Usage of monophonic and biphonic calls by free-ranging resident killer whales (Orcinus orca) in Kamchatka, Russian Far East

Killer whale discrete calls include types containing an overlapping high-frequency component (biphonic calls) and types without an overlapping high-frequency component (monophonic calls). In the resident killer whales of the Northeast Pacific, biphonic discrete calls exhibit higher source levels than monophonic calls, which suggests different active space and consequently different functions for monophonic and biphonic call types. In this study we investigate the potential communicative functions of monophonic and biphonic discrete calls produced by killer whales from Kamchatka (Northwest Pacific). We analyze how the usage of these calls depends on the number of pods present in the area and type of activity. Our results show that the usage of monophonic and biphonic calls in Kamchatkan killer whales depends on the number of pods in the area and is less dependent on the type of activity. Biphonic calls are more common when more than one pod is present in the area and could therefore function as markers of pod and matriline affiliation, serving mainly as cohesion signals. Monophonic calls dominated the vocalizations when a single pod was present, while in the presence of more than one pod both categories were used in equal proportions.     

Harassment and killing of porpoises (“phocoenacide”) by fish-eating Southern Resident killer whales (Orcinus orca)

Endangered Southern Resident killer whales (Orcinus orca) are fish-eaters that preferentially prey on adult Chinook salmon (Oncorhynchus tshawytscha). Despite being salmon specialists, individuals from all three killer whale pods (J, K, L) have been observed harassing and killing porpoises (family Phocoenidae) without consuming them. Retrospectively, we identified and analyzed 78 episodes of Southern Resident killer whales harassing porpoises between 1962 and 2020, of which 28 resulted in the porpoise's death (“phocoenacide”). Fifty-six episodes involved harbor porpoise (Phocoena phocoena), 13 involved Dall's porpoise (Phocoenoides dalli), and the porpoise species was unreported for nine episodes. Southern Resident killer whales often targeted young porpoises that were similar in size to adult Chinook salmon. Both sexes participated in porpoise harassment. Juveniles engaged in the behavior the most; however, their rates of engagement were not found to differ significantly from most other age classes. The behavior was passed through generations and social groupings, as it was first observed in L pod and spread to the other two pods. Killer whales are highly complex animals known to exhibit social learning and cultural transmission of learned behaviors, but the reason(s) for this behavior is unknown. Hypotheses include the social and developmental benefits of play, hunting practice, or displaced epimeletic behavior.     

DISTRIBUTION OF KILLER WHALE PODS IN PRINCE WILLIAM SOUND, ALASKA 1984–1996

Thirteen years of encounter data (1984–1996) were used to examine killer whale distribution within Prince William Sound, Alaska. Four patterns of area use were found, which comprised differences between resident pods and transient groups and differences among resident groups. Resident pods frequented large open passages, while transient groups used the narrow passages and bays in the southwest. This dichotomy likely reflects resident use of salmon and transient use of pinniped prey resources, as well as the different foraging strategies required for these prey types. Four resident pods (AB, AI, AJ, and AN) used Knight Island Passage more than other areas of the Sound; two (AE and AK) used all areas of the Sound more evenly. Use of the Sound by the AT1 transient whales declined in the latter part of the study. Nearshore foraging for pinniped prey by the AT1 transient whales was more common in areas where these whales spend a disproportionate amount of time, suggesting that these areas were critical foraging habitat for them. No similar pattern emerged for Open-water Foraging for cetaceans by AT1 whales, nor for foraging by the resident whales.     

Cultural transmission within maternal lineages: vocal clans in resident killer whales in southern Alaska

Cultural lineages are based on learned social traditions that are stable for several generations. When cultural lineages also reflect common ancestry and/or are shared by individuals that live together they are called clans. The existence of clans among killer whales has been previously proposed but has not been confirmed. Here, we show that clans exist among resident type killer whales, Orcinus orca, in southern Alaska. Resident killer whales live in stable matrilines from which emigration of either sex has not been observed. Matrilines that associate regularly (≥50% observation time) are called pods. Pods are believed to consist of closely related matrilines and share a unique repertoire of discrete call types. Pods that share parts of their repertoire form what Ford (1991, Canadian Journal of Zoology,69, 1454-1483) called an acoustic clan. Here, we identified discrete call types of seven pods from southern Alaska, using a method based on human discrimination of distinct aural and visual (spectrogram) differences. Mitochondrial DNA of members of each pod was also analysed. The repertoires of the seven pods were compared and two acoustically distinct groups of pods were identified. Each group was monomorphic for a different mitochondrial D-loop haplotype. Nevertheless, pods from different clans associated frequently. It thus appears that the acoustic similarities within groups, which we presume to be cultural, reflect common ancestry, and that these groups therefore meet the above definition of clans. We also argue that a combination of cultural drift and selection are the main mechanisms for the maintenance of clans. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Interactions between killer whales (<Emphasis Type="Italic">Orcinus orca</Emphasis>) and Steller sea lions (<Emphasis Type="Italic">Eumetopias jubatus</Emphasis>) in the vicinity of Brat Chirpoev Island,Kuril Islands

