Southern resident orcas
The southern resident orcas, also known as the southern resident killer whales (SRKW), are the smallest of four communities of the exclusively fish-eating ecotype of orca in the northeast Pacific Ocean. The southern resident orcas form a closed society with no emigration or dispersal of individuals, and no gene flow with other orca populations.[1] The fish-eating ecotype was historically given the name 'resident,' but other ecotypes named 'transient' and 'offshore' are also resident in the same area.
The U.S.
The world's oldest known orca, Granny or J2, had belonged to and led J pod of the SRKW population. J2 was initially estimated to have been born around 1911, which would mean she would have been 105 years old at the time of her disappearance and death which occurred probably in late 2016.[8] However, this estimate was later revealed to have been based on mistaken information and more recent studies put her at 65–80 years old.[9][10][11]
Society
Social structure
All groupings in southern resident society are essentially friendly. The basic social unit is the matriline. A matriline is formed by a matriarch and all her descendants of all generations. A number of matrilines form a southern resident pod, which is ongoing and stable in membership, and has its own dialect which is stable over time. A southern resident calf is born into the pod of their mother and remains in it for life. The southern resident pod is their normal traveling unit. The three southern resident pods form the single clan of this small killer whale community. The clan is possibly a single lineage that split into pods in the past. The clan has a unique stable dialect that shares no calls with other killer whale clans.[12]
The following is a listing of southern resident social units:[13]
- Community
- Southern Resident orca community
- Clans
- J Clan
- Pods
- J Pod (25 members)[a]
- K Pod (15 members)[b]
- L Pod (34 members)
- Matrilines
Note that in several matrilines the matriarch is absent because deceased; nonetheless her descendants continue to associate as a group. Date of census is January 1, 2024.
J11s: J27, J31, J39, J56
J14s: J37, J40, J45, J49, J59
J16s: J16, J26, J36, J42
J17s: J35, J44, J46, J47, J53, J57
J19s: J19, J41, J51, J58
J22s: J22, J38
K12s: K12, K22, K33, K37, K43
K13s: K20, K27, K38, K45
K14s: K14, K26, K36, K42
K16s: K16, K35
L4s: L55, L82, L86, L103, L106, L109, L116, L118, L123, L125
L11s: L77, L94, L113, L119, L121, L124, L126, L127
L22s: L22, L85 (1st cousin), L87 (brother)
L25: L25, the oldest southern resident, has no surviving close relatives since the death of the captive southern resident
L47s: L83, L91, L110, L115, L122
L54s: L54, L108, L117, plus the unrelated L88 who is an adult male born in 1993 with no living close relatives and who always travels with the L54s.
L72s: L72, L105
L90: L90 is an adult female born 1993 who has no living close relatives. She associates with the L47s.[13][14]
Splitting in L Pod
While J Pod always travels as a unit, and so does K Pod, L Pod orcas are usually encountered in two separate regular units traveling apart. The L4s, L47s, L90, and L72s are one consistent group; the L11s, L22s, L25, and L54s are the other; but sometimes the four L54s strikingly travel independently of all the others.[15][14] The part of L Pod containing the L11s is often referred to as the L12s after long-lived matriarch L12 Alexis, who died in 2012 after outliving L11 Squirty. L11 had been estimated by association to be L12's daughter, although her birth took place many years before research began.[16][17]
Social system research
Current knowledge of the society
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. There are no unidentified orcas in these waters, and every individual's place in their society is known. 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.[18][19]
"The social lives of resident killer whales are without doubt as rich and complex as those of the most advanced land mammals."[18] The lifelong bonds within a matriline are the most significant feature of the Southern Residents' social structure.[18] The basic rule is that individuals remain, for life, in the pod into which they were born and to which they are tied by dialect.[20] By 1990, Michael Bigg and fellow researchers had come to that conclusion,[21] and there has been no fundamental change in the Southern Resident social system documented since then.
