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Andrew D Foote - One of the best experts on this subject based on the ideXlab platform.
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runs of homozygosity in Killer Whale genomes provide a global record of demographic histories
bioRxiv, 2020Co-Authors: Rebecca Hooper, Phillip A Morin, Thomas M P Gilbert, Laurent Excoffier, Karin A Forney, Michael D Martin, Jochen B W Wolf, Andrew D FooteAbstract:Runs of homozygosity (ROH) occur when offspring receive the same ancestral haplotype from both parents, and, accordingly, reduce individual heterozygosity. Their distribution throughout the genome contains information on the probability of inbreeding mediated by mating system and population demography. Here, we investigate variation in Killer Whale demographic history as reflected in genome-wide heterozygosity, using a global dataset of 26 genomes. We find an overall pattern of lower heterozygosity in genomes sampled at high latitudes, with hundreds of short ROH (
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Killer Whale genomes reveal a complex history of recurrent admixture and vicariance
Molecular Ecology, 2019Co-Authors: Andrew D Foote, Mikkelholger S Sinding, Kelly M Robertson, Michael D Martin, Marie Louis, George Pacheco, Ana R Amaral, Robin W BairdAbstract:Reconstruction of the demographic and evolutionary history of populations assuming a consensus tree‐like relationship can mask more complex scenarios, which are prevalent in nature. An emerging genomic toolset, which has been most comprehensively harnessed in the reconstruction of human evolutionary history, enables molecular ecologists to elucidate complex population histories. Killer Whales have limited extrinsic barriers to dispersal and have radiated globally, and are therefore a good candidate model for the application of such tools. Here, we analyse a global data set of Killer Whale genomes in a rare attempt to elucidate global population structure in a nonhuman species. We identify a pattern of genetic homogenisation at lower latitudes and the greatest differentiation at high latitudes, even between currently sympatric lineages. The processes underlying the major axis of structure include high drift at the edge of species' range, likely associated with founder effects and allelic surfing during postglacial range expansion. Divergence between Antarctic and non‐Antarctic lineages is further driven by ancestry segments with up to four‐fold older coalescence time than the genome‐wide average; relicts of a previous vicariance during an earlier glacial cycle. Our study further underpins that episodic gene flow is ubiquitous in natural populations, and can occur across great distances and after substantial periods of isolation between populations. Thus, understanding the evolutionary history of a species requires comprehensive geographic sampling and genome‐wide data to sample the variation in ancestry within individuals.
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genome wide snp data suggest complex ancestry of sympatric north pacific Killer Whale ecotypes
Heredity, 2016Co-Authors: Andrew D Foote, Phillip A MorinAbstract:Genome-wide SNP data suggest complex ancestry of sympatric North Pacific Killer Whale ecotypes
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genome culture coevolution promotes rapid divergence of Killer Whale ecotypes
Nature Communications, 2016Co-Authors: Andrew D Foote, Maria C Avilaarcos, John W Durban, Robin W Baird, Nagarjun Vijay, Matteo Fumagalli, Richard A GibbsAbstract:Analysing population genomic data from Killer Whale ecotypes, which we estimate have globally radiated within less than 250,000 years, we show that genetic structuring including the segregation of potentially functional alleles is associated with socially inherited ecological niche. Reconstruction of ancestral demographic history revealed bottlenecks during founder events, likely promoting ecological divergence and genetic drift resulting in a wide range of genome-wide differentiation between pairs of allopatric and sympatric ecotypes. Functional enrichment analyses provided evidence for regional genomic divergence associated with habitat, dietary preferences and post-zygotic reproductive isolation. Our findings are consistent with expansion of small founder groups into novel niches by an initial plastic behavioural response, perpetuated by social learning imposing an altered natural selection regime. The study constitutes an important step towards an understanding of the complex interaction between demographic history, culture, ecological adaptation and evolution at the genomic level.
