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"Kayla"
conservation status: Dependent and Threatened The Orca or Killer Whale is the largest member of the oceanic dolphin family and is the second most widely distributed mammal on earth, (after humans) found in all of the world's oceans. Pinnacle on the food chain, the killer whale is an apex predator, not preyed upon in the wild. A pod of orca is capable of taking down a large whale. Females mature at fifteen years of age and calve approximately every five years. They breed until they are forty years old. Typical life span of the female is fifty years with some documented cases of females in their eighties and nineties. Males mature at fifteen years of age but don't reproduce until they are twenty-one. The male life span is from thirty to fifty years. Orca have a complex system of social grouping. A matriline consists of a single female (matriarch) and her descendants. Sons and daughters of the matriarch form part of the line as well as sons and daughters of those daughters. The sons and daughters of the sons of the matriarch join the matriline of their mates. It is common for four or five generations to travel together. No casting out has been recorded. Interestingly, individuals in each matriline have the same dialect. Each pod has its own vocal repertoire or set of particular stereotyped underwater calls. Clans are formed by matriline joining which have a similar dialect and a common heritage on the maternal side. A community of orca is a set of clans who are regularly seen traveling together. Orcas hunt differently, depending on the species, with some eating only fish and others eating mammals. Possessing great physical prowess as well as intelligence, orcas use complex hunting strategies to find and subdue their prey. For example, a captive orca found that he could regurgitate fish onto the surface, attract sea gulls and eat them! Other individuals learned this process by example. In the wild, they will "spy-hop" to locate seals (come out of the water vertically and stay out of the water like a human treading water). In "carousel feeding" hundreds of herring are forced into a tight ball by several individuals releasing bursts of bubbles to encircle them. When the bubbles disperse and the fish attempt to escape they are caught in waiting mouths. The Exxon Valdez oil spill had an adverse effect on orca in Prince William Sound and the Kenai Fjords region of Alaska. One resident pod was caught in the spill. One half of the pod had disappeared the following year. The spill reduced the amount of available prey and has thus been responsible for the local population to decline to only seven individuals who have failed to reproduce. This population, called the AT 1 pod, is expected to go extinct. Orca is also particularly susceptible to poisoning via the accumulation of polychlorinated bephenyls or PCBs in the body. On November 15, 2005 the U.S. government listed the southern resident population of killer whales as an endangered species due to the deterioration of the three pods which spend most of the year in Georgia and Puget Sound. High levels of persistent pollutants are compromising their reproductive and immune systems. Greatest threat - Man |