Evolution of social studies
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. Relationships have been quantified using two methods: by measuring the distance between whales in photographs, and by counting the number of times individuals appeared together.[22][18]
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.[12]
During their long-term studies of resident orcas, researchers John Ford, Graeme Ellis and Ken Balcomb changed their conception of the male's position in the matriline:[23]
"It was not without some surprise that we came to the realization that resident society is so strongly matrilineal. When the study began, many speculated that killer whale pods were the primary breeding units. The mature males in the group were thought to be the "harem masters," and they mated with the pod's cows. The calves and juveniles were therefore their offspring. This was not an unreasonable assumption, however, as many social carnivores live in groups with this kind of social system. But numerous other mammals, including some of the most socially advanced species, such as primates, live in multi-generation, matrilineal societies. However, in most of these matrilineal species, offspring, usually just males, disperse from the group upon reaching maturity and join or form new groups. This is probably also the case for certain other species of toothed cetaceans, such as bottlenose dolphins and sperm whales, which appear to live in matrilineal groups for at least part of their lives. Dispersal is thought to be primarily a mechanism by which the animals prevent excessive inbreeding."
The Southern Resident social system never separates the sexes for long. The fact that the sons stay with their mothers for life and are their closest associates is exceptional.[23] The males in the smallest social unit, the matriline, are all descendants of the matriarch.[12] In the case of resident killer whales, association has only indicated maternal relatedness. Fathers are not present in the same matriline as their offspring. Paternity remained unknown prior to genetic studies.[18]
In 1978, John Ford began the highly innovative thesis research that revealed killer whale dialects.[24] Dialects came to partially supplant association modeling as a method for verifying the social structure because the orcas can "choose different travel associates at different times, based probably on social factors, such as age and sex composition. Dialects are very stable over time, however, and appear to better indicate pod genealogies than do associations."[25]
The acoustic evidence of dialects revealed the clan to be the largest vocal, and probably matrilineal, unit. Because the Southern Resident community is only a single clan, the nature of the larger, community level of social grouping is clearer in the multi-clan Northern Resident community. Unlike the clan, the community is "defined by travel patterns and not on genealogy or acoustics."[23]
Stability in social groups
The social units of resident orcas are mostly very stable. 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.[20] In the Southern Residents, a tendency for splitting in L Pod, the largest, has been recorded since surveys began. Although pods can split, the matrilines remain stable.[26] Normally when the mother dies, moreover, her offspring maintain the matriarch's matriline. Nevertheless, a matriline in which there are no living potentially reproductive females is destined to die out as a social unit, no matter how many males or post-reproductive females are in it.[20]
Foraging implications
The foraging specializations that distinguish between orca populations appear to represent distinct animal cultures.[27] The sympatric transient (Bigg's) orcas travel in small, family groups, with individuals cooperating to kill and eat marine mammals together.[28] By contrast, the large, multi-family, multi-generation southern resident pods behave in a way that may increase their success in hunting the salmon that forms the southern resident orca diet.[29]
Salmon migrations aggregate the fish in different locations at different times of year, and the resident pods' movement patterns coincide with these salmon runs, which are especially large towards large rivers. The orcas seek to move from one good feeding spot to another, learning from elders the local seasonal movements of salmon. In the southern resident territory, Chinook salmon runs occur in every season, depending on the location.[29]
When they find the salmon, the orcas spread out, and mostly eat the fish individually, although some sharing occurs, especially from a mother to her offspring. Pod members use underwater calls from their dialect to maintain contact at a distance.[29]
Researchers concluded that "making a living on salmon undoubtedly requires specialized knowledge that is passed on from generation to generation, and a whale's survival is enhanced by staying with its pod and taking advantage of these behavioural traditions."[29]
Sport, recreation, and socializing
Orcas have good vision above the surface as well as below.[30] Southern resident socializing includes a great variety of tactile interactions and surface activities. Breaches are a speciality of the southern residents, as well as other surface behaviors including spyhopping, tail slapping, and pec slapping (with pectoral fins). Researchers wrote that in play, they “often chase one another, or roll and thrash together at the surface.”[31][32] They "have been seen riding the wake of all types of vessels, from small skiffs to the largest cruise ships."[30] Juvenile southern residents spend more time in these activities. Vocalizations produced during socializing are excited, highly variable and less confined to the stereotyped calls of the dialect.[33]
