Publications by authors named "John K B Ford"

25 Publications

  • Page 1 of 1

A deepening understanding of animal culture suggests lessons for conservation.

Proc Biol Sci 2021 04 21;288(1949):20202718. Epub 2021 Apr 21.

Sea Mammal Research Unit, School of Biology, University of St Andrews, St Andrews KY16 8LB, UK.

A key goal of conservation is to protect biodiversity by supporting the long-term persistence of viable, natural populations of wild species. Conservation practice has long been guided by genetic, ecological and demographic indicators of risk. Emerging evidence of animal culture across diverse taxa and its role as a driver of evolutionary diversification, population structure and demographic processes may be essential for augmenting these conventional conservation approaches and decision-making. Animal culture was the focus of a ground-breaking resolution under the Convention on the Conservation of Migratory Species of Wild Animals (CMS), an international treaty operating under the UN Environment Programme. Here, we synthesize existing evidence to demonstrate how social learning and animal culture interact with processes important to conservation management. Specifically, we explore how social learning might influence population viability and be an important resource in response to anthropogenic change, and provide examples of how it can result in phenotypically distinct units with different, socially learnt behavioural strategies. While identifying culture and social learning can be challenging, indirect identification and parsimonious inferences may be informative. Finally, we identify relevant methodologies and provide a framework for viewing behavioural data through a cultural lens which might provide new insights for conservation management.
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http://dx.doi.org/10.1098/rspb.2020.2718DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8059593PMC
April 2021

Pathology findings and correlation with body condition index in stranded killer whales (Orcinus orca) in the northeastern Pacific and Hawaii from 2004 to 2013.

PLoS One 2020 2;15(12):e0242505. Epub 2020 Dec 2.

The SeaDoc Society, Karen C. Drayer Wildlife Health Center - Orcas Island Office, UC Davis School of Veterinary Medicine, Eastsound, Washington, United States of America.

Understanding health and mortality in killer whales (Orcinus orca) is crucial for management and conservation actions. We reviewed pathology reports from 53 animals that stranded in the eastern Pacific Ocean and Hawaii between 2004 and 2013 and used data from 35 animals that stranded from 2001 to 2017 to assess association with morphometrics, blubber thickness, body condition and cause of death. Of the 53 cases, cause of death was determined for 22 (42%) and nine additional animals demonstrated findings of significant importance for population health. Causes of calf mortalities included infectious disease, nutritional, and congenital malformations. Mortalities in sub-adults were due to trauma, malnutrition, and infectious disease and in adults due to bacterial infections, emaciation and blunt force trauma. Death related to human interaction was found in every age class. Important incidental findings included concurrent sarcocystosis and toxoplasmosis, uterine leiomyoma, vertebral periosteal proliferations, cookiecutter shark (Isistius sp.) bite wounds, excessive tooth wear and an ingested fish hook. Blubber thickness increased significantly with body length (all p < 0.001). In contrast, there was no relationship between body length and an index of body condition (BCI). BCI was higher in animals that died from trauma. This study establishes a baseline for understanding health, nutritional status and causes of mortality in stranded killer whales. Given the evidence of direct human interactions on all age classes, in order to be most successful recovery efforts should address the threat of human interactions, especially for small endangered groups of killer whales that occur in close proximity to large human populations, interact with recreational and commercial fishers and transit established shipping lanes.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0242505PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7710042PMC
January 2021

Postreproductive killer whale grandmothers improve the survival of their grandoffspring.

Proc Natl Acad Sci U S A 2019 Dec 9. Epub 2019 Dec 9.

