A California sea lion created concern among Lincoln Park beach walkers today. The sea lion was regulating his body temperature (“thermoregulation”) by floating and raising his flippers out of the water, a behavior called “sailing.” This is often mistaken for injury or illness and even sometimes reported to authorities as an injured orca or other whale. The sight was particularly disturbing to onlookers following the recent shootings of sea lions in our area. When a number of sea lions group together and exhibit this behavior, sometimes sleeping with their noses just above water, it is termed “rafting”. In the winter of 2007, an estimated 200 sea lions “rafted” off Jack Block Park, flooding the NOAA Stranding Hotline with calls reporting an “orca pod” in Elliott Bay.

So, what exactly is thermoregulation? Sea lions and other pinnipeds have a system of veins and arteries that transfer heat to the rest of their bodies and organs. By extending their flippers out of the water, the blood in that less insulated part of the body absorbs heat from the sun or warmer air, and circulates it through the body to their internal organs. Conversely, on a hot day, you may see a sea lion with flippers to the wind, cooling the blood which then circulates and reduces body temperature. Read more about sea lions on our website.

Tags: thermoregulation, sailing sea lion, rafting behavior