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Longevity and Causes of Death

A. Longevity/Aging Studies

1. No one knows for sure how long killer whales live.

2. For unknown reasons, killer whales have a high calf mortality rate in some areas of the world. In the Pacific Northwest, for example, 43% of all calves die in the first six months. In other killer whale populations, calf mortality may be as high as 50% during the first year.

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.

Researchers can estimate a killer whale's age by examining a sliced section of tooth and counting growth layer groups.

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.

B. Disease and parasites.

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.

C. Predators.

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.

E. Stranding.

1. On rare occasions, killer whales strand along the shoreline. Why this happens is largely unknown.

a. One theory behind this is that killer whales accidentally strand when they chase prey into shallow waters.

b. During one mass stranding of 14 killer whales in northern Norway, it is thought that the whales became stranded while chasing herring. All 14 were successfully pulled back into the water and swam off to rejoin their herd a short time later.

E. Human impact.

1. Humans have long been fascinated by killer whales, but until recently very little was known about their lives at sea.

a. The image of a killer whale was found on cave drawings in northern Norway, and it is estimated to be some 9,000 years old.

b. A few cultures respected killer whales, yet much of the ancient world did not. During the first century AD, a Roman scholar named Pliny the Elder wrote that killer whales "cannot be properly depicted or described except as an enormous mass of flesh armed with savage teeth."

c. In 1835, R. Hamilton wrote that the killer whale "...has the character of being exceedingly voracious and warlike. It devours an immense number of fishes of all sizes... when pressed by hunger, it is said to throw itself on every thing it meets with..."

d. Many in modern civilization still envisioned killer whales as terrifying threats to humans, with a 1973 United States Navy diving manual warning that killer whales "will attack human beings at every opportunity."

e. Killer whales are animals shrouded in myth, and many times this misinformation has led to the destruction of these whales.

2. In certain areas of the world, killer whales and fishermen compete for the same food sources.

a. This is especially true in the Bering Sea, where killer whales and Alaskan and Japanese fishermen regularly clash over black cod (Anoplopoma fimbria).

b. A similar conflict occurs between Brazilian fishermen in the Atlantic who target tunas (Thunnus spp.) and swordfish (Xiphias gladius).

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:

NAVAL AVIATION NEWS December, 1956, pg. 19 Killer Whales Destroyed VP-7 Accomplishes Special Task Adm. Jerauld Wright, Commander in Chief, Atlantic Fleet, has announced the completion of another successful mission by VP-7 against killer whales off the coast of Iceland Killer whales annually plague Icelandic fishermen by damaging and destroying thousands of dollars worth of fishing nets. Last year, VP-18 destroyed hundreds of killer whales with machine guns, rockets and depth charges. Before the Navy lent a hand last year, killer whales threatened to cut the Icelandic fish catch in half. This created a crisis because the fishing industry employs about 20% of the population and accounts for the majority of Iceland's foreign currency income. The Icelandic Office requested help, and Capt. Sherrill, Commander of the Naval Forces in Iceland, assigned VP-7 to the task of ridding the coastal areas of killer whales. Ranging from 20 to 30 feet in length, they are feared as one of the deadliest of ocean animals.

4. Killer whales have been exploited as a natural resource or have been taken incidentally during other whaling operations.

a. In 1958, the government of Japan sanctioned the use of 50-caliber guns to be used against killer whales. An average of 60 killer whales were caught annually off the waters of Japan, with the meat being sold in local markets and the viscera (internal organs) used as fertilizer or bait.

b. The most valuable commodity from these killer whales was oil derived from boiling the blubber.

c. Sometimes their thick hides were made into soles of shoes.

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.

a. Alaskan fishermen have attempted a variety of methods in order to deter killer whale depredation on long-line catches of codfish including the use of decoy boats, combining hauling operations, fishing at night, acoustic harassment devices, and the use of electric currents.

b. Other more aggressive attempts to discourage them included using high-powered explosive devices and even illegally shooting the whales. None of these methods have proven effective.

c. Other methods being examined to eliminate long-line depredation include the use of sparker devices (which emits a flash of light to startle the whales), rubber bullets, bubble screens (to interfere with the acoustical senses of the whales), using chemicals such as lithium chloride and ether (to promote sickness/vomiting), reducing sound levels generated by backhauling equipment to avoid attracting killer whales to fishing operations, and playing recordings of previous long-line operations to confuse the whales.

d. To date, the only effective strategies for reducing killer whale interactions with fishing boats were temporarily stopping fishing operations, moving the fishing fleet to distances greater than 111 km (60 nautical mi.) away, and changing the target species from black cod to Pacific cod.

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.

1. Where once whaling boats pursued killer whales to hunt them, a new group of thrill-seeking humans venture forth to see these amazing creatures just to enjoy their beauty.

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.

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