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At least 559 records · Page 31Linked to original sources
USGS2014

Serologic evidence of influenza A(H1N1)pdm09 virus in northern sea otters

Sporadic epizootics of pneumonia among marine mammals have been associated with multiple animal-origin influenza A virus subtypes (1–6); seals are the only known nonhuman host for influenza B viruses (7). Recently, we reported serologic evidence of influenza A virus infection in free-ranging northern sea otters ( Enhydra lutris kenyoni ) captured off the coast of Washington, USA, in August 2011 (8). To investigate further which influenza A virus subtype infected these otters, we tested serum samples from these otters by ELISA for antibody-binding activity against 12 recombinant hemagglutinins (rHAs) from 7 influenza A hemagglutinin (HA) subtypes and 2 lineages of influenza B virus (Technical Appendix Table 1). Estimated ages for the otters were 2–19 years (Technical Appendix Table 2); we also tested archived serum samples from sea otters of similar ages collected from a study conducted during 2001–2002 along the Washington coast (9).

Washington↗
USGS1973

Bird collections in the United States and Canada

This survey was initiated in 1966 as a project of a subcommittee of the A.O.U.'s Committee on Research, at that time chaired by Paul H. Baldwin. The subcommittee consisted of the authors and Ralph J. Raitt. In 1968 the project was separated from the Committee on Research and the temporary Committee on Collections was established, with the present authors as its members. This paper is the final report of the committee. In the past, many studies utilizing museum materials have been handicapped by ignorance of the existence of potentially important specimens. We hoped, by means of this survey, to enable future workers to take full advantage of all available material. The objectives of the survey were to determine the locations of collections of ornithological material with research potential, particularly skins, skeletons, fluid-preserved specimens, eggs, and nests; to assess the sizes and particular geographic or systematic strengths of the various collections; to locate former private collections; to learn what collections include holotypes, and who is responsible for the collections. These basic points are generally well-known for the larger institutions that specialize in maintaining research collections, but not for many smaller collections containing valuable material. The survey was inspired by and patterned after a series made of mammal collections (see Anderson et al. 1963, J. Mammal. 44: 471-500).

The Auk↗
USGS2011

Evaluating gull diets: A comparison of conventional methods and stable isotope analysis

Samples such as regurgitated pellets and food remains have traditionally been used in studies of bird diets, but these can produce biased estimates depending on the digestibility of different foods. Stable isotope analysis has been developed as a method for assessing bird diets that is not biased by digestibility. These two methods may provide complementary or conflicting information on diets of birds, but are rarely compared directly. We analyzed carbon and nitrogen stable isotope ratios of feathers of Glaucous Gull ( Larus hyperboreus) chicks from eight breeding colonies in northern Alaska, and used a Bayesian mixing model to generate a probability distribution for the contribution of each food group to diets. We compared these model results with probability distributions from conventional diet samples (pellets and food remains) from the same colonies and time periods. Relative to the stable isotope estimates, conventional analysis often overestimated the contributions of birds and small mammals to gull diets and often underestimated the contributions of fish and zooplankton. Both methods gave similar estimates for the contributions of scavenged caribou, miscellaneous marine foods, and garbage to diets. Pellets and food remains therefore may be useful for assessing the importance of garbage relative to certain other foods in diets of gulls and similar birds, but are clearly inappropriate for estimating the potential impact of gulls on birds, small mammals, or fish. However, conventional samples provide more species-level information than stable isotope analysis, so a combined approach would be most useful for diet analysis and assessing a predator's impact on particular prey groups.

