The main problem with this is that they really shouldn’t be breeding the giraffes if they don’t have either the space or inclination to rehome them. The same zoo, in the past, has allowed the leopards to breed then euthanized the cubs when they stopped being cute.
I mean, from a pure conservation standpoint, I suppose I can see the sense, but I don’t see how allowing a large zoo animal to breed when there is no home for the young is any less irresponsible than letting your domestic cat breed freely. It’s seen as bad practice in almost all other zoos, and I think rightly so. Yes, ‘surplus’ males are a common problem in some species (how can they not be in species where females are happiest in groups, only one male can be kept with them, and equal numbers of each are born?) but it’s a problem most decent places go to great lengths to minimise, maintaining bachelor groups (as happens in the wild), rehoming them, and only euthanising when all other avenues have been explored.
It’s not that hard in a good set-up to prevent most large animals from breeding; you can seperate them in season, get them sterilised permanently, or even get temporary contraceptives for some species. I don’t see why we should hold zoos to a lower standard of animal care than domestic pet owners.
Incidently, I do say this as someone who’s worked in several UK zoos- and my family run one. The only healthy ‘surplus’ animal that’s been put down there in the last 22 years was a male meerkat that was thrown out of the group, and we spent over 6 months trying to rehome him before it became obvious that he was not coping at all with a solitary life, and was starting to mentally suffer. Everyone was miserable about it for weeks. Meerkats form large family groups- you can’t really stop them from breeding but keep them in a natural colony. Giraffes don’t have the same issue.