Department of Biology, The University of York, York YO10 5DD, United Kingdom;

Understanding why females of some mammalian species cease ovulation prior to the end of life is a long-standing interdisciplinary and evolutionary challenge. In humans and some species of toothed whales, females can live for decades after stopping reproduction. This unusual life history trait is thought to have evolved, in part, due to the inclusive fitness benefits that postreproductive females gain by helping kin. In humans, grandmothers gain inclusive fitness benefits by increasing their number of surviving grandoffspring, referred to as the grandmother effect. Among toothed whales, the grandmother effect has not been rigorously tested. Here, we test for the grandmother effect in killer whales, by quantifying grandoffspring survival with living or recently deceased reproductive and postreproductive grandmothers, and show that postreproductive grandmothers provide significant survival benefits to their grandoffspring above that provided by reproductive grandmothers. This provides evidence of the grandmother effect in a nonhuman menopausal species. By stopping reproduction, grandmothers avoid reproductive conflict with their daughters, and offer increased benefits to their grandoffspring. The benefits postreproductive grandmothers provide to their grandoffspring are shown to be most important in difficult times where the salmon abundance is low to moderate. The postreproductive grandmother effect we report, together with the known costs of late-life reproduction in killer whales, can help explain the long postreproductive life spans of resident killer whales.
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http://dx.doi.org/10.1073/pnas.1903844116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6936675PMC
December 2019

Consequences of culturally-driven ecological specialization: Killer whales and beyond.

J Theor Biol 2018 11 10;456:279-294. Epub 2018 Aug 10.

Pacific Biological Station, Nanaimo, Canada.

Culturally-transmitted ecological specialization occurs in killer whales, as well as other species. We hypothesize that some of the remarkable demographic and ecological attributes of killer whales result from this process. We formalize and model (using agent-based stochastic models parametrized using killer whale life history) the cultural evolution of specialization by social groups, in which a narrowing of niche breadth is spread and maintained in a group through social learning. We compare the demographic and ecological results of cultural specialization to those of a similar model of specialization through natural selection. We found that specialization, through either the cultural or natural selection routes, is adaptive in the short term with specialization often increasing fitness. Generalization, in contrast, is rarely adaptive. The cultural evolution of specialization can lead to increased rates of group extirpation. Specialization has little effect on group size but tends to reduce population size and resource abundance. While the two specialization processes produce similar results, cultural specialization can be very much faster. The results are generally consistent with what we know of the formation and maintenance of specialist ecotypes in killer whales, and have implications for the persistence, nature and ecological effects of these apex predators.
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http://dx.doi.org/10.1016/j.jtbi.2018.08.015DOI Listing
November 2018

Infanticide in a mammal-eating killer whale population.

Sci Rep 2018 03 20;8(1):4366. Epub 2018 Mar 20.

Pacific Biological Station, Fisheries and Oceans Canada, 3190 Hammond Bay Road, Nanaimo, BC, V9T 6N7, Canada.

Infanticide can be an extreme result of sexual conflict that drives selection in species in which it occurs. It is a rarely observed behaviour but some evidence for its occurrence in cetaceans exists in three species of dolphin. Here we describe observations of an adult male killer whale (Orcinus orca) and his post-reproductive mother killing a neonate belonging to an unrelated female from the same population in the North Pacific. This is the first account of infanticide reported in killer whales and the only case committed jointly by an adult male and his mother outside of humans. Consistent with findings in other social mammals, we suggest that infanticide is a sexually selected behaviour in killer whales that could provide subsequent mating opportunities for the infanticidal male and thereby provide inclusive fitness benefits for his mother.
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http://dx.doi.org/10.1038/s41598-018-22714-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5861072PMC
March 2018

Fine-scale foraging movements by fish-eating killer whales () relate to the vertical distributions and escape responses of salmonid prey ( spp.).

Mov Ecol 2017 20;5. Epub 2017 Feb 20.

Marine Mammal Research Unit, Institute for the Oceans and Fisheries, University of British Columbia, AERL Building, Room 247 - 2202 Main Mall, Vancouver, BC V6T 1Z4 Canada.

Background: We sought to quantitatively describe the fine-scale foraging behavior of northern resident killer whales (), a population of fish-eating killer whales that feeds almost exclusively on Pacific salmon ( spp.). To reconstruct the underwater movements of these specialist predators, we deployed 34 biologging Dtags on 32 individuals and collected high-resolution, three-dimensional accelerometry and acoustic data. We used the resulting dive paths to compare killer whale foraging behavior to the distributions of different salmonid prey species. Understanding the foraging movements of these threatened predators is important from a conservation standpoint, since prey availability has been identified as a limiting factor in their population dynamics and recovery.

