Patterns of winter occurrence of three sympatric killer whale populations off eastern Vancouver Island, Canada, based on passive acoustic monitoring

Understanding habitat use patterns of animal populations across space and time is fundamental to identifying ecological requirements, and informing threat mitigation and conservation strategies. Persistent data gaps tend to occur with cryptic species in difficult-to-access environments, where the use of appropriate monitoring tools is indispensable for detection. Three populations of threatened and endangered killer whales occur year-round in waters off British Columbia, Canada; however, their winter habitat use patterns are not well known. Here we quantify wintertime use of the northern Strait of Georgia by these sympatric killer whale populations, revealing the importance of this previously understudied region. Using a network of passive acoustic monitoring devices deployed over three winter periods, we examine site-specific and regional patterns of occurrence of Bigg’s, and Southern and Northern Resident killer whales. All three populations frequented these waters in nearly every month from November to April, and across all study years. Bigg’s killer whales were detected most frequently, followed by Southern Residents, then Northern Residents. Population-specific differences in site use was apparent, with Southern Resident detections occurring more often than expected off the southwest side of Texada Island, while Northern Residents appeared to favor the east side of Texada Island. Remarkably, the patterns of winter use we observe in this region by Resident killer whale populations have seemingly persisted for at least 50 years. Additionally, we evaluate and discuss the effect of using multiple simultaneous recorders to characterize habitat use patterns. Lastly, we present a data-driven approach for estimating acoustic residence time, describe inter-population differences in winter residency in the northern Strait of Georgia, and discuss implications for critical habitat designation. This study fills important knowledge gaps related to killer whale winter occurrence off western Canada, highlighting the significance of the northern Strait of Georgia for these at-risk populations

Postreproductive killer whale grandmothers improve the survival of their grandoffspring

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A long post-reproductive lifespan is a shared trait among genetically distinct killer whale populations

This is the final version. Available on open access from Wiley via the DOI in this recordData availability: Data to replicate the analyses are available from the online repository: https://doi.org/10.5061/dryad.6t1g1jwxx. Requests for access to raw data can be directed to the authors, the Center for Whale Research (www.whaleresearch.com) or Fisheries and Oceans Canada (www.dfo-mpo.gc.ca)The extended female post-reproductive lifespan found in humans and some toothed whales remains an evolutionary puzzle. Theory predicts demographic patterns resulting in increased female relatedness with age (kinship dynamics) can select for a prolonged post reproductive lifespan due to the combined costs of inter-generational reproductive conflict and benefits of late-life helping. Here we test this prediction using >40 years of longitudinal demographic data from the sympatric yet genetically distinct killer whale ecotypes: resident and Bigg’s killer whales. The female relatedness with age is predicted to increase in both ecotypes, but with a less steep increase in Bigg’s due to their different social structure. Here, we show that there is a significant post-reproductive lifespan in both ecotypes with >30% of adult female years being lived as post-reproductive, supporting the general prediction that an increase in local relatedness with age predisposes the evolution of a post reproductive lifespan. Differences in the magnitude of kinship dynamics however, did not influence the timing or duration of the post-reproductive lifespan with females in both ecotypes terminating reproduction before their mid-40s followed by an expected post reproductive period of ~20 years. Our results highlight the important role of kinship dynamics in the evolution of a long post-reproductive lifespan in long-lived mammals, while further implying that the timing of menopause may be a robust trait that is persistent despite substantial variation in demographic patterns among populations.Nuffield FoundationNatural Environment Research Council (NERC)Leverhulme TrustEarthwatch InstituteNOAA FisheriesFisheries and Oceans Canada Species At Risk Progra

A long postreproductive life span is a shared trait among genetically distinct killer whale populations.

