Rats were large rodents similar to mice.
Role in the History of Narnia[]
Talking rats helped to moor Caspian X's ship on his return to Narnia shortly before his death.
In the last days of Narnia, a water rat told Tirian about the arrangement--seemingly approved by Aslan--that allowed Calormenes to fell talking trees in Lantern Waste and export their lumber to Calormene.