Genetically Resistant to Cold

Introduction

Unlike brown and black bears, polar bears do not hibernate during winters. So how do they survive the harsh Arctic weather? The answer is in their genes which control nitric oxide production. Nitric oxide plays an important role in body metabolism and is likely to be a trigger for thermogenesis, a process in which cells produce heat instead of energy. High levels of nitric oxide in polar bears are behind their resistance to cold. 

Source

Down To Earth, March 2014