The extended female postreproductive life span found in humans and some toothed whales remains an evolutionary puzzle. Theory predicts demographic patterns resulting in increased female relatedness with age (kinship dynamics) can select for a prolonged postreproductive life span due to the combined costs of intergenerational reproductive conflict and benefits of late-life helping. Here, we test this prediction using >40 years of longitudinal demographic data from the sympatric yet genetically distinct killer whale ecotypes: resident and Bigg's killer whales. The female relatedness with age is predicted to increase in both ecotypes, but with a less steep increase in Bigg's due to their different social structure. Here, we show that there is a significant postreproductive life span in both ecotypes with >30% of adult female years being lived as postreproductive, supporting the general prediction that an increase in local relatedness with age predisposes the evolution of a postreproductive life span. Differences in the magnitude of kinship dynamics however did not influence the timing or duration of the postreproductive life span with females in both ecotypes terminating reproduction before their mid-40s followed by an expected postreproductive period of about 20 years. Our results highlight the important role of kinship dynamics in the evolution of a long postreproductive life span in long-lived mammals, while further implying that the timing of menopause may be a robust trait that is persistent despite substantial variation in demographic patterns among populations

Extrapolating cetacean densities to quantitatively assess human impacts on populations in the high seas

Funding for this study came from the U.S. Fleet Forces Command (Cooperative Agreement N62470-13-2-8008), NASA (NNX08AK73G) and NOAA/NMFS (EE-133F-14-SE-3558).As human activities expand beyond national jurisdictions to the high seas, there is an increasing need to consider anthropogenic impacts to species inhabiting these waters. The current scarcity of scientific observations of cetaceans in the high seas impedes the assessment of population-level impacts of these activities. We developed plausible density estimates to facilitate a quantitative assessment of anthropogenic impacts on cetacean populations in these waters. Our study region extended from a well-surveyed region within the U.S. Exclusive Economic Zone into a large region of the western North Atlantic sparsely surveyed for cetaceans. We modeled densities of 15 cetacean taxa with available line transect survey data and habitat covariates and extrapolated predictions to sparsely surveyed regions. We formulated models to reduce the extent of extrapolation beyond covariate ranges, and constrained them to model simple and generalizable relationships. To evaluate confidence in the predictions, we mapped where predictions were made outside sampled covariate ranges, examined alternate models, and compared predicted densities with maps of sightings from sources that could not be integrated into our models. Confidence levels in model results depended on the taxon and geographic area and highlighted the need for additional surveying in environmentally distinct areas. With application of necessary caution, our density estimates can inform management needs in the high seas, such as the quantification of potential cetacean interactions with military training exercises, shipping, fisheries, and deep-sea mining and be used to delineate areas of special biological significance in international waters. Our approach is generally applicable to other marine taxa and geographic regions for which management will be implemented but data are sparse.Publisher PDFPeer reviewe

Taking movement data to new depths : Inferring prey availability and patch profitability from seabird foraging behavior

Funded byNatural Environment Research Council. Grant Number: NE/K007440/1 and Marine Scotland Science and Seabird Tracking and Research (STAR) Project led by the Royal Society for the Protection of Birds (RSPB)Peer reviewedPublisher PD

Evidence from sperm whale clans of symbolic marking in non-human cultures

Culture, a pillar of the remarkable ecological success of humans, is increasingly recognized as a powerful force structuring nonhuman animal populations. A key gap between these two types of culture is quantitative evidence of symbolic markers—seemingly arbitrary traits that function as reliable indicators of cultural group membership to conspecifics. Using acoustic data collected from 23 Pacific Ocean locations, we provide quantitative evidence that certain sperm whale acoustic signals exhibit spatial patterns consistent with a symbolic marker function. Culture segments sperm whale populations into behaviorally distinct clans, which are defined based on dialects of stereotyped click patterns (codas). We classified 23,429 codas into types using contaminated mixture models and hierarchically clustered coda repertoires into seven clans based on similarities in coda usage; then we evaluated whether coda usage varied with geographic distance within clans or with spatial overlap between clans. Similarities in within-clan usage of both “identity codas” (coda types diagnostic of clan identity) and “nonidentity codas” (coda types used by multiple clans) decrease as space between repertoire recording locations increases. However, between-clan similarity in identity, but not nonidentity, coda usage decreases as clan spatial overlap increases. This matches expectations if sympatry is related to a measurable pressure to diversify to make cultural divisions sharper, thereby providing evidence that identity codas function as symbolic markers of clan identity. Our study provides quantitative evidence of arbitrary traits, resembling human ethnic markers, conveying cultural identity outside of humans, and highlights remarkable similarities in the distributions of human ethnolinguistic groups and sperm whale clans

