1. Baleen whales are some of the largest animals.
a. Large size allows for protection from predators and is an advantage in species that compete for mates.
b. As an animal increases in size, its ability to retain body heat also increases. This is due to a large area (body core) to produce metabolic heat surrounded by a relatively smaller surface area (the skin) to conduct that heat to the environment. Thus, large size is a metabolic advantage.
c. On land, animals must support their weight. In the aquatic environment, water helps support an animal's body weight, allowing for the potential for greater size.
d. Large size allows whales to take advantage of high food productivity and store that energy in the form of blubber.
2. The largest baleen whale species is the blue whale. Blue whales may be larger than any other living or extinct animal.
a. Blue whales reach average lengths of 21 m (70 ft.), and the largest individuals alive today probably measure about 26 m (85 ft.). The record size for a blue whale--for a specimen taken during the whaling years--is 34 m (110 ft.).
b. An average weight for an adult blue whale is about 64,348 kg (142,000 lb.). A
record-size individual weighed 172,330 kg (380,000 lb.).
3. Pygmy right whales are among the smallest baleen whale species. Adult females reach lengths of 6.5 m (21 ft.), and adult males may reach 6.1 m (20 ft.). This species is rarely recorded, so details of its physical size are poorly documented.
4. In general, female baleen whales are about 5% longer than males of the same species.
5. Some species exhibit differences in sizes depending on the stock.
a. Sei whales reach 20 m (65 ft.) in length in the southern hemisphere, 18.6 m (61 ft.) in the North Pacific, and 17.3 m (57 ft.) in the North Atlantic.
b. In the northern hemisphere, baleen whales are usually slightly smaller than their
southern hemisphere counterparts.
All baleen whales show some variation of a characteristic fusiform (torpedo-shaped)
body shape. This body shape reduces drag and is energy efficient for swimming.
1. Most baleen whales exhibit skin color variations of black and gray.
2. Some species exhibit some extent of countershading; the dorsal (top) surface is darker than the ventral (bottom) surface. This coloration, typical of many marine animals, provide camouflage. The result is that predators or prey do not see a contrast between the countershaded animal and the environment.
a. Blue whales sometimes exhibit a yellowish ventral surface, a result of diatom growth. (Diatoms are one-celled algae.)
b. Barnacles and whale lice give a gray whale its characteristic light gray color.
4. Some species, such as gray whales and sei whales, have white or faintly colored markings or scars. Scarring can be caused by barnacle growth, shark bites, killer whale teeth marks, or from natural pigmentation differences.
5. Blue whales are named for a steel blue-gray skin color.
6. Minke, humpback, bowhead, and fin whales are distinctively colored.
a. Northern hemisphere Minke whales have a band of white across the otherwise black flipper. Individuals in the southern hemisphere may or may not have the flipper band.
b. Humpback whales are black or gray except for their flippers and the undersides of their flukes, which are white.
c. Bowhead whales are dark gray to black except for a white chin.
d. A fin whale's head is asymmetrically colored. The right lower lip is white, and the
rest of the head is black or gray. Fin whales also have a grayish white chevron-shaped
mark on their backs.
1. The forelimbs of baleen whales are pectoral flippers. Pectoral flippers have all the skeletal elements of the forelimbs of terrestrial mammals, but they're foreshortened and modified into paddle-shaped appendages. In rorquals and gray whales, there are four digits instead of five; the thumb bones are not present.
Pectoral flippers have all the skeletal elements of the forelimbs of
terrestrial mammals, but they're foreshortened and modified into paddle-shaped appendages.
2. The skeletal elements are rigidly supported by connective tissue. Thick cartilage pads lie lengthwise between the bones.
3. Baleen whales use their pectoral flippers mainly to steer and, with the help of the flukes, to stop.
4. Humpback whales have pectoral flippers that are up to one third of their body length
and are a contrasting white color.
1. Each lobe of the tail is called a fluke.
2. Flukes are flattened pads of tough, fibrous connective tissue, completely without bone or muscle.
3. Flukes are oriented horizontally. Longitudinal muscles of the back and caudal
peduncle move the flukes up and down.
1. In baleen whales all traces of hind limbs have disappeared except for two reduced, rod-shaped pelvic bones that are buried deep in body muscle.
