A. Size.
1. Male beluga whales average 3.4 to 4.6 m (11.2-15.1 ft.) and weigh about 1,500 kg (3,307 lb.) (Nowak, 1991).
2. Female beluga whales average 3 to 4 m (9.8-13.1 ft.) and weigh about 1,360 kg (2,998 lb.) (Nowak, 1991).
3. Beluga whales reach full size at about 10 years (Ridgway and Harrison, 1981).
B. Body shape.
A beluga whale's body is fusiform, but robust and stocky. It may have thick folds of blubber, especially along its ventral surface.
C. Coloration.
1. Adult belugas are yellowish-white to creamy white. Belugas attain their white coloration upon reaching sexual maturity (Katona, Rough, and Richardson, 1983).
2. Calves are born dark gray to bluish or brownish gray and become darker after the first month. Thereafter they gradually become more pale. This is caused by a reduction of melanin in the skin (Nowak, 1991).
D. Pectoral flippers.
1. A beluga whale's forelimbs are pectoral flippers. Pectoral flippers have the major skeletal elements of the forelimbs of land mammals, but they're foreshortened and modified.
2. The skeletal elements are rigidly supported by connective tissue. Thick cartilage pads lie lengthwise between the bones of each digit. Connective tissue lies between the digits.
3. The pectoral flippers are small in proportion to the body. They're rounded, paddlelike, and slightly upcurled at the tips (Leatherwood and Reeves, 1983).
4. Beluga whales use their pectoral flippers mainly to steer and, with the help of the flukes, to stop.
5. Blood circulation in the flippers adjusts to help maintain body temperature.
a. Arteries in the flippers 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 belugas in conserving body heat.
b. 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.
Pectoral flippers have all the major skeletal elements of the forelimbs of
land mammals.
E. Flukes.
1. Each lobe of the tail is called a fluke. A deep median notch separates the two flukes.
2. Flukes are flattened pads of tough, dense, fibrous connective tissue, completely without bone.
3. The flukes of beluga whales are distinctly curved along the trailing edges.
4. Longitudinal muscles of the back (both above and below the spine) and caudal peduncle move the flukes up and down.
5. Like the arteries of the flippers, the arteries of the flukes are surrounded by veins to help maintain body temperature.
F. Hind limbs.
1. All traces of hind limbs have disappeared except for two reduced, rod-shaped pelvic bones, which are buried deep in body muscle.
2. These reduced hind limbs are not connected to the vertebral column.
G. Dorsal fin.
1. Beluga whales lack a dorsal fin. A dorsal fin would greatly impede the whale's ability to swim under ice; it must be able to swim just below the ice to locate a breathing hole.
2. The beluga has a dorsal ridge that runs from just behind the midpoint of the back to the tail flukes. The dorsal ridge may be notched, forming a series of small bumps, and may be dark gray.
H. Head.
1. Neck.
The seven neck vertebrae of a beluga whale are not fused, as they are in most cetaceans. Belugas have greater mobility and flexibility in their necks.
2. Rostrum.
Beluga whales have small, but distinct beaks (Leatherwood and Reeves, 1983).
3. Teeth.
a. Belugas have 8 to 10 peg-shaped teeth on each side of both upper and lower jaws. Belugas have an average of 34 teeth (Nowak, 1991).
b. Teeth are adapted for grasping and tearing rather than chewing.
4. Melon.
a. The melon is a rounded structure on the dorsal surface of a whale's head, just in
front of the blowhole. On beluga whales it is prominent and overhangs the rostrum. The
melon is composed of lipids (fats).
b. The melon probably facilitates sound production. It can change shape when the whale is producing sounds (Haley, 1978). For more information on sound production.
5. Eyes.
A beluga whale's small, dark eyes are located behind the corners of the mouth.
6. Ears.
Ears, located just behind the eyes, are inconspicuous openings with no external pinnae (flaps).
7. Blowhole.
A single blowhole, located on the dorsal surface of the head, is covered by a muscular flap. The flap provides a water-tight seal.
a. A beluga whale breathes through its blowhole.
b. The blowhole is relaxed in a closed position. To open the blowhole, a beluga contracts the muscular flap.
I. Skin.
1. Like most other cetaceans, beluga whales lack hair as adults.
2. Unlike other cetaceans, which tend to generate and shed skin continuously, beluga whales appear to undergo a seasonal molt of the outer layer of skin. During the winter, the top layer of a beluga's skin may turn yellow, especially on its back and flippers. Rubbing on gravel river bottoms helps a beluga to shed this layer of skin (St. Aubin, Smith, and Geraci, 1989).
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