Wild canids and the ecological traps facing the climate change and deforestation in the Amazon Forest.

Ecological traps occur when species choose to settle in lower-quality habitats, even if this reduces their survival or productivity. This happens in situations of drastic environmental changes, resulting from anthropogenic pressures. In long term, this could mean the extinction of the species. We investigated the dynamics of occurrence and distribution of three canid species (Atelocynus microtis, Cerdocyon thous, and Spheotos venaticus) considering human threats to their habitats in the Amazon Rainforest. We analyzed the environmental thresholds for the occurrence of these species and related to the future projections of climatic niches for each one. All three species will be negatively affected by climate change in the future, with losses of up to 91% of the suitable area of occurrence in the Brazilian Amazon. A. microtis appear to be more forest-dependent and must rely on the goodwill of decision-makers to be maintained in the future. For C. thous and S. venaticus, climatic variables and those associated with anthropogenic disturbances that modulate their niches today may not act the same way in the future. Even though C. thous is least dependent on the Amazon Forest; this species may be affected in the future due to the ecological traps. S. venaticus, can also undergo the same process, but perhaps more drastically due to the lower ecological plasticity of this species compared to C. thous. Our results suggest that the ecological traps may put these two species at risk in the future. Using the canid species as a model, we had the opportunity to investigate these ecological effects that can affect a large part of the Amazonian fauna in the current scenario. Considering the high degree of environmental degradation and deforestation in the Amazon Rainforest, the theory of ecological traps must be discussed at the same level as the habitat loss, considering the strategies for preserving the Amazon biodiversity.

Insights into bear evolution from a Pleistocene polar bear genome.

The polar bear (Ursus maritimus) has become a symbol of the threat to biodiversity from climate change. Understanding polar bear evolutionary history may provide insights into apex carnivore responses and prospects during periods of extreme environmental perturbations. In recent years, genomic studies have examined bear speciation and population history, including evidence for ancient admixture between polar bears and brown bears (Ursus arctos). Here, we extend our earlier studies of a 130,000- to 115,000-y-old polar bear from the Svalbard Archipelago using a 10× coverage genome sequence and 10 new genomes of polar and brown bears from contemporary zones of overlap in northern Alaska. We demonstrate a dramatic decline in effective population size for this ancient polar bear's lineage, followed by a modest increase just before its demise. A slightly higher genetic diversity in the ancient polar bear suggests a severe genetic erosion over a prolonged bottleneck in modern polar bears. Statistical fitting of data to alternative admixture graph scenarios favors at least one ancient introgression event from brown bears into the ancestor of polar bears, possibly dating back over 150,000 y. Gene flow was likely bidirectional, but allelic transfer from brown into polar bear is the strongest detected signal, which contrasts with other published work. These findings may have implications for our understanding of climate change impacts: Polar bears, a specialist Arctic lineage, may not only have undergone severe genetic bottlenecks but also been the recipient of generalist, boreal genetic variants from brown bears during critical phases of Northern Hemisphere glacial oscillations.

Glacial ice supports a distinct and undocumented polar bear subpopulation persisting in late 21st-century sea-ice conditions.

Polar bears are susceptible to climate warming because of their dependence on sea ice, which is declining rapidly. We present the first evidence for a genetically distinct and functionally isolated group of polar bears in Southeast Greenland. These bears occupy sea-ice conditions resembling those projected for the High Arctic in the late 21st century, with an annual ice-free period that is >100 days longer than the estimated fasting threshold for the species. Whereas polar bears in most of the Arctic depend on annual sea ice to catch seals, Southeast Greenland bears have a year-round hunting platform in the form of freshwater glacial mélange. This suggests that marine-terminating glaciers, although of limited availability, may serve as previously unrecognized climate refugia. Conservation of Southeast Greenland polar bears, which meet criteria for recognition as the world's 20th polar bear subpopulation, is necessary to preserve the genetic diversity and evolutionary potential of the species.

High genomic diversity in the endangered East Greenland Svalbard Barents Sea stock of bowhead whales (Balaena mysticetus).

