The Copenhagen Zoo recently killed four members of a lion family because the cats didn’t meet the needs of the zoo’s captive breeding program. The same zoo killed Marius the giraffe last month for similar reasons.

The lions weren’t useful for reproduction anymore because the 16-year-old adults had passed their peak breeding years, reported the AP. Their final offspring, two 10-month-old cubs would have been killed by a 3-year-old lion destined to rule the Copenhagen Zoo’s pride. The zoo recently acquired the young male as a stud for two 18-month-old females.

Although animal advocates question the zoo’s ethics, the Copenhagen Zoo mimicked nature by killing the old and young. In the wild, young lions attack and sometimes kill dominant older males. The marauders seek to displace old kings and conquer their harems of lionesses.

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At the Copenhagen Zoo, the new king of the pride wouldn’t have tolerated the presence of cubs he hadn’t sired. When young male lions take over a new pride, the cats kill cubs younger than approximately nine-months-old, despite the fierce protection of their mothers.

Once the cubs die, a biological signal sends the females back into fertility. Infanticide allows the newcomer to focus his energy on fathering his own cubs before he too becomes sick, wounded or old, then loses control of the pride to yet another interloper.

However, People for the Ethical Treatment of Animals and others have questioned the ethics of culling cubs.

“Like domesticated cats, big cats breed, unless you make sure that they are sterilized, and that is exactly what the zoo had an ethical obligation to do, rather than bringing cubs into the world simply to bump them off,” a PETA spokesperson said in the Daily Mail.

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Last month, the Copenhagen Zoo attracted similar criticism for killing Marius the giraffe, dissecting him in public and feeding him to lions. The zoo killed Marius because he had a common pedigree. The zoo couldn’t use him as a stud because he as too related to other giraffes in captivity, nor did the zoo want to pay for the upkeep of a genetically-useless giraffe.

A zoo spokesman stated that the zoo doesn’t use contraceptive techniques to prevent unwanted giraffe births because it interferes with natural breeding cycles and biological rhythms.

Besides contraception or killing, other potential options for the lions included donation to another zoo or even rehabilitation for reintroduction into African conservation areas, like captive-bred Christian the Lion or orphaned Elsa the Lioness.

A Copenhagen Zoo spokesman told CNN that efforts to place the lion cubs with other institutions had failed. The European Association of Zoos and Aquaria told CNN that the Copenhagen Zoo met high standards of animal welfare and culled the lions in accordance with established policies.

Photo: An image of a lion. Credit: Flickr: elPadawan