|Cetaceans can maintain or lose body heat by adjusting their circulatory
system accordingly. The arteries in the limbs are surrounded by veins. The heat in the
arterial blood can be moved to the venous blood returning to the body core to maintain body
heat. This is called a countercurrent heat exchange system and is advantageous when the water
is cold or the cetacean is not active. During diving, the blood is transported only in the body
core, away from the surface to preserve heat.(Ridgway, 1972)
When a cetacean needs to lose body heat either because it is very active or the water is warm, more blood is transported to the veins near the surface of the limbs and the heat is lost to the environment. This decreases the blood in the body core, therefore decreasing body heat.(Ridgway, 1972).