Chihuahuas are cute little dogs, but they are dogs nonetheless. It is easy to not take them seriously when they behave aggressively. A snarling, snapping Chihuahua may be thought of as “being cute” and the behavior dismissed as not important. This is a huge mistake. Your Chihuahua is a dog, and if he is behaving aggressively, he is not respecting your leadership or other people. Although a Chihuahua may not be as dangerous as a larger dog, a Chihuahua is still capable of biting and causing damage, especially to a child or older person. Chihuahuas are prone to acting aggressively for the same reasons any dog may behave aggressively, due to anxiety, territorial behavior, or to show dominance. It can not be stressed enough that Chihuahuas are dogs like any other dog, and should be treated similarly with regards to expectations for training and behavior; they should not be allowed to behave dominantly. Obedience expectations and positive socialization should not be allowed to slide as a requirement when caring for a Chihuahua.
If your dog suddenly starts acting aggressive and they were not aggressive before, you should consider taking your Chihuahua to a veterinarian in case he is experiencing medical problems. Pain or discomfort can cause aggression that can be addressed by relief of the condition. Once a medical condition has been ruled out, make sure all members of the household are on board to counteract aggressive behavior, as consistency is important. Avoid punishing or yelling at a Chihuahua that is behaving aggressively, as this will only contribute to anxiety and aggression. Instead, be prepared to reward alternate behaviors and provide opportunities for positive socialization and to establish yourself and members of your household as leaders that need to be respected. This will require time, patience and consistency.