We are considering adding another dog to hour household. We currently have two chihuahuas - a 12 year old female and her 11 year old son. I have been doing some reading on different breeds and have read multiple times that Chihuahuas are breed discriminatory - meaning they are able to recognize other Chihuahuas and get along with them better than they do other breeds. We are very much considering not getting a full blooded Chihuahua this time but instead rescuing from a shelter. There are a lot of Chihuahua mix breeds. Some look like Chihuahuas for the most part while others look like the breed they are mixed with or truly have an appearance of the two breeds. My question is how do they know if another dog is chihuahua? Is it by physical appearance or something else?