The East Greenland-Svalbard-Barents Sea (EGSB) bowhead whale stock (Balaena mysticetus) was hunted to near extinction and remains Endangered on the International Union of Conservation of Nature Red List. The intense, temporally extensive hunting pressure may have left the population vulnerable to other perturbations, such as environmental change. However, the lack of genomic baseline data renders it difficult to evaluate the impacts of various potential stressors on this stock. Twelve EGSB bowhead whales sampled in 2017/2018 were re-sequenced and mapped to a previously published draft genome. All individuals were unrelated and void of significant signs of inbreeding, with similar observed and expected homo- and heterozygosity levels. Despite the small population size, mean autosome-wide heterozygosity was 0.00102, which is higher than that of most mammals for which comparable estimates are calculated using the same parameters, and three times higher than a conspecific individual from the Eastern-Canada-West-Greenland bowhead whale stock. Demographic history analyses indicated a continual decrease of Ne from ca. 1.5 million to ca. 250,000 years ago, followed by a slight increase until ca. 100,000 years ago, followed by a rapid decrease in Ne between 50,000 and 10,000 years ago. These estimates are lower than previously suggested based on mitochondrial DNA, but suggested demographic patterns over time are similar.

A risk assessment review of mercury exposure in Arctic marine and terrestrial mammals.

There has been a considerable number of reports on Hg concentrations in Arctic mammals since the last Arctic Monitoring and Assessment Programme (AMAP) effort to review biological effects of the exposure to mercury (Hg) in Arctic biota in 2010 and 2018. Here, we provide an update on the state of the knowledge of health risk associated with Hg concentrations in Arctic marine and terrestrial mammal species. Using available population-specific data post-2000, our ultimate goal is to provide an updated evidence-based estimate of the risk for adverse health effects from Hg exposure in Arctic mammal species at the individual and population level. Tissue residues of Hg in 13 species across the Arctic were classified into five risk categories (from No risk to Severe risk) based on critical tissue concentrations derived from experimental studies on harp seals and mink. Exposure to Hg lead to low or no risk for health effects in most populations of marine and terrestrial mammals, however, subpopulations of polar bears, pilot whales, narwhals, beluga and hooded seals are highly exposed in geographic hotspots raising concern for Hg-induced toxicological effects. About 6% of a total of 3500 individuals, across different marine mammal species, age groups and regions, are at high or severe risk of health effects from Hg exposure. The corresponding figure for the 12 terrestrial species, regions and age groups was as low as 0.3% of a total of 731 individuals analyzed for their Hg loads. Temporal analyses indicated that the proportion of polar bears at low or moderate risk has increased in East/West Greenland and Western Hudson Bay, respectively. However, there remain numerous knowledge gaps to improve risk assessments of Hg exposure in Arctic mammalian species, including the establishment of improved concentration thresholds and upscaling to the assessment of population-level effects.

An on-ice aerial survey of the Kane Basin polar bear (Ursus maritimus) subpopulation.

There is an imminent need to collect information on distribution and abundance of polar bears (Ursus maritimus) to understand how they are affected by the ongoing decrease in Arctic sea ice. The Kane Basin (KB) subpopulation is a group of high-latitude polar bears that ranges between High Arctic Canada and NW Greenland around and north of the North Water polynya (NOW). We conducted a line transect distance sampling aerial survey of KB polar bears during 28 April-12 May 2014. A total of 4160 linear kilometers were flown in a helicopter over fast ice in the fjords and over offshore pack ice between 76° 50' and 80° N'. Using a mark-recapture distance sampling protocol, the estimated abundance was 190 bears (95% lognormal CI: 87-411; CV 39%). This estimate is likely negatively biased to an unknown degree because the offshore sectors of the NOW with much open water were not surveyed because of logistical and safety reasons. Our study demonstrated that aerial surveys may be a feasible method for obtaining abundance estimates for small subpopulations of polar bears.

Strong and lasting impacts of past global warming on baleen whales and their prey.

