Denmark, the land of enchanting fairy tales and liberal social values, is becoming known as the land of dead zoo animals.

The Copenhagen Zoo, which generated global outrage last month when it killed a healthy 18-month-old giraffe named Marius, said it had to euthanize four lions this week to clear the path for a newly arrived young male lion. The zoo’s decision created a backlash on social media on Wednesday, with some calling the zoo’s staff members “serial killers” and “murderers.”

The zoo justified the killings of the two parents, ages 14 and 16, and their cubs on the grounds of genetic purity and conservation, noting that the new lion would invariably prey on the cubs, while there was a risk that the older male lion would try to breed with one of the female lions that were his offspring.

“If the zoo had not made the change in the pride now, then we would have risked that the old male would mate with these two females — his own offspring — and thereby give rise to inbreeding,” it said in a statement on Wednesday.