Stranding of one of the long-beaked common dolphins in Puget Sound (March, 2012)

Another rare visitor to Southern Puget Sound found dead: Long-beaked common dolphin stranded in South Puget Sound, 28 March, 2012

A 1.8m (5.9 foot) juvenile female long-beaked common dolphin, a species not usually seen north of central California, was found dead in Little Skookum Inlet near Shelton, WA on the afternoon of 28 March. The animal was picked up by Cascadia Research (CRC) personnel and transported to Washington Department of Fish and Wildlife (WDFW) in Lakewood where a detailed examination was performed by biologists from CRC and WDFW the same day.

The animal was in good body and good post mortem condition, allowing for a very thorough external and internal examination. The skin appeared to be abnormal in texture over roughly 50% of the body; with some places of algal or diatom growth on the surface of the skin, and numerous small parasites that had penetrated into the blubber and to the surface of the muscle layer. There were a number of healed teeth marks from other small cetaceans (species unknown). There were no signs of recent trauma or entanglement. 

Internal examination revealed abnormalities in the thoracic cavity, including dark congested lungs with portions that appeared unable to function. We suspect these abnormalities played a significant role in cause of mortality, but the specific cause of death will not be determined until samples have been processed. A number of other samples were collected for genetics, biotoxin, food habit, and contaminant analyses and will be processed during the coming weeks and months. The skeleton has been retained for preservation and educational/scientific use.

Common Dolphins are not typically found in the Puget Sound; however, at least two different individual long-beaked common dolphins were sighted and photographed in June 2011 off Burfoot Park in Olympia (see http://www.cascadiaresearch.org/CommonDolphin2011.htm for info and photographs). Additional sightings were frequent in south Sound during the summer months and occasional throughout the fall and winter, with the most recent sighting on 25 March in Eld Inlet. Photographs from the Eld Inlet sighting are distant so we cannot be certain, but the animal appears to have similar pigmentation to the stranded dolphin. Photographs of the stranded dolphin were compared to the two identified individuals from 2011; it has been determined that the stranded dolphin is a different individual.  

The stranding of this dolphin represents the third unusual species of whale and dolphin to be sighted and subsequently found dead in southern Puget Sound in recent years. Since 2010, two Bryde's whales and two bottlenose dolphins were sighted in southern Puget Sound prior to stranding; all are warm water species not generally known to occur this far north. While these sightings and strandings suggest a troubling pattern and appear to be related, they thus far have only involved small numbers of animals and it is unclear how these strandings relate to changing ocean conditions.

The presence of other common dolphins in the region at this time is unknown—any sightings, photographs, or video of these or other cetaceans are greatly appreciated. Please report any porpoise, dolphin, or whale sightings to Cascadia Research at 360-943-7325.

Stranded common dolphin