WHAT IS AN ORCA? What is an Orca?


By taking photographs of the dorsal fin, Dr. Bigg and his colleagues at the Pacific Biological Station in Nanaimo B.C. and at the Center for Whale Research in Friday Harbour, Washington, were able to identify each individual orca. After compiling thousands of photographs of the orcas of British Columbia and Washington State, they were able to define the composition of the orca population. Each individual was assigned a number and as well an alphabetical letter which designated the individual's pod. This alpha-numerical system, and yearly photographic updates, has enabled researchers to keep track of pod members.

Orcas are the largest member of the dolphin family, Delphinidae. Males grow to a maximum length of about 32ft (9.8m) and weight of 10 - 11 tons (9 - 10,000 kg) Females are smaller and grow to a maximum length of about 28ft ( 8.5m ), weighing as much as 7 -8 tons (6,500 to 7,500 kg). Calves at birth are about 8ft (2.4m) long and weigh about 400lbs (180 kg).

Orca bodies have distinctive black and white markings. Both females and males have similar markings except on the underside, where it is possible to distinguish male from female. The dorsal fin also distinguishes male and female adults. In the mature male the erect dorsal fin may reach a height of 5 1/2 ft. (1.7m) but the female dorsal fin grows only to an average of 3 ft. (0.9m)

male orca

Orcas are one of the toothed whales (Odontoceti), as are other dolphins and porpoises, pilot whales and sperm whales etc. Orcas have 10 to 13 pairs of interlocking conical teeth in the upper and lower jaws, usually a total of 48. Sperm whales have teeth only in the lower jaw. Orcas use their teeth primarily for grabbing prey. The number of rings within the teeth (anuili) may indicate how old an individual orca is, until about 30 years of age, when discrimination of new rings becomes difficult.

No one knows for sure how long an orca may live for, as the species has only been intensively observed since about 1970. However, studies show that for the Resident orcas along the Washington and B.C. coasts, females live an average of 50 years and may live as long as 80 years. It is not clear why, but males live significantly shorter lives, on average only about 30 years... and may reach a maximum age of 50 years. The oldest males in the Pacific Northwest study area are estimated to be just over forty years old. The mortality rate of newborn orcas is still unclear, but it is almost certainly quite high. Bigg et al estimated that it might be as high as 43% but did not have a lot of confidence in this number as the sample rate was so small. Largely, it was based on expected rates of reproduction and the pregnancy rate of large numbers of orcas killed by "small-type" whaling in the North Atlantic.

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