Physical Characteristics
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Film
clip review of killer whale adaptations. (14.4 Mb)
A. Size.
1. Although small compared to some whales, killer whales are the largest predators of mammals ever known. Male killer whales, or bulls, average 5.8 to 6.7 m (19-22 ft.) and usually weigh between 3,628 and 5,442 kg (8,000-12,000 lb.).
2. Females, or cows, average 4.9 to 5.8 m (16-19 ft.) and usually weigh between 1,361 and 3,628 kg (3,000-8,000 lb.).
3. Individual sizes vary significantly between geographical areas. Length estimates for more than 2,000 killer whales taken by North Atlantic whaling operations show male North Atlantic killer whales average about 6.1 m (20 ft.) while females average about 5.5 m (18 ft.).
4. The largest male ever recorded was 9.8 m (32 ft.) and weighed 10,000 kg (22,000 lb.). The largest female recorded was 8.5 m (28 ft.) and weighed 7,500 kg (16,500 lb.).
B. Body shape.
A killer whale has a sleek, streamlined, fusiform (tapered at both ends) body shape.
female
male
A killer whale has a sleek, streamlined, fusiform body.
Its physical characteristics are adapted for life in an aquatic environment.
C. Coloration.
1. These animals are easily recognized due to their striking black and white coloration.
2. The dorsal surface and pectoral flippers are black, except for the area below and behind the dorsal fin.
3. The dorsal surface and pectoral flippers are black, except for the gray saddle area located just behind the dorsal fin. The ventral (bottom) surface, lower jaw, and undersides of the tail flukes are mostly white. The undersides of the tail flukes are fringed with black.
4. A white 'eyespot' is located just above and slightly behind each eye.
5. The coloration of killer whales may enhance their ability to hunt.
a. Killer whales are counter-shaded; they are dark on their dorsal surface and white on their ventral surface. The dark side blends in with the murky ocean depths when viewed from above. The light ventral side blends in with the lighter surface of the sea when seen from below. The result is that prey have a difficult time seeing a contrast between the counter-shaded animal and the environment.
b. In addition, killer whales have disruptive coloration, a camouflage in which the color pattern of an animal contradicts the animal's body shape. In the flickering, filtered sunlight of the sea, other animals may not recognize a killer whale as a potential threat.
6. Albinism in killer whales has been reported 74 times in a 36-year period, and as recently as 1970 an all-white killer whale calf was studied in British Columbia.
D. Pectoral flippers.
1. A killer whale's rounded and paddle-like forelimbs are pectoral flippers. Pectoral flippers have the major skeletal elements of the forelimbs of land mammals, but they are shortened and modified.
2. The skeletal elements are rigidly supported by connective tissue. Thick cartilage pads lie lengthwise between the bones.
3. Killer whales use their pectoral flippers mainly to steer and, with the help of the flukes, to stop.
4. One particularly large male had pectoral fins that measured 203 cm (80 in.) long and 109 cm (43 in.) wide.
E. Flukes.
1. Each lobe of the tail is called a fluke.
2. Flukes are flattened pads of tough, dense, connective tissue, completely without bone or cartilage.
3. Longitudinal muscles of the back (both above and below the spine) and caudal peduncle (tail stalk) move the flukes up and down.
4. Although killer whales have 50 to 54 vertebrae, no bones extend into the flukes. Without bones or even cartilage in the flukes, it is not unusual to see them curved, especially in larger males.
5. One male is reported to have had flukes that measured 2.7 m (9 ft.) from tip to tip.
F. Dorsal fin.
1. Like the flukes, the dorsal fin is made of dense, fibrous connective tissue, with no bones or cartilage.
2. The dorsal fin acts as a keel. The dorsal fin probably helps stabilize a killer whale as it swims at high speeds but is not essential to a whale's stability.
3. The dorsal fins of male killer whales are the tallest of any cetacean in the world, growing up to 1.8 m (6 ft.). Female dorsal fins are smaller at about 0.9 to 1.2 m (3-4 ft.) and may be slightly curved back.
4. For male killer whales, dorsal fin growth is thought to be a secondary sexual characteristic as peak growth of the fin coincides approximately with the onset of sexual maturity.
5. Female and male killer whales can have dorsal fins that may be curved, wavy, twisted, scarred, and completely bent over. Some may even have bullet holes in them.
6. No one is exactly sure why the dorsal fins of killer whales bend, but it may have to do with genetics, injuries, or because the fins can be taller than many humans without any hard bones or muscles for support.
7. A recent survey of killer whales around New Zealand has documented that 23% of wild males had bent fins.
8. Because of the huge diversity of killer whale dorsal fins and the adjacent saddle patch, researchers take pictures of these fins to identify individuals and their pods, much like fingerprints are taken to identify humans.
