The Animorphs find themselves stranded in the Arctic, without any morphs suited for very cold temperatures. Four of them do have wolf morphs. Ax and Tobias have to resort to morphing flea and hiding on the wolves. (Why hadn't either Ax or Tobias ever acquired wolves?).
PP 98-99 of paperback "The Extreme". In wolf form, Jake, Cassie, Rachael, and Marcos eat a seal carcass left by a polar bear. Ax and Tobias have already drunk blood in flea form. The seal meat appears to satisfy Jake et al in both wolf form and their regular human form. (I see no indication that they were starving in human form after eating in wolf form). The blood Ax and Tobias drank in flea form likewise seems to have carried over to their regular forms. This feature of morphing (being able to eat in morphed form and having it carry over to one's demorphed form) is very interesting. If an Animorph is short on food, he could just morph an ant, eat a crumb, and be full once he returns to human form! This would be very useful in famine stricken areas!