Results: Three-dimensional dive tracks indicated that foraging ( = 701) and non-foraging dives ( = 10,618) were kinematically distinct (Wilks' lambda:  = 0.321,  < 0.001). While foraging, killer whales dove deeper, remained submerged longer, swam faster, increased their dive path tortuosity, and rolled their bodies to a greater extent than during other activities. Maximum foraging dive depths reflected the deeper vertical distribution of Chinook (compared to other salmonids) and the tendency of Pacific salmon to evade predators by diving steeply. Kinematic characteristics of prey pursuit by resident killer whales also revealed several other escape strategies employed by salmon attempting to avoid predation, including increased swimming speeds and evasive maneuvering.

Conclusions: High-resolution dive tracks reconstructed using data collected by multi-sensor accelerometer tags found that movements by resident killer whales relate significantly to the vertical distributions and escape responses of their primary prey, Pacific salmon.
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http://dx.doi.org/10.1186/s40462-017-0094-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5319153PMC
February 2017

Causes of mortality of harbor porpoises Phocoena phocoena along the Atlantic and Pacific coasts of Canada.

Dis Aquat Organ 2017 Jan;122(3):171-183

Canadian Wildlife Health Cooperative, Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE C1A 4P3, Canada.

There is increasing public interest in the overall health of the marine environment. Harbor porpoises Phocoena phocoena have a coastal distribution, and stranded animals function as sentinels for population and ecosystem health. The goal of this retrospective study was to join datasets from the western Atlantic and eastern Pacific coasts of Canada to investigate causes of morbidity and mortality in this species. A total of 241 necropsy records were reviewed including 147 (61%) from the Pacific region and 94 (39%) from the Atlantic region from 1988 to 2011. A cause of death could be determined with confidence in 118 (49%) of these cases. Of these 118 cases, the leading cause of mortality for both regions, together and separately, was infectious disease. In the Pacific region, this was followed by traumatic and anthropogenic causes, whereas in the Atlantic region, it was followed by emaciation/starvation, mortality of dependent calves, and anthropogenic causes. Pathogens of potential zoonotic significance or indicative of environmental contamination, e.g. Salmonella sp. and Cryptococcus gattii, were identified. Numerous parasitic species were observed within the lungs, liver, stomach, middle ear, and subcutaneous tissues, although they were usually interpreted as incidental findings. Anthropogenic causes may be underrepresented as they are notoriously difficult to diagnose with certainty, thereby making up a proportion of the 'unknown causes of death' (51%) category. Improved standardization of data collection and documentation is required to better understand harbor porpoise and ecosystem health.
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http://dx.doi.org/10.3354/dao03080DOI Listing
January 2017

Reproductive Conflict and the Evolution of Menopause in Killer Whales.

Curr Biol 2017 Jan 12;27(2):298-304. Epub 2017 Jan 12.

Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE, UK.

Why females of some species cease ovulation prior to the end of their natural lifespan is a long-standing evolutionary puzzle [1-4]. The fitness benefits of post-reproductive helping could in principle select for menopause [1, 2, 5], but the magnitude of these benefits appears insufficient to explain the timing of menopause [6-8]. Recent theory suggests that the cost of inter-generational reproductive conflict between younger and older females of the same social unit is a critical missing term in classical inclusive fitness calculations (the "reproductive conflict hypothesis" [6, 9]). Using a unique long-term dataset on wild resident killer whales, where females can live decades after their final parturition, we provide the first test of this hypothesis in a non-human animal. First, we confirm previous theoretical predictions that local relatedness increases with female age up to the end of reproduction. Second, we construct a new evolutionary model and show that given these kinship dynamics, selection will favor younger females that invest more in competition, and thus have greater reproductive success, than older females (their mothers) when breeding at the same time. Third, we test this prediction using 43 years of individual-based demographic data in resident killer whales and show that when mothers and daughters co-breed, the mortality hazard of calves from older-generation females is 1.7 times that of calves from younger-generation females. Intergenerational conflict combined with the known benefits conveyed to kin by post-reproductive females can explain why killer whales have evolved the longest post-reproductive lifespan of all non-human animals.
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http://dx.doi.org/10.1016/j.cub.2016.12.015DOI Listing
January 2017

Physical constraints of cultural evolution of dialects in killer whales.

