Longevity & Causes of Death

Killer Whales

Longevity & Causes of Death

Longevity

  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.
  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.

Aging Studies

  1. As a killer whale ages, it periodically produces growth layer groups of dental material. Age can be estimated by examining a sliced section of a tooth and counting these layers. These estimations can be accurate in young whales, before the tooth's pulp cavity fills in, but in general are not reliable for animals older than about 20 years.
  2. At SeaWorld parks, animal trainers routinely take a variety of measurements - including length, girth, and fin height - of killer whales. For a whale born at SeaWorld, experts are able to relate these measurements to the known age of the whale. This information helps provide a baseline for growth studies on wild killer whales.

Disease

  1. Killer whales and other whales develop stomach ulcers, skin diseases, tumors, heart disease, and respiratory disorders.
  2. Hodgkin's disease has been seen in killer whales.
  3. Stranded killer whales have shown severe atherosclerosis of the coronary arteries.
  4. Killer whales suffer from viral, bacterial, and fungal infections.
  5. Jaw abscess, resulting from tooth wear and exposure to the pulp cavity, is a common observation among killer whales in the wild.

Parasites

  1. Parasites - including roundworms, tapeworms, and flukes - may affect a killer whale's health. In most cases, parasite infestations alone are unlikely to debilitate otherwise healthy animals, but they may harm animals that are already weakened by other illnesses or injuries.

Predators

  1. Killer whales are a top predator. Healthy adult killer whales have no predators. Sharks may prey on older, younger, or ill killer whales.

Stranding

  1. A marine animal may strand if it is affected by a severe, debilitating illness or injury, or if it is too weak to swim or hunt for food.
  2. On rare occasions, killer whales strand, individually or in groups (called mass stranding). Mass strandings of whales and dolphins are natural phenomena that are largely unexplained. In most cases, the stranded animals are ill.
  3. During one mass stranding in northern Norway, 14 killer whales became stranded - it is believed - while chasing herring. All 14 were successfully pulled back into the water and swam off to rejoin their herd a short time later.