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| ORCAS
(Orcinus orca) are marine mammals: they are warm blooded, air breathing, and bear their young alive. They are found in all the oceans throughout the world. The most persistent sightings have been near the continental shelves off Japan, the North American Pacific Northwest, Iceland, Norway, Scotland and Antarctica. However, nowhere are their populations very large. There is only one species of orca, however geographic isolation may have created different unique races and populations. Near the Washington, British Columbian and Alaskan coasts we know that there are at least two distinct races of orcas. These are referred to as Transients and Residents. Even though these two groups share the same ocean space they differ in their social habits, range, diet and to some extent even their physical appearance. In recent years a third population, the Offshores, has been discovered living along this coast. Not much is known about this group, as sightings have been infrequent. We do not know if they represent another unique race or another community. The study of Orcinus orca is relatively new. Prior to 1964 there were few systematic, scientific investigations of orcas. Their lives as ocean animals made studies difficult for researchers. There was also a very negative attitude toward orcas, who were considered, at best, as a nuisance to the fishing industry and at worst as vicious predators deserving extermination. After the first attempts to capture and display live orcas, in the mid 1960s, public attitudes began to change and scientific curiosity was heightened. The failures of the early captures did not deter the rash of subsequent captures. The easily accessible populations along the Pacific Northwest were hit the hardest. Throughout the latter part of the 1960s and in the 1970s, many whales were taken for the quickly growing captive industry . Many died during capture attempts. The result was that nearly 70 whales were removed permanently from this population. Most devastated was what is known today as the Southern Resident Community. All this happened before any real understanding of this whale population had been acquired. 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) 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. |