J Acoust Soc Am 2016 Nov;140(5):3755

Whale and Dolphin Conservation, Park House, Allington Park, Bridport, Dorset DT65DD, United Kingdom.

Odontocete sounds are produced by two pairs of phonic lips situated in soft nares below the blowhole; the right pair is larger and is more likely to produce clicks, while the left pair is more likely to produce whistles. This has important implications for the cultural evolution of delphinid sounds: the greater the physical constraints, the greater the probability of random convergence. In this paper the authors examine the call structure of eight killer whale populations to identify structural constraints and to determine if they are consistent among all populations. Constraints were especially pronounced in two-voiced calls. In the calls of all eight populations, the lower component of two-voiced (biphonic) calls was typically centered below 4 kHz, while the upper component was typically above that value. The lower component of two-voiced calls had a narrower frequency range than single-voiced calls in all populations. This may be because some single-voiced calls are homologous to the lower component, while others are homologous to the higher component of two-voiced calls. Physical constraints on the call structure reduce the possible variation and increase the probability of random convergence, producing similar calls in different populations.
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http://dx.doi.org/10.1121/1.4967369DOI Listing
November 2016

Killer whale call frequency is similar across the oceans, but varies across sympatric ecotypes.

J Acoust Soc Am 2015 Jul;138(1):251-7

Vancouver Aquarium Marine Science Centre, Vancouver, British Columbia V6B 3X8, Canada.

Killer whale populations may differ in genetics, morphology, ecology, and behavior. In the North Pacific, two sympatric populations ("resident" and "transient") specialize on different prey (fish and marine mammals) and retain reproductive isolation. In the eastern North Atlantic, whales from the same populations have been observed feeding on both fish and marine mammals. Fish-eating North Pacific "residents" are more genetically related to eastern North Atlantic killer whales than to sympatric mammal-eating "transients." In this paper, a comparison of frequency variables in killer whale calls recorded from four North Pacific resident, two North Pacific transient, and two eastern North Atlantic populations is reported to assess which factors drive the large-scale changes in call structure. Both low-frequency and high-frequency components of North Pacific transient killer whale calls have significantly lower frequencies than those of the North Pacific resident and North Atlantic populations. The difference in frequencies could be related to ecological specialization or to the phylogenetic history of these populations. North Pacific transient killer whales may have genetically inherited predisposition toward lower frequencies that may shape their learned repertoires.
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http://dx.doi.org/10.1121/1.4922704DOI Listing
July 2015

Ultrasonic whistles of killer whales (Orcinus orca) recorded in the North Pacific (L).

J Acoust Soc Am 2012 Dec;132(6):3618-21

Department of Vertebrate Zoology, Faculty of Biology, Moscow State University, Moscow, 119992, Russia.

Ultrasonic whistles were previously found in North Atlantic killer whales and were suggested to occur in eastern North Pacific killer whales based on the data from autonomous recorders. In this study ultrasonic whistles were found in the recordings from two encounters with the eastern North Pacific offshore ecotype killer whales and one encounter with the western North Pacific killer whales of unknown ecotype. All ultrasonic whistles were highly stereotyped and all but two had downsweep contours. These results demonstrate that specific sound categories can be shared by killer whales from different ocean basins.
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http://dx.doi.org/10.1121/1.4764874DOI Listing
December 2012

Habitat-based PCB environmental quality criteria for the protection of endangered killer whales (Orcinus orca).

Environ Sci Technol 2012 Nov 6;46(22):12655-63. Epub 2012 Nov 6.

School of Resource and Environmental Management, Faculty of Environment, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada.

