北極熊は、生きていくために体を適温に保ち、数日か数ヶ月もあくかもしれない食事の間持ちこたえられるだけの十分なエネルギーを蓄えねばならない。
To survive, the polar bear must keep its body at the right temperature and store enough energy to last between meals that could be a few days or a few months apart.