Emperor penguins have a large volume but small flippers and bill.  They make excellent swimmers. Figure used with permission from Guillaume Dargaud

The emperor penguin has developed incredible highly adaptive traits which allow it to survive both the duration of fasting and the harsh Antarctic winter.   These traits help to depress the penguins' lower critical temperature to -100C.  Below -100C, the penguins' metabolic rate increases linearly with an increase in temperature and emperors form tortues to deal with the cold.  Having  lowered critical temperature through special traits helps the penguin to maintain a normal metabolic rate.  Adaptive traits include:2,4: 1)  The emperor penguin has a large body size and a low surface area to volume ratio, which allows for less area for the dissipation of heat. 2)  The flippers and bill are proportionately 25% smaller than other penguins (see left).  This reduces the contact of body surfaces with the cold.  The penguin also walks on it heels.

4)  The nasal passages have a highly developed nasal heat-recovery system.  The system helps to reduce the amount of heat gain from the environment, and reduce heat loss from the body during exhalation.

 5)  Emperor penguins have an exceptional insulation with long feathers.  These feathers have a high density, are double-layered, and extend over the legs to reduce heat loss from the extremities.  The emperor undergoes motling once a year before the breeding season to replenish the insulating feathers³ .