The development of an area-based polychlorinated biphenyl (PCB) food-web bioaccumulation model enabled a critical evaluation of the efficacy of sediment quality criteria and prey tissue residue guidelines in protecting fish-eating resident killer whales of British Columbia and adjacent waters. Model-predicted and observed PCB concentrations in resident killer whales and Chinook salmon were in good agreement, supporting the model's application for risk assessment and criteria development. Model application shows that PCB concentrations in the sediments from the resident killer whale's Critical Habitats and entire foraging range leads to PCB concentrations in most killer whales that exceed PCB toxicity threshold concentrations reported for marine mammals. Results further indicate that current PCB sediment quality and prey tissue residue criteria for fish-eating wildlife are not protective of killer whales and are not appropriate for assessing risks of PCB-contaminated sediments to high trophic level biota. We present a novel methodology for deriving sediment quality criteria and tissue residue guidelines that protect biota of high trophic levels under various PCB management scenarios. PCB concentrations in sediments and in prey that are deemed protective of resident killer whale health are much lower than current criteria values, underscoring the extreme vulnerability of high trophic level marine mammals to persistent and bioaccumulative contaminants.
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http://dx.doi.org/10.1021/es303062qDOI Listing
November 2012

Adaptive prolonged postreproductive life span in killer whales.

Science 2012 Sep;337(6100):1313

Centre for Research in Animal Behaviour, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QG, UK.

Prolonged life after reproduction is difficult to explain evolutionarily unless it arises as a physiological side effect of increased longevity or it benefits related individuals (i.e., increases inclusive fitness). There is little evidence that postreproductive life spans are adaptive in nonhuman animals. By using multigenerational records for two killer whale (Orcinus orca) populations in which females can live for decades after their final parturition, we show that postreproductive mothers increase the survival of offspring, particularly their older male offspring. This finding may explain why female killer whales have evolved the longest postreproductive life span of all nonhuman animals.
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http://dx.doi.org/10.1126/science.1224198DOI Listing
September 2012

PCB-associated changes in mRNA expression in killer whales (Orcinus orca) from the NE Pacific Ocean.

Environ Sci Technol 2011 Dec 2;45(23):10194-202. Epub 2011 Nov 2.

Institute of Ocean Sciences, Fisheries & Oceans Canada, P.O. Box 6000, 9860 West Saanich Road, Sidney, British Columbia V8L 4B2, Canada.

Killer whales in the NE Pacific Ocean are among the world's most PCB-contaminated marine mammals, raising concerns about implications for their health. Sixteen health-related killer whale mRNA transcripts were analyzed in blubber biopsies collected from 35 free-ranging killer whales in British Columbia using real-time quantitative polymerase chain reaction. We observed PCB-related increases in the expression of five gene targets, including the aryl hydrocarbon receptor (AhR; r(2) = 0.83; p < 0.001), thyroid hormone α receptor (TRα; r(2) = 0.64; p < 0.001), estrogen α receptor (ERα; r(2) = 0.70; p < 0.001), interleukin 10 (IL-10; r(2) = 0.74 and 0.68, males and females, respectively; p < 0.001), and metallothionein 1 (MT1; r(2) = 0.58; p < 0.001). Best-fit models indicated that population (dietary preference), age, and sex were not confounding factors, except for IL-10, where males differed from females. While the population-level consequences are unclear, the PCB-associated alterations in mRNA abundance of such pivotal end points provide compelling evidence of adverse physiological effects of persistent environmental contaminants in these endangered killer whales.
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http://dx.doi.org/10.1021/es201541jDOI Listing
December 2011

Divergence of a stereotyped call in northern resident killer whales.

J Acoust Soc Am 2011 Feb;129(2):1067-72

Graduate Program in Acoustics, Applied Research Laboratory, The Pennsylvania State University, State College, Pennsylvania 16804, USA.