The behaviors of breeding Steller sea lions in response to encounters with killer whales near the shore were observed on Brat Chirpoev Island, Kuril Islands between May and July 2002–2007. Approaches by killer whales and sea lion behavior was observed visually and recorded. Killer whales approached the rookery 104 times during the entire period of observations (289 days). In most cases (n = 95), beached sea lions did not show any apparent reactions to the presence of killer whales, and there were no observed interactions. Sea lions showed agitation during nine of the approaches; five of these events were considered to be predation attempts. The killer whales attacked the sea lions three times, however all the attacks were unsuccessful. We recorded two different types of responses towards the killer whales: (1) beaching on the shore (three times) and (2) mass exodus from the rookery with subsequent formation of a tight, actively swimming and vocalizing group (six times). The latter is the first recorded observation of this behavior for Steller sea lions. The observation suggests a low degree of interactions between these two species near the studied rookery. Despite the numerous observations of killer whales near the rookery, there were no observations of direct predation on sea lions. It is likely the killer whale predation has little or no direct impact on the Steller sea lion population on Brat Chirpoev Islands during the breeding period.     

The function of multi-pod aggregations of fish-eating killer whales (<Emphasis Type="Italic">Orcinus orca</Emphasis>) in Kamchatka,Far East Russia

In fish-eating North Pacific killer whales, large multi-pod aggregations of up to 100 animals often occur. These aggregations are thought to be reproductive gatherings where mating between members of different pods takes place. However, killer whales are social animals, and the role of these aggregations might also be establishing and maintaining social bonds between pods. Alternatively, it is also possible that multi-pod aggregations are in some way connected with foraging or searching for fish. In this study of killer whales in the western North Pacific, we describe multi-pod aggregations quantitatively and suggest their functional role in the life of fish-eating killer whales. We show that foraging is rare in multi-pod aggregations, whether inter-clan or intra-clan, and thus they are unlikely to play an important role in cooperative foraging. Socialising occurs more frequently in inter-clan rather than in intra-clan aggregations, which suggests the higher arousal level and possible mating during inter-clan aggregations. In summary, multi-pod aggregations of Kamchatka killer whales might be both reproductive assemblages and “clubs” of some kind in which whales gather to establish and maintain social bonds.     

KILLER WHALE PREDATION ON SPERM WHALES: OBSERVATIONS AND IMPLICATIONS

In October 1997 we observed a herd of approximately 35 killer whales ( Orcinus orca ) attack a pod of nine sperm whales ( Physeter macrocephalus ) 130 km off the coast of central California. During the four hours we watched, adult female killer whales, including some with calves, attacked in waves of four to five animals in what was apparently a "wound and withdraw" strategy. Adult male killer whales stood by until the very end when one charged in and quickly killed a seriously wounded sperm whale that had been separated from the group. The sperm whales appeared largely helpless: their main defensive behavior was the formation of a rosette ("marguerite"-heads together, tails out). When the killer whales were successful in pulling an individual out of the rosette, one or two sperm whales exposed themselves to increased attack by leaving the rosette, flanking the isolated individual, and leading it back into the formation. Despite these efforts, one sperm whale was killed and eaten and the rest were seriously, perhaps mortally, wounded. We also present details of two other encounters between sperm whales and killer whales that we observed. Although sperm whales, because of various behavioral and morphological adaptations, were previously thought to be immune to predation, our observations clearly establish their vulnerability to killer whales. We suggest that killer whale predation has potentially been an important, and underrated, selective factor in the evolution of sperm whale ecology, influencing perhaps the development of their complex social behavior and at-sea distribution patterns.     

Killer whale predation on subantarctic fur seals at Prince Edward Island, Southern Indian Ocean

Killer whales at subantarctic Marion Island have been subjected to several scientific studies. In contrast, up until recently, there has been only one record of these animals documented for neighbouring Prince Edward Island. We here report on killer whale observations at Prince Edward Island during March 2012. During 3?days of opportunistic observations at a fur seal colony on the island, killer whales were sighted on six occasions. These probably represented three different pods numbering 11 individuals in total. During all sightings, individuals were seen hunting subantarctic fur seal pups, with four successful predatory events observed.     

