Stopping on the bridge I heard a sound a metre or so from the creek bank that sounded like gnawing on bones. I assumed a Rakali so tried to locate it without success apart from seeing some rustling of reeds. A short time later I hear a plop at the creek and watched this Rakali swim towards the silt trap. The gnawing sound then continued for at least another 2 mintes but after it finally stopped I didn't observe a second rat but assume that there were more than one feasting on perhaps a dead bird in the reeds.