Sometimes, zoos can have too much of a good thing

The San Diego Zoo's female elephants, including these two, are all on contraception. Their advanced age could cause complications during a pregnancy, said zoo spokeswoman Yadira Galindo.  /  Photo by Peggy Peattie, U-T
A couple of female Visayan warty pigs dig for food in their enclosure at the San Diego Zoo. They are kept separate from their male counterparts to prevent breeding. / Photo by Peggy Peattie, U-T

At the San Diego Zoo and Safari Park, animal births are normally celebrated. Photographs are snapped. Naming contests are held. Pandas? Oh, the zoo goes ape when it comes to the arrival of a new panda.

In some cases, though, the zoo doesn’t want a bundle of joy.

An animal may be getting up in age and a pregnancy might be dangerous. The males and females could be too closely related, causing concerns about inbreeding. The animals may be just too good at making babies, leading to overpopulation.

So like zoos nationwide, the one here does gender separation or puts the creatures on birth control. Affected species include lions, Visayan warty pigs, sika deer and elephants, among others.

“The zoo’s female elephants are all on contraception,” said Yadira Galindo, a zoo spokeswoman. “The advanced age could cause complications during a pregnancy, so the decision was made to put them on contraception.”

Zoos nationwide do this. It’s a little bit ironic, though. Many zoos work tirelessly to preserve those species that are threatened and endangered in the wild. But the zoos also have to make sure some animals they house don’t strain their facilities’ limited spaces by procreating at a rate that’s unsustainable.

Take the sika deer at the Safari Park, for instance. That species of Asian deer doesn’t have a problem when it comes being fruitful and multiplying. So some of the males have undergone vasectomies. If males are needed again to breed, the vasectomies are reversed.

These are the more drastic measures undertaken to avoid unwanted pregnancies, though. The zoo prefers, when it’s possible, merely to separate the males and females.

That’s the case with Visayan warty pigs. They’re critically endangered and hadn’t been bred in zoos outside of the Philippines, according to the zoo. But they must like the air in San Diego or something. They were so prolific they had to be separated. All the ones on exhibit at the zoo are females.

For some species, that’s perfectly natural. In the wild, many deer species form bachelor herds and stay away from the females until nature calls.

But for others, it’s more complicated. Take the zoo’s lions, Mbari and Etosha. They live together because that’s what lions do in the wild. But Etosha has given birth twice and suffered complications, so the zoo made the decision to sterilize her.

Contraception for zoo animals is not something that’s universally accepted. A number of European zoos don’t believe in the practice, arguing that it’s unfair for animals not to experience the joys of sex, pregnancies and parenthood. In the wild, after all, this is what animals do.

But that philosophy causes its own set of problems. If the offspring is unwanted, it’s sometimes killed. In some cases, the meat is fed to the lions.

“It’s a cultural difference,” said Cheryl Asa, the director of the Association of Zoos and Aquariums’ Wildlife Contraceptive Center at the St. Louis Zoo. “I can’t imagine people in the United States accepting that practice.”

It is, however, a more natural one, she said. Young animals in the wild are susceptible to disease and predators. They do indeed die. “But what’s not more natural is humans, not Mother Nature, doing the killing.”

The practice has come under fire. In 2008, in a Switzerland zoo, a baby hippo was born that quickly captivated the nation. But there was one problem: There was no room for the new guy. Once he reached maturity, he and his dad were going to battle for dominance. It’s what male hippos do.

The baby hippo ended up being shipped to a game reserve in South Africa last year.

U.S. zoos have little choice but to use birth control because many animals breed quite well in zoo environments, Asa said. “You always hear about the animals that don’t breed well. What you don’t hear about are the ones that breed too easily.”

Big cats, for one.

At a Bangladesh zoo, new lions and tigers began overwhelming the facility recently. It had room for 16, but the number jumped to 36. It had to put the animals on contraceptives.

While separating the animals is an effective tool, that practice should also be limited, Asa said. It dates back to the early days of zoos, when it was the only option available. But some animals are social creatures and enjoy the company of other animals. Keeping them apart can cause behavior problems.

It also lessens the zoo-going experience for the public. It’s not as enthralling to see animals all by their lonesome, she said. The zoos are supposed to duplicate the animals’ experience in the wild as closely as possible.

There are a number of safe birth-control methods, she said. For primates, human birth control, such as the Pill, can work. Implants containing a synthetic progestin which block ovulation are also a popular method.

Still, this is relatively new science. Zoos started using contraceptives in the 1970s. The AZA Wildlife Contraception Center was established in 1989. It doesn’t recommend which animal should be on birth control, Asa said. It just provides the different methods.

They don’t always work, apparently. Last August, at the Topeka Zoo in Kansas, a hippo gave birth. She was on contraceptives so the zoo was quite shocked. It didn’t realize the hippo was pregnant until a day before the big day.

Just recently, the father was flown to the San Francisco Zoo because the three wouldn’t be able to live together at the Topeka Zoo.

The San Diego Zoo said it couldn’t provide a complete list of animals on birth control because that number changes regularly. “This season an individual animal may not be breeding but next season it will,” Galindo said.

Nor could the zoo give a tally of how many animals are born at the zoo yearly. That shifts because of the “changes based on recommended breeding programs,” Galindo said.


The breeding of captive animals has become a very sophisticated operation. The AZA runs a national program called the “species survival plan.” Breed diversity is an important goal, particularly when it comes to animals that are endangered or threatened. Creating the most genetically diverse offspring is goal, so the animals don’t suffer from disease or other health problems.

The San Diego Zoo has been hit with criticism when it comes to handling surplus animals. In 1991, it sold two surplus sika deer to an private conservation organization that had ties to a hunting ranch. The zoo didn’t realize that, so it had to get the deer back. The zoo suffered a terrible public relations hit for not vetting the ranch more carefully.

The current practice of vasectomizing the animals is not related to that incident, the zoo said.

In Defense of Animals fully supports the use of contraceptives in zoos. Many zoos have reached capacity when it comes to some species, said Anand Ramanathan, the chief executive officer for the animal rights organization.

Big cats and hoofed animals are examples, he said. If they were allowed to breed at will, the zoos would be overwhelmed.

And some of those animals might be doomed, he added.

“These surplus animals can end up in roadside zoos, with unscrupulous individuals or even in canned hunts or in illegal wildlife trade,” he said.