About 5% of the resultant comments were shrill parents squealing "Won't somebody please think of the children?" and denouncing the zoo for posting it, calling it downright pornographic. The other 95% of the comments were devoted to making fun of those 5%.
I was with the 95%.
There is no aspect of zoo animal life, I've noticed - not euthanasia, not predation, not pooping, not nursing - that makes visitors so uncomfortable as sex. Sex trumps all. I've had guests cover their children's eyes and hurry them away from mating animals. I've had guests (and keepers) shout bawdy encouragement to breeding animals. Some have been outraged and demanded that I stop the animals from doing it, at least during public hours (How? Shock collars?). I've also had lots of visitors try to make me uncomfortable by asking questions, in front of audiences, about the sex lives of our animals. Never try to make a zookeeper uncomfortable, especially on their home turf. We'll always win.
There have also been plenty of people who are just so naive about what they are seeing and how it works that I swear, they've had a paper bag over their head for their entire life, up until the exact moment they walk through the front gate. And I'm not talking about children, either... to the kids, I usually just explain, "That monkey is just playing a game with the other one." Close enough.
The fact is, for those who are willing to blush a little bit, there's a lot of fun animal facts relating to sex and mating. Female spotted hyenas have almost identical reproductive organs to the male. Snakes have forked penises; ducks have corkscrew shaped ones. Slugs and snails are hermaphrodites. The antechinus (a mouse-like marsupial from Australia) will literally have sex until he dies of exhaustion. Being hung like a Malayan tapir is a compliment. Being hung like a gorilla is not.
Lots of fun facts - if you're willing to hear them.
I once gave a tour to some teenage boys, and saw their interest was flagging a little bit, no doubt wondering where the girls were. So when we got to the lions, I told them how the male has keratinized spines on his penis, which jolt the female as he withdraws, thereby stimulating ovulation. Only drawback for him is it hurts the lioness just enough to make her bitch-slap him in irritation. That got their attention. After the tour, one of the attending mothers came up to me to let me know that one of the other mothers was offended by that story. Or at least I think that's what she was trying to tell me. She couldn't stop laughing, much to the chagrin of the other mother, who was pacing awkwardly in the background.
I don't how what that lady thought her son and his friends were talking about when she wasn't in the room... but probably not baseball.
Sex at the zoo (for animals - not visitors or staff... though I have come across a few examples of both before) is perfectly natural. It's how we replenish our collections. It's how we build populations of animals, some of which may (someday) be used to restock the wild. But the animals don't think of it in those terms. To them, it's just part of life, as natural as eating or sleeping.
Spend enough time with them, and you may start to view it the same way too. Just be careful sharing the details with everyone else.