Maybe there were a lot of dogs supporting the humans at first (like around 90% of them), but they have been obliterated a bit before the roleplay starts. They had the upper hand against the cats when it was mainly just those two fighting, but then the wolves came in and showed how powerful they were before allying with the other animals, winning the war in record time. The dog army was probably being used to buy more time for the humans to build up their defenses. There are still some dogs on the human side, but their moral is slowly being crushed both by opposition and the humans themselves, so only the most loyal dogs remain. The rest ran away after their defeat or joined the animals, but there are not nearly as many dogs as there were originally. 

Any other animals you want to know more about? What animal were you planning on being?