A theory known to biologists as Bergmann's Rule, which generally holds that animals get bigger the farther north they are found. (snip) The reason, the theory holds, is that larger animals can retain heat better and are therefore better able to survive at higher latitudes.
Wyoming isn't a lot north of my part of northern California, but it is at a substantially higher altitude, which makes it much colder - creating a similar advantage for larger members of a species.
I propose we call this addendum to Bergmann's Rule - concerning larger body sizes at higher elevations - Cotton's Corollary.