Southern residents also playfully interact with objects, in particular floating driftwood and kelp.[34][31]
Kelping
While northern resident orcas are culturally known for beach rubbing, southern residents have never been seen to do that. On the other hand, southern residents have long been observed seeking tactile pleasure in kelping. This behavior can be seen close to shore from Lime Kiln Point State Park. The orcas drape the kelp over their body or lift it above the water with their tail flukes.[35][32][36][37]
Greeting ceremony
A particular way of socializing among southern resident pods is a behaviour referred to as a "greeting ceremony." The pods in the clan sometimes forage in the same area, but often travel separately to locations far apart. Sometimes when two pods reunite after travelling apart for a period, all the members of each pod group up in formation and swim side by side at the surface in a precise line facing the other pod's line. They pause when 10 to 50 metres (33 to 164 feet) apart. “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.[35]
Caring behavior
Epimeletic behavior
“Epimeletic” refers to the behavior of animals standing by others in danger, or caring for injured, ill or dead individuals.[38][39] Examples in cetaceans include when a mother carries a dead calf, or when an animal is helped to survive by being lifted by others to the surface to breathe.[40] When healthy individuals stay with a distressed individual in danger, this epimeletic behavior is called standing by. The companions may also attempt to protect or rescue the individual from the danger.[38][41]
Early observations of epimeletic behavior
- During an ill–conceived Marineland of the Pacific capture attempt in 1962, a female southern resident was lassoed. A male joined her to thump the collector's boat with their flukes, but she was shot and killed as a result.[42]
- During Moby Doll's capture in 1964, pod–mates raised the J Pod juvenile to the surface after he was harpooned.[43] One orca followed as the captors’ boat led Moby Doll by the harpoon line from Saturna Island to Vancouver.[44] Plausibly the same orca exchanged long–distance pulsed calls with him over two miles (3.2 kilometres) the next day when he was at Burrard Dry Dock.[45]
- In 1967, K Pod orcas were being herded in the Yukon Harbor capture operation. Two members of the pod escaped from nets. Even though they had already seen a relative die after being entangled,[46] they did not flee from the scene. Rather, they went towards their still trapped pod–mates and kept swimming around the outside of the capture net,[47][48] “squeaking” vocally at those within it.[49]
Mourning
One day in 2010, L72 Racer was seen with her dead neonate in her mouth. She then travelled carrying it on her rostrum. Despite the body regularly sliding off into the sea, she would double back and retrieve it and resume carrying it on her rostrum. This was observed throughout the day for over six hours. The next day, when she was seen again, the carcass was gone.[50][51]
In 2018, J35 Tahlequah carried her dead neonate for 17 days and an estimated minimum of 1,600 km.
Epimeletic behaviors including an initial rescuing response understandably aid survival of the species,
Have these cetaceans failed to recognize the individual has died? When cetaceans care for the dead, possibly a strong attachment has resulted in grieving.[57] The behavior is not frequently reported, and difficulties in observing wild cetaceans make for a small sample size of verifiable incidents; there is much more to learn about cetacean responses to death.[57]
Recent births and deaths
The Center for Whale Research records all births and deaths, and collects demographic data of the southern resident orca population.[60] From 1990 to 2023, 61 southern resident orca calves have survived beyond birth, while 107 southern residents have died.[5]
In late 2014, J50 Scarlet was born into the J pod; her mother J16 Slick was 42 years old, the oldest recorded age for an orca mother.[61] In August 2018, the pod attracted international attention after the death of a female calf born to J35 Tahlequah, who carried the body for 17 days.[62]
In September 2020, J57 Phoenix was first seen traveling with J35 Tahlequah and is her second calf. His sex was determined as male a short time later.[63] On September 24, 2020, J58 Crescent's birth was observed and she was confirmed as the second calf of J41 Eclipse by the Center for Whale Research the next day. Her sex was later confirmed as female by the Center for Whale Research.[64]
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. Only 73 Southern Residents were counted in the July 1, 2022, census conducted by the Center for Whale Research. This consisted of 32 whales in L Pod, its lowest point since 1976, 16 orcas in K Pod, its lowest in the last 20 years, and 25 in J Pod, which remained stable. In the year up to July 2022, three individuals died: K21, K44, and L89.[65] On June 30, 2023, Center for Whale Research confirmed the birth of two new calves in the L12s. In the encounter on the same day, both appeared healthy, and were at least two months old. They were designated L126 and L127. The pair are cousins of the same age in the same matriline.[66]
Sounds
Orca vocal production is classified in three categories: clicks, whistles, and pulsed calls.
