Southern resident killer whales

The research vessel Noctiluca of the Northwest Fisheries Science Center in close proximity to a killer whale

The southern resident killer whales (SRKW) represent the smallest of four resident communities within the northeastern portion of the North America North Pacific Ocean. It is the only killer whale population listed under the Endangered Species Act by the National Marine Fisheries Service, National Oceanic and Atmospheric Administration. The National Marine Fisheries Service listed this distinct population segment of killer whales as endangered, effective in 2005, under the Endangered Species Act.^[1] In Canada the SRKW are listed as endangered on Species at Risk Act Schedule 1.^[2] They are commonly referred to as the "orcas of the Salish Sea",^[3] "fish-eating orcas", or the "SRKW" population. Unlike other resident communities, the SRKW is only one clan (J) that consists of 3 pods (J, K, L) with several matrilines within each pod.^[4] As of September 2020 there are only 74 individuals.^[5] The world's oldest known killer whale, Granny or J2, had belonged to and led the J pod of the SRKW population. As of October 2016, she is missing and presumed deceased.^[6] J2 was estimated to have been born around 1911, which means she would have been 105 years old at the time of her death, and the oldest known Orca to date.^[7] On July 24, 2018 the first calf born in three years died after being alive for only half an hour.^[8]

Social structure[]

Photo identification over the last 38 years has allowed researchers to track the southern resident population quite accurately, such as the Orca ID site^[9] offered through the . Their population is built upon a matrilineal system where these strong hierarchical groups of individuals are connected by maternal descent. Each matriline consists of a female, her sons and daughters and the offspring of her daughters; averaging anywhere from one to seventeen individuals and one to five generations within each of these matrilines.^[4] Pods are groups of matrilines that share a maternal ancestor, in which the southern residents consist of three pods. The number of individuals changes due to birth and deaths.

The Orca Network provides a list (last updated September 2017). The following is the basic social structure:^[10]

Community

Southern Resident

Clan

J

Pods

J Pod (23 members)

K Pod (18 members)

L Pod (35 members)

Matrilines

J2 (believed deceased as of October 2016), J4, J5, J7, J10, J11, J32 (found dead on a beach on Vancouver Island on December 4, 2014.)

K4, K7, K8, K11, K18

L2, L4, L9, L12, L21, L25, L26, L28, L35, L37

In 2014, L120 was born into L pod but didn't survive more than a month. In late 2014, J50 Scarlet was born into the J pod. After a lot of speculation, J16 Slick was confirmed to be J50's mother, making the 42-year-old the oldest ever recorded orca mother. The gender of the calf is confirmed to be female.^[11]

In February 2015, two new calves were spotted, a male calf in J pod, designated J51 Nova, and another male in L pod, designated L121 Windsong. J51's mother is ten-year-old J41 Eclipse and L121's mother is twenty-year-old L94 Calypso. A fourth calf, designated J52 was born in March 2015 to J36 Alki, who is J16's daughter. In early 2016, J52 Sonic was confirmed to be male, however he died in September 2017, presumably from starvation.^[12] Since 1998, 40 orca calves have been born to J, K & L pods and survived, while 72 orcas have gone missing (presumed dead) or have been confirmed dead.^[13]

In August 2018, the pod attracted international attention after the death of a female calf born to J35 Tahlequah and the sickness and death of another calf, J50.^[14]

Dialect[]

Similar dialects amongst pods create the social grouping called "clans". It is believed that the more similar their dialect is within the pods, the more closely related they are. The southern dialect is very different from that of other communities. For instance, northern residents use whistles as their main type of close-range communication and the southern residents use whistles for regular social interactions and long-range communications. Southern residents appear to be much more vocal but it could be due to their vocal usage during travel and the fact that they seem to travel more than the northern residents.^[4]

Location[]

The southern residents have been seen off the coast of California, Oregon, Washington, and Vancouver Island, British Columbia. 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. Members of L pod have been seen as far north as Southeast Alaska. During the late spring through fall, the southern residents tend to travel around the inland waterways of Puget Sound, the Strait of Juan de Fuca, and southern Georgia Strait - an area known as the Salish Sea.^[15] More information is now available about their range and movements during the winter months, which appears to follow returns of Chinook salmon to major rivers in the Pacific Northwest and California.

