There's a perceived behavioral tendency among dogs to associate with their own breed in groups where dogs of different breeds are represented. In my neighborhood that means that the Boston Terriers hang out with the Boston Terriers and the Pugs hang out with the Pugs.
The thing is, that topic veers off in a pretty uncomfortable direction pretty quickly. Like, as soon as someone starts to say, "You know, people do the same thing... ."
OK, slow down, Hitler.
True or not* I'm not sure that you're supposed to talk about it, right?