Animals that are smaller in size have a larger surface area. Animals that are larger in size have a larger surface area. The larger the surface area, the faster the animal loses heat, and at a faster rate. The smaller the surface area, the slower the animal loses heat. Thus, a smaller gorilla would lose heat at a faster rate than a larger than life gorilla such as Kong. The smaller gorilla can have hair for this reason. Kong cannot as he would get too hot too quickly.