Orca Whales of the Pacific Northwest
Killer Whale Populations of Puget Sound and the Straits of Georgia
Jun 30, 2009
The genetics, vocalizations and "cultures" of the three groups of orca or killer whales seen in the inland waters of northwest Washington and southwest British Columbia are distinctly different.
Orcas Look Alike, but Have Different Behaviors and Genetics
To the casual observer, the transients and southern resident orcas appear very similar, but researchers from the Center for Whale Research in Friday Harbor, Washington, have documented several major differences, including vocalization patterns, diet, habitat ranges, and social behaviors. Recent DNA studies by Dr. Lance Barrett-Lennard, senior marine mammal scientist at the Vancouver Aquarium Marine Science Centre suggests that resident orcas and transient orcas have been genetically separate groups for thousands of years. Though the residents and transients are often found in the same area at the same time, they do not appear to interact in any way.
The Southern Resident Orcas Whales
There are approximately 84 individuals in the southern resident group of orcas, living in three family-based pods called J, K and L. These whales feed on salmon, primarily chinook, and are frequently seen from whale watch boats during the spring and summer. They are also often spotted from shore-based lookout spots on the west side of San Juan Island. The southern resident orcas are gregarious and very vocal. They produce nearly 30 distinct sounds, with slight variations, similar to accents in human speech, between the pods. Experienced researchers can often tell by listening whether an individual is from J, K or L pod.
Southern Residents' name is a Misnomer
The name "southern residents" implies these whales spend their entire lives in Salish Sea. This is not true. Members of K and L pods are not usually seen in Puget Sound during the winter months, and have been spotted as far south as Monterey Bay. There are documented sightings of J-pod in Puget Sound during every month of the year, although J-pod too spends a large amount of time in the open ocean during the winter months, hunting salmon.
The Transient Orca Whales
Scientist believe there are about 600 transients orcas distributed along the west coast of North America between the Gulf of Alaska and Baja. One of the most notable difference between transients and residents is their diet. While residents feed primarily on fish, transients feed on marine mammals such seals, sea lions, porpoises, and other whales. Since transients prey upon intelligent sea mammals, they must use stealth to surprise their prey. Transients usually hunt in small, silent packs of 3 or 4 individuals. Unlike the residents, they produce a very limited number of vocalizations. Transients spend most of their time off shore, but are seen periodically in Puget Sound and the Straits of Georgia, particularly in the summer when the harbor seals are giving birth to pups.
The Off-shore Orcas
Researchers have identified about 200 to 250 individual off-shore orcas. These whales travel in large pods of 25 to 30 from Alaska to California, and generally stay several miles off shore, . Due the wear patterns observed on their teeth, researchers speculate that off-shore orcas may feed largely on sharks, a fish with very abrasive skin. Off-shores are genetically close to the southern resident orcas, but their vocalizations are completely different from both the residents and transients. Off-shore orcas are very rarely seen in the inland waters east of Victoria, BC. Researchers know the least about this group of orcas because of their vast range,
Further research is needed to understand how three populations of orca whales, living in the same waters, came to be so distinctly different from one another.
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