How to stop my possessive chihuahua from attacking new puppy?

There are a couple things you can do that may help smooth the introduction. Give the adult Chihuahua a lot of exercise prior to meeting the puppy so that she is physically tired. Have a barrier such as a baby gate in place so that she can smell the puppy but not cause injury. Make sure the puppy does not jump on her or otherwise cause her stress. You are correct that you need to always make sure the puppy is protected as the adult dog may hurt it. You should also keep in mind that not all dogs like other dogs. Some of them prefer to live in single dog households and that is simply their personality. Make sure to correct any bad behavior from the adult dog. Correct the puppy to but this will be a little bit different because it is still learning. Best of luck and please feel free to post any additional questions. And yes, this is a free service! We do have private consultations available for a fee.

Introduce them to one another gradually. First, by allowing them to hear and smell one another through a closed door, then by sight without physical contact, then supervised contact. You will need to progress gradually through each phase. Correct any aggressive behavior immediately and praise good behavior consistently. A pheromone product, such as the Adaptil collar or DAP plug in diffuser, may decrease any anxiety or aggression.

Introducing a new dog into the house can certainly pose some challenges. Female/female dog pairings have a higher rate of problems than male/female dog pairings. Initially, keeping the dogs in separate rooms with a solid door between them can be beneficial. Allow them to smell one another under the door for a few days, then use an open barrier, such as a baby gate between them. This will allow them to see and smell one another without direct contact. A slow introduction can ease the transition. If both dogs are food motivated, try giving each a small treat at the same time. Avoid giving a larger treat that the dogs would need to put down to chew as this could create additional problems. Hope this helps!

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.

it is important to remember that Chico was there first, and is used to a certain level of attention from you. This newcomer has no expectations, so be sure to dote on Chico as much as ever so he feels secure. Then, gradually, you can increase the amount of time you give the new guy (without taking anything away from Chico). The second issue you are facing is that the dogs have to sort out, for themselves, who's who at the zoo. In other words, they may have one order of inportance to you, but they need to determine amongst themselves who's top dog, who's in the middle, and who's on the bottom. There may be a bit of snapping and barking going on, but as long as there are no injuries or serious fighting, leave them to it. Once they get it squared away, everyone will know his place in the pecking order and will (usually) behave accordingly.

In addition to a gradual introduction or acclimation, consider using a pheromone product such as the Adaptil collar or DAP plug in diffuser. Either may decrease any anxiety or aggression. Correct any aggression or negative behavior immediately. Praise and reward good behavior. Be consistent and be patient.

It may take some time for her to accept him. If she is being aggressive toward him than you should not allow them to be together unsupervised, espeically around feeding time or any toys/bones that she may protect. Give her extra attention, praise, and treats while the puppy is around so she knows he is not there to replace her. You could also try an Adaptil collar or diffuser and see if that helps. If she doesn't start accepting him than you could talk to your vet about trying an anti-anxiety medication, like Prozac or Trazodone and see if that helps.