Why are my two Chihuahuas fighting? How to stop their aggression?

I hate to hear this is happening. Unfortunately, it's impossible to know how best to advise you without being able to read the body language of the dogs. It's possible this is occurring because they are maturing. Both dogs also need to be spayed/neutered because this can help to decrease aggression. Intact dogs are much more likely to fight and have problems. Canine aggression is a complex behavior as it can stem from dominance, possessiveness, fear, anxiety, resource guarding or a combination. Most people are not familiar with reading canine body language and training. Because of this, I recommend to work with a professional trainer. Researching on your own will also be helpful. Familiarizing yourself with canine body language and dog training can help you to recognize what your pet is trying to say. You can find many books written on the topic and there is a trainer named Victoria Stilwell who I think is particularly helpful. Best of luck.

When you have two bitches together, they will show aggression to compete for territory and intact males especially if they are in heat. The best thing to do is to have both of them spayed. This will reduce the aggression between them as it is most likely hormonally related. It will also eliminate the risk of a pyometra, which is a life threatening infection of the uterus. Without spaying them, you will have a very hard time reducing the aggression because it's hormonally related. Removing the source of the hormones is the best way to stop the aggression.

If they are not spayed then you should start with that. Hormones can certainly cause aggression. After the surgery it takes about 30 days for the hormone levels to decrease to a level that may change aggressive behavior. If that does not help then you should consult with a professional in-home dog trainer to help you sort out the root of the problem. I see you are in Puerto Rico. There is a HUGE free spay/neuter campaign coming there in November. I suggest you check it out if you want to get your dogs spayed. Search "Spayathon for Puerto Rico" on Facebook to find their page. Hope this helps. Best wishes.

Hormonal changes that occur after being spayed or neutered can sometimes cause tensions. Keeping the dogs separated unless supervised may help reduce fights. If you notice one or both dogs becoming too excited or agitated, separating them and giving them a chance to cool off can help. Removing items of contention such as treats or toys can also help reduce fighting. If the fighting continues, or they are unable to be together at all, seeking out a local veterinary behaviorist or trainer in person that can observe their behavior may be useful for formulating a training plan to help both dogs get along again.

Unfortunately it's impossible to know without being able to observe the dogs. Certainly if both males are not neutered, that could be a big reason. Typically, intact males are more prone to fighting. It's possible now that the Bulldog is 2, he is now officially an adult and could be competition to the older male. That's just a guess. Canine aggression is a complex behavior as it can stem from dominance, possessiveness, fear, anxiety, resource guarding or a combination. Most people are not familiar with reading canine body language and training. Because of this, I recommend to work with a professional trainer. Researching on your own will also be helpful. Familiarizing yourself with canine body language and dog training can help you to recognize what your pet is trying to say. You can find many books written on the topic and there is a trainer named Victoria Stilwell who I think is particularly helpful. Best of luck.

I hate to hear this is happening. I;m sure it's not only scary but stressful as well. Canine aggression is a complex behavior as it can stem from dominance, possessiveness, fear, anxiety, resource guarding or a combination. Most people are not familiar with reading canine body language and training. Because of this, I recommend to work with a professional trainer. Researching on your own will also be helpful. Familiarizing yourself with canine body language and dog training can help you to recognize what your pet is trying to say. You can find many books written on the topic and there is a trainer named Victoria Stilwell who I think is particularly helpful. Also, dogs who are spayed and neutered are less likely to fight though this is not always the case. I recommend to discuss having both dogs altered with their veterinarian. Best of luck.

I would make sure the dog that has become aggressive isn't having any other issues like pain or discomfort. Also, has anything change in your schedule or house that could have made her feel more insecure or anxious? You could talk to your vet about starting her on an anti-anxiety medicine like fluoxetine as this may help. I would also make sure they aren't becoming aggressive over any treats, bones, toys, etc. I hope this helps and she starts to act like herself soon.