People around the world were stunned when Copenhagen Zoo killed a healthy 2-year-old giraffe named Marius, butchered its carcass in front of a crowd that included children and then fed it to lions. But Marius' fate isn't unique—thousands of animals are euthanized in European zoos each year for a variety of reasons. Zoo managers say their job is to preserve species, not individual animals. In the U.S., zoos try to avoid killing animals by using contraceptives to make sure they don't have more offspring than they can house, but that method has also been criticized for disrupting animals' natural behavior.
HOW OFTEN ARE LARGE MAMMALS KILLED IN ZOOS?
U.S. and European zoological organizations refuse to release figures for the total number of animals killed. But David Williams Mitchell, spokesman of the European Association of Zoos and Aquaria, or EAZA, estimates an average zoo in its 347-member organization annually kills about five large mammals, which adds up to 1,735.
The number doesn't include zoos and animal parks that don't belong to the association. Animal rights groups suggest numbers are much higher. The Associated Press contacted 10 zoos in Europe— two refused to comment, four said they never kill any animals unless severely ill and four said they kill between one and 30 animals every year. Two zoos in the U.S. said they only ever kill animals for "quality of life reasons."
WHY ARE ANIMALS KILLED?
Zoos euthanize animals because of poor health, old age, lack of space or conservation management reasons. EAZA policy for zoos in Europe suggests euthanasia may be used as a last resort to achieve a balanced population within breeding programs—Marius was killed to prevent inbreeding. But Williams Mitchell insists only "a fraction of 1 percent" of the killings are for such reasons. The idea is to maintain a group of genetically healthy animals in zoos that can be used to reintroduce the species into the wild should it become extinct.
Some U.S. zoos were reluctant to comment on Copenhagen's practices, but there is a philosophical divide between U.S. and European zoos over best practices. The U.S. Association of Zoos and Aquariums said Thursday that incidents such as the giraffe killing "do not happen at AZA-accredited zoos."
Mike McClure, general curator at the Maryland Zoo in Baltimore, says his zoo's policies theoretically allow for killing animals for breeding purposes or lack of housing, but it's not something his zoo has done. Generally, he says, animals are only killed due to quality of life issues such as old-age or ill-health.
In Asia, the parent company for the Singapore Zoo said in a statement that "euthanasia of animals is necessary to maintain the health and welfare of the herd, as overcrowding could lead to injuries, stress, and disease outbreak. "
"All animals in zoos die at some point and maybe zoos forgot to tell people," said Jens Sigsgaard, zoological director at Aalborg Zoo in Denmark, which, like Copenhagen Zoo, performs open dissections of animals for educational purposes. "They come year after year. They probably think it's the same animals that were there when they came as kids."
WHAT DO ZOOS DO TO AVOID KILLING ANIMALS?
When animals reproduce, most zoos first try to find another one in their network they can send the offspring to. Earlier this week, a German zoo said it would send a monkey to the Czech Republic because he's produced so many offspring that he would soon start having children with his own relatives.
Zoos generally avoid selling the animals on the open market, fearing they will end up in poor conditions. Some European zoos and most zoos in the U.S. choose to use contraceptives, sterilization or separation of males and females to avoid breeding more animals than they can house.
Sharon Dewar, spokeswoman for the U.S. animal Population Management Center, says animals there are recommended to "breed only when sustainable housing for any offspring can be assured." That approach is dismissed as "totally wrong" by Bengt Holst at Copenhagen Zoo, who says breeding is important for an animal's well-being. EAZA's Williams Mitchell says there is an ongoing discussion and expects Marius' case to intensify the debate.
Cheryl Asa, director of the AZA Wildlife Contraception Center, says just because contraceptives are used it doesn't mean an animal will never breed. She also says "most of us are very happy to have our pet dogs and cats spayed and neutered, and I've not heard any of my friends or neighbors talk about worrying that their dog or cat was missing out on something in life if they hadn't had a litter of puppies or kittens."
WHAT KINDS OF ANIMALS ARE KILLED?
Both endangered species and other animals are killed at zoos. EAZA says five giraffes have been killed in European zoos since 2005.
On Thursday, Jyllands Park Zoo in Denmark said it may have to kill another giraffe soon for similar reasons as in Marius' case. Coincidentally, the giraffe's name is also Marius.
Skansen zoo in Stockholm says it euthanized one bear and one Eurasian lynx last year, while Helsinki Zoo killed one Alpine ibex. Aalborg Zoo in Denmark kills up to 15 animals a year, including red river hogs, antelopes and capybaras.
In addition to Marius, Copenhagen Zoo says it kills 20-30 antelopes, llamas, goats and other animals yearly. Some zoos also raise pigs, goats and cattle to feed carnivores.
WHAT DO CRITICS SAY?
Animal rights groups have said Marius' case highlights what they believe is the overall problem with zoos. The Captive Animals' Protection Society says its studies show between 7,500-200,000 animals are considered "surplus animals" at European zoos at any one time and director Liz Tyson says the only solution to the problem is not to visit zoos.
Will Travers, president of the Born Free Foundation, questioned whether the zoos' breeding programs contribute that much to conservation. He says research by his foundation has shown the majority of species kept in zoos aren't threatened with extinction in the wild and called for an immediate review of EAZA's euthanasia policies.
Explore further: Are zoos really a setting for ecotourism?