Longevity and Causes of Death
1. No one knows for sure how long killer whales live.
3. Long-term studies will ultimately answer this question. By counting growth layers in teeth, scientists find that killer whales in the North Atlantic may live at least 35 years. Studies are still refining this method of aging.
4. Scientists in the Pacific Northwest estimate life expectancies by using information derived from field observations that began in the 1970s. These scientists believe that if a killer whale survives the first six months, a female's life expectancy is 50 years and a male's is 30 years.
5. With continued research, it is likely that differences in longevity will be
found in killer whale populations around the world.
Killer whales succumb to numerous natural diseases and parasites. Killer whale parasites include tapeworms, roundworms, and flukes. Whales in general may suffer from viral, bacterial, and fungal infections. In addition, they may develop stomach ulcers, skin diseases, and tumors. Hodgkin's disease has been seen in killer whales and severe atherosclerosis of the coronary arteries was found in a stranded specimen.
Killer whales are top predators in the sea. Healthy adults have no natural predators, but sharks prey on older, younger, or ill killer whales.
D. Human interaction.
Coastal killer whales are more likely to be affected by pollution, competition with humans for limited stocks of fish, and other environmental factors.
1. On rare occasions, killer whales strand along the shoreline. Why this happens is largely unknown.
E. Human impact.
2. In certain areas of the world, killer whales and fishermen compete for the same food sources.
3. In the past, confrontations between humans and killer whales led angry fishermen to demand the destruction of these cetaceans. Governments, such as the United States, were inclined to side with the fishing communities. One such example of this historic, bitter conflict can be found in the following 1956 article prepared by the United States Navy:
4. Killer whales have been exploited as a natural resource or have been taken incidentally during other whaling operations.
5. From 1954 to 1977, for example, Norwegian and Japanese whalers took a combined 2,963 killer whales. Russian whalers took 1,945 between 1948 and 1980. Today, the whaling industry does not target killer whales, although killer whales are legally subsistence-hunted by certain indigenous arctic peoples.
6. Some fishermen blame the destruction of millions of dollars of equipment and fish loss on killer whales, and on rare occasions some have taken to shooting killer whales.
7. Others are attempting to find alternatives to destroying killer whales.
8. High concentrations of chemical such as PCBs and DDT have been found in North Pacific killer whales. These industrial pollutants have been introduced to the marine environment through mining operations, offshore oil development, agriculture, pulp mills, and other coastal industrial developments. The pollutants enter the food chain through dinoflagellates and zooplankton, which are eaten by larger animals. These animals are eventually eaten by larger fishes and other predators. The pollutants become concentrated and reach high levels in the bodies of larger predators, such as killer whales.
9. In one study, tissue samples from killer whales stranded in Washington, Alaska, and British Columbia showed three whales with DDT concentrations above 400 parts per million and PCBs exceeding 100 parts per million in other killer whales. How these pollutants affect killer whales is not fully understood and research continues in this field.
F. Whale watching.
2. Tours specifically designed to view killer whales are concentrated in the area of British Columbia and Puget Sound off the west coast of North America. Western Johnstone Straits and Blackfish Sound off the southern end of Vancouver Island are places where encountering killer whales is likely, depending on the time of the year.
3. For the adventurous, there are boat tours that take guests to the frigid waters of Antarctica, where killer whales are plentiful.
4. These whale watching tours are a huge, growing business. The economic impact of these tours is estimated to be well over $4 million U. S. dollars for the Vancouver Island area alone.
5. The steady growth of recreational whale watching has raised some concerns with
killer whale researchers. For example, it has been recently noticed that many killer
whales avoid the shallow beaches where they rub their skin if any boats, even
non-motorized ones, are in the general area. Also, whale watchers along the beaches
seem to force the killer whales to leave.
Scientific Classification|Habitat and Distribution|Physical Characteristics|Senses|Adaptations for an Aquatic Environment|Behavior|Diet and Eating Habits|Reproduction|Birth and Care of Young|Longevity and Causes of Death|Conservation and Research|Books for Young Readers|Bibliography|Index
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