On February 9, 2014, the giraffe Marius was shot dead in 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 10-month-old cubs were killed in the same zoo. The lions "had reached the end of their natural life in captivity and had to make way for a new generation." The cubs were killed because "they were not able to take care of themselves," according to 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 traders, but most often killed. As long as European zoos do not apply contraception to prevent surplus animals, the killing of healthy animals will continue.