My 8mth Chihuahua Barks Intermittently - Is There an Easy Way to Dissuade Her?

I know that chi's are predisposed to bark - but she was very quiet the first few months. It wasn't until she was 5mths or something that she began barking. It's only when I'm home (thank god), but she barks when people knock on my door as a warning/greeting, and barks at things on the balcony, and then sometimes very randomly it seems at people. For instance, my friend and I had taken her for a long walk a few days ago, and were sitting on a bench on the seawall. Several people passed us by, but of the eight or so people she ran after two of them barking madly. We could detect no correlation between these people and her barking, she just ran after them. Another day it seemed to be people on bikes. Today it was two people we met in the hallway as we were coming in for a walk. It wasn't a fear or warning bark - she went dashing up to them, tail wagging crazily, and continued to bark as she was lavished with their affection. In this case, it was probably just excitement. But still not acceptable. I caught her twice as she ran up to them and held her down, but she just kept at it.

I've tried iPhone apps (rubbish), and coins in a glass jar. Those little Pet Corrector aerosols and also a bark collar (out of sheer desperation). Nothing seems to work, and the bark collar didn't work I think because even the smallest I could find was too big for her (she weighs less than five pounds.)

Has anyone had any success with other methods that might work? I'm wondering about using a high frequency dog whistle. If used as an attention-grabber, do you think that might work? My neighbours are getting annoyed, and I'd really rather not get evicted. She's wonderful in every other way.

Teach your dog not to bark every time the door bell rings. Request a partner during the training process, whether it's a neighbor or a friend.

Uh… Chihuahuas are stupid. They won't stop barking. You can try, but the thing is an overgrown rat.

You could try teaching her a command for stopping barking! This sounds made but it does work!
First you teach her a command to bark. Find something that sets her off and give her a treat and command until she knows it, make sure you say it in an excited encouraging tone or the next step will be difficult!
Then you tell her to bark in a loud, excited voice and tell her to stop in a firm but quiet and calm voice.stand tall and make a wide movement with your arms to act as a visual cue. She should stop barking out of confusion of your behavior and then you need to reward her and praise her a lot! If you keep doing this and proof this command well (that means to gradually make it more difficult for her gradually so she listens under any circumstances. For example start with stopping her after the command then after the doorbell then when she barks at bikes). If this is successful you should be able to tell her to be quiet any time she barks!