We have three dogs now. We got a new border collie puppy from the local shelter yesterday and my chihuahua is having issues. Normally, he is very protective of our female boxer and so now he is trying to "protect" her from the new puppy. Every time she gets near the puppy's crate he runs over and stands between the crate and her and starts growling. I think he is afraid of the new dog. What is the best way to handle his fear?

no he's not scared. he has big dog syndrom, he thinks and he is accepted as the dominant one. what you need to do since you should be the one who is the pact leader, is put a leash on her and just leave it on her. when she goes to do that, pick up the leash and correct her, pull her back and make her sit down. if she resists, correct her again. most likely your going to have to put her on her side in the most submissive state, do not let her get up until she can lay there perfectly still without you holding her down. then let the puppy come over and sniff her. she should not be the one in charge, you should be. she is showing alpha behavior. she needs to know that you are in charge, and that the puppy has no more power than she does.

It sounds as if he's showing the puppy that he's the dominant one in the group and to "listen" to him. I wouldn't worry about it too much unless he's attacking the puppy.

I agree with tahari01.. Just keep an eye out for hostility.. you can tell this if the dog tail is pointing upward towards the sky. Also every time you see him do the aggressive behavior corrected immediately otherwise it can continue.

He may be afraid or he may be 'guarding' (not protecting) the crate. You need to manage this situation and help your dog feel good about having the pup around. You do this by associating good things with the pup, usually this is super good food treats. Interrupt the inappropriate behavior and hand out treats to all the dogs for sitting or paying attention to you. Change the way the dog feels and you'll change the behavior.www.fearfuldogs.com