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tracking niche variation over millennial timescales in sympatric Killer Whale lineages
Proceedings of The Royal Society B: Biological Sciences, 2013Co-Authors: Andrew D Foote, Aqqalu Rosingasvid, Maria C Avilaarcos, Mikkelholger S Sinding, Thomas M P Gilbert, Jason Newton, Marielouise Kampmann, Jose Alfredo Samaniego, Klaas PostAbstract:Niche variation owing to individual differences in ecology has been hypothesized to be an early stage of sympatric speciation. Yet to date, no study has tracked niche width over more than a few generations. In this study, we show the presence of isotopic niche variation over millennial timescales and investigate the evolutionary outcomes. Isotopic ratios were measured from tissue samples of sympatric Killer Whale Orcinus orca lineages from the North Sea, spanning over 10 000 years. Isotopic ratios spanned a range similar to the difference in isotopic values of two known prey items, herring Clupea harengus and harbour seal Phoca vitulina. Two proxies of the stage of speciation, lineage sorting of mitogenomes and genotypic clustering, were both weak to intermediate indicating that speciation has made little progress. Thus, our study confirms that even with the necessary ecological conditions, i.e. among-individual variation in ecology, it is difficult for sympatric speciation to progress in the face of gene flow. In contrast to some theoretical models, our empirical results suggest that sympatric speciation driven by among-individual differences in ecological niche is a slow process and may not reach completion. We argue that sympatric speciation is constrained in this system owing to the plastic nature of the behavioural traits under selection when hunting either mammals or fish.
Patrick J O Miller - One of the best experts on this subject based on the ideXlab platform.
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Killer Whale call frequency is similar across the oceans but varies across sympatric ecotypes
Journal of the Acoustical Society of America, 2015Co-Authors: Olga A Filatova, Filipa I P Samarra, John K B Ford, Patrick J O Miller, Harald Yurk, Craig O Matkin, Erich Hoyt, Lance G BarrettlennardAbstract: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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cultural evolution of Killer Whale calls background mechanisms and consequences
Behaviour, 2015Co-Authors: Olga A Filatova, Filipa I P Samarra, Volker B Deecke, John K B Ford, Patrick J O Miller, Harald YurkAbstract:Cultural evolution is a powerful process shaping behavioural phenotypes of many species including our own. Killer Whales are one of the species with relatively well-studied vocal culture. Pods have distinct dialects comprising a mix of unique and shared call types; calves adopt the call repertoire of their matriline through social learning. We review different aspects of Killer Whale acoustic communication to provide insights into the cultural transmission and gene-culture co- evolution processes that produce the extreme diversity of group and population repertoires. We argue that the cultural evolution of Killer Whale calls is not a random process driven by steady error accumulation alone: temporal change occurs at different speeds in different components of Killer Whale repertoires, and constraints in call structure and horizontal transmission often degrade the phylogenetic signal. We discuss the implications from bird song and human linguistic studies, and propose several hypotheses of Killer Whale dialect evolution.
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Killer Whale presence in relation to naval sonar activity and prey abundance in northern norway
Ices Journal of Marine Science, 2013Co-Authors: Sanna Kuningas, Petter H Kvadsheim, Patrick J O MillerAbstract:In this study, retrospective data on naval sonar activity and prey abundance were correlated with Killer Whale sightings within a fjord basin in northern Norway. In addition, passive acoustic and visual marine mammal surveys were conducted before, during, and after a specific navy exercise in 2006. Herring abundance was the main factor affecting Killer Whale presence. Naval sonar, either operational navy sonar exercises (Flotex) or experimental sonar activity (CEE) alone, did not explain Killer Whale occurrence. However, naval sonar activity during a period of low prey availability seemed to have had a negative effect on Killer Whale presence. We conclude that the level of reaction to sonar can be influenced by multiple factors, including availability of prey. © 2013 International Council for the Exploration of the Sea.
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responses of male sperm Whales physeter macrocephalus to Killer Whale sounds implications for anti predator strategies
Scientific Reports, 2013Co-Authors: Charlotte Cure, Petter H Kvadsheim, Ricardo Antunes, Ana Alves, Fleur Visser, Patrick J O MillerAbstract:Interactions between individuals of different cetacean species are often observed in the wild. Killer Whales (Orcinus orca) can be potential predators of many other cetaceans, and the interception of their vocalizations by unintended cetacean receivers may trigger anti-predator behavior that could mediate predator-prey interactions. We explored the anti-predator behaviour of five typically-solitary male sperm Whales (Physeter macrocephalus) in the Norwegian Sea by playing sounds of mammal-feeding Killer Whales and monitoring behavioural responses using multi-sensor tags. Our results suggest that, rather than taking advantage of their large aerobic capacities to dive away from the perceived predator, sperm Whales responded to Killer Whale playbacks by interrupting their foraging or resting dives and returning to the surface, changing their vocal production, and initiating a surprising degree of social behaviour in these mostly solitary animals. Thus, the interception of predator vocalizations by male sperm Whales disrupted functional behaviours and mediated previously unrecognized anti-predator responses.