Habitat selection and niche characteristics of rorqual whales in the northern Gulf of St. Lawrence (Canada)

Habitat selection influences the distribution patterns of animals and how they partition their ecological niches. However, studies of habitat selection seldom model temporal variability and focus primarily on terrestrial ecosystems where habitat patches change over comparatively long time scales. In marine ecosystems, ignoring the time-varying characteristics of habitats might lead to a poor understanding of ecological relationships. Blue (Balaenoptera musculus), finback (B. physalus), humpback (Megaptera novaeangliae) and minke (B. acutorostrata) whales occur in sympatry in the Gulf of St. Lawrence (Canada) during the feeding season. I combined boat surveys with remote-sensing technology and computer ocean models to study habitat selection and niche characteristics of these rorqual whales for the years 1997-2002. All four species responded to the temporal variability of their environment by selecting a combination of time-varying and static factors that differed from the available habitat and were likely linked with prey availability, namely shallow banks, steep seabed slope, cold and saline surface waters, deep and cold intermediate layer. Moreover, distribution of whale sightings was highly correlated with thermal fronts, a dynamic meso-scale process that increases biological productivity and aggregates prey. Spatial distribution differed among species, likely reflecting differences in feeding strategies that could have evolved to alleviate inter-specific competition. There was clear spatial partitioning of the habitat use between species, and some separation in time. Fine-scale selection of dynamic variables appears to be the main mechanism facilitating co-occurrence. Minke whales had a specialised niche centred on shallow coastal waters. Deeper offshore waters and a colder intermediate layer characterised the niches of finback and humpback whales. The endangered blue whale had the narrowest niche, characterised by high salinity cold surface temperature and sLa sélection de l'habitat influence la distribution des animaux et la manière dont ils coexistent. Cependant, les études prennent rarement en compte la variabilité temporelle et se penchent surtout sur les écosystèmes terrestres où les caractéristiques évoluent sur des échelles de temps relativement longues. Dans les écosystèmes marins en revanche, ignorer le caractère dynamique de l'habitat peut conduire à une mauvaise compréhension des relations écologiques. Des rorquals bleus (Balaenoptera musculus), communs (B. physalus), à bosse (Megaptera novaeangliae) et des petits rorquals (B. acutorostrata) se rencontrent en situation de sympatrie dans le golfe du Saint-Laurent (Canada) durant leur saison d'alimentation. J'ai combiné des relevés en bateau avec des technologies d'échantillonnage à distance et des modèles informatiques du Saint-Laurent pour étudier la sélection de l'habitat et les niches écologiques de ces rorquals entre les années 1997 et 2002. Dans ma zone d'étude, les quatre espèces répondaient à la variabilité temporelle de leur environnement en sélectionnant une combinaison de facteurs dynamiques et statiques qui différaient de l'habitat disponible et étaient liés à la disponibilité de leurs proies : bancs peu profonds, topographie sous-marine pentue, eaux de surface froides et salées, couche intermédiaire plus froide et plus profonde. De plus, la distribution des observations de baleines était hautement corrélée avec les fronts thermiques, un processus dynamique qui augmente la productivité biologique et regroupe les proies. Les schémas de distribution spatiale différaient entre les espèces, reflétant probablement des différences de stratégie alimentaire apparues afin d'alléger la compétition interspécifique. Les quatre espèces semblaient se partager l'habitat dans l'espace et dans le temps, principalement au moyen d'une sélection à petite échelle des variables dynamiques. Les petits rorquals a