In general, the larger the body size (in terms of surface area to volume ratio) of an organism, the higher will be the heat loss from the body. This is simply due to large surface area which is exposed to the environment and which facilitates the heat loss. A direct effect of this relationship is the habitat of animals. Animals that have smaller surface area to volume ratio, such as polar bears, generally live in colder climate. Under such conditions, the heat generated from metabolism need to be conserved and the small surface area to volume ratio allows that. In comparison, thin, slender organisms that have large surface area to volume ratio generally live in much warmer weather (say equatorial regions). Under warm climatic conditions, it is necessary for an organism to be able to dissipate as much heat as possible to survive. Larger surface area to volume ratio allows that.
Hence, a direct relationship exists between surface area (to volume ratio) and heat loss.
Hope this helps.