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Killer Whale

By Bdarkshadow Apr 17, 2013 823 Words
Killer Whale
Introduction
The killer whale (Orcinus orca), also referred to as the orca whale or orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas. Killer whales as a species have a diverse diet, although individual populations often specialize in particular types of prey. Some feed exclusively on fish, while others hunt marine mammals such as sea lions, seals, walruses, and even large whales. Killer whales are regarded as apex predators, lacking natural predators.

Populations

* Resident: These are the most commonly sighted of the three populations in the coastal waters of the northeast Pacific. Residents' diets consist primarily of fish and sometimes squid and they live in complex and cohesive family groups called pods.

* Transient: The diets of these whales consist almost exclusively of marine mammals. Transients generally travel in small groups, usually of two to six animals, and have less persistent family bonds than residents. Transients vocalize in less variable and less complex dialects. Female transients are characterized by more triangular and pointed dorsal fins than those of residents. The gray or white area around the dorsal fin, known as the "saddle patch", often contains some black colouring in residents.

* Offshore: A third population of killer whales in the northeast Pacific was discovered in 1988, when a humpback whale researcher observed them in open water. As their name suggests, they travel far from shore and feed primarily on schooling fish. Offshores appear to be smaller than the others, and females are characterized bydorsal fin tips that are continuously rounded.

Types of Killer Whales
* Type A looks like a "typical" killer whale, a large, black and white form with a medium-sized white eye patch, living in open water and feeding mostly onminke whales. * Type B is smaller than type A. It has a large white eye patch. Most of the dark parts of its body are medium gray instead of black. * Type C is the smallest type and lives in larger groups than the others. Its eye patch is distinctively slanted forwards, rather than parallel to the body axis. * Type D was identified based on photographs of a 1955 mass stranding in New Zealand and six at-sea sightings since 2004. It is immediately recognizable by its extremely small white eye patch, shorter than usual dorsal fin, and bulbous head.

Why is it endangered?
* Pollution
The Exxon Valdez oil spill adversely affected killer whales in Prince William Sound and Alaska's Kenai Fjords region. The spill damaged salmon and other prey populations, which in turn damaged local killer whales.The Killer Whale is particularly at risk of poisoning from accumulation of toxins, including polychlorinated biphenyls (PCBs).  * Depletion of Prey Species

In the Pacific Northwest, wild salmon stocks, a main resident food source, have declined dramatically in recent years. On the west coast of Alaska and the Aleutian Islands, seal and sea lion populations have also substantially declined. * Habitat Disturbance

U.S Navy sonar may harm killer whales. In May 2003, Balcomb noticed uncharacteristic behavior displayed by the killer whales. The whales seemed "agitated and were moving haphazardly, attempting to lift their heads free of the water" to escape the sound of the sonars. "Balcomb confirmed at the time that strange underwater pinging noises detected with underwater microphones were sonar. The sound originated from a U.S. Navy frigate 12 miles (19 kilometers) distant, Balcomb said." The impact of sonar waves on killer whales is potentially life-threatening. Three years prior to Balcomb's discovery, research in the Bahamas showed 14 whales washed up on the shore. These whales were beached on the exact day U.S Navy destroyers were activated into sonar exercise.

Ways to Prevent it from Extinction
Killer whales can actually be separate, endangered species. For example, in 2005 the United States government listed the southern resident community as an endangered population under the Endangered Species Act. This community comprises three pods which live mostly in the Georgia and Haro Straits and Puget Sound in British Columbia and Washington. They do not breed outside of their community, which was once estimated at around 200 animals and later shrank to around 90. In October 2008, the annual survey revealed seven were missing and presumed dead, reducing the count to 83. This is potentially the largest decline in the population in the past ten years.

Reducing pollution is the one way to prevent the killer whale from extinction. Oil spills decrease the population of food (mainly salmons) for whales. Oil spills also affect their rate of reproduction, causing their population to decrease and finally cause extinction. Killer whales live together or in “pods”, therefore they do not breed with other whales from another pod.

Habital disturbance such as sonar activities should also be reduced to prevent whales from being accidentally beached due to their reaction to the sound.

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