Spring marks the beginning of whale season here in Alaska. The humpbacks and grey whales begin arriving from their long migrations north from their wintering grounds, and the north Pacific Ocean teems with life as the waters warm and phytoplankton blooms. Swarms of krill and other zooplankton feast on the abundant plant life, and fish such as herring, eulachon, and similar species follow the zooplankton into the bays on Kodiak Island. In turn, huge baleen whales, including fin, sei, and humpback, gather to eat the krill and small fish. I am thrilled any time I see a whale, but I think it’s a special treat to stand in my front yard and watch these magnificent creatures feed and blow.
Sea mammals evolved from land mammals, and they resemble us in many ways. Whales, like humans, have lungs and must breathe air to survive. They are warm-blooded, and they bear live young. Whales nurse their young with milk, and while you might not think of a whale having hair, all whales do have hair at some stage in their development. All members of the order Cetacea evolved 45 million years ago from hoofed mammals, such as cows, sheep, and camels. Comparisons of specific milk protein genes indicate the hippopotamus is the closest, living, land relative to whales.
The order Cetacea contains more than eighty species; although, taxonomists debate the precise number. Biologists have recorded thirty-nine cetacean species in the North American Pacific.
Cetacea comes from the Greek word “ketos,” which means “whale.” All cetaceans have forelimbs modified into flippers and no hind limbs. They have horizontally flattened tails, and they breathe through a nostril, or blowhole, located on the top of the head. A blowhole has a nasal plug that remains closed except when forced open by muscular contractions to breathe. This plug seals when the whale dives. A whale has internal sensory and reproductive organs to reduce drag while swimming, and they do not have external ears but instead have a complex internal system of air sinuses and bones to detect sounds.The lungs of a cetacean are relatively small, highly elastic, and elongated. A whale has a muscular diaphragm, allowing the animal to purge a large amount of air in a short time. With each respiration, a whale replaces 80% to 90% of the air in its lungs. During a deep dive, a cetacean slows its heart rate and decreases blood flow to peripheral tissues.
Cetaceans living in the cold ocean waters of the North Pacific must somehow maintain a body temperature nearly the same as a human’s body temperature. A whale uses several mechanisms to accomplish this feat. First, it has a thick layer of blubber with few blood vessels, reducing the heat loss at the body surface. A whale has a counter-current heat exchanger, with arteries surrounding veins at the periphery. Hence, vessels flowing from the cold periphery to the warm core partially absorb heat lost by vessels flowing from the core toward the surface. A cetacean also has a high metabolic rate to produce heat, and it has a low body surface to volume ratio, which conserves heat. Finally, a whale has a slower respiration rate than a land mammal, so the whale expels warm air less frequently.
Most cetaceans produce large calves, and the large body volume relative to surface area minimizes heat loss in the calf. Calves are born tail first, and as soon as the calf emerges from the birth canal, the mother or another whale nudges it to the surface for its first few breaths.[3] Cetacean mothers nurse their calves with a pair of teats concealed in slits along the body wall. The milk has a high-fat content, and the calves grow at a rapid rate. Whale mothers tend and guard their calves closely, and a calf often rides the bow wave or the convection currents produced by its mother or another adult when the whales travel. This method of travel is so efficient that the calf barely needs to move its flukes to keep up with the group.
Two suborders comprise the order Cetacea: The Mysticeti or baleen whales and the Odontoceti, or toothed whales. We most commonly see fin whales in Uyak Bay, but we also spot sei, humpback, minke, and killer whales. No matter the species, whenever I see a spout of water, excitement buzzes through me while I watch one of the largest animals on the planet.
Robin Barefield is the author of four Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter, and Karluk Bones. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska, and listen to her podcast, Murder
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