Journal of Field Ornithology↗
USGS2023

Does coat colour influence survival? A test in a cyclic population of snowshoe hares

Some mammal species inhabiting high-latitude biomes have evolved a seasonal moulting pattern that improves camouflage via white coats in winter and brown coats in summer. In many high-latitude and high-altitude areas, the duration and depth of snow cover has been substantially reduced in the last five decades. This reduction in depth and duration of snow cover may create a mismatch between coat colour and colour of the background environment, and potentially reduce the survival rate of species that depend on crypsis. We used long-term (1977–2020) field data and capture–mark–recapture models to test the hypothesis that whiteness of the coat influences winter apparent survival in a cyclic population of snowshoe hares ( Lepus americanus ) at Kluane, Yukon, Canada. Whiteness of the snowshoe hare coat in autumn declined during this study, and snowshoe hares with a greater proportion of whiteness in their coats in autumn survived better during winter. However, whiteness of the coat in spring did not affect subsequent summer survival. These results are consistent with the hypothesis that the timing of coat colour change in autumn can reduce overwinter survival. Because declines in cyclic snowshoe hare populations are strongly affected by low winter survival, the timing of coat colour change may adversely affect snowshoe hare population dynamics as climate change continues.

Proceedings of the Royal Society of London Ser B.↗
USGS2018

Adaptive population divergence and directional gene flow across steep elevational gradients in a climate‐sensitive mammal

The American pika is a thermally sensitive, alpine lagomorph species. Recent climate-associated population extirpations and genetic signatures of reduced population sizes range-wide indicate the viability of this species is sensitive to climate change. To test for potential adaptive responses to climate stress, we sampled pikas along two elevational gradients (each ~470 to 1640 m) and employed three outlier detection methods, BAYESCAN, LFMM, and BAYPASS, to scan for genotype-environment associations in samples genotyped at 30,763 SNP loci. We resolved 173 loci with robust evidence of natural selection detected by either two independent analyses or replicated in both transects. A BLASTN search of these outlier loci revealed several genes associated with metabolic function and oxygen transport, indicating natural selection from thermal stress and hypoxia. We also found evidence of directional gene flow primarily downslope from large high-elevation populations and reduced gene flow at outlier loci, a pattern suggesting potential impediments to the upward elevational movement of adaptive alleles in response to contemporary climate change. Finally, we documented evidence of reduced genetic diversity associated the south-facing transect and an increase in corticosterone stress levels associated with inbreeding. This study suggests the American pika is already undergoing climate-associated natural selection at multiple genomic regions. Further analysis is needed to determine if the rate of climate adaptation in the American pika and other thermally sensitive species will be able to keep pace with rapidly changing climate conditions.

Washington↗
USGS2012

Long-distance swimming by polar bears (Ursus maritimus) of the southern Beaufort Sea during years of extensive open water

Polar bears ( Ursus maritimus Phipps, 1774) depend on sea ice for catching marine mammal prey. Recent sea-ice declines have been linked to reductions in body condition, survival, and population size. Reduced foraging opportunity is hypothesized to be the primary cause of sea-ice-linked declines, but the costs of travel through a deteriorated sea-ice environment also may be a factor. We used movement data from 52 adult female polar bears wearing Global Positioning System (GPS) collars, including some with dependent young, to document long-distance swimming (>50 km) by polar bears in the southern Beaufort and Chukchi seas. During 6 years (2004-2009), we identified 50 long-distance swims by 20 bears. Swim duration and distance ranged from 0.7 to 9.7 days (mean = 3.4 days) and 53.7 to 687.1 km (mean = 154.2 km), respectively. Frequency of swimming appeared to increase over the course of the study. We show that adult female polar bears and their cubs are capable of swimming long distances during periods when extensive areas of open water are present. However, long-distance swimming appears to have higher energetic demands than moving over sea ice. Our observations suggest long-distance swimming is a behavioral response to declining summer sea-ice conditions.

