The cargo hold / baggage compartments on jets are pressurized & reasonably warm. Certainly warm enough that Alaskan wildlife wouldn’t be bothered.
Critters getting loose and trying to claw / chew their way out are not unheard of.
Back in about 1960 my Dad used a fire axe to kill a thoroughbred race horse that had gotten loose in the main cabin area of a cargo-only plane. The horse was gonna tear the airplane apart if he wasn’t stopped. He’d already done a bunch of dangerous damage before the situation got really insane. It was one hell of a mess.