Well, Mirks are more aquatic creatures than anything. Arctic Mirks do tend to have slightly larger feet than other Mirks, but their main purpose is still to be used as flippers, as opposed to moving over ice and snow easily. Their feet are still fairly big... but their major thing is that they can spread their toes quite wide to maximize the effect of the webbing.... They rarely walk anything other than short distances as well- swimming is their preferred method of transportation.

I'm actually working on a sketch of just that! :D