How do animals know what group of animlas they belong to?

Dog's do not see themself and recognize themself, or see what they look like.  So, how would a dog know, when it encounters another animal, which animals are the same as them and which are not dogs?

Plus, there are so many breeds of dogs, that look nothing like the same species, a chihuahua and Saint Bernard?  But they are the same species, in they can mate and produce offspring.



How do they know not to pack with deer and cats and rats?
So, do dogs know when another animal is dog vs a cat or deer?  Or, just the difference between, "dog" and "not dog".  How would a dog know who "we" is? If they don't more significantly know who "me" is?  

Well, look at that.  "Me" comes first.  It's like "Park", in order to move, you have allow and effect a change in gears.  Change from "me" to "we".