Rats are small animals which can be found in numerous locations, mostly in cities, sewers and dungeons. They are best found outside and on the first floor of Lumbridge Castle. Their tails are most commonly used for the completion of the Witch's Potionminiquest, and they are one of the weakest creatures in RuneScape. The only rats that drop bones are those in the Stronghold of Security. Curiously enough, rats never drop bones anywhere else. They are good for training on as they have low life points and defence and respawn in only a few seconds, but they can be hard to click as they're small and move very fast.
Players who have a cat or a kitten can tell it to chase vermin, in which case it will try to attack any rat in range. If your cat catches at least 100 rats you can go to Gertrude to get a cat training medal (no special bonuses). Also, if you have a rat pole, a rat will be added to it each time a rat is caught by your cat.