Bigger isn’t always better: benefits of small surface area to volume ratio in thermoregulation

Erin Francis, Giovanni Penna, Jillian Wormington



            Carl Bergmann’s rule explains that an increase of animal size in Northern areas is attributed to the heat conservation that occurs during thermoregulation (Mayr, 1956).  This correlation is found using an animal’s surface area to volume ratio, which is essential for maintaining a stable core body temperature. Larger animals have a smaller surface area to volume ratio.  We tested this theory using different sized clay spheres immersed in an ice bath.  Next, the rate of internal cooling in each sphere for two trials was measured.  We found that the largest sphere retained a higher core temperature and had the smallest rate of cooling in both trials.  Therefore, animals with smaller surface area to volume ratios are able to survive in colder climates due to their ability to maintain a stable core body temperature.  This conclusion supported our hypothesis.


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