Marine Mammals of Georgia Strait

June-July 2005

This is an article from WaveLength Magazine, available in print in North America and globally on the web.
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by Mary Borrowman

Four populations of orca are found in the waters of the Northeastern Pacific Ocean: Northern Residents, Southern Residents, Offshore and West Coast Transients, making for a total of some 750 animals.

All four populations travel through the Blackfish Archipelago in British Columbia, but it is the Northern Resident orca that are so often sighted in the waters of Johnstone Strait. Transients are often present but are far less predictable. Historically, orca are encountered on over 90% of whale watching trips.

The Resident and Transient populations are highly differentiated, likely due to their different diets. The Transient orca have evolved to be cunning hunters of other marine mammals: seals, sea lions, other cetaceans, even birds and an occasional swimming bear or deer make up their diet. As such, they have secretive behaviors in order not to alert their prey. They have longer dives, they vocalize and echo locate less, and travel alone or in small, fluid hunting parties. The West Coast Transients range from Southern Alaska to California.

By contrast, the Resident orca have a much more predictable food source— salmon. This has allowed them to evolve to be highly social animals. They travel in family units called matrilines, are highly vocal and are far more surface active than the Transient orca. A matriline is a tight social association of up to three generations of orca, descendent from one female.

Members of the 200+ Northern Resident population frequent the Johnstone Strait area from mid-June to January, depending on availability of fish. An additional draw to the area are the rubbing beaches. The Northern Residents are the only orca known to have the social behavior of rubbing on smooth stone beaches.

The population has three distinct acoustic clans. The differing vocalizations of the Northern Residents allow the orca to recognize ‘otherness’ and thereby avoid inbreeding.

The Southern Resident orca pass through Johnstone Strait before the return of the Northern Residents and travel to their fishing grounds which are further to the south. This population of only 84 animals is endangered and their welfare is a source of critical concern.

PACIFIC WHITE-SIDED DOLPHINS

Pacific white-sided dolphins come into the area in spectacular numbers in spring and fall. These highly acrobatic and vocal animals are a mystery, since identification of individuals is such a challenge. They are often seen interacting with other marine mammals. Their chosen interaction with the Resident orca is to ‘mob’ them. The raking marks of the Pacific white-sided dolphins are often found on their Resident orca cousins.

DALL’S PORPOISE

The speedy Dall’s porpoise are abundant in Johnstone Strait. They are believed to be present year-round, with the sheltered inland waters their preference for mating and calving. When without young, they often sprint towards a vessel at up to 55 km/hr, creating the water displacement known as ‘rooster tail’, and they may choose to bow-ride. Dall’s are the only porpoise species known to ride the bow wave of boats and this behavior offers an ideal opportunity for observation.

HARBOR PORPOISE

Harbor porpoise are also abundant but far shyer than the Dall’s. They are often seen in the inland channels, and when feeding, allow for good observation. They are the smallest cetacean of the area. Recent research has confirmed that the male harbor porpoise will mate with the female Dall’s porpoise. These porpoise hybrids have been seen in Johnstone Strait, appearing to have much lighter coloration than their Dall’s relatives.

MINKE WHALES

The Minke Whales of the area are frequently sighted but move in unpredictable patterns, unless feeding. Their speed and long dives make study challenging. They have been seen breaching, bow riding, surfing and interacting with Resident orca.

STELLER SEA LIONS

While the global population of Steller sea lions has dropped by two thirds, the population in British Columbia is stable. It is the male Steller that most often graces our local waters. Their presence is less common in the summer months when the successful males have managed to establish themselves among the females in rookeries further to the north. However, from early fall to spring, these growling giants are easy to find and delightful to observe in groups of up to 60 animals at a haulout.

HARBOR SEALS

Pacific harbor seals are the most commonly encountered marine mammal. Peak pupping is in mid-July. Their territorial and predictable behavior results in harbor seals making up half of the Transient orca diet. Seal haulouts can be the site of spectacular Transient orca attacks.

HUMPBACK WHALES

Humpback whale sightings are becoming increasingly common. It appears that these glorious giants are rediscovering the inland waters of Vancouver Island as a migration route. It may be that some do not complete their migration to Alaska but stay in the area of Northern Vancouver Island to feed. These humpbacks are members of the North Pacific population which is believed to have grown to some 8,000 animals (from 2,000 in 1965). It is thought that their numbers may now be increasing by as much as 10% per year.

TELEGRAPH COVE

Highly conductive to the study of marine mammals, secluded Telegraph Cove on Northern Vancouver Island is the main point of departure for Johnstone Strait marine mammal viewing. Telegraph Cove is a picturesque, boardwalk community with a rich history. The Cove opens up onto Johnstone Strait and Blackfish Sound. This area has one of the richest marine ecosystems in the world and has proven to be the ideal location to study marine mammals.

The Michael Bigg Ecological Reserve at Robson Bight was established as a sanctuary for the orca and is only 12 km from Telegraph Cove. It is an especially important habitat for the Northern Community of Resident orca due to its concentration of rubbing beaches. The Reserve encompasses 1248 hectares of marine area and 505 hectares of landmass, all under the protection of British Columbia Parks.

Orca Skeleton hangs at Telegraph Cove outside the whale museum.

It is in this area that Dr. John Ford, Graeme Ellis and the late Dr. Michael Bigg conducted pioneer research into the distinct populations of orca, their vocalizations and social structure. Research continues here with further insights into orca populations’ evolution and behaviors provided by the research of Dr. Lance Barrett-Lennard, Volker Deeke and Alexandra Morton, among others. The work of Dr. Michael Bigg spearheaded subsequent research after he discovered a system for identifying individual orca by their markings.

Dr. Paul Spong and Helena Symonds have established OrcaLab as a center of cetacean acoustics research near Johnstone Strait. Here, vocalization samples are collected 24 hours a day. They have had great success in increasing global awareness about the marine ecosystem with their ‘Orca-live’ website that relays live images and vocals from the area (www.orca-live.net).

Telegraph Cove is also home to a unique collection of marine mammal bones. My husband, Jim Borrowman, has avidly collected specimens for educational purposes. The collection includes a fully assembled orca, Pacific white-sided dolphin, harbor porpoise, Dall’s porpoise, Steller sea lion, harbor seal, sea otter, common otter, minke whale and an 18 meter fin whale (70% complete), among others.

© Mary Borrowman is with Stubbs Island Whale Watching, Telegraph Cove, BC. stubbs@island.net, www.stubbs-island.com Toll Free: 1-800-665-3066

Editor’s Note: Stubbs Island Whale Watching is offering 4 and 5 day Magnificent Seven Marine Mammal Tours: Sept. 11-16, 2005; Sept. 18-24, 2005; Sept. 10-15, 2006; Sept. 17-23, 2006.