is a gekko really a concept would  it be better in characters or  a object?

Concept is fine. It wouldn't be a character because there is more than one of them. And I wouldn't consider them too much of an object since they have living tissue.

I agree with Chojin, since character applies also to characters that are not one of a kind, but also a specie, like "Hobbe" or Koopa troopa.

I think they would be better suited as an object. If a cow is an object, then I think a Gekko should be an object.