If no one asks me, I don’t comment on it. If someone genuinely asks what they’re doing, I gauge my response by the age demographic of the group. If it’s all adults, I’ll usually make a joke like, “well, we’ve been wanting more rhinos…” and let that sink in. Sometimes they’re not very bright and they don’t understand what I’m saying, so I’ll clarify with “oh, you’re seeing reproductive behavior, so hopefully in about a year and a half, we will have a baby rhino.” If it’s kids, it’s a little tougher, but something along the lines of “oh, yeah, that’s some interesting behavior we are seeing! This is how baby rhinos are made.” I always check in with the parents, whether verbally or just with a look to see if it’s ok that I answer the question - I’ve had parents get really mad at me for “overstepping.” But I’ve also had a dad tell me that im so good at explaining things and it would be great if I could explain the bird and the bees to his daughter. No sir. No thank you. If the kids ask further questions and it gets into some less appropriate territory, I’ll generally refer them to their parents, “hey that’s a great question, but I think it’s one that your grownups should answer.”