Southern resident orcas

[14] The following is a listing of southern resident social units:[15] Note that in several matrilines the matriarch is absent because deceased; nonetheless her descendants continue to associate as a group.

[18][19] The closed society[1] of the southern resident orcas has exceptionally stable social groupings, and they have been encountered with some predictability in the easily accessible, sheltered coastal waters of the Salish Sea, where scientists have been able to study them more readily than many other cetacean populations.

Continuous field studies since Michael Bigg's in 1973 have created a near-complete genealogy of the living Southern Residents, with only one individual born prior to the 1970s remaining alive as of August 2023: L25 Ocean Sun.

In studies of resident orcas, groupings have been inferred from measurements of the association of individuals in travel patterns with the aim of quantifying social bond strength.

[24][20] In the years after Michael Bigg's early surveys, with continuing recordings of births and observations of calves, it gradually became clear that the Southern Resident social structure is a stable ordering of a series of units from small to large according to matrilineal relatedness.

Especially in periods of population growth, however, travel patterns can reveal the gradual splitting of pods into two separate units, more evidently in the Northern Resident community.

[29] The sympatric transient (Bigg's) orcas travel in small, family groups, with individuals cooperating to kill and eat marine mammals together.

Researchers wrote that in play, they “often chase one another, or roll and thrash together at the surface.”[33][34] They "have been seen riding the wake of all types of vessels, from small skiffs to the largest cruise ships.

“After less than a minute, the two groups then submerge and a great deal of social excitement and vocal activity ensues as they swim and mill together in tight subgroups," researchers observed.

When other researchers from the center located the pod of orcas again a half hour later near Discovery Island, the neonate was dead and being carried on J35 Tahlequah's rostrum.

[59] The Center for Whale Research records all births and deaths, and collects demographic data of the southern resident orca population.

[67] Only two calves were born in 2022 and the total population of the Southern Residents fell to one of its lowest numbers since the end of the live-capture era in 1974, when 71 individuals were counted.

"[72][73] The pulsed calls of orcas may sound to humans like forms of speech, music, or wordless squeals,[74][75] "with distinct tonal qualities and harmonic structure.

Inside the lower mandible, sound travels through wide fat pads acting as ear canals, reaching the orca's version of eardrums, bony tympanic plates, which vibrate in response.

"[74] Discrete orca calls "can be readily identified by the trained ear or sound analyzer—some dialects are so distinctive that even an inexperienced listener can immediately discern the differences.

[86] The discrete calls "appear to serve generally as contact signals, coordinating group behaviour and keeping pod members in touch when they are out of sight of each other.

The researchers concluded that, with minor variation, this was one call that crossed the cultures of clans and even ecotypes, and was not acquired through social learning like the rest of the repertoire.

[90] Recordings of this 'excitement call' included northern as well as southern residents, and also Gulf of Alaska transients, who produce it in characteristic celebrations after a kill.

J Pod had been recorded in Dabob Bay on October 20, 1960, by US Navy personnel;[92][93] and in Saanich Inlet by Canada's Defence Research Establishment Pacific on February 19, 1958, and in spring, 1961.

[94] Harold Dean Fisher recorded Moby Doll at Burrard Dry Dock, and the tape he kept at UBC would years later have great significance for pivotal researcher John Ford (see below), who heard it as a student.

[99][95] The scientists demonstrated the sharp, directional nature of his echolocation, giving support to Kenneth Norris's new hypothesis that the fatty melon of a delphinid might function as an acoustic lens.

Ford recalled the moment he heard a call by Moby Doll being produced by living southern residents:[95]"I put the hydrophone on the side of the boat, and I was recording the sounds, and they all sounded pretty alien to me, because the dialects are very different from the northern residents, which I had started becoming familiar with, and then, all of the sudden, in the middle of these calls, is the one I remembered so vividly from the Moby Doll tapes.

Historic sightings and more recent data from satellite-tagged individuals show frequent use of coastal waters as far south as Monterey Bay, California in the winter and early spring.

[103] More information is now available about their range and movements during the winter months, which appears to follow the return of Chinook salmon to major rivers in California and North America's Pacific Northwest region.

Pacific Northwest orca are among the most contaminated marine mammals in the world, due to the high levels of toxic anthropogenic chemicals that accumulate in their tissues.

While many chemicals can be found in the tissues of orca, the most common are the insecticide DDT, polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs).

L25 "Ocean Sun", Tokitae's mother, the only remaining Southern Resident that was alive during the captures, was among those present with L Pod as they entered Penn Cove on November 4.

The Lummi are using "traditional ecological knowledge" practices to help sustain the orca population, including feeding of malnourished individuals, which has been criticized by NOAA as unsustainable.

[105] Current conservation efforts are listed as:[134] There was a Washington state-wide task force created in March 2018 to make recommendations on how to preserve the Southern Residents from extinction.

[135] Some of the recommendations include stopping the use of hormone disruptors and other toxins in consumer products[136] and removing dams that interfere with the salmon's access to breeding grounds.