Canadian Journal of Zoology↗
USGS2009

Transient dwarfism of soil fauna during the Paleocene-Eocene Thermal Maximum

Soil organisms, as recorded by trace fossils in paleosols of the Willwood Formation, Wyoming, show significant body-size reductions and increased abundances during the Paleocene-Eocene Thermal Maximum (PETM). Paleobotanical, paleopedologic, and oxygen isotope studies indicate high temperatures during the PETM and sharp declines in precipitation compared with late Paleocene estimates. Insect and oligochaete burrows increase in abundance during the PETM, suggesting longer periods of soil development and improved drainage conditions. Crayfish burrows and molluscan body fossils, abundant below and above the PETM interval, are significantly less abundant during the PETM, likely because of drier floodplain conditions and lower water tables. Burrow diameters of the most abundant ichnofossils are 30-46% smaller within the PETM interval. As burrow size is a proxy for body size, significant reductions in burrow diameter suggest that their tracemakers were smaller bodied. Smaller body sizes may have resulted from higher subsurface temperatures, lower soil moisture conditions, or nutritionally deficient vegetation in the high-CO 2 atmosphere inferred for the PETM. Smaller soil fauna co-occur with dwarf mammal taxa during the PETM; thus, a common forcing mechanism may have selected for small size in both above- and below-ground terrestrial communities. We predict that soil fauna have already shown reductions in size over the last 150 years of increased atmospheric CO 2 and surface temperatures or that they will exhibit this pattern over the next century. We retrodict also that soil fauna across the Permian-Triassic and Triassic-Jurassic boundary events show significant size decreases because of similar forcing mechanisms driven by rapid global warming.

Proceedings of the National Academy of Sciences of↗
USGS2003

Seabird, fisheries, marine mammal, and oceanographic investigations around Kasatochi, Koniuji, and Ulak Islands, August 1996 (SMMOCI 96-3)

Although islands in the Aleutians are known to support some of the highest densities of seabirds in the world, their remoteness has limited systematic research on the at-sea distribution of seabirds near these colonies. Kasatochi, Koniuji, and Ulak islands, in the central Aleutian Islands, together comprise one of nine ecological sites monitored once every 5 years on an annual rotation since 1996 by the Alaska Maritime National Wildlife Refuge (AMNWR). To supplement annual colony monitoring and examine seabird distribution away from colony sites, the AMNWR personnel in conjunction with U.S. Geological Survey (USGS) researchers, conducted a pelagic survey of the waters around these 3 islands in 1996. Previous research in this area has focused on the seabird colony sites located on Kasatochi, Koniuji, and Ulak islands. Although boat-based circumnavigations have been used to evaluate colony populations (Early et al. 1981; Bailey and Trapp 1986; Byrd and Williams 1994; Byrd 1995a, 1995b), wide ranging pelagic surveys to examine foraging patterns had not previously been conducted near the islands. The goal of this survey was to examine foraging patterns of the seabirds nesting in the study area and identify factors that may explain seabird distribution patterns.

Alaska↗
USGS2010

Distribution of the non-native gastropod Melanoides tuberculatus in Biscayne National Park, Florida

Introduction Melanoides tuberculatus (fig. 1), a gastropod that is not native to South Florida, was identified in Biscayne National Park (BNP) while researchers from the U.S. Geological Survey were conducting other studies around the Black Point canals in the summer of 2003. A study to determine the distribution, genetics, and salinity tolerance of this freshwater species began in 2004. For park managers and the recreational users of BNP, the presence of Melanoides tuberculatus is cause for concern because it is the intermediate host for several trematode parasites that affect humans and animals in multiple ways: Human health concerns include parasites (trematode worms) that affect the lung (Paragonimus westermani) and the liver ( Clonorchis sinensis , and Opisthorchis sp. ). Skin irritations and lesions can also be caused by trematodes that normally infect other species. Animal health concerns include parasites that affect the eyes of waterfowl ( Philophthalmus megalurus ), a trematode that burrows into the cartilage of fish and can lead to death ( Centrocestus formosanus ), and a trematode that infects the muscle tissue of fish and causes multiple abnormalities ( Haplorchis sp. ). When parasite-infected fish or crustaceans are eaten by birds or mammals, the next stage of the life cycle is in place (fig. 2). Native snail species concerns include the potential displacement of invertebrate species that make up the natural nearshore benthic communities in BNP. M. tuberculatus has very high reproductive rates, reproduces via parthenogenesis, and is live bearing, factors which increase the survivability of the offspring and increase competition for limited resources. These snails are considered to be freshwater animals in their native habitat of Southeast Asia. However, they have been collected in BNP in both estuarine and marine waters along the western margins of BNP and, as far as 1.7 kilometers (km) from shore at the Black Point canal inflow into Biscayne Bay (383 live per square meter (/m 2 ). In BNP, M. tuberculatus is a benthic inhabitant grazing on micro algal components at the sediment surface. A documented population with as many as 23,000/m 2 was observed at Snapper Creek, near Coral Gables, FL (Roessler and others, 1977), north of BNP.

