My dog attacked her littermate after parvo. What caused this aggression?

Sometimes dogs don't like the change in smell when another dog comes back from the vet. You may want to wipe down the older dog with a damp cloth and brush her to get the vet smell off her. It also can be that he now sees she is weak and he wants to take over being the top dog. This can be dangerous as he could fight with her and hurt her so you are right to keep them separate when you are not there to monitor their behavior. If your younger dog is well trained I would make it clear to him that this is inappropriate behavior by your voice and placing him in a crate or outside when he exhibits this behavior. Hopefully in a few days things will settle back into the normal routine. Thanks for using Petco Pet Education Center, formerly Petcoach to help you get answers to your veterinary questions.

Im so glad you found your dog! She may need some time to reacclimate to him. Consider having him examined by your veterinarian since he was gone so long. Afterwards a good bath and a gradual re-introduction would be recommended. A pheromone product, such as the Adaptil collar or DAP plug in diffuser, may decrease any anxiety or aggression associated with his return.

Separate them for a few days then gradually reintroduce them. First with a door between them so they can hear and smell one another then separated so they can see but not reach one another and finally a supervised physical introduction. Use leash, collars and muzzles if necessary. Pheromone products such as the Adaptil collar or DAP plug in diffuser may decrease any anxiety or aggression. Provide adequate numbers of bowls, beds and toys to prevent food aggression or resource protection.

Gradually increase the amount of time they are physically together as long as there is no aggression. Correct any negative behavior immediately. Consider a pheromone product, such as the Adaptil collar or DAP plug in diffuser, to decrease any anxiety or aggression. Provide additional bowls, toys and blankets to prevent resource protection. If the behavior persists, consider a consultation with a certified veterinary behaviorist.

Thanks for using Petco Pet Education Center, formerly Petcoach. This sounds like it could be anxiety related, probably due to (or worsened by) the recent trip. Try separating them for a day or so, then taking them for a walk together. If it continues for more than a day or so, talk with your vet about anti-anxiety medications which can help tremendously with this sort of thing. Best wishes to you, Charlie, and Grey!

WIth some patience and training, they may be able to get along. Consider a pheromone product, such as the Adaptil Collar or DAP plug in diffusers, to decrease any anxiety or aggression in the home. If you have cats, use Feliway Spray or plug in diffusers. You didn't specify the species in the post. Keep them separate, then gradually introduce (or re-introduce) them. First, allow them to hear and smell one another through a closed door. As they progress, you can allow them to see one another but without physical contact. Correct any aggressive or negative behavior immediately. The next step would be to place one of them in a closed carrier and leave them in the same room. Do this for ever increasing periods of time until they are acclimated. Finally, allow short, supervised playtime. Be consistent and praise/reward good behavior. Separate them if they get "rowdy" until they settle down, then reintroduce them.

It sounds like Remy may be more irritable than usual because he's been confined and isn't feeling well - this is common in dogs, just like it is in people. So, he may not be feeling very tolerant of puppy antics right now. It's likely that he's acting aggressive towards the puppy now as a kind of preemptive defense - he's used to having to growl and snap at the puppy for the past couple of weeks, so it's becoming a bit of a habit. I would recommend making sure that Remy has plenty of room to avoid the puppy if he wants to - if needed, you may need to keep the puppy on-leash or in a separate room with a baby gate between them. Praise and reward Remy with treats if you can, whenever the puppy is nearby. Also praise any friendly behavior like sniffing or tail wagging when the puppy approaches. As long as you manage things carefully to avoid letting the puppy bother him while he's ill, I would expect their relationship to return to normal once he's feeling better.