2. These reduced hind limbs are not connected to the vertebral column.
1. Rorqual whales and the pygmy right whale have a fin on top of the back called a dorsal fin.
a. Humpback whales have a small dorsal fin located on a hump. The shape of the dorsal fin varies among the humpback whales.
b. Other rorqual species have a falcate (backward-curving) dorsal fin, located about two-thirds of the way down the back.
c. Dorsal fin size ranges from about 25 to 60 cm (1-2 ft.), depending on the species.
2. Right, bowhead, and gray whales have no dorsal fin. Gray whales have a dorsal hump followed by a series of bumps.
3. Like the flukes, the dorsal fin is made of dense, fibrous connective tissue, with no bones.
4. Dorsal fins are often scarred or marked. Photos of baleen whale dorsal fins can be
used for photo-identification.
1. Right whales have huge heads-one-forth to one-third of the entire body length in adults.
a. Their narrow elongated upper jaw bones arch upwards to house extremely long baleen. The lower jawline is deeply curved upwards in profile.
b. Encrusting growths, called callosities, on the head, jaws, and blowhole areas of right whales are yellow-white. Accumulations of natural markings such as these aid researchers in photo-identification studies.
2. Rorquals have a broad, flat rostrum and a slightly curved jawline. Some species have ridges on the rostrum and a V-or U-shape to the tip of the snout. Humpback whales have several knobs on their heads.
3. Gray whales have a narrow head with a slight curve to the jawline.
4. The neck vertebrae are unfused in rorquals and gray whales, which allows for some flexibility at the head and neck. In right whales, all seven vertebrae are fused, and right whales are incapable of side-to-side head movement.
5. Blowhole.
a. Baleen whales have two blowholes (modified nasal openings) located on top of the head.
b. Blowholes are covered by muscular flaps. These flaps provide a water-tight seal. There is a "splash guard" in front of the blowhole region in some species. This prevents water from entering the blowholes upon surfacing to breathe.
c. Each blowhole leads to an air passage that leads to a baleen whale's trachea and
then to its lungs.
1. Baleen is an adaptation for filter-feeding. In baleen whales, stiff plates of baleen grow down from the gums of the upper jaw. The baleen plates are arranged in rows that extend down each side of the mouth.
a. Baleen is made of keratin (a protein that also composes hair and fingernails). It is strong, yet elastic.
b. Baleen plates arise in the fetus as thickenings of skin on the upper jaw. At birth, baleen is soft and short, but it soon stiffens.
c. Baleen grows throughout the whale's lifetime; the terminal end continually wears off.
2. The outer (facing outside) edge of each plate is smooth while the inner edge is frayed. The frayed edge of each plate intertwines to form a mat which functions as a strainer during filter feeding.
3. Gray whales have about 130 to 180 baleen plates on each side. Their baleen plates are about 5 to 25 cm (2-10 in.) long.
4. The right whale family, notably the bowhead whales, have the longest baleen. In bowheads, between about 230 and 360 plates on each side of the jaw reach lengths of 4 m (13 ft.).
5. Rorqual baleen arrangements range from the blue whale, with 260 to 400 plates that reach 91 cm (3 ft.) on each side, to the Minke whale, which has 230 to 360, 12 to 20 cm (5 to 8 in.) plates on each side.
6. Baleen plates range in color from black to yellow or white, depending on the species.
7. Baleen is sometimes referred to as "whalebone," and baleen whales are referred to as "whalebone whales."
8. Baleen whales retain tooth buds during the embryonic stage. These tooth buds
disappear before birth.
1. Baleen whales have a smooth skin surface with no oil glands or pores. The epidermis is about 5 to 7 mm (.02-.03 in.) thick.
2. Many species have several hairs located on the snout, jaws, and chin. The lack of a fur coat is an important advantage to swimming: as an animal swims, smooth skin creates less drag than fur does.
3. Samples of skin and blubber have been collected by shooting a hollow dart into a
whale's body. Such samples can provide vital genetic information. This sampling technique,
called biopsy darting, does not harm the whale.
1. Rorqual, gray, and pygmy right whales have ventral throat grooves that extend from the throat to the flipper area or farther. These folds of skin and blubber expand the capacity of the mouth area during feeding.
2. Because excess skin folds into grooves when the whales isn't feeding, the overall body shape remains streamlined.
3. Members of the rorqual family have between 25 and 100 throat grooves, depending on the species.
4. The pygmy right whale has just two throat grooves, and the gray whale has between two and seven throat grooves.
5. The right whales and bowhead whales do not have throat grooves.
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