic diversity is an important and legitimate consideration for a breeding program. So should European zoos use contraceptives to prevent surplus animals in the first place?

I would like to think science would be the guide. The Saint Louis program has produced a book laying out both risks and benefits of wildlife contraception, and there is a track record in U.S. zoos that European zoos can evaluate. But value judgments are sure to come into play wherever animal welfare is concerned. After all, how many times have you heard a cat or dog owner refer to neutering a pet as cruel?

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