Seals practice a behaviour known as sailing to regulate body temperature. While sailing, a seal raises one or more flippers out of the water. Seals use this in both hot and cold conditions, and they can also use it on land. Sailing is an adaptation that helps seals to adjust to the surrounding environment.
Like all animals, seals have developed adaptations that enable them to survive in their environment. Sailing is an adaptation that allows a seal to actively adjust its body temperature. The seal does this by raising a flipper and holding it away from the body. During warm conditions, a seal may wave the flipper as if waving to a friend. This is sometimes known as sailing and sometimes as jughandling, but the scientific term is thermoregulation.
A seal’s flippers transfer heat more easily than the rest of its body. Seal flippers have no fur, no internal layer of blubber, and an excess of blood vessels. In cold conditions the blood vessels will constrict to hold heat in. In warmer conditions the blood vessels will expand and release heat. As the Friends of the Elephant Seal point out, the flipper functions to "maintain a steady body temperature."
According to the Brookfield Zoo, seals may employ sailing in both hot and cold conditions. A seal may use sailing in extremely cold water to prevent heat loss. In warmer water, a seal may use sailing to disperse excess heat. Overheating can also be a problem on land, and a seal will often sail a flipper and expose the armpit, the only other place on its body without a blubber layer under the skin, to help cool off.
While it seems that sailing is typical seal behaviour, not all seals have the same environmental factors to cope with. Habitat will dictate a seal's use of sailing. Generally, a seal is likely to employ sailing only when its temperature begins to drop or rise beyond the norm. A seal may incorporate other behaviours to adjust body temperature, like swimming to different waters, finding shade or sun, and throwing sand on its body.
Sailing benefits seals in important ways. Excessive temperatures are harmful to seal physiology and can damage internal organs. While seals have a complex automatic thermoregulation system, sometimes it is not enough. Behavioural thermoregulation gives a seal more control of its internal temperature when the external climate warrants it. The ability to cope with its ever-changing environment means continued survival for the seal.