Global warming is affecting the population dynamics and trophic interactions across a wide range of ecosystems and habitats. Translating these real-time effects into their long-term consequences remains a challenge. The rapid and extreme warming period that occurred after the Last Glacial Maximum (LGM) during the Pleistocene-Holocene transition (7-12 thousand years ago) provides an opportunity to gain insights into the long-term responses of natural populations to periods with global warming. The effects of this post-LGM warming period have been assessed in many terrestrial taxa, whereas insights into the impacts of rapid global warming on marine taxa remain limited, especially for megafauna. In order to understand how large-scale climate fluctuations during the post-LGM affected baleen whales and their prey, we conducted an extensive, large-scale analysis of the long-term effects of the post-LGM warming on abundance and inter-ocean connectivity in eight baleen whale and seven prey (fish and invertebrates) species across the Southern and the North Atlantic Ocean; two ocean basins that differ in key oceanographic features. The analysis was based upon 7032 mitochondrial DNA sequences as well as genome-wide DNA sequence variation in 100 individuals. The estimated temporal changes in genetic diversity during the last 30,000 years indicated that most baleen whale populations underwent post-LGM expansions in both ocean basins. The increase in baleen whale abundance during the Holocene was associated with simultaneous changes in their prey and climate. Highly correlated, synchronized and exponential increases in abundance in both baleen whales and their prey in the Southern Ocean were indicative of a dramatic increase in ocean productivity. In contrast, the demographic fluctuations observed in baleen whales and their prey in the North Atlantic Ocean were subtle, varying across taxa and time. Perhaps most important was the observation that the ocean-wide expansions and decreases in abundance that were initiated by the post-LGM global warming, continued for millennia after global temperatures stabilized, reflecting persistent, long-lasting impacts of global warming on marine fauna.

Microstructure, elemental composition and mechanical properties of enamel and dentine in the polar bear Ursus maritimus.

OBJECTIVE: To investigate the microstructure, elemental composition and mechanical properties of polar bear teeth. DESIGN: Incisors, canines and fourth premolar teeth of two subadult male museum specimens were analysed. Teeth were measured, photographed, embedded in Epoxy resin, sectioned, polished and etched for scanning electron microscope (SEM) imaging, elemental composition and nanomechanical testing analyses. RESULTS: The thickness of enamel ranged from 350-430 µm in canines, 220-330 µm in incisors and 320-510 µm in premolars. SEM images showed distinct transversely-oriented undulating Hunter Schreger bands from the enamel-dentine junction (EDJ) to the outer enamel surface. Enamel prisms had a hexagonal shape, with open prism sheaths. Prisms measured 6-8 µm in diameter. The EDJ was straight with no evidence of scalloping. Larger tubules adjacent to the EDJ were observed in the mantle dentine zone. Enamel Hardness and Elastic modulus values were higher in premolars (6.9 GPa and 269 GPa), followed by canines (6.5 GPa and 230 GPa) and incisors (4.9 GPa and 187 GPa). Dentine Hardness and Elastic modulus values were higher in canines. CaO and P2O5 were the components with higher oxide weight percentage in both enamel and dentine. CONCLUSIONS: Understanding the microstructure, elemental composition and mechanical properties of polar bear teeth can help elucidate the biology and functional morphology of this globally threatened species and could be used as a proxy for studies with fossil ursids.

Sea ice reduction drives genetic differentiation among Barents Sea polar bears.

Loss of Arctic sea ice owing to climate change is predicted to reduce both genetic diversity and gene flow in ice-dependent species, with potentially negative consequences for their long-term viability. Here, we tested for the population-genetic impacts of reduced sea ice cover on the polar bear (Ursus maritimus) sampled across two decades (1995-2016) from the Svalbard Archipelago, Norway, an area that is affected by rapid sea ice loss in the Arctic Barents Sea. We analysed genetic variation at 22 microsatellite loci for 626 polar bears from four sampling areas within the archipelago. Our results revealed a 3-10% loss of genetic diversity across the study period, accompanied by a near 200% increase in genetic differentiation across regions. These effects may best be explained by a decrease in gene flow caused by habitat fragmentation owing to the loss of sea ice coverage, resulting in increased inbreeding of local polar bears within the focal sampling areas in the Svalbard Archipelago. This study illustrates the importance of genetic monitoring for developing adaptive management strategies for polar bears and other ice-dependent species.

Modeling the demography of species providing extended parental care: A capture-recapture multievent model with a case study on polar bears (Ursus maritimus).

