One of my housemates is an APPALLING human being - What do I Do?

Moved into a place a month ago in Melbourne. All my housemates are great except for one lad. He owns a dog. The lease says no pets unless agreed beforehand. The landlord agreed with him (and nobody else) that he could have a dog in the house, and as he was one of the first to move in, the landlord has said that all subsequent housemates have "implied" that they accept there is a dog in the house when signing the lease.

This guy is the rudest, most selfish tw@t i've ever met. He works as a chef and is rarely around to look after his dog as a result. One day he came back at 11pm and the dog wasnt in the back garden and he asked me did I see it and I said I saw it trying to escape a few hours earlier, and he went mad at me for not trying to stop HIS dog escape. Told him the thing is not my responsibility!

2 mornings in a row last week myself and one of the girls (both of our rooms are facing the back garden) were woken up at 7am both mornings by the dog crying and roaring at the top of its lungs in misery at being left outside in the pissing rain. The 2nd morning I got fed up and shouted from my bed "shut the f**k up you stupid dog". I didnt know the guy was outside and he shouted back at me "what do you expect me to do you d1ckhead, you w@nker". UNBELIEVABLE!! He also said to one of the girls that as he pays the most rent he has the most rights or some sh1te like that.

He is the worst dog owner ever. That dog is miserable. It is the sadest, most depressed dog I have ever seen. It spends most of its time crying. He usually brings the dog into his room at night but he actually left the dog outside all night last night, outside our bedroom windows. Incredibly rude. The thing cried with misery, then roared with anger, knocked over the bins completely getting agitated. The thing doesnt get much exercise, he never takes it for walks really. The dog was left outside for 23 hours in total.

Today it got worse. After bringin his dog in for an hour last night he quickly sent it back outside where it remained for another 24 hours. Then he brought it in for another hour and he has since sent it back outside (right outside my bedroom) for the night again. Enough was enough and I asked him why is he leaving the dog outside and that its inconsiderate of other people. He got very pissed off, and told me I'd want to watch myself and that I wouldnt want to get him angry. I said why is he not bringing the dog into his room at night anymore and he said because its p1ssing in his room. I said that it needs to be trained and he told me not to tell him what to do. He says he pays more rent than me (no sh1t shirlock considering he chose the most expensive room) so I dont have much of a say. I tried to talk to him in as much of a peaceful way as possible but he looked on the verge of becoming agressive. I said that I have every right to air my concerns, and he said "well you've aired your concerns and I dont give two sh1ts about them".

In addtion to this the dog (who is still a puppy, and not trained at all) has destroyed peoples clothes hanging to dry on the clothes line, chewed up one of the girls computer mouse, jumped in through the open window and knocked all the rubbish bins over. I cant blame the dog, its not his fault of course.

The landlord says basically he doesnt care. He agreed for him to have a dog in the house an as a result everybody else must agree to being around it (which is gas considering the others who moved in the same day as him a few months ago werent told anything about the dog).

I'm basically tied here for 2 more months as the minimum time I have to stay is 3 months or I lose my deposit.

What on earth do I do?