Florida↗
USGS2002

Polar bear management in Alaska 1997-2000

Since the Twelfth Working Meeting of the IUCN/SSC Polar Bear Specialist Group in 1997, a number of changes in the management of polar bears have occurred in Alaska. On October 16, 2000, the governments of the United States and the Russian Federation signed the “Agreement on the Conservation and Management of the Alaska-Chukotka Polar Bear Population.” This agreement provides substantial benefits for the effective conservation of polar bears shared between the U.S. and Russia. It will require enactment of enabling legislation by the U.S. Congress and other steps by Russia before the agreement has the force of law. A copy of the agreement is included as Appendix 1 to this report. Also, during this period, regulations were developed to implement 1994 amendments to the Marine Mammal Protection Act (MMPA), which allow polar bear trophies taken in approved Canadian populations by U.S. citizens to be imported into the U.S. A summary of the regulatory actions and a table listing populations approved for importation and the number of polar bears imported into the U.S. since 1997 is included in this report. Regarding oil and gas activities in polar bear habitat, three sets of regulations were published authorizing the incidental, non-intentional, taking of small numbers of polar bears concurrent to oil and gas activities. Cooperation continued with the Alaska Nanuuq Commission, representing the polar bear hunting communities in Alaska, as well as with the North Slope Borough and the Inuvialuit Game Council in their agreement for the management of the Southern Beaufort Sea polar bear population. Harvest summaries and technical assistance in designing and assistance in conducting a National Park Service/Alaska Nanuuq Commission study to collect traditional ecological knowledge of polar bear habitat use in Chukotka were provided. In addition, a long-range plan was developed to address and minimize polar bear-human conflicts in North Slope communities. We continued to monitor the harvest of polar bears in Alaska and collect and analyze specimens for presence and level of organochlorine compounds and trace elements. A paper on genetic assessment of hunter reported sex of harvested bears was recently published (Schliebe et al. 1999). Population status and trend assessment efforts continued. An aerial survey of polar bears in the Eastern Chukchi Sea and western portions of the Southern Beaufort Sea was conducted from the U.S. Coast Guard icebreaker “Polar Star” in August 2000. The first year of a multi-year survey of barrier islands and coastlines during the open water and freeze-up phase was conducted in the central Southern Beaufort Sea during fall 2000.

Alaska↗
USGS2025

Paralytic shellfish toxins and seabirds: Evaluating sublethal effects, behavioral responses, and ecological implications of saxitoxin ingestion by common murres (Uria aalge)

Paralytic shellfish toxins (PSTs), including saxitoxin (STX) and its congeners, are neurotoxins that can be produced during harmful algal blooms and cause illness or death in humans, fish, seabirds, and marine mammals. Since 2014, multiple large-scale seabird mortality events have occurred in Alaska waters, with STXs detected in some carcasses. To investigate the sublethal behavioral and ecological effects of STX on seabirds, we conducted captive dosing trials with common murres ( Uria aalge ). We gavaged purified STX (dehydrated STX dihydrocholoride, STX-diHCl) or an Alexandrium catenella culture extract into murres, monitored behavioral responses and recovery times, and assessed tissue concentrations in individuals that died or were euthanized. Using a modified up-and-down dose-finding scheme, we estimated a median effective dose (ED 50 ) of 89 µg STX-equivalents (eq) kg -1 for STX-diHCl and 366 µg STX-eq kg -1 for the A. catenella extract based on ecologically relevant behavior. Differences between the ED 50 estimates could reflect uncertainties in toxin equivalency factors for PST congeners, which are based on studies using purified toxins in mice and may vary across taxa or toxin matrices. Post-dosing concentrations of STX varied by tissue type across individuals, with quantifiable levels ranging from 3 to 379 µg STX-eq 100g -1 . Evidence of biotransformation of STX in A. catenella extract-dosed birds was observed. We also measured the chronic effects of dosing with sublethal levels of STX-diHCl over seven-days, which resulted in lower fish intake among treatment birds compared to controls (-187 g day -1 ). This investigation improves our understanding of the ecological effects of PSTs on seabird health.