GENETIC ANALYSIS OF KILLER WHALE (ORCINUS ORCA) HISTORICAL BONE AND TOOTH SAMPLES TO IDENTIFY WESTERN U.S. ECOTYPES

Little is known about the historical range of killer whale ecotypes in the eastern North Pacific (ENP). It is possible that ranges have shifted in the last few decades because of changes in availability of food. In particular, the southern resident ecotype, currently found primarily in the inland waters of Washington State, is known to prey extensively on salmon, which have declined in recent decades along the outer coasts of Washington, Oregon, and California. To investigate historical distributions of this and the other ENP ecotypes, samples of teeth and bones were obtained from NMFS and museum collections. We amplified a short section of the mitochondrial DNA control region that contains four diagnostic sites that differentiate between haplotypes found in ecotypes of ENP killer whales. Results did not show any southern resident haplotypes in samples from south of the Washington State inland waterways. One whale genetically identified as a northern resident extends the known southernmost distribution of the population from Oregon to California. Items of diet identified from stomach contents of six of the whales genetically identified to ecotype conformed with what is known of the feeding habits of the various ecotypes.     

Horizontal transmission of vocal traditions in killer whale (<Emphasis Type="Italic">Orcinus orca</Emphasis>) dialects

Unlike most other mammals, killer whales are capable of vocal learning and learn the dialect of their natal pod from their mothers. The classical model of killer whale dialect development suggests that the repertoire of calls is learned only “vertically” from mother to offspring, and calls evolve gradually with time by random drift caused by the accumulation of copying errors. However, some observations suggest that not only “vertical” (from mother to offspring) vocal learning can occur in killer whales, but also “horizontal” (between adult animals). In this study we analyzed the distribution of different call types and similarity of calls from the same type in different pods of killer whales from Kamchatka waters to estimate the probability of existence of interpod horizontal transmission of vocal traditions in killer whales. We found that the degree of similarity of K1 calls and K5 calls in different pods can differ. This situation contradicts the classical hypothesis and is possible in two cases: if different call types change with various speed in different pods, or if horizontal transmission of call features takes place. The distribution of K4 and K10 call types across pods also suggests the existence of horizontal transmission: K4 calls occur in the dialects of five of ten pods, and K10 calls, in six of ten pods, but only one pod has both K4 and K10 calls. Our results suggest that the real picture of the distribution of call features and call types in killer whale dialects contradicts the classical hypothesis of killer whale dialect evolution through the accumulation of copying errors.     

Dependence of killer whale (Orcinus orca) acoustic signals on the type of activity and social context

We investigated the influence of the type of activity and the social context on the proportion of four different structural categories of stereotyped calls in the acoustic communication of Kamchatkan killer whales. Using generalized linear models, we described the dependence of each sound category on the type of activity, the number of killer whale pods and the presence of mixed-pod groups. We found that the proportion of different sound categories depended on the number of pods and the presence of mixed-pod groups, while the type of activity did not affect the proportion of sounds of different categories. Based on the observed differences we suggest that biphonic and high-frequency monophonic calls are mainly used as family and pod markers, and help to track the position of family members at long ranges, and low-frequency monophonic calls are used as close-range intra-group signals to maintain contact between pod members in the conditions of limited underwater visibility.     

Using a multi-disciplinary approach to identify a critically endangered killer whale management unit

A key goal for wildlife managers is identifying discrete, demographically independent conservation units. Previous genetic work assigned killer whales that occur seasonally in the Strait of Gibraltar (SoG) and killer whales sampled off the Canary Islands (CI) to the same population. Here we present new analyses of photo-identification and individual genotypes to assess the level of contemporary gene flow and migration between study areas, and analyses of biomarkers to assess ecological differences. We identified 47 different individuals from 5 pods in the SoG and 16 individuals in the CI, with no matches found between the areas. Mitochondrial DNA control region haplotype was shared by all individuals sampled within each pod, suggesting that pods have a matrifocal social structure typical of this species, whilst the lack of shared mitogenome haplotypes between the CI and SoG individuals suggests that there was little or no female migration between groups. Kinship analysis detected no close kin between CI and SoG individuals, and low to zero contemporary gene flow. Isotopic values and organochlorine pollutant loads also suggest ecological differences between study areas. We further found that one individual from a pod within the SoG not seen in association with the other four pods and identified as belonging to a potential migrant lineage by genetic analyses, had intermediate isotopic values and contaminant between the two study areas. Overall our results suggest a complex pattern of social and genetic structuring correlated with ecological variation. Consequently at least CI and SoG should be considered as two different management units. Understanding this complexity appears to be an important consideration when monitoring and understanding the viability of these management units. Understand the viability will help the conservation of these threatened management units.     

