Beluga Whales

Beluga Whales
A. 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 (Nowak, 1991; Ridgway and Harrison, 1981).

2. Belugas can swim forward and backward (Nowak, 1991).

3. Beluga whales often swim at depths barely covering their bodies (Ridgway and Harrison, 1981).
B. Diving.

1. Beluga whales typically don?t dive very deep, usually to about 20 m (66 ft.). Belugas are not generally thought of as deep-diving marine mammals, but they 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 even dove to a depth of 647 m (2,123 ft.) (Nowak, 1991; Ridgway et. al., 1984).

2. A typical dive usually lasts three to five minutes, but belugas can stay submerged for as long as 15 minutes (Nowak, 1991; Ridgway and Harrison, 1981).

3. In estuaries the usual diving sequence lasts about two minutes; the sequence consists of five to six shallow dives followed by a one-minute-long deeper dive (Ridgway and Harrison, 1981).

4. All marine mammals have physiological adaptations for diving. These adaptations enable a beluga whale to conserve oxygen while it?s under water.

a. 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 (Ridgway, 1972).

When diving, blood is shunted away from tissues tolerant of low oxygen levels toward the heart, lungs, and brain, where oxygen is needed.
c. 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, and similar to a Weddell seal?s (a deep-diving marine mammal). One study found a female beluga to have 16.5 l (17.4 qt.) of oxygen in her blood (Ridgway et. al., 1984).

d. The muscle of beluga whales has a high content of the oxygen-binding protein myoglobin. Myoglobin stores oxygen and helps prevent muscle oxygen deficiency.

C. Respiration.

1. A beluga whale breathes through a single blowhole, a modified nasal opening.

a. 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.
c. 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 (Slijper, 1979).

3. Beluga whales have a breath-hold period that is longer than a human?s, and they exchange more lung air with each breath.

D. Thermoregulation.

1. Beluga whales deposit most of their body fat into a thick layer of blubber that lies just underneath the skin. Blubber accounts for more than 40% of a beluga whale?s weight (Sergeant and Brodie, 1969). This blubber layer insulates the whale and streamlines the body. It also functions as an energy reserve.

2. A beluga whale?s circulatory system adjusts to conserve or dissipate body heat and maintain body temperature.

a. 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.

When a beluga whale dives, blood is shunted away from the surface of the skin. This decrease in circulation conserves body heat.
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 0-C (32-F) pack ice to a 12-C to 18-C (54-64-F) shallow estuarine habitat in less than one hour (Bonner, 1980).

Beluga Whales 8 of 10 on the basis of 2155 Review.