User blog comment:Wrath022/Episode 267: Fairy Tail Zerø: The Adventure Begins, Review/@comment-24039234-20160116112936/@comment-7418318-20160117102733

True we never learned the reason for their aggressiveness. The animales also have been defending their territory or the candidates wandered too close to their young...

But I'm not aware of any eco-system without any kind of predator and/or carrioneaters, so it's only logical to assume that Tenrou also has some.

Speaking of the taking one: Wasn't that the same species as the one that Mavis lived together with in the small stable (at least going by Memory without actually checking)?

If so I wonder if the species might be long-lived and it is the very same one that lived with Mavis and that's how it learned Human speech.