While evading the Yeerks, Tobias became trapped in the form of a red-tailed hawk. He was able to regain his ability to morph in Book #13: The Change, but in this case his hawk form remained his 'default' body. While he was able to regain his human form, this was the result of him being briefly sent back in time to acquire his own past self, with the result that his human body is just another morph rather than his natural state. In an effort to prevent David from exposing their secrets, the Animorphs executed a plan to trap him in the body of a white rat.