Explore the vast range of titles available.

Apex predators are typically considered dietary generalists, which often masks individual variability. However, individual specialization—consistent differences among individuals in resource use or ecological role—is common in apex predators. In some species, only a few specialized individuals can significantly impact prey populations. Leopard seals (Hydrurga leptonyx) are apex predators important to the structure and function of the Southern Ocean ecosystem. Though broadly described as generalists, little is known about their trophic ecology at the population or individual level. We analyzed δ13C and δ15N profiles in whiskers (n = 46) from 34 leopard seals in the Western Antarctic Peninsula to assess trophic variation. We also evaluated individual consistency across years using repeat samples from 7 seals over 2–10 years. We compared population and individual isotopic niche space and explored drivers of intraspecific variation in leopard seal trophic ecology. We find that leopard seals have a broad trophic niche (range: 6.96%–15.21‰) and are generalists at the population level. However, most individuals are specialists (59% for δ15N and δ13C), with only a few generalists (13% for δ15N, 6% for δ13C). Individuals also specialize at different trophic levels. Most variation in trophic ecology is driven by individual specialization, but sex and mass also contribute. We also find that some seals specialize over time, consistently foraging at the same trophic level, while others switch within and between years. This suggests some seals may disproportionately impact prey, especially when specialists consistently target specific species. Long‐term specialization by a few leopard seals likely contributed to the decline of the local Antarctic fur seal population. Our findings show the importance of examining individual specialization in leopard seals across their range to understand their impact on other prey populations. This approach should be applied to other apex predator populations, as a few specialists can significantly impact ecosystems. Leopard seals are apex predators in the Southern Ocean. The species is broadly described as generalists; however, our study shows that most individual leopard seals are dietary specialists. This specialization has led to niche partitioning among individuals. Individual specialization, drives trophic variation, and we find differences between individuals based on sex and body size. We also find that some leopard seals forage consistently at one trophic level, while others switch trophic levels. In our study location, long‐term specialization by a few large adult female leopard seals has likely contributed to the decline of their prey, Antarctic fur seals. Our study highlights the ecological significance of individual variability in apex predators.

Conservation science requires quickly acquiring information and taking action in order to protect species at risk of extinction. Stable isotope measurements are one way to rapidly gather data regarding species’ foraging ecology and habitat use, and passively collected samples limit additional stress to at-risk species. For these samples to be useful, however, we must know how representative they are of the stable isotope ratios of the entire organism. Bone tissue, often stored in museum collections or research centers, may be the most readily available tissue from rare, endangered, or extinct vertebrates, but using bone requires practitioners to understand intraskeletal stable isotope variation. We sampled the same eight skeletal elements from 72 cetacean skeletons from 14 species to evaluate intraskeletal variation in carbon and nitrogen isotope values. We found considerably more variation than anticipated. Carbon intraskeletal ranges varied from 0.4 to 7.6‰, with 84.7% (n = 61) of skeletons having a range >1‰, and 55.5% (n = 40) exhibiting a range >2‰. Similarly, nitrogen intraskeletal ranges varied from 0.4 to 5.2‰, with 59.7% (n = 43) of skeletons exhibiting a range >1‰, and 15.3% (n = 11) with a range >2‰. There were differences in which bones contributed most to intraskeletal variation; however, we advise against using humeri and mandibles as these bones presented the most consistent trends in deviation from the intraskeletal means for both isotopes. The large intraskeletal variation we observed is likely due to changes in foraging behavior or habitat use being reflected differently in bone isotope ratios due to differences in bone turnover rates. We suggest that for cetaceans, intraskeletal carbon isotope ranges >1‰ and nitrogen ranges >2‰ are ecologically relevant, and that using different bones from animals of the same population may produce false positive differences in foraging behavior or habitat within the population if intraskeletal variation is not considered. Future studies should use the same bones from each animal and conduct species-specific analyses of intraskeletal variation, if possible, when using specimens of opportunity. Failure to consider this variation could lead to erroneous conclusions regarding a species range or key habitats, jeopardizing conservation efforts.

Elusive wildlife are challenging to study, manage, or conserve, as the difficulty of obtaining specimens or conducting direct observations leads to major data deficiencies. Specimens of opportunity, such as salvaged carcasses or museum specimens, are a valuable source of fundamental biological and ecological information on data-deficient, elusive species, increasing knowledge of biodiversity, habitat and range, and population structure. Stable isotope analysis is a powerful indirect tool that can be used to infer foraging behavior and habitat use retrospectively from archived specimens. Beaked whales are a speciose group of cetaceans that are challenging to study in situ , and although Sowerby's beaked whale ( Mesoplodon bidens ) was discovered >200 years ago, little is known about its biology. We measured δ 13 C and δ 15 N stable isotope composition in bone, muscle, and skin tissue from 102 Sowerby's beaked whale specimens of opportunity collected throughout the North Atlantic Ocean to infer movement ecology and spatial population structure. Median δ 13 C and δ 15 N values in Sowerby's beaked whale bone, muscle, and skin tissues significantly differed between whales sampled from the east and west North Atlantic Ocean. Quadratic discriminant analysis that simultaneously considered δ 13 C and δ 15 N values correctly assigned >85% of the specimens to their collection region for all tissue types. These findings demonstrate Sowerby's beaked whale exhibits both short- and long-term site fidelity to the region from which the specimens were collected, suggest that this species is composed of two or more populations or exhibits a metapopulation structure, and have implications for conservation and management policy. Stable isotope analysis of specimens of opportunity proved a highly successful means of generating new spatial ecology data for this elusive species and is a method that can be effectively applied to other elusive species.

