Why animals in cold climates are comparatively bigger ??

  We must have noticed animals found in polar regions are comparatively larger to their southern counterparts.

There is a scientific reason for this.

It is BERGMANN'S RULE 

It States that " warm blooded animals in colder climate tend to be larger than those in warmer climates "  

It is the simple allometric relationship between body size and surface area.

Larger animals have proportionately smaller surface area compared to smaller amimals.

Because all warm blooded animals lose their internal heat generated by their metabolism to their environment through their body surface.

Larger bodied animals lose their heat at a lower rate compared to smaller body animals .......

Hence, animals in colder regions have larger body so that they can conserve energy for a long time   !!!!