AMSTERDAM, Netherlands -- Joerg Jebram, who oversees the European Endangered Species Program for giraffes, explains why he believes the Copenhagen Zoo was correct in its decision to kill 2-year-old Marius.

Q: How did the zoo end up with a young giraffe it couldn't keep?

A: Whether male or female, giraffes born in zoos will eventually need to be moved away from their family group once they reach sexual maturity. That's because breeding groups in zoos are made up of a single bull together with a group of females. Female offspring must eventually be removed to prevent inbreeding, and bulls must be removed somewhere around the age of 18-24 months, depending on the individual, to prevent fighting.

Q: What usually happens with giraffes ready to leave their family?

A: Females are normally moved to a new breeding group when they are old enough. Bulls are sent to zoos that keep a "bachelor" group. When there are no females present, males can coexist peacefully. In this case there were no acceptable openings. Historically, many of the 347 zoos that belong to the Amsterdam-based European Association of Zoos and Aquaria (EAZA) were eager to have giraffes of any kind. But in the past several years zoo breeding programs have produced enough of some subspecies. Jebram says he believes two other young bulls have been euthanized in Europe since 2012.

Q: Aren't there other options?

A: Zoos could design new giraffe facilities, but many don't have that option. A young bull could theoretically be sent to an all-female group as stud, but experts prefer a larger, more mature male for that, and Marius didn't fit that bill. A final option is sending the giraffe to a zoo that doesn't participate in the EAZA-led breeding program, but that could leave the giraffe or its offspring being sold into worse circumstances, such as those of a circus or private collection.

He said it must be remembered that Marius was not from a rare subspecies.

Q: Weren't contraceptives or castration viable options?

A: Yes and no. Until recently, either would have required sedation, which is a relatively high-risk operation with giraffes. They are liable to break their necks when they fall while sedated. In the past several years, a contraceptive has been developed that can be injected into females from a distance.