In species providing extended parental care, one or both parents care for altricial young over a period including more than one breeding season. We expect large parental investment and long-term dependency within family units to cause high variability in life trajectories among individuals with complex consequences at the population level. So far, models for estimating demographic parameters in free-ranging animal populations mostly ignore extended parental care, thereby limiting our understanding of its consequences on parents and offspring life histories.We designed a capture-recapture multievent model for studying the demography of species providing extended parental care. It handles statistical multiple-year dependency among individual demographic parameters grouped within family units, variable litter size, and uncertainty on the timing at offspring independence. It allows for the evaluation of trade-offs among demographic parameters, the influence of past reproductive history on the caring parent's survival status, breeding probability, and litter size probability, while accounting for imperfect detection of family units. We assess the model performance using simulated data and illustrate its use with a long-term dataset collected on the Svalbard polar bears (Ursus maritimus).Our model performed well in terms of bias and mean square error and in estimating demographic parameters in all simulated scenarios, both when offspring departure probability from the family unit occurred at a constant rate or varied during the field season depending on the date of capture. For the polar bear case study, we provide estimates of adult and dependent offspring survival rates, breeding probability, and litter size probability. Results showed that the outcome of the previous reproduction influenced breeding probability.Overall, our results show the importance of accounting for i) the multiple-year statistical dependency within family units, ii) uncertainty on the timing at offspring independence, and iii) past reproductive history of the caring parent. If ignored, estimates obtained for breeding probability, litter size, and survival can be biased. This is of interest in terms of conservation because species providing extended parental care are often long-living mammals vulnerable or threatened with extinction.

Genomes of Pleistocene Siberian Wolves Uncover Multiple Extinct Wolf Lineages.

Extant Canis lupus genetic diversity can be grouped into three phylogenetically distinct clades: Eurasian and American wolves and domestic dogs.1 Genetic studies have suggested these groups trace their origins to a wolf population that expanded during the last glacial maximum (LGM)1-3 and replaced local wolf populations.4 Moreover, ancient genomes from the Yana basin and the Taimyr peninsula provided evidence of at least one extinct wolf lineage that dwelled in Siberia during the Pleistocene.35 Previous studies have suggested that Pleistocene Siberian canids can be classified into two groups based on cranial morphology. Wolves in the first group are most similar to present-day populations, although those in the second group possess intermediate features between dogs and wolves.67 However, whether this morphological classification represents distinct genetic groups remains unknown. To investigate this question and the relationships between Pleistocene canids, present-day wolves, and dogs, we resequenced the genomes of four Pleistocene canids from Northeast Siberia dated between >50 and 14 ka old, including samples from the two morphological categories. We found these specimens cluster with the two previously sequenced Pleistocene wolves, which are genetically more similar to Eurasian wolves. Our results show that, though the four specimens represent extinct wolf lineages, they do not form a monophyletic group. Instead, each Pleistocene Siberian canid branched off the lineage that gave rise to present-day wolves and dogs. Finally, our results suggest the two previously described morphological groups could represent independent lineages similarly related to present-day wolves and dogs.

Transient benefits of climate change for a high-Arctic polar bear (Ursus maritimus) subpopulation.

Kane Basin (KB) is one of the world's most northerly polar bear (Ursus maritimus) subpopulations, where bears have historically inhabited a mix of thick multiyear and annual sea ice year-round. Currently, KB is transitioning to a seasonally ice-free region because of climate change. This ecological shift has been hypothesized to benefit polar bears in the near-term due to thinner ice with increased biological production, although this has not been demonstrated empirically. We assess sea-ice changes in KB together with changes in polar bear movements, seasonal ranges, body condition, and reproductive metrics obtained from capture-recapture (physical and genetic) and satellite telemetry studies during two study periods (1993-1997 and 2012-2016). The annual cycle of sea-ice habitat in KB shifted from a year-round ice platform (~50% coverage in summer) in the 1990s to nearly complete melt-out in summer (<5% coverage) in the 2010s. The mean duration between sea-ice retreat and advance increased from 109 to 160 days (p = .004). Between the 1990s and 2010s, adult female (AF) seasonal ranges more than doubled in spring and summer and were significantly larger in all months. Body condition scores improved for all ages and both sexes. Mean litter sizes of cubs-of-the-year (C0s) and yearlings (C1s), and the number of C1s per AF, did not change between decades. The date of spring sea-ice retreat in the previous year was positively correlated with C1 litter size, suggesting smaller litters following years with earlier sea-ice breakup. Our study provides evidence for range expansion, improved body condition, and stable reproductive performance in the KB polar bear subpopulation. These changes, together with a likely increasing subpopulation abundance, may reflect the shift from thick, multiyear ice to thinner, seasonal ice with higher biological productivity. The duration of these benefits is unknown because, under unmitigated climate change, continued sea-ice loss is expected to eventually have negative demographic and ecological effects on all polar bears.