Diversity in sound pressure levels and estimated active space of resident killer whale vocalizations

Signal source intensity and detection range, which integrates source intensity with propagation loss, background noise and receiver hearing abilities, are important characteristics of communication signals. Apparent source levels were calculated for 819 pulsed calls and 24 whistles produced by free-ranging resident killer whales by triangulating the angles-of-arrival of sounds on two beamforming arrays towed in series. Levels in the 1–20 kHz band ranged from 131 to 168 dB re 1 μPa at 1 m, with differences in the means of different sound classes (whistles: 140.2±4.1 dB; variable calls: 146.6±6.6 dB; stereotyped calls: 152.6±5.9 dB), and among stereotyped call types. Repertoire diversity carried through to estimates of active space, with “long-range” stereotyped calls all containing overlapping, independently-modulated high-frequency components (mean estimated active space of 10–16 km in sea state zero) and “short-range” sounds (5–9 km) included all stereotyped calls without a high-frequency component, whistles, and variable calls. Short-range sounds are reported to be more common during social and resting behaviors, while long-range stereotyped calls predominate in dispersed travel and foraging behaviors. These results suggest that variability in sound pressure levels may reflect diverse social and ecological functions of the acoustic repertoire of killer whales.     

Temporal and Contextual Patterns of Killer Whale (Orcinus orca) Call Type Production

Fish-eating killer whales Orcinus orca in the northeastern Pacific live in highly stable matrifocal social groups called pods. Each pod produces a repertoire of seven or more stereotyped call types. We compared the relative production of call types of free-ranging killer whale pods over time and between social contexts. The relative production of call types by each pod during directional travel was distinct over a 27-yr period; however, both temporal stability and pod distinctiveness were strongly influenced by a subset of dominant call types within the repertoire of each pod. Some call types within the repertoires contain biphonation (two overlapping independently modulated tones) and have a higher estimated active space than call types containing just one tone. In multi-pod aggregations the relative production of the dominant call types of each pod decreased and the relative production of a subset of call types that are rarely recorded from single-pod groupings increased. The majority of these contained biphonation. The data suggest a distinction between a subset of dominant call types that may function to identify the pod and a subset of less common call types including several call types containing biphonation that are more commonly produced during inter-pod affiliations.     

Behavioral context of echolocation and prey-handling sounds produced by killer whales (Orcinus orca) during pursuit and capture of Pacific salmon (Oncorhynchus spp.)

Availability of preferred salmonid prey and a sufficiently quiet acoustic environment in which to forage are critical to the survival of resident killer whales (Orcinus orca) in the northeastern Pacific. Although piscivorous killer whales rely on echolocation to locate and track prey, the relationship between echolocation, movement, and prey capture during foraging by wild individuals is poorly understood. We used acoustic biologging tags to relate echolocation behavior to prey pursuit and capture during successful feeding dives by fish-eating killer whales in coastal British Columbia, Canada. The significantly higher incidence and rate of echolocation prior to fish captures compared to afterward confirms its importance in prey detection and tracking. Extremely rapid click sequences (buzzes) were produced before or concurrent with captures of salmon at depths typically exceeding 50 m, and were likely used by killer whales for close-range prey targeting, as in other odontocetes. Distinctive crunching and tearing sounds indicative of prey-handling behavior occurred at relatively shallow depths following fish captures, matching concurrent observations that whales surfaced with fish prior to consumption and often shared prey. Buzzes and prey-handling sounds are potentially useful acoustic signals for estimating foraging efficiency and determining if resident killer whales are meeting their energetic requirements.     

FORAGING STRATEGIES OF SYMPATRIC KILLER WHALE (ORCINUS ORCA) POPULATIONS IN PRINCE WILLIAM SOUND, ALASKA

Killer whales ( Orcinus orca ) feed on a wide variety of fish, cephalopods, and marine mammals throughout their cosmopolitan range; however, the dietary breadth that characterizes the species is not reflected in all populations. Here, we present the findings of a 14-yr study of the diet and feeding habits of killer whales in Prince William Sound, Alaska. Two non-associating forms of killer whale, termed resident and transient (Bigg et al. 1987), were identified. All prey seen taken by transients were marine mammals, including harbor seals ( Phoca vitulina ), Dall's porpoises ( Phocoenoides dalli ), Steller sea lions ( Eumetopias jubatus ), and harbor porpoises ( Phocoena phocoena ). Resident killer whales appeared to prey principally on salmon ( Oncorhynchus spp.), preferring coho salmon ( O. kisutch ) over other, more abundant salmon species. Pacific herring ( Clupea pallasi ) and Pacific halibut ( Hippocampus stenolepis ) were also taken. Resident killer whales frequently were seen to interact in non-predatory ways with Steller sea lions and Dall's porpoises, while transients were not. Differences in the social organization and behavior of the resident and transient killer whales in Prince William Sound are discussed in the light of the dietary differences documented here.     