Alaska↗
USGS2025

Highly pathogenic avian influenza virus exposure and infection in free-ranging bobcats (Lynx rufus) in New York, USA

Highly pathogenic H5N1 influenza A virus (HP H5N1) cases in wild mammals have been increasing globally. Carnivora has been the most affected mammal order; however, the extent of morbidity and mortality in carnivores exposed to HP H5N1 remains undefined. We assessed the presence of antibodies to H5 and N1 in the sera of 16 live-captured bobcats ( Lynx rufus ) in New York State, USA; reported on postcapture outcomes of HP H5N1-exposed bobcats; and reported on a case of HP H5N1 infection in one bobcat. In 2024, 4/16 bobcats (25%) tested positive for antibodies to H5 and N1. Two bobcats were confirmed alive as of November 2024 according to GPS data; the other two were alive as of June 2024, when their GPS collars stopped communicating. Another bobcat, which was negative for HP H5N1 antibodies at capture, died from HP H5N1 infection within 5 wks of capture. Our results provide evidence of bobcats both surviving and succumbing to HP H5N1 infection and highlight the importance of focused health studies paired with monitoring data to better understand exposure, infection, and outcomes for novel pathogens and species.

New York↗
USGS2006

Variation in probability of first reproduction of Weddell seals

Summary 1. For many species, when to begin reproduction is an important life-history decision that varies by individual and can have substantial implications for lifetime reproductive success and fitness. 2. We estimated age-specific probabilities of first-time breeding and modelled variation in these rates to determine age at first reproduction and understand why it varies in a population of Weddell seals in Erebus Bay, Antarctica. We used multistate mark?recapture modelling methods and encounter histories of 4965 known-age female seals to test predictions about age-related variation in probability of first reproduction and the effects of annual variation, cohort and population density. 3. Mean age at first reproduction in this southerly located study population (7.62 years of age, SD =1.71) was greater than age at first reproduction for a Weddell seal population at a more northerly and typical latitude for breeding Weddell seals (mean =4?5 years of age). This difference suggests that age at first reproduction may be influenced by whether a population inhabits the core or periphery of its range. 4. Age at first reproduction varied from 4 to 14 years, but there was no age by which all seals recruited to the breeding population, suggesting that individual heterogeneity exists among females in this population. 5. In the best model, the probability of breeding for the first time varied by age and year, and the amount of annual variation varied with age (average variance ratio for age-specific rates =4.3%). 6. Our results affirmed the predictions of life-history theory that age at first reproduction in long-lived mammals will be sensitive to environmental variation. In terms of life history evolution, this variability suggests that Weddell seals display flexibility in age at first reproduction in order to maximize reproductive output under varying environmental conditions. Future analyses will attempt to test predictions regarding relationships between environmental covariates and annual variation in age at first reproduction and evaluate the relationship between age at first reproduction and lifetime reproductive success.

