Please have him fixed...Tinkerbelle, a chihuahua, is going to be 4 years old this week and she really doesn't have behavior issues...She rarely barks, only if you ring the doorbell or if one rings on TV that sounds like ours...or if you are the UPS man.(she knows that he is afraid of her and she puts on a great show, barking, snarling.)
My son also has a chihuahua, but he waited till he was about 1 1/2 to fix him...bad behavior was already learned...