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pilot Whales attracted to Killer Whale sounds acoustically mediated interspecific interactions in cetaceans
PLOS ONE, 2012Co-Authors: Charlotte Cure, Filipa I P Samarra, Petter H Kvadsheim, Ricardo Antunes, Ana Alves, Fleur Visser, Patrick J O MillerAbstract:In cetaceans’ communities, interactions between individuals of different species are often observed in the wild. Yet, due to methodological and technical challenges very little is known about the mediation of these interactions and their effect on cetaceans’ behavior. Killer Whales (Orcinus orca) are a highly vocal species and can be both food competitors and potential predators of many other cetaceans. Thus, the interception of their vocalizations by unintended cetacean receivers may be particularly important in mediating interspecific interactions. To address this hypothesis, we conducted playbacks of Killer Whale vocalizations recorded during herring-feeding activity to free-ranging long-finned pilot Whales (Globicephala melas). Using a multi-sensor tag, we were able to track the Whales and to monitor changes of their movements and social behavior in response to the playbacks. We demonstrated that the playback of Killer Whale sounds to pilot Whales induced a clear increase in group size and a strong attraction of the animals towards the sound source. These findings provide the first experimental evidence that the interception of heterospecific vocalizations can mediate interactions between different cetacean species in previously unrecognized ways.
Thomas M P Gilbert - One of the best experts on this subject based on the ideXlab platform.
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runs of homozygosity in Killer Whale genomes provide a global record of demographic histories
bioRxiv, 2020Co-Authors: Rebecca Hooper, Phillip A Morin, Thomas M P Gilbert, Laurent Excoffier, Karin A Forney, Michael D Martin, Jochen B W Wolf, Andrew D FooteAbstract:Runs of homozygosity (ROH) occur when offspring receive the same ancestral haplotype from both parents, and, accordingly, reduce individual heterozygosity. Their distribution throughout the genome contains information on the probability of inbreeding mediated by mating system and population demography. Here, we investigate variation in Killer Whale demographic history as reflected in genome-wide heterozygosity, using a global dataset of 26 genomes. We find an overall pattern of lower heterozygosity in genomes sampled at high latitudes, with hundreds of short ROH (
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tracking niche variation over millennial timescales in sympatric Killer Whale lineages
Proceedings of The Royal Society B: Biological Sciences, 2013Co-Authors: Andrew D Foote, Aqqalu Rosingasvid, Maria C Avilaarcos, Mikkelholger S Sinding, Thomas M P Gilbert, Jason Newton, Marielouise Kampmann, Jose Alfredo Samaniego, Klaas PostAbstract:Niche variation owing to individual differences in ecology has been hypothesized to be an early stage of sympatric speciation. Yet to date, no study has tracked niche width over more than a few generations. In this study, we show the presence of isotopic niche variation over millennial timescales and investigate the evolutionary outcomes. Isotopic ratios were measured from tissue samples of sympatric Killer Whale Orcinus orca lineages from the North Sea, spanning over 10 000 years. Isotopic ratios spanned a range similar to the difference in isotopic values of two known prey items, herring Clupea harengus and harbour seal Phoca vitulina. Two proxies of the stage of speciation, lineage sorting of mitogenomes and genotypic clustering, were both weak to intermediate indicating that speciation has made little progress. Thus, our study confirms that even with the necessary ecological conditions, i.e. among-individual variation in ecology, it is difficult for sympatric speciation to progress in the face of gene flow. In contrast to some theoretical models, our empirical results suggest that sympatric speciation driven by among-individual differences in ecological niche is a slow process and may not reach completion. We argue that sympatric speciation is constrained in this system owing to the plastic nature of the behavioural traits under selection when hunting either mammals or fish.