Northern resident killer whale pods (Orcinus orca) have distinctive stereotyped pulsed call repertoires that can be used to distinguish groups acoustically. Repertoires are generally stable, with the same call types comprising the repertoire of a given pod over a period of years to decades. Previous studies have shown that some discrete pulsed calls can be subdivided into variants or subtypes. This study suggests that new stereotyped calls may result from the gradual modification of existing call types through subtypes. Vocalizations of individuals and small groups of killer whales were collected using a bottom-mounted hydrophone array in Johnstone Strait, British Columbia in 2006 and 2007. Discriminant analysis of slope variations of a predominant call type, N4, revealed the presence of four distinct call subtypes. Similar to previous studies, there was a divergence of the N4 call between members of different matrilines of the same pod. However, this study reveals that individual killer whales produced multiple subtypes of the N4 call, indicating that divergence in the N4 call is not the result of individual differences, but rather may indicate the gradual evolution of a new stereotyped call.
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http://dx.doi.org/10.1121/1.3531842DOI Listing
February 2011

The structure of stereotyped calls reflects kinship and social affiliation in resident killer whales (Orcinus orca).

Naturwissenschaften 2010 May 9;97(5):513-8. Epub 2010 Mar 9.

Sea Mammal Research Unit, Scottish Oceans Institute, University of St. Andrews, St. Andrews, Fife KY168LB, Scotland, UK.

A few species of mammals produce group-specific vocalisations that are passed on by learning, but the function of learned vocal variation remains poorly understood. Resident killer whales live in stable matrilineal groups with repertoires of seven to 17 stereotyped call types. Some types are shared among matrilines, but their structure typically shows matriline-specific differences. Our objective was to analyse calls of nine killer whale matrilines in British Columbia to test whether call similarity primarily reflects social or genetic relationships. Recordings were made in 1985-1995 in the presence of focal matrilines that were either alone or with groups with non-overlapping repertoires. We used neural network discrimination performance to measure the similarity of call types produced by different matrilines and determined matriline association rates from 757 encounters with one or more focal matrilines. Relatedness was measured by comparing variation at 11 microsatellite loci for the oldest female in each group. Call similarity was positively correlated with association rates for two of the three call types analysed. Similarity of the N4 call type was also correlated with matriarch relatedness. No relationship between relatedness and association frequency was detected. These results show that call structure reflects relatedness and social affiliation, but not because related groups spend more time together. Instead, call structure appears to play a role in kin recognition and shapes the association behaviour of killer whale groups. Our results therefore support the hypothesis that increasing social complexity plays a role in the evolution of learned vocalisations in some mammalian species.
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http://dx.doi.org/10.1007/s00114-010-0657-zDOI Listing
May 2010

Linking killer whale survival and prey abundance: food limitation in the oceans' apex predator?

Biol Lett 2010 Feb 15;6(1):139-42. Epub 2009 Sep 15.

Fisheries and Oceans Canada, Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, British Columbia, Canada , V9T 6N7.

Killer whales (Orcinus orca) are large predators that occupy the top trophic position in the world's oceans and as such may have important roles in marine ecosystem dynamics. Although the possible top-down effects of killer whale predation on populations of their prey have received much recent attention, little is known of how the abundance of these predators may be limited by bottom-up processes. Here we show, using 25 years of demographic data from two populations of fish-eating killer whales in the northeastern Pacific Ocean, that population trends are driven largely by changes in survival, and that survival rates are strongly correlated with the availability of their principal prey species, Chinook salmon (Oncorhynchus tshawytscha). Our results suggest that, although these killer whales may consume a variety of fish species, they are highly specialized and dependent on this single salmonid species to an extent that it is a limiting factor in their population dynamics. Other ecologically specialized killer whale populations may be similarly constrained to a narrow range of prey species by culturally inherited foraging strategies, and thus are limited in their ability to adapt rapidly to changing prey availability.
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http://dx.doi.org/10.1098/rsbl.2009.0468DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2817236PMC
February 2010

Whistle sequences in wild killer whales (Orcinus orca).

J Acoust Soc Am 2008 Sep;124(3):1822-9

Department of Zoology, University of Oklahoma, 730 Van Vleet Oval, Norman, Oklahoma 73019, USA.

