Snow avalanches are a primary climate-linked driver of mountain ungulate populations.

Snow is a major, climate-sensitive feature of the Earth's surface and catalyst of fundamentally important ecosystem processes. Understanding how snow influences sentinel species in rapidly changing mountain ecosystems is particularly critical. Whereas effects of snow on food availability, energy expenditure, and predation are well documented, we report how avalanches exert major impacts on an ecologically significant mountain ungulate - the coastal Alaskan mountain goat (Oreamnos americanus). Using long-term GPS data and field observations across four populations (421 individuals over 17 years), we show that avalanches caused 23-65% of all mortality, depending on area. Deaths varied seasonally and were directly linked to spatial movement patterns and avalanche terrain use. Population-level avalanche mortality, 61% of which comprised reproductively important prime-aged individuals, averaged 8% annually and exceeded 22% when avalanche conditions were severe. Our findings reveal a widespread but previously undescribed pathway by which snow can elicit major population-level impacts and shape demographic characteristics of slow-growing populations of mountain-adapted animals.

Ecology of fear alters behavior of grizzly bears exposed to bear-viewing ecotourism.

Humans are perceived as predators by many species and may generate landscapes of fear, influencing spatiotemporal activity of wildlife. Additionally, wildlife might seek out human activity when faced with predation risks (human shield hypothesis). We used the anthropause, a decrease in human activity resulting from the COVID-19 pandemic, to test ecology of fear and human shield hypotheses and quantify the effects of bear-viewing ecotourism on grizzly bear (Ursus arctos) activity. We deployed camera traps in the Khutze watershed in Kitasoo Xai'xais Territory in the absence of humans in 2020 and with experimental treatments of variable human activity when ecotourism resumed in 2021. Daily bear detection rates decreased with more people present and increased with days since people were present. Human activity was also associated with more bear detections at forested sheltered sites and less at exposed sites, likely due to the influence of habitat on bear perception of safety. The number of people negatively influenced adult male detection rates, but we found no influence on female with young detections, providing no evidence that females responded behaviorally to a human shield effect from reduced male activity. We also observed apparent trade-offs of risk avoidance and foraging. When salmon levels were moderate to high, detected bears were more likely to be females with young than adult males on days with more people present. Should managers want to minimize human impacts on bear activity and maintain baseline age-sex class composition at ecotourism sites, multiday closures and daily occupancy limits may be effective. More broadly, this work revealed that antipredator responses can vary with intensity of risk cues, habitat structure, and forage trade-offs and manifest as altered age-sex class composition of individuals using human-influenced areas, highlighting that wildlife avoid people across multiple spatiotemporal scales.

Human disturbance in riparian areas disrupts predator-prey interactions between grizzly bears and salmon.

Wildlife must increasingly balance trade-offs between the need to access important foods and the mortality risks associated with human-dominated landscapes. Human disturbance can profoundly influence wildlife behavior, but managers know little about the relationship between disturbance-behavior dynamics and associated consequences for foraging. We address this gap by empirically investigating the consequences of human activity on a keystone predator-prey interaction in a region with limited but varied industrial disturbance. Using stable isotope data from 226 hair samples of grizzly bears (Ursus arctos horribilis) collected from 1995 to 2014 across 22 salmon-bearing watersheds (88,000 km2) in British Columbia, Canada, we examined how human activity influenced their consumption of spawning salmon (Oncorhynchus spp.), a fitness-related food. Accounting for the abundance of salmon and other foods, salmon consumption strongly decreased (up to 59% for females) with increasing human disturbance (as measured by the human footprint index) in riparian zones of salmon-bearing rivers. Declines in salmon consumption occurred with disturbance even in watersheds with low footprints. In a region currently among the least influenced by industrial activity, intensification of disturbance in river valleys is predicted to increasingly decouple bears from salmon, possibly driving associated reductions in population productivity and provisioning of salmon nutrients to terrestrial ecosystems. Accordingly, we draw on our results to make landscape-scale and access-related management recommendations beyond current streamside protection buffers. This work illustrates the interaction between habitat modification and food security for wildlife, highlighting the potential for unacknowledged interactions and cumulative effects in increasingly modified landscapes.

The diversity of animals identified as keystone species.

