Gerbils are small animals of the order Rodentia, known for their tunneling behavior. They are known to typically be non-aggressive in nature.
Gerbils are not known to be pets in the Wizarding world, but are fairly popular as pets in Muggle society. When he first met with the Prime Minister of Muggles, Cornelius Fudge used the spell Teacup to gerbil in order to prove himself to be a wizard. The Prime Minister later gave the gerbil to his niece as part of his attempt to rid himself of all reminders of his encounter with Fudge.
Another kind of gerbil is the fanged gerbil which is a gerbil with fangs. Augusta Longbottom once found a fanged gerbil in her handbag, as a joke by her husband. After that she always kept a mousetrap in her bag.