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mitogenomic insights into a recently described and rarely observed Killer Whale morphotype
Polar Biology, 2013Co-Authors: Andrew D Foote, Phillip A Morin, Robert L Pitman, Maria C Avilaarcos, John W Durban, Anton L Van Helden, Mikkelholger S Sinding, Thomas M P GilbertAbstract:Identifying evolutionary divergent taxonomic units, e.g. species and subspecies, is important for conservation and evolutionary biology. The ‘type D’ Killer Whale, Orcinus orca, is a rarely observed morphotype with a pelagic, circumpolar subantarctic distribution, making dedicated research and therefore taxonomic study extremely difficult to date. In this study, we used DNA target enrichment hybridisation capture coupled to high throughput sequencing, to obtain the first DNA sequence from the only known museum specimen of this recently described morphotype. The high coverage, complete mitogenome sequence was compared to a previously published global dataset of 139 individuals, indicating that this type is highly divergent to all previously genetically sequenced Killer Whale forms. The estimated divergence time (390,000 years ago) from its most recent common ancestor with other extant Killer Whale lineages was the second oldest split within the Killer Whale phylogeny. This study provides the first genetic support of type D potentially being a distinct subspecies or species of Killer Whale, although further samples are needed to identify whether there is monophyly of mitogenome sequences and whether nuclear DNA also indicates reproductive isolation. These findings also highlight the value of natural history museum collections and new technologies to investigate the taxonomy of rare, cryptic or difficult to access species.
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positive selection on the Killer Whale mitogenome
Biology Letters, 2011Co-Authors: Andrew D Foote, Phillip A Morin, Robert L Pitman, John W Durban, Thomas M P Gilbert, Paul R Wade, Eske Willerslev, Rute R Da FonsecaAbstract:Mitochondria produce up to 95 per cent of the eukaryotic cell's energy. The coding genes of the mitochondrial DNA may therefore evolve under selection owing to metabolic requirements. The Killer Whale, Orcinus orca, is polymorphic, has a global distribution and occupies a range of ecological niches. It is therefore a suitable organism for testing this hypothesis. We compared a global dataset of the complete mitochondrial genomes of 139 individuals for amino acid changes that were associated with radical physico-chemical property changes and were influenced by positive selection. Two such selected non-synonymous amino acid changes were found; one in each of two ecotypes that inhabit the Antarctic pack ice. Both substitutions were associated with changes in local polarity, increased steric constraints and α-helical tendencies that could influence overall metabolic performance, suggesting a functional change.
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ecological morphological and genetic divergence of sympatric north atlantic Killer Whale populations
Molecular Ecology, 2009Co-Authors: Andrew D Foote, Eske Willerslev, James Newton, Stuart B Piertney, Thomas M P GilbertAbstract:Ecological divergence has a central role in speciation and is therefore an important source of biodiversity. Studying the micro-evolutionary processes of ecological diversification at its early stages provides an opportunity for investigating the causative mechanisms and ecological conditions promoting divergence. Here we use morphological traits, nitrogen stable isotope ratios and tooth wear to characterize two disparate types of North Atlantic Killer Whale. We find a highly specialist type, which reaches up to 8.5 m in length and a generalist type which reaches up to 6.6 m in length. There is a single fixed genetic difference in the mtDNA control region between these types, indicating integrity of groupings and a shallow divergence. Phylogenetic analysis indicates this divergence is independent of similar ecological divergences in the Pacific and Antarctic. Niche-width in the generalist type is more strongly influenced by between-individual variation rather than within-individual variation in the composition of the diet. This first step to divergent specialization on different ecological resources provides a rare example of the ecological conditions at the early stages of adaptive radiation.
Christophe Guinet - One of the best experts on this subject based on the ideXlab platform.
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demographic consequences of fisheries interaction within a Killer Whale orcinus orca population
Marine Biology, 2017Co-Authors: Paul Tixier, Nicolas Gasco, Christophe Barbraud, Deborah Pardo, Guy Duhamel, Christophe GuinetAbstract:Individual heterogeneity in foraging behavior has been widely documented within predator populations. In highly social apex predators such as Killer Whales (Orcinus orca), specialization may occur at the matriline level. A small population of Killer Whales has been documented to occur around the Crozet Islands. These Whales feed on a wide range of prey items including seals, penguins and large Whales, as well as depredate the local Patagonian toothfish (Dissostichus eleginoides) longline fishery. The level of interactions with fisheries varies greatly between matrilines. Here, we present the results on the effects of such behavioral heterogeneity on the demographic trends of this Killer Whale population. We used photo-identification data from 1977 to 2011 in a mark–recapture framework to test the effect of varying levels of fisheries interactions on adult survival. We documented significant differences in survival between depredating and non-depredating Whales, resulting in divergent intra-population demographic trends. These differences showed low survival, and thus a negative effect, for depredating Whales when illegal fishing occurred (poachers used lethal methods to deter Killer Whales from depredating longlines). After illegal fishing stopped (2003–2011), the survival rates of depredating individuals exceeded the survival rates of non-depredating individuals, suggesting a positive influence of “artificial food provisioning”. This effect was further supported by a higher population growth rate for depredating Whales. This study highlights the potential demographic costs and benefits that cetaceans face from depredating fisheries and addresses the demographic consequences of both intra-population feeding specialization and the influence of anthropogenic changes in resource availability.