Successful conservation of endangered, migratory species requires an understanding of habitat use throughout life stages. When dedicated scientific studies are difficult to conduct, local expert knowledge can provide crucial baseline data to guide study design and aid data interpretation. In 2008, fishers in El Salvador demonstrated that eastern Pacific hawksbill sea turtles ( Eretmochelys imbricata )—a population conservation biologists considered virtually extirpated—use mangrove estuaries as nesting habitat rather than open-coast beaches used by hawksbills in other regions. We confirmed and amplified this observation by using fishers' ecological knowledge to guide biological sampling for stable isotope analysis to assess if eastern Pacific hawskbills use mangrove-dominated estuaries as developmental habitats. We found that immature hawksbills experience a pelagic stage and then recruit to estuaries at ~37 cm curved carapace length, where they increase reliance on estuarine resources until they approach adult sizes. This life history strategy makes them especially vulnerable to in-water nearshore threats, and necessitates targeted expansion of conservation efforts throughout the eastern Pacific. Our analysis also provides a model for integrating traditional scientific approaches with local knowledge—a model that could yield crucial advances in other understudied regions.

Elusive species are challenging to study and conserve because basic elements of their biology may be unknown. Specimens of opportunity provide a means of collecting information on these species and may be critical for elusive species’ conservation. We used snowball sampling to identify Sowerby’s beaked whale (Mesoplodon bidens) specimens in museums and research institutions. Snowball sampling proved highly effective: we located 180 specimens from 24 institutions in North America and Europe, 62 of which were not listed in online collections databases, resulting in the largest collated dataset for this species. Analysis of these data resulted in several new findings for this species, including significant morphological variation between specimens from different collection regions, suggesting the presence of previously unidentified population structuring in this species. These data provide critical information regarding this species and demonstrate the effectiveness of specimens of opportunity for elusive species research and conservation. We recommend other researchers consider snowball sampling when designing research projects utilizing specimens of opportunity. Our results demonstrate the usefulness of snowball sampling and specimens of opportunity to elusive species research and conservation, and the methods of our study can be readily adapted for other species.

Northern elephant seals ( Mirounga angustirostris ), like many marine mammals, rely on internal lipid stores, specifically fatty acids (FAs) stored in the blubber layer, to meet metabolic needs. The energetic demands of northern elephant seals vary with ontogeny, as each life-history stage experiences different metabolic requirements due to development, growth, and breeding. To date, no comprehensive study has reported on changes in blubber FA profiles across northern elephant seal age groups or sex. Therefore, our objective was to determine how blubber FAs differ across ontogeny and sex in northern elephant seals. As a sexually dimorphic mammal, northern elephant seals go through sex-specific ontogenetic changes in morphology and physiology; we hypothesized that these changes would be reflected in their FAs profiles. To determine this, FAs profiles were compared from full blubber cores collected from 79 northern elephant seals across four age groups. We provide the first evidence of blubber fatty acids differing across ontogeny as NES transition from young, developing seals to mature fully developed adults. However, we did not find differences in blubber FAs profiles between the sexes. Monounsaturated fatty acids (MUFAs) are found in the highest proportions across all NES age classes and sexes, followed by SFAs and PUFAs; this highlights the important role MUFAs play in maintaining fluidity of the blubber layer and in thermoregulation. The individual FAs with the highest concentrations (C16:1, C18:1n9 and C16:0) in northern elephant seal blubber are similar to those in other marine mammals. Weaned pup FAs profiles were significantly different from all other age classes; adults and juveniles also showed age-specific differences. Specifically, weaned pups had the highest proportions of SFAs and the lowest proportions of PUFA, suggesting use of PUFAs to aid development. Each life history stage of NES is interconnected to previous and future stages, making FA accumulation, mobilization, and storage an important process throughout an individual’s life. Further, any changes to this process can have cascading consequences throughout ontogeny in this species. Future monitoring of the FA composition of blubber across age classes could potentially indicate the costs of different environmental changes on blubber storage in NES.

The aim of this article is to describe a successful attack by a group of killer whales on a Bryde's whale in the Galapagos Islands, Ecuador, with a description of their attack behavior. This article presents information related to a resighting of one of the killer whales involved in the attack off the coast of Ecuador. Previous observations of killer whale interactions with marine mammals and attacks on baleen whales have frequently occurred in the past, but these observations were not documented in detail. In Galapagos waters, killer whales feed on and interact with a broad group of marine vertebrates, dolphins and large whales. The predatory attacks involving tropical baleen whales are of particular interest given that similar behaviors have been reported for transient killer whales. These insights might be used as evidence to further support future studies investigating population and feeding ecology, photo-identification, and the ecotypes occurring in the Galapagos region.

