I find zoos to be one of the most depressing places on earth, keeping animals caged up is just vile especially when they aren't from the geographical region. The only exception i'd have to that rule are domesticated animals - ie when some fuck has decided that a leopard would make a great pet and then it dawns on them that its a big animal that will kill them. We had an exotic animal rescue centre near aberystwyth, where I did my undergrad degree, and they had an abandoned leopard . The other exception would be animals at risk of extinction from human interference (not fucking Panda's, its their own fault and we can do nothing to stop it)/poaching.
But when I end up in a zoo the Monkeys always fascinate me, esp the gorillas.
I love Cracked & QI, but the love they've generated for that animal is irritating. A polar/grizzly bear is far more badass than that. A natural resilience to venom isn't unique to them, its just a wonder of evolution.