Many people feel it is a pity that the 18 months-old giraffe Marius were killed at the Copenhagen Zoo this weekend. But what was really the rational justification for it? And what does this case say about our relationship to animals? The Commissioner of the Copenhagen Zoo are receiving death threats and have in recent days had his inbox full of hate mail.

This weekend the Zoo in Copenhagen took the life of a 18 months old giraffe by the name of Marius. They then fed the remains to the lions at the Zoo. And this has caused outrage, especially abroad, where the big and dramatic headlines have dominated the media.

But what exactly is the Zoo's arguments for putting down a young and healthy giraffe?

The man who did the actual killing, the zoo's own veterinarian Mads Frost Bertelsen, says that, overall, there is a very positive situation behind the Zoo's actions, writes

- Up until now it had not come to this. But now we have reached the point, where we could not rearrange Marius living arrangements. So the best solution was to put him down, says Mads Frost Bertelsen.

The vet explained that a central European coordinator keeps track of pedigrees and which genes are represented by individual giraffes in European zoos. The coordinator estimated from these data that Marius' genes were already well represented. The Coordinator recommended that Marius was killed to protect the population best suited to the gene pool.

- If Marius was placed in a different zoo, he would take the place of a better suited animal. There was nothing wrong with Marius as an animal. There were just others that are better suited, says Mads Frost Bertelsen.

Marius' genes were all well represented among giraffes in European zoos, and he had to give way for a young giraffe with rare genes.

Photos: Here are the remains of the giraf 'Marius' in the cages

Marius was allowed to live for one and a half years. And that was it. At that age you can describe him as a 'teenager'. And his father had already started giving him some bruises - roughing him up .

- In the wild he would leave the group. If he was lucky, he would meet and join forces with a group of other young giraffe males. If he was unlucky he would be killed by lions, says Mads Frost Bertelsen, explaining that it was not unnatural for Marius to leave life at a young age.

In fact, it is the typical young male giraffer who are most at risk of being eaten on the savannah because they do not have the pack to protect themselves in the period, where they are looking for females.

In Copenhagen Zoo they choose to let the animals breed at an early age. Because one of the biggest challenges of having animals in captivity, is that they are bored. They don't have to either find nor hunt for food, fear enemies or diseases.

Therefore it is a great activity for the animals in captivity to have to find a partner, nesting, feeding and raise offspring and finally use the energy to throw the kids out of the pack.

- The side effect is that we have a surplus of animals. It is in fact fortunate that we can use them as food. Instead of killing 20 goats or a cow to, we can use the giraffe to fulfill that function, said Mads Frost Bertelsen.

He points out that in a zoo you use thousands of rats, mice, chickens, pigs, cows, etc. every year.

Chief Zoologist at Aalborg Zoo Jens Sigsgaard says that there is nothing unusual in that, in the Copenhagen Zoo has killed a giraffe that was left over. According to Jens Sigsgaard this is done in all zoos - Also in Aalborg Zoo.

- Our function is not to keep the individual animal alive, but to keep the species alive, says zoologist and continues:

- We have decided to say that even if an animal is over-represented in the gene pool, we would rather let them breed and to have as normal a life as possible. We would rather kill 'surplus-animals' than sending them to zoos we can not accept, he says, explaining that 'surplus-animals' biologically are already dead in the sense that they do not contribute to the next generation.

Aalborg Zoo has several arguments for allowing animals to breed, as it my result in too many babies. As an example, Jens Sigsgaard mentions theOryx Antilope:

- We have a bunch of Orys Antilopes that breed. Some of the calves are genetically inferior to others and will therefore be less likely to get into breeding, but it has happened that suddenly it is possible to relocate them to another zoo. It always depends on the current gene pool (the sum of antelope genes in zoos, which are constantly changing ). Therefore, we let them breed, and when there are animals that can not be placed somewhere else, they will be used as food, says Jens Sigsgaard .

For the females it is also important to have offspring. Offspring that they - as it is in nature - will have to part way with, when they have grown old enough.

- The animals were allowed to breed because it is an important part of their natural behavior that they get offspring and experience parental care. Parental care is one of the best and most natural ways to occupy animals in captibity, says Jens Sigsgaard and continues:

- But in nature there comes a time when the baby is old enough to break away for the mother and maybe become part of another group. That is the time, where we try to find another well-suited zoo. And if that can't be done. The young animal has to be put down.

- The animals can also be adversely affected if we do not allow them to breed and have offspring . Because they may find it difficult to start breeding again.

And if there are no kids in the crowd, the younger animals will not get the experience of how to care for babies. Besides contraceptives for animals, such as p-rods (a contraceptive where a hormone stake is put under the skin), are not as well-tested and proven effective as in humans, and as a result the kids can be born with birth defects .

Also it is rarely an solution to put the 'surplus animals' back in the wild again. Because it requires at least four conditions:

1. Resources - money and manpower: It's a big and expensive project to set animals free.

2. Each animal must be able to survive in the wild. It's far from all surplus animals, that are suitable for it.

3. The animals we put back in the wild must be the most appropriate to the population, we want to build or supplement. And that is not often the case

4. Location. Zoologists need to find a suitable place to let the animals out, and the local population must be prepared to pay more, which is not always possible, for example, lions, people rarely want to sneak around the neighborhood.

In the Aalborg Zoo they recently put down several warthogs that was in excess. At that point there was no major reactions of the audience.