Clicks made by toothed whales are very brief vocal sounds produced in rapid series for echolocation.
"Whistles are non-pulsed continuous signals with much simpler harmonic structure"
The pulsed calls of orcas may sound to humans like forms of speech, music, or wordless squeals,[69][70] "with distinct tonal qualities and harmonic structure. These calls, typically 0.5–1.5 s in duration, are the primary social vocalization of killer whales."[67] "By varying the timbre and frequency structure of the calls, the whales can generate a variety of signals...Most calls contain sudden shifts or rapid sweeps in pitch, which give them distinctive qualities recognizable over distance and background noise," wrote the researchers.[71]
Echolocation
Echolocation in an orca was first described by William E. Schevill and William A. Watkins in their study of the J Pod orca Moby Doll.[72]
The orca produces vocalizations inside the blowhole, its nose. Echolocation clicks are anatomically reflected forwards, and focused and directed by fats in the
Dialect
Cetacean cultures are marked by socially-determined vocal traditions. Toothed whales, including orcas, are known for large brains and complex social structure with correspondingly complex vocal communication systems.[75]
Some vocalizations produced by southern residents are unrepeated, but the majority are repetitions of the same calls that have been produced for many years in a specific social group. These distinct and traditional calls are referred to as discrete, or stereotyped calls. Each southern resident pod's set of discrete calls is their dialect.[67]
The three southern resident pods share some calls with one another, and also have unique calls. Together, the three pods form a clan, J-Clan. Clans share no calls with other clans. Thus the three clans of northern resident orcas and the single southern resident clan share no calls.[69]
Among orcas born and observed in captivity, calves at first babbled without making the discrete calls of adults. The calves gradually began to make the calls their mother made, but never made the calls of other, unrelated orcas. In the wild, juvenile southern residents use only their matrilineal pod's dialect, including a limited number of vocalizations shared with other pods. Southern residents do not make the calls unique to a different pod's dialect even though southern resident pods frequently mix with the other pods in the clan and the orcas could in theory learn the other pods' calls.[76] Discussing the function of resident orca dialects, researchers John Ford, Graeme Ellis and Ken Balcomb wrote, "It may well be that dialects are used by the whales as acoustic indicators of group identity and membership, which might serve to preserve the integrity and cohesiveness of the social unit."[69]
Identifying calls and whistles
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."[69]
"J-Clan discrete calls were classified alphanumerically"[67] by John Ford[77] "with the letter “S” preceding the number to indicate that it is from a Southern Resident (S1, S2, etc.). All three pods share some calls in common, while other calls are produced by only a single pod,"[67] or by K Pod and only one of the other two pods. For example, the S42 is one of three pulsed calls produced in all three pods, whereas the S17 is not produced in J Pod. It is unsurprising and perhaps genealogically significant that it is K Pod that 'pairs' with the other two pods, while J Pod and L Pod are vocally far apart.[77][69]
Because it is unique to a particular group of orcas, a dialect makes it possible to identify which orcas are present from acoustic evidence without visual detection.[78] At the Center for Whale Research, Ken Balcomb identified which pods were passing from their pulsed calls relayed by distant hydrophones.[70]
The most common call for identifying each pod is:
S1: J Pod, also produced in K Pod
S16: K Pod, also produced in L Pod
S2iii: L12s
S19: rest of L Pod
Vocal divergence between the two parts of L Pod supports the idea that L Pod may actually (almost?) be two pods.[77] [78]
While whistles are rarer than pulsed calls among southern resident orcas, many are also stereotyped and form part of their dialects. Southern resident orca stereotyped whistles have been given "a similar alphanumeric designation (SW1, SW2, etc.)."[67]
Meaning of vocalizations
Early research found that most sequences of orca calls included the same call being repeated at least five times.[79][80] This would not occur if the calls were letters or words in a syntactical language.[80]
In the example of the northern resident orcas, shared discrete calls are not necessary for social interactions, as the three clans in this community mix without sharing any discrete calls in their dialects. On the other hand, as markers of group identity, unique discrete calls may help matriarchs keep track of their pod mates when navigating or mixing with other pods in murky waters.[81] 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."[71]
