By Caitlin Birdsall
The acrobatic and gregarious Pacific white-sided dolphins don’t just cause a lot of splash in the water, they also cause quite a ‘buzz’ on land! Last week, the B.C. Cetacean Sightings Network received numerous reports of Pacific white-sided dolphins from observers around the Nanaimo and Gabriola Island area!
Pacific white-sided dolphins are a small cetacean, typically around 2.5 meters, but they frequently travel in large groups and demonstrate very acrobatic behaviour, making them quite conspicuous as they race along the coastline. In fact, up to 6000 have been spotted travelling together in the open ocean and they are known to breach, porpoise and even flip repeatedly! The groups seen last week weren’t quite so enormous – around 50-100 dolphins were seen – but to the delight of our observers, most reports depicted their gymnastics and high speed sprints.
Prior to the 1980s, seeing this species of dolphin near Nanaimo would have been quite unusual. For much of the 20th century, Pacific white-sided dolphins were thought to be an open-ocean species. In the mid-1980s groups of dolphins began appearing in the inshore waters of British Columbia, especially around the northern tip of Vancouver Island. Were these dolphins exploring new habitats, or had they ever used these areas before?
The answer came from archeologist Donald Mitchell who was studying First Nations middens that were nearly 2000 years old in the Queen Charlotte Strait in the mid-1980s. There he found the teeth of Pacific white-sided dolphins, showing that they had long been present on our coast. Researchers aren’t sure why this species of dolphin was absent from our coast for several decades, but they suspect that changes in ocean temperature or fish populations may have encouraged their return.
While they are becoming increasingly abundant on the coast, most dolphins seen in B.C. still spend some of the year in offshore waters. Dolphins seen around the Johnstone Strait and Queen Charlotte Strait areas of northen Vancouver Island frequently have a brownish colouration. This colouring is associated with diatoms picked up on their bodies while they spend time in the open ocean.
Although Pacific white-sided dolphins may be the most abundant species of dolphin in the north Pacific, very little is known about them in B.C. waters. No accurate population estimate currently exists, and little is known about their seasonal movements. The group of dolphins seen last week near Nanaimo may help our researchers answer some of these questions. Kathy Heise, a research associate with the Vancouver Aquarium who specializes in Pacific white-sided dolphins, believes that groups of dolphins seen in the Strait of Georgia may belong to a population of approximately 100 animals that has potentially become resident in this area.
In 2007, a group of dolphins even spent the summer in Sechelt Inlet from March to August. Long term locals were amazed to see them for the first time in these sheltered waters! In the spring, observers reported groups of up to 200 animals, while later in the summer the groups were 25-40 animals, indicating that the dolphins may have dispersed into smaller groups as the summer wore on. Heise believes that the Sechelt Inlet group may belong to the potential resident population of dolphins in the Strait of Georgia. “This is an exciting opportunity for scientists to learn more about this species!” she says. A small group, resident in the Strait of Georgia, may provide the opportunity to investigate their diet, life histories, reproduction and the impact of human activity on the animals.
You can be part of this exciting research! Help scientists locate dolphins in the Strait of Georgia, and around the BC coast, by reporting your sightings here.
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