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mitigating Killer Whale depredation on demersal longline fisheries by changing fishing practices
Ices Journal of Marine Science, 2015Co-Authors: Paul Tixier, Nicolas Gasco, Guy Duhamel, Jade Vacquie Garcia, Christophe GuinetAbstract:Odontocete depredation on longlines involves socioeconomic and conservation issues with significant losses for fisheries and potential impacts on wild populations of depredating species. As technical solutions to this conflict are limited and difficult to implement, this study aimed to identify fishing practices that could reduce odontocete depredation, with a focus on Killer Whales (Orcinus orca) interacting with Patagonian toothfish (Dissostichus eleginoides) longliners off the Crozet islands. Data collected by fishery observers from 6013 longline sets between 2003 and 2013 allowed us to statistically detect the significant influence of five operational variables using GLMMs. The probability of interactions between vessels and Killer Whales was decreased by (i) the number of vessels operating simultaneously in the area: the limited number of depredating Killer Whales may induce a dilution effect with increased fleet size, and (ii) depth of longline sets: vessels operating in shallow waters may be more accessible to Whales that are initially distributed on peri-insular shelves. The cpue was negatively influenced by (iii) length of longlines: longer sets may provide Killer Whales access to a greater proportion of hooked fish per set, and positively influenced by (iv) hauling speed: increased speed may shorten the time during which toothfish are accessible to Whales during hauling. The time it takes for Killer Whales to reach vessels was positively correlated to (v) the distance travelled between longline sets with an estimated threshold of 100 km beyond which Whales seem to temporarily lose track of vessels. These findings provide insightful guidelines about what fishing strategy to adopt given these variables to reduce Killer Whale depredation here and in similar situations elsewhere. To a greater extent, this study is illustrative of how collaborative work with fishermen i na fully controlled fishery framework may lead to the definition of cost-limited and easy-to-implement mitigation solutions when facing such humanwildlife conflict.
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influence of artificial food provisioning from fisheries on Killer Whale reproductive output
Animal Conservation, 2015Co-Authors: Paul Tixier, Matthieu Authier, Nicolas Gasco, Christophe GuinetAbstract:Prey availability is a critical factor influencing demographic trajectories of long-lived, top predators, which may therefore be strongly affected by artificial food provisioning. In the Crozet archipelago, Killer Whales feed on a wide range of species including birds, marine mammals and fish. Following the development of the Patagonian toothfish fisheries in 1996, Killer Whales began to also depredate longlines. Social groups, hereafter referred to as matrilines, exhibited different levels of interaction; some were involved in most of the depredation events, while others were never observed interacting with fisheries. These differences in interaction levels influenced reproduction. An extensive photo-identification effort from 2003 to 2012 allowed us to estimate the probability of calving for 21 reproductive females. Using multi-model inference, we found a positive effect of depredation on female calving rate. These results suggest an effect of artificial food provisioning on female reproductive output with potentially far-reaching consequences on the demography of the Crozet Killer Whale population. Our findings evidence the need to account for both intra-population heterogeneity and level of interaction with fisheries when assessing conservation strategies of long-lived marine predators involved in similar depredation worldwide.