Journal of Animal Ecology↗
USGS2021

Reconstructing population dynamics of a threatened marine mammal using multiple data sets

Models of marine mammal population dynamics have been used extensively to predict abundance. A less common application of these models is to reconstruct historical population dynamics, filling in gaps in observation data by integrating information from multiple sources. We developed an integrated population model for the Florida manatee ( Trichechus manatus latirostris ) to reconstruct its population dynamics in the southwest region of the state over the past 20 years. Our model improved precision of key parameter estimates and permitted inference on poorly known parameters. Population growth was slow (averaging 1.02; 95% credible interval 1.01–1.03) but not steady, and an unusual mortality event in 2013 led to an estimated net loss of 332 (217–466) manatees. Our analyses showed that precise estimates of abundance could be derived from estimates of vital rates and a few input estimates of abundance, which may mean costly surveys to estimate abundance don’t need to be conducted as frequently. Our study also shows that retrospective analyses can be useful to: (1) model the transient dynamics of age distribution; (2) assess and communicate the conservation status of wild populations; and (3) improve our understanding of environmental effects on population dynamics and thus enhance our ability to forecast.

Florida↗
USGS2021

Seal body condition and atmospheric circulation patterns influence polar bear body condition, recruitment, and feeding ecology in the Chukchi Sea

Polar bears ( Ursus maritimus ) are experiencing loss of sea ice habitats used to access their marine mammal prey. Simultaneously, ocean warming is changing ecosystems that support marine mammal populations. The interactive effects of sea ice and prey are not well understood yet may explain spatial‐temporal variation in the response of polar bears to sea ice loss. Here, we examined the potential combined effects of sea ice, seal body condition and atmospheric circulation patterns on the body condition, recruitment, diet, and feeding probability of 469 polar bears captured in the Chukchi Sea, 2008‐2017. The body condition of ringed seals ( Pusa hispida ), the primary prey of females and subadults, was related to dietary proportions of ringed seal, feeding probability, and the body condition of females and cubs. In contrast, adult males consumed more bearded seals ( Erignathus barbatus ) and exhibited better condition when bearded seal body condition was higher. The litter size, number of yearlings per adult female, and the condition of dependent young were higher following winters characterized by low Arctic Oscillation (AO) conditions, consistent with a growing number of studies. Body condition, recruitment, and feeding probability were either not associated or negatively associated with sea ice conditions, suggesting that, unlike some subpopulations, Chukchi Sea bears are not currently limited by sea ice availability. However, spring sea ice cover declined 2% per year during our study reaching levels not previously observed in the satellite record and resulting in the loss of polar bear hunting and seal pupping habitat. Our study suggests that the status of ice seal populations is likely an important factor that can either compound or mitigate the response of polar bears to sea ice loss over the short‐term. In the long‐term, neither polar bears nor their prey are likely robust to limitless loss of their sea ice habitat.

Alaska↗
USGS2018

A multi-species synthesis of satellite telemetry data in the Pacific Arctic (1987–2015): Overlap of marine mammal distributions and core use areas

We collated available satellite telemetry data for six species of ice-associated marine mammals in the Pacific Arctic: ringed seals ( Pusa hispida ; n = 118), bearded seals( Erignathus barbatus, n = 51), spotted seals ( Phoca largha , n = 72), Pacific walruses ( Odobenus rosmarus divergens, n = 389); bowhead whales ( Balaena mysticetus , n = 46), and five Arctic and sub-arctic stocks of beluga whales ( Delphinapterus leucas , n = 103). We also included one seasonal resident, eastern North Pacific gray whales ( Eschrichtius robustus , n = 12). This review summarized the distribution of daily locations from satellite-linked transmitters during two analysis periods, summer (May–November) and winter (December–April), and then examined the overlap among species. Six multi-species core use areas were identified during the summer period: 1) Chukotka/Bering Strait; 2) Norton Sound; 3) Kotzebue Sound; 4) the northeastern Chukchi Sea; 5) Mackenzie River Delta/Amundsen Gulf; and 6) Viscount Melville Sound. During the winter period, we identified four multi-species core use areas: 1) Anadyr Gulf/Strait; 2) central Bering Sea; 3) Nunivak Island; and 4) Bristol Bay. During the summer period, four of the six areas were centered on the greater Bering Strait region and the northwestern coast of Alaska and included most of the species we examined. The two remaining summer areas were in the western Canadian Arctic and were largely defined by the seasonal presence of Bering-Chukchi-Beaufort stock bowhead whales and Eastern Beaufort Sea stock beluga whales, whose distribution overlapped during both summer and winter periods. During the winter period, the main multi-species core use area was located near the Gulf of Anadyr and extended northwards through Anadyr and Bering Straits. This area is contained within the Bering Sea “green belt”, an area of enhanced primary and secondary productivity in the Bering Sea. We also described available telemetry data and where they can be found as of 2017. These data are important for understanding ice-associated marine mammal movements and habitat use in the Pacific Arctic and should be archived, with appropriate metadata, to ensure they are available for future retrospective analyses.

