"Tigers are a kind of animal" is correct

tigers are a kind of animal ..

"Tigers are a kind of animal." Not animals Pretty sure the pattern is always: X is/are a kind of (Y singular) Penguins are a kind of bird. Wolves are a kind of predator. Whales are a kind of mammal.

Tigers are a kind of animal. Kinda hard to explain but in this case animal is not plural because a tiger is one type of animal not multiple animals. So tiger can be plural because you are talking about tigers generally. Correct me if i am wrong but as native speaker the second option doesn't sound correct. Source: Native Speaker