Understanding body size dynamics in Carnivores--why are animals of the same species generally larger in size in Northern Climes?

Bergmann's Rule: larger body size provides animals protection from cold temperatures.

 

Rensch's Rule: larger body size leads to sexual dimorphism(males tend to be larger in size than females of the same species).

 

Steven Ferguson(Fisheries and Oceans Canada) and Serge Lariviere(Cree Hunters and Trappers Income Security Board) penned a very thorough and insightful article in 2008 in The Open Ecology Journal where their field work led them to the conclusion that BODY SIZE IN CARNIVORES WAS NOT INFLUENCED DIRECTLY BY ENVIRONMENT BUT RATHER THROUGH THE INTERMEDIARY VARIABLES, HOME RANGE OR DENSITY. THOSE ANIMALS LIVING IN 4 DISTINCT(winter, summer fall and spring) SEASONAL LATITUDES WERE ASSOCIATED WITH LARGER HOME RANGES AND LOW DENSITY THAT IN TURN SELECTED FOR LARGER BODY MASS AND GREATER SEXUAL SIZE DIMORPHISM.

 

Greater body size allows animals to range far distances to overcome food shortages due to severe winters.................also provides energy to pursue mates who are spaced out widely over extensive home ranges.

 

Since males are the pursuers of females, additional heft provides for additional energy in finding females and successfully mating with them.

 

Polygamous Carnivores(think Cougars)  that roam large home ranges seeking females tend to be larger in size than monogamous Carnivores(think coyotes and foxes) who tend to mate with one female over long periods of time and also help out with child raising activities.

 

Enjoy the full article attached: