The zoo official who euthanized a giraffe and four lions earlier this year may be stoking more controversy.
Many zoos, especially in the United States, are perpetuating a fairy-tale world that masks the realities of nature from visitors, he said this week in Copenhagen.
"We should not tell the Disney story that animals are only cute and only get born and never die," said Bengt Holst, the Copenhagen Zoo's science director, at the 2014 Euroscience Open Forum. "We have to tell the real story: 'Death is a natural consequence of life.' If [we] don't tell that story, [we're doing] a bad job, because then we don't work for conservation—we work for an imaginary world." (Related: "Hey Kids, All Deer Aren't Like Bambi.")
Zoos in Europe have been euthanizing, or culling, captive animals for about 30 years. The goal has been to create a healthy and genetically diverse population of different species, many of which are threatened by extinction. Animals are sometimes killed to make room for other animals or to avoid inbreeding.
European zoos also breed more animals than they need, because it's impossible to predict how many females will get pregnant and give birth to healthy offspring.
Holst told National Geographic on Wednesday that the need to euthanize is actually a "positive sign," since it means that zoos are breeding animals well enough to create a surplus.
The Mercy Rule
According to rules set by the European Association of Zoos and Aquaria, a "quick death without suffering" is permitted when a captive-breeding program yields too many animals.
The U.S. Association of Zoos and Aquariums did not respond to a request for comment. But in a previous email interview, the AZA's senior vice president of external affairs, Rob Vernon, said that euthanizing healthy animals is not as common in the United States as it is in Europe.
"Each of our accredited zoos and aquariums follow humane euthanasia practices, which are most often used for medical reasons related to quality-of-life issues or to prevent the transmission of disease," he said.
According to Holst, culling zoo animals is the same as what happens in the wild. For instance, only one in four African lion cubs makes it to adulthood; many are eaten by adult lions.
Zoos "are afraid to talk about the real thing," Holst said. "Some zoos in the U.S. don't dare show that animals eat carcasses, or [that the zoos] feed them cat food. That's crazy, because that's not telling the right story."
Dalia Conde, a biologist at the University of Southern Denmark who studies and supports zoos, says that too many of them avoid shocking or saddening visitors, which is counterproductive to saving rare species.
"People say, 'We don't want to talk about the biodiversity crisis in zoos because people are so depressed.' Ten percent of the planet's population [goes] to the zoo every year. If all those zoos really have a strong commitment [to] education and conservation, they can make a huge difference."
But Conde says there are other factors at play. Some U.S. zoos, for instance, avoid putting bonobos—a chimp relative—on public display because of their frequent sexual activity, whereas European zoos don't have such rules.
"It's really challenging to [determine] the role of zoos," she said. "[Should they present a] fairy-tale Bambi story? Or [should they] show ecology, evolution, mortality, and reproduction to the general public?" (Read more about zoos and saving rare species in National Geographic magazine.)
Others experts, like Marc Bekoff, professor emeritus of ecology and evolutionary biology at the University of Colorado, Boulder, say killing zoo animals in most instances is simply ethically wrong.
"None of the [Copenhagen Zoo] deaths were euthanasia, which is a mercy killing when an animal is suffering or lingering near death and must be 'put down,' as zoos always refer to such situations," Bekoff wrote in a March opinion piece.
"Rather, it was 'zoothanasia,' or killing done by zoo workers because an animal is no longer needed for one reason or another and is deemed to be a disposable object rather than a sentient being." (Related: "Opinion: Killing of Marius the Giraffe Exposes Myths About Zoos.")
Many in the public agree.
In February, an online petition—which asked the Copenhagen Zoo to hold off on killing its unwanted giraffe named Marius until another home could be found—received tens of thousands of signatures from around the world. Wildlife parks in Britain, Sweden, and the Netherlands also offered to take Marius in. (Related: "National Zoo Deaths: 'Circle of Life' or Animal Care Concerns?")
But Holst says the decision not to relocate the giraffe was based on his zoo's commitment to "always take responsibility for our animals from A to Z. We don't just send the animals to strange places that don't cooperate under the same framework as we do."
Though Holst says he was "surprised" by the global outcry, he's glad that the question of how to best manage zoo populations is now "on the agenda all over the world."
For instance, the controversy has highlighted many countries' restrictions on moving animals across borders, which prevents facilities from maintaining viable populations of zoo animals. For instance, if new animals aren't introduced to zoo populations, the existing animals can become inbred. (See "Is Breeding Pandas in Captivity Worth It?")
"Strict legislation is good at protecting animals from illegal trade," Conde said in a statement, "but unfortunately it can also prevent zoos from exchanging animals."
The Copenhagen Zoo is working its way through what Holst calls nine months of "bureaucratic red tape" as it tries to send two endangered Amur leopards to the U.S. He said zoos should work together to get these laws changed in order to allow movement of animals.
"Too many zoos all over the world are bragging of working for conservation without doing what they're actually supposed to do," he said. "That destroys [the reputation] of zoos—they have to take on that role even if it costs money. Those who are only talking about it should get [it] together."