Transient ( Bigg’s) Killer Whales of Monterey Bay

Identification Catalog and Field Guide for Transient (Bigg’s) Killer Whales of Monterey Bay and California Waters

Identification Catalog and Field Guide for Transient (Bigg’s) KillerWhales of Monterey Bay and California Waters

2023 Edition

By Josh D. McInnes, Chelsea R. Mathieson, Peggy J.West-Stap, Stephanie L. Marcos, Victoria L. Wade, Jeffrey E. Moore, Sarah L. Mesnick, and Lawrence M. Dill

Killer Whales

Killer whales (Orcinus orca) are the largest member of the dolphin family, and the only species of cetacean known to regularly consume marine mammals. They were given the name “whale killers” byearly sailors who observed them preying upon large whale species. This eventually became the name “killer whale” that we use today.

Killer whales are apex predators with a cosmopolitan distribution meaning they are found in all major ocean basins. They are

largely concentrated in high latitudes along coastal regions where prey are abundant, but have also been documented in oceanic or offshore ecosystems and at lower latitudes.

Currently, one species of killer whale is recognized globally, but 10 different ecotypes, or forms, havebeen described. Prey specialization among ecotypes has been the driving force in shaping many aspectsof their ecology and natural history. In the Northeastern Pacific, long term studies have described three sympatric ecotypes known as residents, transients, and offshores. These ecotypes differ in their diet, behavior, distribution, morphology, acoustics, and genetics. Resident killer whales specialize in foraging for fish, in particular salmonids, live in stable matrilineal pods ranging in size from 10 to 50 whales, and consist of three adjacent distinct population segments that are socially isolated. These are the so-called southern residents distributed from the waters off southern British Columbia down to California’s Central Coast, the northern residents, distributedfrom British Columbia to Southeastern Alaska, and the Alaskan residents that range from Southeastern Alaska to the Aleutian Islands. Offshore killer whales are also piscivorous, but appear to feed on upper trophic level species (e.g. sharks). They are rarely encountered, often travel in groups of 50 or more animals, and are found in offshore waters ranging from Alaska to SouthernCalifornia. Transients (or Bigg’s killer whales, named in honor of the late Dr. Michael Bigg), are marine mammal hunting specialists. They travel in smaller matrilineal groups usually consisting of three to 10 individuals, with a fluid social system, and are distributed from Alaska to Southern California.

Outer Coast Transient Killer Whales

Considerably less is known regarding the distribution of transient killer whales in offshore and oceanic waters.The vastness of the open ocean often inhibits research due to unpredictable weather, infrequent sightings, and operational costs of large survey ships. Sightings of killer whales also tend to decrease further offshore from the continental shelf. There is growing evidence that at least a portion of the WC transient population utilizes offshore waters. A study conducted in British Columbia by the Department of Fisheries and Oceans Canada in 2013 identified 217 transient killer whales sighted predominantly off the continental shelf break, spatially discrete from the coastal assemblage. Interestingly, 46 of these transients were matched to whales previously cataloged off central California. . Monterey Bay, off the central coast of California, provides a unique opportunity to research transients in a deep-water ecosystem with relative ease. Killer whale photo-identification studies in Monterey Bay began in the 1980’s, and initially identified over 100individual transients thought to be a subset of the WC population based on acoustic similarities and occasional mixing. However, since 1997, very little has been published regarding transients in this region. A reassessment by the Department of Fisheries and Oceans Canada published in 2007 stated there is not enough information to conclusively include this assemblage as part of the WC transient population. Due to the lack of knowledge regarding transient killer whales in Monterey Bay and surrounding outer coast waters, we prepared this field guide, in conjunction with our technical memorandum, Transient Killer Whales of Central and Northern California and Oregon: A Catalog ofPhoto-identified Individuals, in order to share information with our fellow researchers, naturalists, whale watchers, and whale enthusiasts. Here, we share 15 years of information collected on killer whales encountered in Monterey Bay, California and surrounding offshore waters.

In addition to information regarding ecology and natural history, we are providing a catalog of 134 individual transient killer whales photographed in this study area.

Download the catalog and guide here: Transient (Brigg’s) Killer Whales of Monterey Bay

2023 Edition By Josh D. McInnes, Chelsea R. Mathieson, Peggy J.West-Stap, Stephanie L. Marcos, Victoria L. Wade, Jeffrey E. Moore, Sarah L. Mesnick, and Lawrence M. Dill