Distinguishing features[]

• Dorsal fin: rounded at the tip (leading edge) and positioned over the rear insertion of the fin towards the back.
• Saddle patch: typically seen as an "open" saddle patch; five different pigmentation patterns have been reported with similarities noted among clans within a community.^[16]

Diet[]

Southern residents are fish-eating orcas that appear to prefer the Chinook salmon to other fish species. From visual sources, necropsy, and feces collection, the following food preferences have been reported:^[4]

• Salmon 97%

  Chinook (78% in late spring and fall)

  Chum (11%, more so in Fall)

  Coho (5%)

  Steelhead (2%)

  Sockeye (1%)

• Other fish 3%

  e.g. Pacific herring and quillback rockfish

They can be known to play with porpoise.

Threats[]

The major threats to this very small community have been listed as:^[4]

• Decreased prey availability
• Pollution and contaminants
• Effects from vessels traffic and vessel sound

Decline in prey[]

The depletion of large quantities of fish in the marine environments, while personal fishing in the salmon’s upstream spawning grounds have further depleted stock replenishment.^[17] Aquaculture has had a negative effect on world fish supplies,^[18] including through the spread of pathogens to the wild fish stock. A study also found that Chinook salmon found in South Puget Sound have less fat than those farther north, causing an increased need for consumption.^[19] Due to four dams in the Lower Snake River Dam System, native salmon flow has been heavily restricted, endangering both Chinook Salmon and Southern Resident Killer Whales.

Chemical contamination[]

Northwest killer whales are among the most contaminated marine mammals in the world, due to the high levels of toxic anthropogenic chemicals that accumulate in their tissues.^[20] Implicated in the decline of Orca populations in the Pacific Northwest, these widespread contaminants pose a large problem for conservation efforts. While many chemicals can be found in the tissues of Orca, the most common are DDT, an insecticide, polybrominated diphenyl ethers, or PBDEs and polychlorinated biphenyls, or PCBs.^[21] Each of these have detrimental physiological effects on orca,^[22] and can be found in such high concentrations in dead individuals that those individuals must be disposed of in hazardous waste sites.^[23]

Correlative evidence shows orca may be vulnerable to effects of PCBs on many levels. Research has identified PCBs as being linked to restricting development of the reproductive system in orcas and dolphins.^[24] High contamination levels leads to low pregnancy rates and high mortality in dolphins. Further effects include endocrine and immune system disruption, both systems being critical to mammalian health and survival.^[22] A study examining 35 Northwest orcas found key genetic alterations that caused changes to normal physiological functions.^[25] These genetic level interferences, combined with the varied effects of PCBs at other physiological levels, suggest these contaminants may be partially responsible for declines in Orca populations.

Marine noise[]

Noise and crowding from tour boats and larger vessels interrupt foraging behavior, or scare away prey. The noise can mask echolocation causing difficulty with catching prey.^[26] Also, sonar is speculated to cause hemorrhaging, and possibly death.^[27]

Conservation efforts[]

There was a Washington state-wide task force created in March 2018 to make recommendations on how to preserve the Southern Residents from extinction.^[28] Some of the recommendations include stopping the use of hormone disruptors and other toxins in consumer products^[29] and removing dams that interfere with the salmon's access to breeding grounds.^[30]

Current conservation efforts are listed as:^[31]

• Support salmon restoration efforts
• Clean up existing contaminated sites
• Continue evaluating and improving guidelines for vessel activity
• Prevent oil spills
• Continue Agency coordination
• Enhance public awareness
• Improve responses to live and dead killer whales
• Coordinate monitoring, research, enforcement
• Conduct research
• Cooperation and coordination

On October 31, 2018, the Government of Canada committed $61.5 million to implement new protections for the Southern Residents.^[32]

See also[]

• List of cetaceans
• Michael Bigg

References[]

External links[]

• The Center for Whale Research
• Orca Network - births and deaths
• Orcas of the Pacific Northwest are starving and disappearing, The New York Times, 9 July 2018