Deceased Risso's Dolphin: Response & Recovery
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Deceased Risso’s Dolphin - Photo by Sydney Dixon.
The body of a male Risso's dolphin (Grampus griseus) was discovered washed up on Chesterman Beach on Wednesday morning, January 13, 2021. The report originally was called into Parks Canada wildlife officers and was soon responded to by Fisheries Officers (DFO) and SIMRS staff around 10:00am. With water levels quickly rising for a mid-day high tide, it soon became a race against the incoming swell to get the animal secured for transport. Our first plan of action was to secure a sling around animal and lift it above the high-tide line where it would be safe from drifting back to sea. However, the dolphin, measuring 3m and weighing several hundred kilograms, posed too heavy for the two DFO and three SIMRS staff members to lift, despite our best efforts. Plan B was to anchor the animal on a nearby log but there were concerns that this would leave the animal far enough below the tide line that we may lose daylight before the body was released from the water's grasp. At this point, the water level was rising rapidly and we knew whatever decision we made, it had to be quick! Our third and final plan was to secure the animal within the sling, anchor it with rope to a tree on the shoreline and manually haul it as high up the beach as we could when the water aided us by lifting the body off the sand. Rope burned hands and thoroughly wet boots later, the dolphin's body was secure and safe. Now, there was nothing to do but wait until the tide dropped low enough again to access the animal.
Risso’s have no teeth in their upper jaw and only a few (two to seven pairs) of peg-like teeth in the front of their lower jaw to capture prey - Photo by Sydney Dixon
Why go through all the trouble? Generally, there is a lack of knowledge of open ocean species. As such, the life history of Risso's dolphins is poorly understood as the species has been little studied. The individual that washed up on Wednesday was relatively fresh and undamaged. The scarring and scratches along their bodies occur naturally, and are caused by teeth raking from other dolphins or by predator or prey interactions. Risso's dolphins are widely distributed throughout temperate and tropical waters of the southern and northern hemispheres. As cephalopod specialists, like sperm whales, they can primarily be found in deep waters along the continental shelf break and slope. In the Pacific Northwest, Risso's dolphins can be found as far north as Alaska but the vast majority of sightings occur in warmer waters between 15-20 °C. Until very recently, Risso's dolphins were considered extremely rare in BC waters. The first confirmed sighting of live individuals was recorded in 1978 by biologist Tom Reimchen in Parry Pass on the northwest tip of Graham Island, Haida Gwaii. Although BC lies within the Risso's dolphin's natural range in the Pacific Northwest, sightings of them are still relatively uncommon. Between 1978 and 2014 there were only 82 reported sightings of the dolphins within BC waters, the majority of which occur around Haida Gwaii (Ford, 2014). Off the west coast of Vancouver Island, Risso's dolphins are most commonly sighted around Barkley and Nitnat canyon, concentrating near the BC/Washington boarder (Ford, 2014). In Tofino, the number of confirmed sightings remain relatively few and far between. SIMRS founder, Rod Palm, encountered a group of 14 individuals 28 nautical miles offshore in 1999. This sighting marked the first for the species within SIMRS official records. The dolphins were sighted again about 16 nautical miles off of Lennard Island in 2002/2003 by local guide and skipper, Chris McCue. Other sightings of the dolphins near Tofino have been made over the years by various tour guides and vessel operators. However, it is unclear as to whether these sightings have been reported to researchers and contribute to official population data.
The dolphin is lifted into the flatbed by the District of Tofino Public Works crew - Photo by Greg Potter
As the tide receded in the afternoon, it was time to jump back into action. The District of Tofino granted permission for a vehicle to be brought onto the beach in order to move the animal. As we learned in the morning, the dolphin was far too heavy to be lifted by man-power alone. A front end loader was brought out to hoist the animal into a large trailer so that it could be transported by DFO. Currently, the animal's cause of death is unknown. There are no external injuries visible that indicate cause of death. To find out, researchers will need to look inside the animal. A necropsy of the dolphin will be conduced by DFO staff and a veterinarian pathologist. This will hopefully give some insight into the animal's life and, ultimately, its' death. This individual is one of several to wash up on the coast of BC in recent months. The cause of these strandings is not clear, but retrieval of the bodies for necropsies may help researchers gain a clearer idea of what’s going on. As a member of The British Columbia Marine Mammal Response Network (BCMMRN), SIMRS goals are to provide direct assistance for responding to marine mammal incidents, to conduct research and monitoring of these incidents, and to promote public awareness of threats to marine mammals. For over 25 years, we have responded to numerous marine mammal incidences including entanglements, vessel strikes, and necropsies. For all three of the current SIMRS staff, this event marked the first time any of us had seen a Risso's dolphin, dead or alive. Unique opportunities like this one are made possible by people reporting their sightings.
You can get involved In citizen science by reporting all of your unusual sightings to your local research group, like SIMRS. See something interesting while on the water or combing the beach? Let is know! Reach us by phone at +1 (250) 266-9090 or send us an email at info@sirmstofino.org. The data and sightings reports we collect are passed onto DFO to help researchers better understand the marine environment and marine life. You can also help by reporting all marine mammals and sea turtles found entangled, stranded, distressed, or dead by calling the toll-free marine mammal incident reporting hotline at 1-800-465-4336.
~ written by Sydney Dixon
Photo by Sydney Dixon.