Deep Sea Research Part II: Topical Studies in Ocea↗
USGS2020

Acute toxicity and clotting times of anticoagulant rodenticides to red-toothed (Odonus niger) and black (Melichthys niger) triggerfish, fathead minnow (Pimephales promelas), and largemouth bass (Micropterus salmoides)

Anticoagulant rodenticides (ARs) areused in rateradication efforts on island wildlife refuges. ARbait pellets can get into coralreefareasduring broadcasting and leadto exposure ofnon-target organisms, such as marine fishes. The objective of this study was to determine the sensitivity of representative saltwater fishes, Red-toothed triggerfish (Odonus niger) and Black triggerfish (Melichthys niger), and common freshwater fishes, fathead minnow (Pimephales promelas), and largemouth bass (Micropterus salmoides) to first generation ARs, diphacinone (DPN) and chlorophacinone (CPN), as well as a second-generation AR, brodifacoum (BROD). Acute toxicity of ARs was evaluated by single dose, intraperitoneal injections. The median lethal dose (LD50) ranges were 137−175μg DPN/g, 155−182μg CPN/g, and 36−48μg BROD/g for Red-toothed triggerfish and 90−122μg DPN/g, 125−164μg CPN/g, and 50−75μg BROD/g for black triggerfish. Laboratory surrogate test fish species fathead minnow and largemouth bass were of similar sensitivity toward AR-induced toxicity compared to triggerfish based on LD50 values. Sublethal effects on elevated clotting time occurred in dose-dependent fashion in all fish tested. Fish appear to have low sensitivity to AR chemicals as compared to other taxa, in particular mammals and birds, based on across-taxa comparisons of species sensitivity distributions of whole body, single dose acute lethality (LD50 values). The sensitivity of fish to waterborne exposures of ARs has yet to be fully evaluated and indeed may prove more hazardous to fish.

Aquatic Toxicology↗
USGS2020

Drivers and consequences of apex predator diet composition in the Canadian Beaufort Sea

Polar bears ( Ursus maritimus ) rely on annual sea ice as their primary habitat for hunting marine mammal prey. Given their long lifespan, wide geographic distribution, and position at the top of the Arctic marine food web, the diet composition of polar bears can provide insights into temporal and spatial ecosystem dynamics related to climate-mediated sea ice loss. Polar bears with the greatest ecological constraints on diet composition may be most vulnerable to climate-related changes in ice conditions and prey availability. We used quantitative fatty acid signature analysis (QFASA) to estimate the diets of polar bears ( n = 419) in two western Canadian Arctic subpopulations (Northern Beaufort Sea and Southern Beaufort Sea) from 1999 to 2015. Polar bear diets were dominated by ringed seal ( Pusa hispida ), with interannual, seasonal, age- and sex-specific variation. Foraging area and sea ice conditions also affected polar bear diet composition. Most variation in bear diet was explained by longitude, reflecting spatial variation in prey availability. Sea ice conditions (extent, thickness, and seasonal duration) declined throughout the study period, and date of sea ice break-up in the preceding spring was positively correlated with female body condition and consumption of beluga whale ( Delphinapterus leucas ), suggesting that bears foraged on beluga whales during entrapment events. Female body condition was positively correlated with ringed seal consumption, and negatively correlated with bearded seal consumption. This study provides insights into the complex relationships between declining sea ice habitat and the diet composition and foraging success of a wide-ranging apex predator.

Northwest Territories, Yukon↗