Arctic-adapted dogs emerged at the Pleistocene-Holocene transition.

Although sled dogs are one of the most specialized groups of dogs, their origin and evolution has received much less attention than many other dog groups. We applied a genomic approach to investigate their spatiotemporal emergence by sequencing the genomes of 10 modern Greenland sled dogs, an ~9500-year-old Siberian dog associated with archaeological evidence for sled technology, and an ~33,000-year-old Siberian wolf. We found noteworthy genetic similarity between the ancient dog and modern sled dogs. We detected gene flow from Pleistocene Siberian wolves, but not modern American wolves, to present-day sled dogs. The results indicate that the major ancestry of modern sled dogs traces back to Siberia, where sled dog-specific haplotypes of genes that potentially relate to Arctic adaptation were established by 9500 years ago.

Two Decades of Mercury Concentrations in Barents Sea Polar Bears (Ursus maritimus) in Relation to Dietary Carbon, Sulfur, and Nitrogen.

Temporal trends of total mercury (THg) were examined in female polar bear (Ursus maritimus) hair (n = 199) from the Barents Sea in 1995-2016. In addition, hair values of stable isotopes (n = 190-197) of carbon (δ13C), sulfur (δ34S), and nitrogen (δ15N) and information on breeding status, body condition, and age were obtained. Stable isotope values of carbon and sulfur reflect dietary source (e.g., marine vs terrestrial) and the nitrogen trophic level. Values for δ13C and δ34S declined by -1.62 and -1.18‰ over the time of the study period, respectively, while values for δ15N showed no trend. Total Hg concentrations were positively related to both δ13C and δ34S. Yearly median THg concentrations ranged from 1.61 to 2.75 µg/g and increased nonlinearly by 0.86 µg/g in total over the study. Correcting THg concentrations for stable isotope values of carbon and sulfur and additionally breeding status and age slightly accelerated the increase in THg concentrations; however, confidence intervals of the raw THg trend and the corrected THg trend had substantial overlap. The rise in THg concentrations in the polar bear food web was possibly related to climate-related re-emissions of previously stored Hg from thawing sea-ice, glaciers, and permafrost.

Environmental factors influencing the abundance of four species of threatened mammals in degraded habitats in the eastern Brazilian Amazon.

On the latest 60 years the degradation and fragmentation of native habitats have been modifying the landscape in the eastern Brazilian Amazon. The adaptive plasticity of an organism has been crucial for its long-term survival and success in these novel ecosystems. In this study, we investigated the response of four endangered species of large terrestrial mammals to the variations in the quality of their original habitats, in a context of high anthropogenic pressure. The distribution of the Myrmecophaga tridactyla (Giant anteater), Priodontes maximus (Giant armadillo), Tapirus terrestris (Lowland tapir) and Tayassu pecari (White-lipped peccary) in all sampled habitats suggests their tolerance to degradation. However, the survival ability of each species in the different habitats was not the same. Among the four species, T. pecari seems to be the one with the least ability to survive in more altered environments. The positive influence of the anthropogenically altered habitats on abundances of three of the four species studied, as observed at the regeneration areas, can be considered as a potential indication of the ecological trap phenomenon. This study reinforces the importance of the forest remnants for the survival of endangered mammal species, in regions of high anthropogenic pressure, as in the eastern Brazilian Amazon.

Interrelated ecological impacts of climate change on an apex predator.

