For most species of vertebrates, body mass increases the closer you get to the poles. The bigger you are, the more fat you can store to help you get through the winter.
The average weight of an adult male white-tailed deer in Florida, for instance, is about 57 kilogrammes, while a mature buck in Montana might weigh 114-125 kg, the 'Live Science' reported.
For many types of animals, it pays to be bigger in the colder climates that exist at high latitudes and altitudes.
Heftier animals have a smaller surface area-to-volume ratio, which helps reduce heat loss