Transient orcas are one of three ecotypes, or kinds, of orcas that inhabit the Pacific Coast. The others are residents and offshores. They differ from each other in diet, range, and family structure.
Diet. Transient orcas eat marine mammals such as seals, porpoise and other whales. They are stealthy hunters, and typically do not use echolocation to find their prey.
Populations and Range. Transient orcas in the Pacific Northwest are known as Bigg’s orcas in honor of Dr. Mike Bigg, the researcher who first studied them. Other populations live along the coasts of California and Alaska.
- Bigg’s orcas travel as far north as Alaska and as far south as the Oregon coast, and throughout the Salish Sea.
- California transients travel from southern California to Oregon, with occasional forays further north or south.
Family Structure. Transient orcas travel in smaller groups than residents. Females separate from their mothers when they have their own offspring, and form their own subgroup.
Identification. Like resident orcas, individual orcas are identified by their saddle patches and dorsal fins. Each individual is given a unique identification with letters indicating population they are from, and a number indicating their birth order in their pods.
- Biggs ID numbers start with “T”.
- California IDs began with CA
- Alaskan transient IDs begin with AT.
Transient orcas may be seen anywhere along The Whale Trail, and at any time of year. It’s challenging to plan a trip around seeing them, since their ranges are wide and their travel patterns are not (yet) as predictable or understood as resident orcas. However there is one exception:
- Monterey Bay, April and May. Transient orcas congregate in Monterey Bay in the spring, where they intercept gray whales on their northbound migration. Gray whale mothers and calves typically travel close to shore, and are especially vulnerable to attack as they cross the wide bay. While it’s unlikely you’ll witness a hunt from shore, it is possible to occasionally see orcas from Whale Trail sites around Monterey Bay, including Lighthouse Park at Santa Cruz and Point Lobos State Park.
Worldwide, transient orca population numbers are holding steady, with a few local exceptions:
- AT1 Pod. The AT1 pod was in Prince William Sound during the Exxon Valdez oil spill. Since then, the pod has steadily declined from 22 individuals to 7, a decline that is attributed to the spill and its impacts. The pod is listed as Depleted and is not expected to recover.
- Bigg’s orcas are listed as Threatened under Canada’s Species at Risk Act (SARA). West Coast transient orcas are highly contaminated with PCBs and other toxins. Because they hunt marine mammals, they ingest the toxins that are present in their prey. Bigg’s orcas are one of the most highly contaminated marine mammal population in the world.
Catalogs, websites and other helpful resources:
- Photo-identification catalogue, population status, and distribution of Bigg’s killer whales known from coastal waters of British Columbia, Canada / Jared R. Towers [and ten others]. This photo ID-catalog includes maps showing distribution and abundance of Bigg’s orcas throughout Washington, British Columbia and Alaska. A comprehensive and indispensable resource. Free and downloadable.
- Bigg’s Orcas (Georgia Strait Alliance)
- California Killer Whale Project (California Killer Whale Project website)
- Killer Whale Research in Alaska (NOAA Fisheries)