On February 9, 2014, the giraffe Marius was shot at the Copenhagen Zoo because he did not fit into the breeding program, and was fed to the lions. A month later, 2 adult lions and 2 cubs of 10 months were killed in the same zoo. The lions "had reached the end of their natural life in captivity and must make way for a new generation". The cubs were killed because "they were not able to take care of themselves," said the zoo.

At any given time, there are about 7500 surplus animals for which there is no money and space, and therefore they are sometimes sold to other zoos or to animal dealers, but are usually killed. As long as European zoos do not apply contraception to prevent surplus animals, the killing of healthy animals will continue to exist.