Most genome-wide association and fine-mapping studies to date have been conducted in individuals of European descent, and genetic studies of populations of Hispanic/Latino and African ancestry are limited. In addition, these populations have more complex linkage disequilibrium structure. In order to better define the genetic architecture of these understudied populations, we leveraged >100,000 phased sequences available from deep-coverage whole genome sequencing through the multi-ethnic NHLBI Trans-Omics for Precision Medicine (TOPMed) program to impute genotypes into admixed African and Hispanic/Latino samples with genome-wide genotyping array data. We demonstrated that using TOPMed sequencing data as the imputation reference panel improves genotype imputation quality in these populations, which subsequently enhanced gene-mapping power for complex traits. For rare variants with minor allele frequency (MAF) < 0.5%, we observed a 2.3- to 6.1-fold increase in the number of well-imputed variants, with 11-34% improvement in average imputation quality, compared to the state-of-the-art 1000 Genomes Project Phase 3 and Haplotype Reference Consortium reference panels. Impressively, even for extremely rare variants with minor allele count <10 (including singletons) in the imputation target samples, average information content rescued was >86%. Subsequent association analyses of TOPMed reference panel-imputed genotype data with hematological traits (hemoglobin (HGB), hematocrit (HCT), and white blood cell count (WBC)) in ~21,600 African-ancestry and ~21,700 Hispanic/Latino individuals identified associations with two rare variants in the HBB gene (rs33930165 with higher WBC [p = 8.8x10-15] in African populations, rs11549407 with lower HGB [p = 1.5x10-12] and HCT [p = 8.8x10-10] in Hispanics/Latinos). By comparison, neither variant would have been genome-wide significant if either 1000 Genomes Project Phase 3 or Haplotype Reference Consortium reference panels had been used for imputation. Our findings highlight the utility of the TOPMed imputation reference panel for identification of novel rare variant associations not previously detected in similarly sized genome-wide studies of under-represented African and Hispanic/Latino populations.

Radical cystectomy is the surgical standard for invasive bladder cancer. Robot-assisted cystectomy has been proposed to provide similar oncological outcomes with lower morbidity. We aimed to compare progression-free survival in patients with bladder cancer treated with open cystectomy and robot-assisted cystectomy. The RAZOR study is a randomised, open-label, non-inferiority, phase 3 trial done in 15 medical centres in the USA. Eligible participants (aged ≥18 years) had biopsy-proven clinical stage T1–T4, N0–N1, M0 bladder cancer or refractory carcinoma in situ. Individuals who had previously had open abdominal or pelvic surgery, or who had any pre-existing health conditions that would preclude safe initiation or maintenance of pneumoperitoneum were excluded. Patients were centrally assigned (1:1) via a web-based system, with block randomisation by institution, stratified by type of urinary diversion, clinical T stage, and Eastern Cooperative Oncology Group performance status, to receive robot-assisted radical cystectomy or open radical cystectomy with extracorporeal urinary diversion. Treatment allocation was only masked from pathologists. The primary endpoint was 2-year progression-free survival, with non-inferiority established if the lower bound of the one-sided 97·5% CI for the treatment difference (robotic cystectomy minus open cystectomy) was greater than −15 percentage points. The primary analysis was done in the per-protocol population. Safety was assessed in the same population. This trial is registered with ClinicalTrials.gov, number NCT01157676. Between July 1, 2011, and Nov 18, 2014, 350 participants were randomly assigned to treatment. The intended treatment was robotic cystectomy in 176 patients and open cystectomy in 174 patients. 17 (10%) of 176 patients in the robotic cystectomy group did not have surgery and nine (5%) patients had a different surgery to that they were assigned. 21 (12%) of 174 patients in the open cystectomy group did not have surgery and one (1%) patient had robotic cystectomy instead of open cystectomy. Thus, 302 patients (150 in the robotic cystectomy group and 152 in the open cystectomy group) were included in the per-protocol analysis set. 2-year progression-free survival was 72·3% (95% CI 64·3 to 78·8) in the robotic cystectomy group and 71·6% (95% CI 63·6 to 78·2) in the open cystectomy group (difference 0·7%, 95% CI −9·6% to 10·9%; pnon-inferiority=0·001), indicating non-inferiority of robotic cystectomy. Adverse events occurred in 101 (67%) of 150 patients in the robotic cystectomy group and 105 (69%) of 152 patients in the open cystectomy group. The most common adverse events were urinary tract infection (53 [35%] in the robotic cystectomy group vs 39 [26%] in the open cystectomy group) and postoperative ileus (33 [22%] in the robotic cystectomy group vs 31 [20%] in the open cystectomy group). In patients with bladder cancer, robotic cystectomy was non-inferior to open cystectomy for 2-year progression-free survival. Increased adoption of robotic surgery in clinical practice should lead to future randomised trials to assess the true value of this surgical approach in patients with other cancer types. National Institutes of Health National Cancer Institute.