Adaptations for an Aquatic Environment - Beluga Whales

SWIMMING

1. In general, beluga whales are slow swimmers. They commonly swim about 3 to 9 kph (1.9-5.6 mph). They are, however, capable of sustaining a maximum speed of 22 kph (13.6 mph) for as long as 15 minutes. 2. Beluga whales are adapted to be highly maneuverable rather than high-speed swimmers. Belugas are slow swimmers but they are highly maneuverable. 3. Belugas can swim forward and backward. 4. Beluga whales often swim at depths barely covering their bodies.

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DIVING

1. Beluga whales typically don't dive very deep, usually to about 20 m (66 ft.). Although they are not generally thought of as deep-diving marine mammals, belugas are capable of diving to extreme depths. Under experimental conditions a trained beluga whale repeatedly dove to 400 m (1,312 ft.) with ease, and one even dove to a depth of 647 m (2,123 ft.). Although beluga whales usually only dive to depths of 20 m (66 ft.) or less, they are capable of much deeper dives. The deepest recorded depth was 647 m (2,123 ft.). 2. A typical dive usually lasts less than ten minutes, but belugas can stay submerged for more than 15 minutes. 3. All marine mammals have physiological adaptations for diving. These adaptations enable a beluga whale to conserve oxygen while it's under water. • Beluga whales, like other marine mammals, have a slower heart rate while diving. A beluga whale's heart rate slows from about 100 to about 12 to 20 beats per minute during a dive. • When diving, blood is shunted away from tissues tolerant of low oxygen levels toward the heart, lungs, and brain, where oxygen is needed. • Beluga whales retain more oxygen in their blood than most mammals do. A beluga whale's blood volume percentage (5.5%) is higher than a land mammal's. One study found a female beluga to have 16.5 liters (17.4 qt.) of oxygen in her blood. • The muscle of beluga whales has a high content of the oxygen-binding protein myoglobin. Myoglobin stores oxygen and helps prevent muscle oxygen deficiency.

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RESPIRATION

1. A beluga whale breathes through a single blowhole, a modified nasal opening. • The beluga whale holds its breath while under water. • It opens its blowhole and begins to exhale just before reaching the surface of the water. • At the surface, the whale quickly inhales and closes the muscular flap. 2. As a beluga whale exhales, seawater around the blowhole is carried up with the respiratory gasses. Seawater and the water vapor condensing in the respiratory gasses as they expand in the cooler air form the visible blow of a beluga whale. A beluga's blow is about 90 cm (35 in.) high. 3. Beluga whales have a breath-hold period that is longer than a human's, and they exchange more lung air with each breath.

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THERMOREGULATION

1. Beluga whales deposit most of their body fat into a thick layer of blubber - a thick layer of fat and fibrous connective tissue that lies just below the skin of most marine mammals. Blubber accounts for more than 40% of a beluga whale's weight. This blubber layer insulates the whale and streamlines the body. It also functions as an energy reserve. Belugas have a thick layer of body fat known as blubber that accounts for more than 40% of their weight. 2. A beluga whale's circulatory system adjusts to conserve or dissipate body heat and maintain body temperature. • Arteries in the flippers and flukes are surrounded by veins. Thus, some heat from the blood traveling through the arteries is transferred to the venous blood rather than the environment. This countercurrent heat exchange aids beluga whales in conserving body heat. A countercurrent heat exchange system exists in the flippers and flukes of beluga whales. • When a beluga whale dives, blood is shunted away from the surface of the skin. This decrease in circulation conserves body heat. • To shed excess body heat, circulation increases in veins near the surface of the flippers and decreases in more insulated veins that lie deeper in the body core. 3. In the Mackenzie Delta region of the Canadian Arctic, river mouths of the delta are less than a mile from the edge of the ice pack. Belugas in this area can move from 0º C (32º F) pack ice to a 12º-18º C (54º-64º F) shallow estuarine habitat in less than one hour.

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SLEEP

1. As in other toothed whale species, scientists have found that deep sleep in belugas occurs in only one hemisphere of the brain at a time.