Cats and dogs are the only large mammals on Umayma. Because dogs are just as often shifters as not, the less commonly used "dog shit" is seen as somewhat offensive to shifters, and is not generally invoked except in Ras Tieg, which has a much harsher view of shifters.
From God's War:
“Catshit. You don’t have anything on me.” ... Five minutes, tops. Anneke was a good catshitter, but not that good.