Marine Science Chapters

5.5.2



Killer Whales

Body Form



A Killer Whale Model from The Whale Museum in Friday Harbor, San Juan Island, Washington
A killer whale model from The Whale Museum in Friday Harbor, San Juan Island, Washington (above).

Killer whales rarely get over 30 feet (the record may be 31 1/2 feet) and are relatively small whales when compared to the "great whales" like the blue whale (that can get close to 100 feet long). Killer whales are members of the dolphin family. They have teeth on both the upper and lower jaws. Their teeth are conical (although blunt at the tip) in shape and function primarily for holding prey and are not designed for chewing. Most have 48 teeth. The whales have two eyes, one on each side of their body. Behind each eye of the killer whale is a white eyepatch. The two nostrils emerge from the head on the top as a single blowhole (this is common in all the odontoceti, toothed whales). Between the blowhole and the mouth is a bulbous forehead called the melon. The shape of the melon can be changed by the whale as it focuses sounds.


Killer whale blowhole, melon, and eyepatch.
Killer whale blowhole, melon, and eyepatch (above).

Sounds are made in the nasal canal, focused by the melon area and released ahead of the whale. Most toothed whales use a series of clicks to echolocate (define their surroundings with received sound back from these echolation bursts much like sonar). Killer whales also produce a series of "songs" unique to their pod that are passed from generation to generation. These "songs" are what scientists refer to as the 'dialects' of each pod.


A pod of killer whales with a male and several females The male killer whale known as Ruffles because of his wavy dorsal fin
A pod of killer whales, with a male and several females (left). Ruffles, a distinctive male killer whale (right).

Killer whales have unique fins. Their dorsal fin is very large and supported only by cartilage. Males have dorsal fins that are often twice as long as females when they are mature (up to 6 feet). As males grow, the cartilage on the leading edge (forward edge) grows slower than the trailing edge (back edge) so that the back edge may take on a wavy appearance for a period of time as the whale grows up. This is very apparent in the whale named "Ruffles," seen here. Just behind the dorsal fin is the "saddle patch," an area of lighter colored skin that has a unique shape in each individual


Inverted Tail Lob Killer whale catching kelp in the notch of the flukes
A killer whale performing an inverted tail lob (left). A killer whale catching kelp in the notch of its flukes - a playful activity for some San Juan Island killer whales.

The tail fin of whales is called the flukes and is also made entirely of cartilage. The base of the tail is called the caudal peduncle. Killer whales often play by slapping their flukes on the water. The resounding clap can be heard for miles. Sometimes they slap it upside down, which is known as an inverted tail lob. They also are known to be quite playful with kelp, catching it in the notch in the middle of their flukes and holding it out of the water.


Skeleton of a Killer Whale from The Whale Museum in Friday Harbor, San Juan Island, Washington Close-up of Flipper on Killer Whale Skeleton from The Whale Museum in Friday Harbor, San Juan Island, Washington
Skeleton of a killer whale (left) and close-up of flipper (right) from The Whale Museum in Friday Harbor, San Juan Island, Washington.

The flippers, or pectoral fins, are supported by bones - the same types of bones as are found in the human arms (upper arm bone, two lower arm bones, wrist bones, hand bones, and finger bones).


A pod of killer whales
Male and female killer whales (above).

Sex can be determined in several different ways in killer whales. A distinct white patch on the underside of the killer whale covers the anus, genital slit, and the mammary slits (in females). By viewing this (seen when killer whales breach) one can tell the sex by the presence or absence of the mammary slits, even in babies. Male killer whales generally have more of an elongated white patch in the area behind their anus. Several anatomical differences can also be used to tell the sex of the mature adults. Adult male killer whales have taller dorsal fins and longer pectoral fins than adult females. As males age the tips of their flukes bend down. This may be to decrease friction as the whale's tail is raised (the downcurved tips bend and reduce the surface area as the tail is raised) but then the tips flare out as the tail is pushed down (the power stroke during swimming that needs the greatest surface area). This is hard to observe because when the killer whales raise their tails they usually do it quickly, and often flop it around which obscures viewing the drooping fluke tips of the older males. DNA analysis can also tell the sex of the killer whales. This is done by taking a small skin and blubber sample (like a biopsy) which does not appear to disturb the killer whale.


Plain white saddle patch Fancy white saddle patch
Plain white saddle patch (left) and fancy white saddle patch (right).


Photo-identification of individual whales is done primarily by photos of the left side (and sometimes the right side) of the dorsal fin and the saddle patch. It is variations in the shape of the dorsal fin and coloration of the saddle (along with scar marks in this area) that is the basis for identification. Identification catalogues began in the 1970s and continue today - each year researchers watch the pods of killer whales in the San Juan Islands and check for deaths and births. In general each of the three main pods that inhabit the San Juan Islands (the southern community) has about 2-3 births a year and 2-3 deaths.
Photo id catalogue front Photo id catalogue opened
Photo identification catalogue of San Juan Island killer whales (left). Inside catalogue (right) are possible relationships between known individuals and photographs of both the left and right sides of the dorsal fin and saddle.




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(Revised 20 April 2004)
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