Because of the Chihuahua in them, however, Chugs can be a little aggressive towards other dogs no matter how big they are which is why early socialisation is so essential. They often inherit the “barking” trait that both parent breeds are known for which is something that needs to be gently nipped in the bud from the word go before it turns into a real problem. Chugs do not like being left alone for long periods of time and if they are, it could lead to a dog suffering from separation anxiety and becoming destructive around the home.