Combining different stereotyped vocal signals into specific sequences increases the range of information that can be transferred between individuals. The temporal emission pattern and the behavioral context of vocal sequences have been described in detail for a variety of birds and mammals. Yet, in cetaceans, the study of vocal sequences is just in its infancy. Here, we provide a detailed analysis of sequences of stereotyped whistles in killer whales off Vancouver Island, British Columbia. A total of 1140 whistle transitions in 192 whistle sequences recorded from resident killer whales were analyzed using common spectrographic analysis techniques. In addition to the stereotyped whistles described by Riesch et al., [(2006). "Stability and group specificity of stereotyped whistles in resident killer whales, Orcinus orca, off British Columbia," Anim. Behav. 71, 79-91.] We found a new and rare stereotyped whistle (W7) as well as two whistle elements, which are closely linked to whistle sequences: (1) stammers and (2) bridge elements. Furthermore, the frequency of occurrence of 12 different stereotyped whistle types within the sequences was not randomly distributed and the transition patterns between whistles were also nonrandom. Finally, whistle sequences were closely tied to close-range behavioral interactions (in particular among males). Hence, we conclude that whistle sequences in wild killer whales are complex signal series and propose that they are most likely emitted by single individuals.
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http://dx.doi.org/10.1121/1.2956467DOI Listing
September 2008

Killer whales (Orcinus orca) face protracted health risks associated with lifetime exposure to PCBs.

Environ Sci Technol 2007 Sep;41(18):6613-9

Environmental and Resource Studies Program, Trent University, Peterborough ON K9J 7B8, Canada.

Polychlorinated biphenyl (PCB) concentrations declined rapidly in environmental compartments and most biota following implementation of regulations in the 1970s. However, the metabolic recalcitrance of PCBs may delay responses to such declines in large, long-lived species, such as the endangered and highly PCB-contaminated resident killer whales (Orcinus orca) of the Northeastern Pacific Ocean. To investigate the influence of life history on PCB-related health risks, we developed models to estimate PCB concentrations in killer whales during the period from 1930 forward to 2030, both within a lifetime (approximately 50 years) and across generations, and then evaluated these in the context of health effects thresholds established for marine mammals. Modeled PCB concentrations in killer whales responded slowly to changes in loadings to the environment as evidenced by slower accumulation and lower magnitude increases in PCB concentrations relative to prey, and a delayed decline that was particularly evident in adult males. Since PCBs attained peak levels well above the effects threshold (17 mg/kg lipid) in approximately 1969, estimated concentrations in both the northern and the more contaminated southern resident populations have declined gradually. Projections suggest that the northern resident population could largely fall below the threshold concentration by 2030 while the endangered southern residents may not do so until at least 2063. Long-lived aquatic mammals are therefore not protected from PCBs by current dietary residue guidelines.
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http://dx.doi.org/10.1021/es0702519DOI Listing
September 2007

Persistent organic pollutants and stable isotopes in biopsy samples (2004/2006) from Southern Resident killer whales.

Mar Pollut Bull 2007 Dec 10;54(12):1903-11. Epub 2007 Oct 10.

NOAA Fisheries, Northwest Fisheries Science Center, 2725 Montlake Boulevard East, Seattle, WA 98112, USA.

"Southern Resident" killer whales include three "pods" (J, K and L) that reside primarily in Puget Sound/Georgia Basin during the spring, summer and fall. This population was listed as "endangered" in the US and Canada following a 20% decline between 1996 and 2001. The current study, using blubber/epidermis biopsy samples, contributes contemporary information about potential factors (i.e., levels of pollutants or changes in diet) that could adversely affect Southern Residents. Carbon and nitrogen stable isotopes indicated J- and L-pod consumed prey from similar trophic levels in 2004/2006 and also showed no evidence for a large shift in the trophic level of prey consumed by L-pod between 1996 and 2004/2006. Sigma PCBs decreased for Southern Residents biopsied in 2004/2006 compared to 1993-1995. Surprisingly, however, a three-year-old male whale (J39) had the highest concentrations of Sigma PBDEs, Sigma HCHs and HCB. POP ratio differences between J- and L-pod suggested that they occupy different ranges in winter.
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http://dx.doi.org/10.1016/j.marpolbul.2007.08.015DOI Listing
December 2007

Echolocation signals of free-ranging killer whales (Orcinus orca) and modeling of foraging for chinook salmon (Oncorhynchus tshawytscha).

