A Cape fur seal doesn’t become a marine mammal until it is several weeks old, spending that time only on land. Stuck on shore with little shade available, the pups have to endure the hot sun, usually unable to take a quick dunk to cool off as its parents would do because the waters are too dangerous. So how does a pup cool off? It doesn’t have to, say scientists reporting in PLOS ONE. When they’re young, these animals have a special coat that keeps them cool.
The researchers studied six Cape fur seal pups that were born between 2010 and 2012 at Zoo Rostock in Germany. They measured the pups’ surface temperatures with an infrared camera as well as skin temperature and rectal temperature with increasingly invasive techniques (there’s never going to be a good way to get that last one remotely).
As long as a pup’s fur was dry, it was able to maintain a stable internal body temperature. But when a pup got wet — when its mom took it for a quick dunk, or it rained — its hair became flattened and stringy, and the pup’s body temperature dropped. Sometimes they shivered. (Adorable note: The pups would shake themselves like dogs when they came out of the water.)
The researchers conclude that the pup’s fur is adapted to the terrestrial lifestyle that marks these animals’ early lives. The fur traps a layer of air near the skin that insulates against heat and cold. The tradeoff is that this fur doesn’t insulate well in water. This fur coat has to change as the seals age and adapt to the marine life.
The fluffy fur may protect a seal pup against the heat, but it’s made it vulnerable to human predators. The Namibian government lets people kill 80,000 Cape fur seal pups each year; a pelt can be sold for $7.
Image courtesy of flickr user DragonWoman