We have a 4 year old male dachshund that has ALWAYS been very protective of the family. He seems even more protective if my husband isn't around. Well, about a year ago he started to develop aggression toward strangers (mainly men) and other dogs. A little over a year ago we got another dachshund (female) and I knew there would be a few arguments until she realized he was alpha. He is alpha and everyone knows it, but I think sometimes she likes to test him. Well, recently (last 3-4 weeks) he has seemed to develop an aggression towards her mainly when playing with toys or when she is doing something he doesn't seem to like (barking, etc). Earlier tonight he was playing with his toy and she came over and pulled at it wanting to tug. He started a low pitch growl (which he has been doing for the past few weeks) and she continued to try to get him to play. Next thing I know he snapped at her in an aggressive tone. As soon as I turned around he went under the computer desk and wouldn't come out. I went to pick him (to put him in his crate) and he snapped at me. He hasn't been listening, he acts like he is in trouble all the time, he knows what he is doing is wrong. He is usually the most well behaved dog in the house. Is this because of the new female in the house? She has been here over a year and he acts perfect around our other female (she has been around him his entire life though). What's going on? Help!