Researchers have been unable to find a consistent correlation of specific calls with specific behaviors. Alexandra Morton's observations of the captured northern residents Corky and Orky found a different kind of correlation, a finding supported by observers of orcas in the wild.[81] The pair of orcas repetitively called in "long 'conversations' while floating side by side" without engaging in any behaviors requiring the exchange of any information. Morton found, nonetheless, an association of some calls with particular moods, or shifts in mood.[82]
Ken Balcomb spoke with Carl Safina about the issues:[83]
"They don’t seem to be saying stuff to each other like 'Big fish here,' or whatever. They don’t seem to have one call for ‘prey’ and another for 'hello.'" Each of their calls may be heard whenever the whales are vocalizing; it doesn’t matter what they’re doing. Ken feels certain, however, that "they know—from just a peep—who that was and what it’s about. I’m sure that to them, their voices are as different and recognizable as our voices are to us. I’m pretty sure they have names for each other like other dolphins do, and that right now some of what we’re hearing repeated are those signature calls." There may be more communicated in the emotion that comes across. "A call might sound like Ee-rah’i, ee-rah’i," says Ken. "Does that mean something specific? Or does its intensity carry meaning? When the pods congregate, you sense intensity, excitement; it sounds like a party. When they’re excited, the calls get higher and shorter—in other words, shrill." The calls might not have syntax, but what comes across among the whales is who, where, mood, and, perhaps, food.
Spectrograms do depict subtle differences among instances of discrete calls, which might communicate emotional state and current behavior.[84]
Not all vocalizations are repetitive and discrete. When closely socializing, for example, the "whales employ a wide range of highly variable" vocalizations, according to researchers.[35]
Excitement sound
In the SRKW catalog, one call, the S10, has come to be viewed in a different light to the others. Shared by all three pods and common in multi-pod aggregations such as superpods, the S10, with a duration of several seconds, has been likened to human laughter by many listeners over the years.[84]
A 2011 study compared sixty-nine calls in tests in which the nine listeners were blind to the sources of the calls. The samples were drawn from multiple North Pacific clans. The results categorized the S10 in a group of calls that showed some variations but seemed associated. 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. They identified it as being an 'excitement' call "associated with arousal behaviours" of various kinds.[85] 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. Each ecotype's behavior may be different, but the happy emotional state of excitement is common to both behaviors.[84]
Moby Doll
A southern resident initiated the scientific study of orca sounds. When the juvenile J Pod member later named Moby Doll was captured in 1964, it was a watershed for the then very misunderstood and hated species. He began the transformation of the species' public image,[86] and made possible the first closeup studies of a live orca.
Orcas had been recorded in the field five times previously; three of the recordings had been of J Pod. J Pod had been recorded in
Harold Dean Fisher recorded Moby Doll at
Schevill and Watkins' study of Moby Doll created the fundamental basis for understanding orca sounds.
At Moby Doll's seapen at
Schevill and Watkins examined orca pulsed calls for the first time, too. They labeled them "screams." Moby Doll never produced the "whistle-like squeal" of other
John K.B. Ford saw Moby Doll the day the captured orca was on display at
In 1978, Ford began making the recordings of orcas in British Columbia that he would use for his Ph. D. thesis. After starting with northern residents, in the autumn he traveled to the mouth of the Fraser River to make his first recordings of southern residents.[90][97]
Ford recalled the moment he heard a call by Moby Doll being produced by living southern residents:[90]
"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. I realized, in that moment, that this was the pod Moby Doll must have come from. It was J pod."
What Ford was hearing was a scientific breakthrough in the study of mammals: it was evidence of an acoustic culture unique to a single pod which outlived an individual mammal. "It was a wonderful moment out there in the boat when I recognized the sounds coming from J pod to be Moby Doll’s signature sounds," Ford said.[90]