Service Project-- Why do certain animals act like other animals?

Sometimes, when animals are together, they start acting like the animals they are around. For example, this cat I know, she grew up with small dogs. They would tackle her and wrestle around, and over the last year she has strengthened up and has started wrestling with the other dogs too. She didn't even like playing with the other cats. She seemed to prefer the company of the dogs better, as if it were more natural. Just as odd, the dogs didn't eat the cat either. They enjoyed the company of the cat. This is not the only thing I've heard of. The story of Pecos Bill and Tarzan, these may possibly be fiction, but it shows that people have tried to explain this strange thing about how animals think in respect to us or other animals.