Climate change has broad ecological implications for species that rely on sensitive habitats. For some top predators, loss of habitat is expected to lead to cascading behavioral, nutritional, and reproductive changes that ultimately accelerate population declines. In the case of the polar bear (Ursus maritimus), declining Arctic sea ice reduces access to prey and lengthens seasonal fasting periods. We used a novel combination of physical capture, biopsy darting, and visual aerial observation data to project reproductive performance for polar bears by linking sea ice loss to changes in habitat use, body condition (i.e., fatness), and cub production. Satellite telemetry data from 43 (1991-1997) and 38 (2009-2015) adult female polar bears in the Baffin Bay subpopulation showed that bears now spend an additional 30 d on land (90 d in total) in the 2000s compared to the 1990s, a change closely correlated with changes in spring sea ice breakup and fall sea ice formation. Body condition declined for all sex, age, and reproductive classes and was positively correlated with sea ice availability in the current and previous year. Furthermore, cub litter size was positively correlated with maternal condition and spring breakup date (i.e., later breakup leading to larger litters), and negatively correlated with the duration of the ice-free period (i.e., longer ice-free periods leading to smaller litters). Based on these relationships, we projected reproductive performance three polar bear generations into the future (approximately 35 yr). Results indicate that two-cub litters, previously the norm, could largely disappear from Baffin Bay as sea ice loss continues. Our findings demonstrate how concurrent analysis of multiple data types collected over long periods from polar bears can provide a mechanistic understanding of the ecological implications of climate change. This information is needed for long-term conservation planning, which includes quantitative harvest risk assessments that incorporate estimated or assumed trends in future environmental carrying capacity.

Specialized sledge dogs accompanied Inuit dispersal across the North American Arctic.

Domestic dogs have been central to life in the North American Arctic for millennia. The ancestors of the Inuit were the first to introduce the widespread usage of dog sledge transportation technology to the Americas, but whether the Inuit adopted local Palaeo-Inuit dogs or introduced a new dog population to the region remains unknown. To test these hypotheses, we generated mitochondrial DNA and geometric morphometric data of skull and dental elements from a total of 922 North American Arctic dogs and wolves spanning over 4500 years. Our analyses revealed that dogs from Inuit sites dating from 2000 BP possess morphological and genetic signatures that distinguish them from earlier Palaeo-Inuit dogs, and identified a novel mitochondrial clade in eastern Siberia and Alaska. The genetic legacy of these Inuit dogs survives today in modern Arctic sledge dogs despite phenotypic differences between archaeological and modern Arctic dogs. Together, our data reveal that Inuit dogs derive from a secondary pre-contact migration of dogs distinct from Palaeo-Inuit dogs, and probably aided the Inuit expansion across the North American Arctic beginning around 1000 BP.

How many cubs can a mum nurse? Maternal age and size influence litter size in polar bears.

Life-history theory predicts that females' age and size affect the level of maternal investment in current reproduction, balanced against the future reproductive effort, maintenance and survival. Using long-term (30 years) individual data on 193 female polar bears ( Ursus maritimus), we assessed age- and size-specific variation on litter size. Litter size varied with maternal age, younger females had higher chances of losing a cub during their first months of life. Results suggest an improvement in reproductive abilities early in life due to experience with subsequent reproductive senescence. Litter size increased with maternal size, indicating that size may reflect individual quality. We also found an optimum in the probability of having twins, suggesting stabilizing selection on female body size. Heterogeneity was observed among the largest females, suggesting that large size comes at a cost.

Mitochondrial genomes of ancient bowhead whales (Balaena mysticetus) from Svalbard.

The endangered Spitsbergen stock of bowhead whales (Balaena mysticetus) has once been large with up to estimated 100,000 individuals. Genetic diversity of the extant Spitsbergen stock is unknown. We present 10 complete mitochondrial genomes of heterochronous ancient bowhead whale samples from Svalbard (14C age estimate range: 215-8885 years) obtained via NGS of total genomic DNA extracts. The ten mitogenomes differed by nucleotide substitutions and/or indels, and there was a total of 160 variable positions. The average nucleotide diversity was π = 0.0029. There was no statistically significant correlation between genetic divergence and time.