Occurrence of false killer whales (Pseudorca crassidens) and their association with common bottlenose dolphins (Tursiops truncatus) off northeastern New Zealand

On a global scale, false killer whales (Pseudorca crassidens) remain one of the lesser‐known delphinids. The occurrence, site fidelity, association patterns, and presence/absence of foraging in waters off northeastern New Zealand are examined from records collected between 1995 and 2012. The species was rarely encountered; however, of the 61 distinctive, photo‐identified individuals, 88.5% were resighted, with resightings up to 7 yr after initial identification, and movements as far as 650 km documented. Group sizes ranged from 20 to ca. 150. Results indicate that all individuals are linked in a single social network. Most observations were recorded in shallow (<100 m) nearshore waters. Occurrence in these continental shelf waters is likely seasonal, coinciding with the shoreward flooding of a warm current. During 91.5% of encounters, close interspecific associations with common bottlenose dolphins (Tursiops truncatus) were observed. Photo‐identification reveals repeat inter‐ and intraspecific associations among individuals with 34.2% of common bottlenose dolphins resighted together with false killer whales over 1,832 d. While foraging was observed during 39.5% of mixed‐species encounters, results suggest that social and antipredatory factors may also play a role in the formation of these mixed‐species groups.     

A winter sighting of killer whales (Orcinus orca ) in Antarctic sea ice

 A group of killer whales was sighted in open leads well inside Antarctic sea ice during August 1995. This was the first winter sighting of killer whales in Antarctic waters since 1955, and contradicts the view that all killer whales migrate north prior to the winter. A small calf was observed, providing the first evidence of a cetacean species breeding in Antarctic waters. Several potential prey species were also present. The sighting highlights the importance of lead and polynya systems to marine mammals, which probably use them to disperse within the winter sea-ice zone. Received: 23 April 1996 / Accepted: 25 August 1996     

IMPACTS OF COMMERCIAL WHALE WATCHING ON MALE SPERM WHALES AT KAIKOURA, NEW ZEALAND

Abstract Male sperm whales are the basis for a commercially important whale-watching industry at Kaikoura, New Zealand. We examined the influence of whale-watching boats and aircraft over three years using observations from an independent research boat and from shore. We employed an information-theoretic approach to determine which factors were necessary to explain variation in blow interval, time at surface, and time to first click. In almost all analyses, models required the inclusion of the presence of the research boat or whale-watching boats or airplanes. The only exception was the model explaining variation in blow intervals observed from shore, which required only season. We also analyzed spatial behavior at the surface. Resident whales changed direction significantly more in the presence of whale-watching boats compared to encounters with only the research boat present. No such difference was observed for encounters with aircraft. Our results thus indicate that sperm whales off Kaikoura respond to whale-watching activities, although these changes are small and most likely not of biological importance. However, resident whales responded less to these activities compared to transient whales, possibly indicating habituation and, more importantly, the need to monitor continued activities closely.     

Estimating Cetacean Carrying Capacity Based on Spacing Behaviour

Conservation of large ocean wildlife requires an understanding of how they use space. In Western Australia, the humpback whale (Megaptera novaeangliae) population is growing at a minimum rate of 10% per year. An important consideration for conservation based management in space-limited environments, such as coastal resting areas, is the potential expansion in area use by humpback whales if the carrying capacity of existing areas is exceeded. Here we determined the theoretical carrying capacity of a known humpback resting area based on the spacing behaviour of pods, where a resting area is defined as a sheltered embayment along the coast. Two separate approaches were taken to estimate this distance. The first used the median nearest neighbour distance between pods in relatively dense areas, giving a spacing distance of 2.16 km (±0.94). The second estimated the spacing distance as the radius at which 50% of the population included no other pods, and was calculated as 1.93 km (range: 1.62–2.50 km). Using these values, the maximum number of pods able to fit into the resting area was 698 and 872 pods, respectively. Given an average observed pod size of 1.7 whales, this equates to a carrying capacity estimate of between 1187 and 1482 whales at any given point in time. This study demonstrates that whale pods do maintain a distance from each other, which may determine the number of animals that can occupy aggregation areas where space is limited. This requirement for space has implications when considering boundaries for protected areas or competition for space with the fishing and resources sectors.