Although the keystone species concept was conceived of over 50 years ago, contemporary efforts to synthesize related literature have been limited. Our objective was to create a list of keystone animal species identified in the literature and to examine the variation in the traits of species and the ecosystem influences they elicit. We documented 230 species considered keystones. A clustering analysis classified them into five archetypes based on combinations of their taxonomic class, body size, trophic level, and role (consumers, modifiers, or prey). Although conservation and public perception of keystones primarily focuses on large vertebrate consumers, our analysis reveals that researchers have defined a wide diversity of keystone species, with large variation in associated ecosystem processes. Future research may confront ambiguity in the definition of keystone status, as well as clarify the type, abundance, and quality of data required to assign the term. Identifying keystones with increased rigor would not only enrich the literature but also inform intervention to safeguard threatened keystones and their associated influences on ecosystems.

Humanity's diverse predatory niche and its ecological consequences.

Although humans have long been predators with enduring nutritive and cultural relationships with their prey, seldom have conservation ecologists considered the divergent predatory behavior of contemporary, industrialized humans. Recognizing that the number, strength and diversity of predator-prey relationships can profoundly influence biodiversity, here we analyze humanity's modern day predatory interactions with vertebrates and estimate their ecological consequences. Analysing IUCN 'use and trade' data for ~47,000 species, we show that fishers, hunters and other animal collectors prey on more than a third (~15,000 species) of Earth's vertebrates. Assessed over equivalent ranges, humans exploit up to 300 times more species than comparable non-human predators. Exploitation for the pet trade, medicine, and other uses now affects almost as many species as those targeted for food consumption, and almost 40% of exploited species are threatened by human use. Trait space analyses show that birds and mammals threatened by exploitation occupy a disproportionally large and unique region of ecological trait space, now at risk of loss. These patterns suggest far more species are subject to human-imposed ecological (e.g., landscapes of fear) and evolutionary (e.g., harvest selection) processes than previously considered. Moreover, continued overexploitation will likely bear profound consequences for biodiversity and ecosystem function.

When the enemy of an enemy is no friend.

Some wildlife species mistakenly seek human-inhabited areas to avoid predators.

Scale-dependent effects of marine subsidies on the island biogeographic patterns of plants.

Although species richness can be determined by different mechanisms at different spatial scales, the role of scale in the effects of marine inputs on island biogeography has not been studied explicitly. Here, we evaluated the potential influence of island characteristics and marine inputs (seaweed wrack biomass and marine-derived nitrogen in the soil) on plant species richness at both a local (plot) and regional (island) scale on 92 islands in British Columbia, Canada. We found that the effects of subsidies on species richness depend strongly on spatial scale. Despite detecting no effects of marine subsidies at the island scale, we found that as plot level subsidies increased, species richness decreased; plots with more marine-derived nitrogen in the soil hosted fewer plant species. We found no effect of seaweed wrack at either scale. To identify potential mechanisms underlying the decrease in diversity, we fit a spatially explicit joint species distribution model to evaluate species level responses to marine subsidies and effects of biotic interactions among species. We found mixed evidence for competition for both light and nutrients, and cannot rule out an alternative mechanism; the observed decrease in species richness may be due to disturbances associated with animal-mediated nutrient deposits, particularly those from North American river otters (Lontra canadensis). By evaluating the scale-dependent effects of marine subsidies on island biogeographic patterns of plants and revealing likely mechanisms that act on community composition, we provide novel insights on the scale dependence of a fundamental ecological theory, and on the rarely examined links between marine and terrestrial ecosystems often bridged by animal vectors.

Physical disturbance by recovering sea otter populations increases eelgrass genetic diversity.

Most knowledge regarding the role of predators is ecological in nature. Here, we report how disturbance generated by sea otters (Enhydra lutris) digging for infaunal prey in eelgrass (Zostera marina) meadows increases genetic diversity by promoting conditions for sexual reproduction of plants. Eelgrass allelic richness and genotypic diversity were, respectively, 30 and 6% higher in areas where recovering sea otter populations had been established for 20 to 30 years than in areas where they had been present <10 years or absent >100 years. The influence of sea otter occupancy on the aforementioned measures of genetic diversity was stronger than those of depth, temperature, latitude, or meadow size. Our findings reveal an underappreciated evolutionary process by which megafauna may promote genetic diversity and ecological resilience.

Of war, tusks, and genes.

Societal conflict leaves an evolutionary signature in wildlife.

Cross-continental comparison of parasite communities in a wide-ranging carnivore suggests associations with prey diversity and host density.