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observations of a distinctive morphotype of Killer Whale orcinus orca type d from subantarctic waters
Polar Biology, 2011Co-Authors: Robert L Pitman, John W Durban, Michael Greenfelder, Christophe Guinet, Morton Jorgensen, Paula A Olson, Jordi Plana, Paul Tixier, Jared R TowersAbstract:Studies have shown that Killer Whale (Orcinus orca) communities in high latitudes regularly comprise assemblages of sympatric ‘ecotypes’—forms that differ in morphology, behavior, and prey preferences. Although they can appear superficially similar, recent genetic evidence suggests that breeding is assortative among ecotypes within individual communities, and species-level divergences are inferred in some cases. Here, we provide information on a recently recognized ‘type D’ Killer Whale based on photographs of a 1955 mass stranding in New Zealand and our own six at-sea sightings since 2004. It is the most distinctive-looking form of Killer Whale that we know of, immediately recognizable by its extremely small white eye patch. Its geographic range appears to be circumglobal in subantarctic waters between latitudes 40°S and 60°S. School sizes are relatively large (mean 17.6; range 9–35; n = 7), and although nothing is known about the type D diet, it is suspected to include fish because groups have been photographed around longline vessels where they reportedly depredate Patagonian toothfish (Dissostichus eleginoides).
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Killer Whale predation on bluefin tuna exploring the hypothesis of the endurance exhaustion technique
Marine Ecology Progress Series, 2007Co-Authors: Christophe Guinet, Lance G Barrettlennard, P Domenici, R De Stephanis, J K B Ford, Philippe VerborghAbstract:Killer Whales Orcinus orca occur in the area of the Strait of Gibraltar, where they prey on migrating bluefin tuna Thunnus thynnus. In the spring, Killer Whales were observed to chase tuna for up to 30 min at a relatively high sustained speed (3.7 ± 0.2 m s -1 ) until they captured them. Using simple models based on previous locomotor performance data on Killer Whales and thunnids, we investigated the hypothesis that Killer Whales push tuna beyond their aerobic limits to exhaust and capture them. To test this hypothesis, the endurance of bluefin tuna was estimated from data on maximum burst and aerobic swimming available for bluefin and yellowfin tuna T. albacares. The endurance performance of Killer Whales was evaluated on the basis of the maximal rate of oxygen uptake during exercise (VO2max). We modelled the maximum aerobic power output for a Killer Whale according to swimming speed using a VO2max ranging between 20 and 30 ml O2 kg -1 min -1 . The out- put of this model was compared to the observed sustained swimming speed of Killer Whales chasing prey over long durations. Our results support the hypothesis that Killer Whales may use an endurance-exhaustion technique to catch small to medium sized (up to 0.8 to 1.5 m) bluefin tuna, while larger tuna may be inaccessible to Killer Whales unless they use cooperative hunting tech- niques or benefit through depredation of fish caught on long lines, drop lines or trap nets.
Paul Tixier - One of the best experts on this subject based on the ideXlab platform.
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demographic consequences of fisheries interaction within a Killer Whale orcinus orca population
Marine Biology, 2017Co-Authors: Paul Tixier, Nicolas Gasco, Christophe Barbraud, Deborah Pardo, Guy Duhamel, Christophe GuinetAbstract:Individual heterogeneity in foraging behavior has been widely documented within predator populations. In highly social apex predators such as Killer Whales (Orcinus orca), specialization may occur at the matriline level. A small population of Killer Whales has been documented to occur around the Crozet Islands. These Whales feed on a wide range of prey items including seals, penguins and large Whales, as well as depredate the local Patagonian toothfish (Dissostichus eleginoides) longline fishery. The level of interactions with fisheries varies greatly between matrilines. Here, we present the results on the effects of such behavioral heterogeneity on the demographic trends of this Killer Whale population. We used photo-identification data from 1977 to 2011 in a mark–recapture framework to test the effect of varying levels of fisheries interactions on adult survival. We documented significant differences in survival between depredating and non-depredating Whales, resulting in divergent intra-population demographic trends. These differences showed low survival, and thus a negative effect, for depredating Whales when illegal fishing occurred (poachers used lethal methods to deter Killer Whales from depredating longlines). After illegal fishing stopped (2003–2011), the survival rates of depredating individuals exceeded the survival rates of non-depredating individuals, suggesting a positive influence of “artificial food provisioning”. This effect was further supported by a higher population growth rate for depredating Whales. This study highlights the potential demographic costs and benefits that cetaceans face from depredating fisheries and addresses the demographic consequences of both intra-population feeding specialization and the influence of anthropogenic changes in resource availability.
