In Zoo Tycoon 2, one of the expansion packs has programming that prevents animals related to each other from mating. At first, it sounds like Fridge Logic; after all, animals do often mate with their relatives. But think about it: in the game, one of the goals is to breed healthy offspring, as is one of the goals of many real life zoos. And in real life, zoos do not allow animals too closely related to each other to mate, even going so far as to perform genetic tests on them.
Why are some of the animal models reused? Because animal families are related. There isn't all that much biologically different between a Lion and a Leopard.
In the Zoo Tycoon Marine Mania expansion pack, you're able to create mermaid exhibits. The mermaids will flirt for visitors and act relatively human, but place a shark of any species in with them... It makes you wonder if this is why there aren't any mermaids. Great whites are particularly fond of them...
The fact that you can keep a clearly sapient creature in a zoo is pretty horrific in itself. Looks like the Zoo Tycoon universe doesn't go in for Inhumanable Alien Rights.
Then again, who’s to say mermaids can’t be kept in zoos by choice? If they don’t mind living there, and they are healthy, well-cared for and have plenty of space in their tanks, I don’t think there should be anything wrong with it. Plus, maybe the zoo could even just release mermaids if they really wanted to be released. Also, mermaids are aquatic creatures, so how else do you expect them to interact with the public (and they're obviously rarely seen in their natural habitat anyway, right?). Even some aquariums in Real Life use mermaids (well, they're actually people dressed as mermaids, of course, and they work there as employees, rather than actually living there).
Then, there's the fact that to get a mermaid, you have to take a mermaid statue and put it in a tank and then the statue starts shaking and then the mermaid bursts out. This raises all sorts of questions, none of them good.
In Zoo Tycoon 2, you can release animals to the wild. That's all well and good, but you can also release extinct animals. And not just the recently extinct like the dodo or thylacine, you can release animals like a T. rex or Deinosuchus. Not only could these animals be a massive threat to any people now living in their native habitats, they'd almost surely cause chaos in the modern ecosystem in the area.