Parasites are integral to ecosystem functioning yet often overlooked. Improved understanding of host-parasite associations is important, particularly for wide-ranging species for which host range shifts and climate change could alter host-parasite interactions and their effects on ecosystem function.Among the most widely distributed mammals with diverse diets, gray wolves (Canis lupus) host parasites that are transmitted among canids and via prey species. Wolf-parasite associations may therefore influence the population dynamics and ecological functions of both wolves and their prey. Our goal was to identify large-scale processes that shape host-parasite interactions across populations, with the wolf as a model organism.By compiling data from various studies, we examined the fecal prevalence of gastrointestinal parasites in six wolf populations from two continents in relation to wolf density, diet diversity, and other ecological conditions.As expected, we found that the fecal prevalence of parasites transmitted directly to wolves via contact with other canids or their excreta was positively associated with wolf density. Contrary to our expectations, the fecal prevalence of parasites transmitted via prey was negatively associated with prey diversity. We also found that parasite communities reflected landscape characteristics and specific prey items available to wolves.Several parasite taxa identified in this study, including hookworms and coccidian protozoans, can cause morbidity and mortality in canids, especially in pups, or in combination with other stressors. The density-prevalence relationship for parasites with simple life cycles may reflect a regulatory role of gastrointestinal parasites on wolf populations. Our result that fecal prevalence of parasites was lower in wolves with more diverse diets could provide insight into the mechanisms by which biodiversity may regulate disease. A diverse suite of predator-prey interactions could regulate the effects of parasitism on prey populations and mitigate the transmission of infectious agents, including zoonoses, spread via trophic interactions.

Intrapopulation foraging niche variation between phenotypes and genotypes of Spirit bear populations.

Foraging niche variation within a species can contribute to the maintenance of phenotypic diversity. The multiniche model posits that phenotypes occupying different niches can contribute to the maintenance of balanced polymorphisms. Using coastal populations of black bears (Ursus americanus kermodei) from British Columbia, Canada, we examined potential foraging niche divergence between phenotypes (black and white "Spirit" coat color) and between genotypes (black-coated homozygote and heterozygous). We applied the Bayesian multivariate models, with biotracers of diet (δ13C and δ15N) together comprising the response variable, to draw inference about foraging niche variation. Variance-covariance matrices from multivariate linear mixed-effect models were visualized as the Bayesian standard ellipses in δ13C and δ15N isotopic space to assess potential seasonal and annual niche variation between phenotypes and genotypes. We did not detect a difference in annual isotopic foraging niche area in comparisons between genotypes or phenotypes. Consistent with previous field experimental and isotopic analyses, however, we found that white phenotype Spirit bears were modestly more enriched in δ15N during the fall foraging season, though with our modest sample sizes these results were not significant. Although also not statistically significant, variation in isotopic niches between genotypes revealed that heterozygotes were moderately more enriched in δ13C along hair segments grown during fall foraging compared with black-coated homozygotes. To the extent to which the pattern of elevated δ15N and δ13C may signal the consumption of salmon (Oncorhynchus spp.), as well as the influence of salmon consumption on reproductive fitness, these results suggest that black-coated heterozygotes could have a minor selective advantage in the fall compared with black-coated homozygotes. More broadly, our multivariate approach, coupled with knowledge of genetic variation underlying a polymorphic trait, provides new insight into the potential role of a multiniche mechanism in maintaining this rare morph of conservation priority in Canada's Great Bear Rainforest and could offer new understanding into polymorphisms in other systems.

Marine subsidy promotes spatial and dietary niche variation in an omnivore, the Keen's mouse (Peromyscus keeni).

Marine-derived resource subsidies can generate intrapopulation variation in the behaviors and diets of terrestrial consumers. How omnivores respond, given their multiple trophic interactions, is not well understood. We sampled mice (Peromyscus keeni) and their food sources at five sites on three islands of the Central Coast of British Columbia, Canada, to test predictions regarding variation in the spatial behavior and consumption of marine-subsidized foods among individuals. About 50% of detections (n = 27 recaptures) occurred at traps closest to shoreline (25 m), with capture frequencies declining significantly inland (up to 200 m). Stable isotope signatures (δ 13C and δ 15N), particularly δ 15N, in plant foods, forest arthropod prey, and mouse feces were significantly enriched near shorelines compared with inland, while δ 13C patterns were more variable. Bayesian isotope mixing models applied to isotope values in mouse hair indicated that over one-third (35-37%) of diet was comprised of beach-dwelling arthropods, a marine-derived food source. Males were more abundant near the shoreline than females and consumed more marine-derived prey, regardless of reproductive status or availability of other food sources. Our results identify how multiple pathways of marine nutrient transfer can subsidize terrestrial omnivores and how subsets of recipient populations can show variation in spatial and dietary response.

Large carnivore hunting and the social license to hunt.

The social license to operate framework considers how society grants or withholds informal permission for resource extractors to exploit publicly owned resources. We developed a modified model, which we refer to as the social license to hunt (SLH). In it we similarly consider hunters as operators, given that wildlife are legally considered public resources in North America and Europe. We applied the SLH model to examine the controversial hunting of large carnivores, which are frequently killed for trophies. Killing for trophies is widespread, but undertaken by a minority of hunters, and can pose threats to the SLH for trophy-seeking carnivore hunters and potentially beyond. Societal opposition to large carnivore hunting relates not only to conservation concerns but also to misalignment between killing for trophies and dominant public values and attitudes concerning the treatment of animals. We summarized cases related to the killing of grizzly bears (Ursus arctos), wolves (Canis lupus), and other large carnivores in Canada, the United States, and Europe to illustrate how opposition to large carnivore hunting, now expressed primarily on social media, can exert rapid and significant pressure on policy makers and politicians. Evidence of the potential for transformative change to wildlife management and conservation includes proposed and realized changes to legislation, business practice, and wildlife policy, including the banning of some large carnivore hunts. Given that policy is ultimately shaped by societal values and attitudes, research gaps include developing increased insight into public support of various hunting policies beyond that derived from monitoring of social media and public polling. Informed by increased evidence, the SLH model can provide a conceptual foundation for predicting the likelihood of transient versus enduring changes to wildlife conservation policy and practice for a wide variety of taxa and contexts.

Cacería de Grandes Carnívoros y la Licencia Social para Cazar Resumen El marco de trabajo de la licencia social para operar considera cómo la sociedad otorga o restringe permisos informales para que los extractores de recursos puedan explotar los recursos públicos. Desarrollamos un modelo modificado, al cual nos referimos como la licencia social para cazar (LSC). En este modelo consideramos a los cazadores como símiles de los operadores puesto que en América del Norte y en Europa a la fauna se le considera legalmente como recurso público. Aplicamos el modelo de la LSC en un análisis de la cacería controversial de grandes carnívoros, a los cuales con frecuencia se les caza para convertirlos en trofeos. La cacería para trofeos es común pero sólo la realiza una minoría de los cazadores y puede presentar una amenaza para la LSC para los cazadores que cazan carnívoros para trofeos e incluso para otros tipos de cazadores. La oposición social a la cacería de grandes carnívoros se relaciona no sólo con el interés de conservación sino también con la discordancia entre la caza para trofeos y las actitudes y valores públicos dominantes con respecto al trato hacia los animales. Resumimos algunos casos relacionados con la muerte de osos pardos (Ursus arctos), lobos (Canis lupus) y otros grandes carnívoros en Canadá, los Estados Unidos y Europa para mostrar cómo la oposición a la cacería de grandes carnívoros, hoy en día expresada principalmente en las redes sociales, puede ejercer una presión rápida y significativa sobre los políticos y los formuladores de políticas. La evidencia de un potencial de cambio transformador en el manejo y conservación de fauna incluye los cambios propuestos y realizados a la legislación, la práctica comercial y las políticas para la fauna, incluyendo la prohibición de la caza de algunos grandes carnívoros. Ya que las políticas están finalmente moldeadas por las actitudes y los valores sociales, las lagunas en la investigación incluyen el desarrollo de un conocimiento mejorado del respaldo público para varias políticas de cacería más allá del conocimiento derivado del monitoreo de las redes sociales y las encuestas públicas. Si se informa con mucha más evidencia, el modelo de la LSC puede proporcionar una base conceptual para predecir la probabilidad de los cambios transitorios versus los duraderos en las políticas y las prácticas de conservación de fauna para una gama amplia de taxones y contextos.

Automated facial recognition for wildlife that lack unique markings: A deep learning approach for brown bears.

Emerging technologies support a new era of applied wildlife research, generating data on scales from individuals to populations. Computer vision methods can process large datasets generated through image-based techniques by automating the detection and identification of species and individuals. With the exception of primates, however, there are no objective visual methods of individual identification for species that lack unique and consistent body markings. We apply deep learning approaches of facial recognition using object detection, landmark detection, a similarity comparison network, and an support vector machine-based classifier to identify individuals in a representative species, the brown bear Ursus arctos. Our open-source application, BearID, detects a bear's face in an image, rotates and extracts the face, creates an "embedding" for the face, and uses the embedding to classify the individual. We trained and tested the application using labeled images of 132 known individuals collected from British Columbia, Canada, and Alaska, USA. Based on 4,674 images, with an 80/20% split for training and testing, respectively, we achieved a facial detection (ability to find a face) average precision of 0.98 and an individual classification (ability to identify the individual) accuracy of 83.9%. BearID and its annotated source code provide a replicable methodology for applying deep learning methods of facial recognition applicable to many other species that lack distinguishing markings. Further analyses of performance should focus on the influence of certain parameters on recognition accuracy, such as age and body size. Combining BearID with camera trapping could facilitate fine-scale behavioral research such as individual spatiotemporal activity patterns, and a cost-effective method of population monitoring through mark-recapture studies, with implications for species and landscape conservation and management. Applications to practical conservation include identifying problem individuals in human-wildlife conflicts, and evaluating the intrapopulation variation in efficacy of conservation strategies, such as wildlife crossings.

Ancient dog diets on the Pacific Northwest Coast: zooarchaeological and stable isotope modelling evidence from Tseshaht territory and beyond.

Domestic dogs are frequently encountered in Indigenous archaeological sites on the Northwest Coast of North America. Although dogs depended on human communities for care and provisioning, archaeologists lack information about the specific foods dogs consumed. Previous research has used stable isotope analysis of dog diets for insight into human subsistence ('canine surrogacy' model) and identified considerable use of marine resources. Here, we use zooarchaeological data to develop and apply a Bayesian mixing model (MixSIAR) to estimate dietary composition from 14 domestic dogs and 13 potential prey taxa from four archaeological sites (2,900-300 BP) in Tseshaht First Nation territory on western Vancouver Island, British Columbia, Canada. Two candidate models that best match zooarchaeological data indicate dogs predominantly consumed salmon and forage fish (35-65%), followed by nearshore fish (4-40%), and marine mammals (2-30%). We compared these isotopic data to dogs across the Northwest Coast, which indicated a pronounced marine diet for Tseshaht dogs and, presumably, their human providers. These results are broadly consistent with the canine surrogacy model as well as help illuminate human participation in pre-industrial marine food webs and the long-term role of fisheries in Indigenous economies and lifeways.

Correction: Publication reform to safeguard wildlife from researcher harm.

[This corrects the article DOI: 10.1371/journal.pbio.3000193.].

Marine subsidies mediate patterns in avian island biogeography.

The classical theory of island biogeography, which predicts species richness using island area and isolation, has been expanded to include contributions from marine subsidies, i.e. subsidized island biogeography (SIB) theory. We tested the effects of marine subsidies on species diversity and population density on productive temperate islands, evaluating SIB predictions previously untested at comparable scales and subsidy levels. We found that the diversity of terrestrial breeding bird communities on 91 small islands (approx. 0.0001-3 km2) along the Central Coast of British Columbia, Canada were correlated most strongly with island area, but also with marine subsidies. Species richness increased and population density decreased with island area, but isolation had no measurable influence. Species richness was negatively correlated with marine subsidy, measured as forest-edge soil δ15N. Density, however, was higher on islands with higher marine subsidy, and a negative interaction between area and subsidy indicates that this effect is stronger on smaller islands, offering some support for SIB. Our study emphasizes how subsidies from the sea can shape diversity patterns on islands and can even exceed the importance of isolation in determining species richness and densities of terrestrial biota.

Trophy hunters pay more to target larger-bodied carnivores.

Hunters often target species that require resource investment disproportionate to associated nutritional rewards. Costly signalling theory provides a potential explanation, proposing that hunters target species that impose high costs (e.g. higher failure and injury risks, lower consumptive returns) because it signals an ability to absorb costly behaviour. If costly signalling is relevant to contemporary 'big game' hunters, we would expect hunters to pay higher prices to hunt taxa with higher perceived costs. Accordingly, we hypothesized that hunt prices would be higher for taxa that are larger-bodied, rarer, carnivorous, or described as dangerous or difficult to hunt. In a dataset on 721 guided hunts for 15 North American large mammals, prices listed online increased with body size in carnivores (from approximately $550 to $1800 USD/day across the observed range). This pattern suggests that elements of costly signals may persist among contemporary non-subsistence hunters. Persistence might simply relate to deception, given that signal honesty and fitness benefits are unlikely in such different conditions compared with ancestral environments in which hunting behaviour evolved. If larger-bodied carnivores are generally more desirable to hunters, then conservation and management strategies should consider not only the ecology of the hunted but also the motivations of hunters.