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mitigating Killer Whale depredation on demersal longline fisheries by changing fishing practices
Ices Journal of Marine Science, 2015Co-Authors: Paul Tixier, Nicolas Gasco, Guy Duhamel, Jade Vacquie Garcia, Christophe GuinetAbstract:Odontocete depredation on longlines involves socioeconomic and conservation issues with significant losses for fisheries and potential impacts on wild populations of depredating species. As technical solutions to this conflict are limited and difficult to implement, this study aimed to identify fishing practices that could reduce odontocete depredation, with a focus on Killer Whales (Orcinus orca) interacting with Patagonian toothfish (Dissostichus eleginoides) longliners off the Crozet islands. Data collected by fishery observers from 6013 longline sets between 2003 and 2013 allowed us to statistically detect the significant influence of five operational variables using GLMMs. The probability of interactions between vessels and Killer Whales was decreased by (i) the number of vessels operating simultaneously in the area: the limited number of depredating Killer Whales may induce a dilution effect with increased fleet size, and (ii) depth of longline sets: vessels operating in shallow waters may be more accessible to Whales that are initially distributed on peri-insular shelves. The cpue was negatively influenced by (iii) length of longlines: longer sets may provide Killer Whales access to a greater proportion of hooked fish per set, and positively influenced by (iv) hauling speed: increased speed may shorten the time during which toothfish are accessible to Whales during hauling. The time it takes for Killer Whales to reach vessels was positively correlated to (v) the distance travelled between longline sets with an estimated threshold of 100 km beyond which Whales seem to temporarily lose track of vessels. These findings provide insightful guidelines about what fishing strategy to adopt given these variables to reduce Killer Whale depredation here and in similar situations elsewhere. To a greater extent, this study is illustrative of how collaborative work with fishermen i na fully controlled fishery framework may lead to the definition of cost-limited and easy-to-implement mitigation solutions when facing such humanwildlife conflict.
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influence of artificial food provisioning from fisheries on Killer Whale reproductive output
Animal Conservation, 2015Co-Authors: Paul Tixier, Matthieu Authier, Nicolas Gasco, Christophe GuinetAbstract:Prey availability is a critical factor influencing demographic trajectories of long-lived, top predators, which may therefore be strongly affected by artificial food provisioning. In the Crozet archipelago, Killer Whales feed on a wide range of species including birds, marine mammals and fish. Following the development of the Patagonian toothfish fisheries in 1996, Killer Whales began to also depredate longlines. Social groups, hereafter referred to as matrilines, exhibited different levels of interaction; some were involved in most of the depredation events, while others were never observed interacting with fisheries. These differences in interaction levels influenced reproduction. An extensive photo-identification effort from 2003 to 2012 allowed us to estimate the probability of calving for 21 reproductive females. Using multi-model inference, we found a positive effect of depredation on female calving rate. These results suggest an effect of artificial food provisioning on female reproductive output with potentially far-reaching consequences on the demography of the Crozet Killer Whale population. Our findings evidence the need to account for both intra-population heterogeneity and level of interaction with fisheries when assessing conservation strategies of long-lived marine predators involved in similar depredation worldwide.
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observations of a distinctive morphotype of Killer Whale orcinus orca type d from subantarctic waters
Polar Biology, 2011Co-Authors: Robert L Pitman, John W Durban, Michael Greenfelder, Christophe Guinet, Morton Jorgensen, Paula A Olson, Jordi Plana, Paul Tixier, Jared R TowersAbstract:Studies have shown that Killer Whale (Orcinus orca) communities in high latitudes regularly comprise assemblages of sympatric ‘ecotypes’—forms that differ in morphology, behavior, and prey preferences. Although they can appear superficially similar, recent genetic evidence suggests that breeding is assortative among ecotypes within individual communities, and species-level divergences are inferred in some cases. Here, we provide information on a recently recognized ‘type D’ Killer Whale based on photographs of a 1955 mass stranding in New Zealand and our own six at-sea sightings since 2004. It is the most distinctive-looking form of Killer Whale that we know of, immediately recognizable by its extremely small white eye patch. Its geographic range appears to be circumglobal in subantarctic waters between latitudes 40°S and 60°S. School sizes are relatively large (mean 17.6; range 9–35; n = 7), and although nothing is known about the type D diet, it is suspected to include fish because groups have been photographed around longline vessels where they reportedly depredate Patagonian toothfish (Dissostichus eleginoides).