J Acoust Soc Am 2004 Feb;115(2):901-9

Marine Mammal Research Program, Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii 96744, USA.

Fish-eating "resident"-type killer whales (Orcinus orca) that frequent the coastal waters off northeastern Vancouver Island, Canada have a strong preference for chinook salmon (Oncorhynchus tshawytscha). The whales in this region often forage along steep cliffs that extend into the water, echolocating their prey. Echolocation signals of resident killer whales were measured with a four-hydrophone symmetrical star array and the signals were simultaneously digitized at a sample rate of 500 kHz using a lunch-box PC. A portable VCR recorded the images from an underwater camera located adjacent to the array center. Only signals emanating from close to the beam axis (1185 total) were chosen for a detailed analysis. Killer whales project very broadband echolocation signals (Q equal 0.9 to 1.4) that tend to have bimodal frequency structure. Ninety-seven percent of the signals had center frequencies between 45 and 80 kHz with bandwidths between 35 and 50 kHz. The peak-to-peak source level of the echolocation signals decreased as a function of the one-way transmission loss to the array. Source levels varied between 195 and 224 dB re: 1 microPa. Using a model of target strength for chinook salmon, the echo levels from the echolocation signals are estimated for different horizontal ranges between a whale and a salmon. At a horizontal range of 100 m, the echo level should exceed an Orcinus hearing threshold at 50 kHz by over 29 dB and should be greater than sea state 4 noise by at least 9 dB. In moderately heavy rain conditions, the detection range will be reduced substantially and the echo level at a horizontal range of 40 m would be close to the level of the rain noise.
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http://dx.doi.org/10.1121/1.1642628DOI Listing
February 2004

On the communicative significance of whistles in wild killer whales (Orcinus orca).

Naturwissenschaften 2002 Sep 15;89(9):404-7. Epub 2002 Aug 15.

Arbeitsbereich Ethologie, Zoologisches Institut, Zoologisches Museum, Universität Hamburg, Germany.

Killer whales (Orcinus orca) use pulsed calls and whistles in underwater communication. Unlike pulsed calls, whistles have received little study and thus their function is poorly known. In this study, whistle activities of groups of individually known killer whales were compared quantitatively across behavioural categories. Acoustic recordings and simultaneous behavioural observations were made of northern resident killer whales off Vancouver Island in 1996 and 1997. Whistles were produced at greater rates than discrete calls during close-range behavioural activities than during long-range activities. They were the predominant sound-type recorded during socializing. The number of whistles per animal per minute was significantly higher during close-range behavioural activities than during long-range activities. Evidently, whistles play an important role in the close-range acoustic communication in northern resident killer whales.
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http://dx.doi.org/10.1007/s00114-002-0351-xDOI Listing
September 2002

Selective habituation shapes acoustic predator recognition in harbour seals.

Nature 2002 Nov;420(6912):171-3

School of Biology, University of St Andrews, Scotland, KY16 9TS, UK.

Predation is a major force in shaping the behaviour of animals, so that precise identification of predators will confer substantial selective advantages on animals that serve as food to others. Because experience with a predator can be lethal, early researchers studying birds suggested that predator recognition does not require learning. However, a predator image that can be modified by learning and experience will be advantageous in situations where cues associated with the predator are highly variable or change over time. In this study, we investigated the response of harbour seals (Phoca vitulina) to the underwater calls of different populations of killer whales (Orcinus orca). We found that the seals responded strongly to the calls of mammal-eating killer whales and unfamiliar fish-eating killer whales but not to the familiar calls of the local fish-eating population. This demonstrates that wild harbour seals are capable of complex acoustic discrimination and that they modify their predator image by selectively habituating to the calls of harmless killer whales. Fear in these animals is therefore focused on local threats by learning and experience.
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http://dx.doi.org/10.1038/nature01030DOI Listing
November 2002
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