Animagi transformation can be performed wandlessly. Sirius and Peter are left wandless for over 10 years, but both retain the ability with no apparent ill effects. When Animagi transform, they take on the appearance of a normal animal. However, in "Harry Potter and the Prisoner of Azkaban", it is noted that Ron's pet rat Scabbers (later revealed as Peter Pettigrew's Animagus form) has lived over twelve years when only expected to live three. Also, an Animagus in animal form retains the ability to think like a human, which is the principal difference between being an animagus and being transfigured into an animal. Otherwise, they would forget that they were a wizard and be trapped, unknowingly, in this form unless transformed back by another wizard. Characteristics of an Animagus' human form can manifest themselves in the animal transformation; McGonagall and Rita Skeeter have markings around their eyes that resemble their glasses, while Pettigrew has a missing toe on one of his front paws representing his missing finger. When an Animagus registers, they must record all the defining physical traits of their animal form so that the Ministry can identify them.