The Stranding of CA189
An Orca stranding on the Juan de Fuca Strait
On Wednesday, Jan 2, 2002, residents of the cliff above Dungeness Spit reported an orca whale, apparently dead, stranded on a low lying sandbar in a marshy area just south of Dungeness Spit on the Olympic Peninsula in Washington State.
Another orca, a male, was nearby in shallow water, alive and staying close to the dead female, thought at the time to be its mother. Scientists and volunteers tried to escort the male orca out to deeper water, but as dark came on he was still inside the Spit & swimming sluggishly.
By the next day, scientists had identified both killer whales by the shape of the saddle patch below their dorsal fins. They were members of a pod of transient orcas last seen in Coos Bay, Oregon, in 1996. Originally spotted off the California coast, they had been given identifying numbers CA188 for the male and CA189 for the female, later named "Hope" by local children.
To bring Hope to dry land, volunteer divers attached buoys to her pectoral fin to make the body float and then towed her several miles to a boat ramp. The orca was then pulled from the water and a necropsy (marine mammal autopsy) was performed to determine the cause of death.
While the necropsy and removal were under way, another group of scientists and volunteers tried to help the male orca move to deeper water. During two nights, the tide went out so far that he was completely out of the water. Volunteers poured seawater over him and covered him with wet sheets and blankets. During the day, they experimented with a variety of different slings to gently assist him to deeper water.
Finally the sixth try was successful. CA188 reached open water and swam towards the Strait of Juan de Fuca which leads to the Pacific Ocean. CA188 has not been seen since then but no conclusions are drawn from this fact. Transient orcas travel over a large territory and may not be seen twice for many years.
Since her stranding in 2002, Hope has become perhaps the most studied killer whale in the wild. The thorough necropsy allowed samples of her organs, blood and blubber to be sampled and analyzed. Scientists compared results of these tests with those of other stranded orcas. Hope's skull was removed and sent to a lab in California for CT scanning, to investigate possible damage due to sonar. The rest of her bones were cleaned and closely inspected as part of the assembly of her complete skeleton.
Hope's findings are now part of the growing body of research on transient killer whales. There is now an increased focus on orcas' exposure to contaminants and an awareness of their possible effects on the health of the population. More transient orcas have been identified, several have been tagged and their movements and predation patterns are being studied. Scientists are also conducting research on orcas' exposure to bacteria and viruses present in surface waters, another possible source of infection.
What Caused Hope's Death?
Many questions remain, but this is what is known:
- Hope had the highest levels of PCBs and DDT ever found in an orca.
Her immune system was almost certainly weakened, making her more susceptible to infections.
- A large abscess was found near the back of her skull.
Although the CT scanning of Hope's scull showed no sign of damage from sonar or underwater explosions, it did reveal serious bone loss. These areas affected are marked in red on the CT scan shown to the right.
- Her heart blood and serum tested positive for an infection of a marine Brucella bacteria.
Related to bacteria that cause brucellosis in land mammals, this marine bacterium is also found in other marine mammals: seals, sea lions, dolphins and porpoises. Infected animals may appear healthy and show no signs of disease. Or they may develop infections of the bone, skin or brain, or be more prone to abort their young. Scientists were able to isolate and identify the bacterium found in Hope, but their efforts to grow it in a lab were unsuccessful.
Scientists and marine mammal veterinarians feel that the evidence does not point to one clear and obvious cause of death. Research on Brucella in marine mammals is still in its infancy. Similarly, little is known about bone loss (osteomyelitis or osteoporosis) in marine mammals. Although Hope's necropsy and CT examination suggest a connection, not enough is known to be certain.
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