Whales are endothermic, or warm-blooded, mammals that occupy a cold environment. As such, they have a fairly constant body temperature, as opposed to ectotherms, which rely on the temperature of their environment to determine their body temperature. The body temperature of a whale is around 38 degrees Celsius, or 100 degrees Fahrenheit.
Thermoregulation is defined as the animal’s ability to maintain a healthy body temperature (varying slightly but not extending beyond healthful boundaries) within a surrounding temperature that may become very hot or very cold. If the core temperature of the endotherm varies too much (even by only a few degrees), the animal will become very sick and will eventually die.
Endotherms have various means of controlling their temperature to some extent. For example, human beings sweat or experience vascular contraction or relaxation, depending on the temperature. Whales also have different methods by which they maintain their body temperature. The methods used may be physical, biochemical, anatomical or behavioural.
The loss of heat happens about 27 times faster in water than in air. Therefore, the following methods are used to regulate and maintain a healthy body temperature in whales:
Blubber is a thick layer of fatty tissue that lies just beneath the surface of the skin. This acts as very effective insulation for the whale, even when it is in the icy waters of the Arctic Ocean. In addition, this blubber provides energy when food sources are scarce, which keeps the metabolism strong and the metabolic functions efficient. This is all vital to ensuring that the animal’s core temperature does not begin to plummet.
In order to maintain this blubber, whales need to consume large quantities of fat-rich foods. As a tissue, blubber is made up of collagen fibres and fat cells. The thickness of the blubber depends on the age of the animal (with newborns having an extremely limited amount) as well as on the species and their habitat. Cetaceans living in warm waters require less blubber than those in cold environments. Typically, the layer of blubber in a Killer Whale will measure between 7.5 and 10 centimetres. In a Sperm Whale, this blubber can get to more than 45 centimetres thick.
By means of an ingenious network of veins and arteries, the blood of the whales is kept warm. This is achieved by a counter-current heat exchange system, which means that blood that is returning to the heart from the extremities (and is cold as a result) runs right next to warm blood that is leaving the heart and going towards the extremities. Heat from the warm blood flows from the arteries to the veins (carrying the cold blood) and heats it up.
The blubber has a rich blood supply, which goes a long way in ensuring that the animal does not overheat because of this warm insulation. When in warmer waters, the animal can open its blood shunts, allowing blood to flow through the blubber and for body heat to be lost through the skin, cooling its body mass down.
The fusiform body shape of cetaceans is another mechanism that aids in the regulation of their core body temperature. Their surface area is kept to a minimum (by not having complex limbs, etc...). This decreases the amount of total area that is exposed to the cold waters.