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Venom represents a key adaptation of many venomous predators, allowing them to immobilise prey quickly through chemical rather than physical warfare. Evolutionary arms races between prey and a predator are believed to be the main factor influencing the potency and composition of predatory venoms. Predators with narrowly restricted diets are expected to evolve specifically potent venom towards their focal prey, with lower efficacy on alternative prey. Here, we evaluate hypotheses on the evolution of prey‐specific venom, focusing on the effect of restricted diet, prey defences, and prey resistance. Prey specificity as a potential evolutionary dead end is also discussed. We then provide an overview of the current knowledge on venom prey specificity, with emphasis on snakes, cone snails, and spiders. As the current evidence for venom prey specificity is still quite limited, we also overview the best approaches and methods for its investigation and provide a brief summary of potential model groups. Finally, possible applications of prey‐specific toxins are discussed. [ABSTRACT FROM AUTHOR]

The declining population of otter species in Malaysia, including the Asian small‐clawed otter (Aonyx cinereus), smooth‐coated otter (Lutrogale perspicillata) and hairy‐nosed otter (Lutra sumatrana), is primarily attributed to habitat changes. Understanding the ecological aspects of otters, including their diets, is crucial for formulating effective conservation management strategies. To address this knowledge gap, we employed Next Generation Sequencing (NGS) as an alternative approach to enhance our understanding of the species' food chain. Specifically, this study investigated the diets of Asian small‐clawed otters and smooth‐coated otters by analysing an ~130 bp segment of the Cytochrome b (Cytb) gene using Illumina Miniseq platform. The analysis successfully generated 572,311 reads, identifying four families, nine genera and 11 food species consumed by both otter species. Smooth‐coated otters primarily consumed fish (96%) and frogs (4%), whereas Asian small‐clawed otters exclusively fed on fish (100%), with the genus Esomus being the predominant fish genus found in the spraints. The diversity analysis of their diets revealed significant differences between two species (p < 0.05). As a result, DNA metabarcoding provides a reliable method for verifying otter dietary information and can serve as a valuable tool in assessing fish diversity, thus contributing significantly to the management and conservation of otter populations, particularly in Malaysia. [ABSTRACT FROM AUTHOR]

This study represents an interaction model including juvenile and adult predators along with prey, involving key characteristics like the inability of juvenile predators to reproduce, the impact of adult predators on juvenile growth rates and the transformation of some juveniles to adulthood. Furthermore, it is supposed that adult predators intake prey for sustenance, and the logistic growth of prey is assumed in the non-appearance of adult predators. Intra-species competition among adult predators, together with predation of juveniles and chasing, is conveyed. To tackle the imprecise biological parameters, most parametric values are considered as triangular intuitionistic fuzzy numbers. The model is further processed into an intuitionistic fuzzy model using the Hukuhara derivative and Yager’s ranking method is implemented to make the model crispified. Non-negativity and boundedness of the model are explored, after that, an investigation of possible equilibrium points is discussed. Local and global stability analyses close to these points are supervised. The study accentuates the significant influence of uncertain model parameters on the solution. Especially, uncertain estimates of intra-species competition among adult predators remarkably regulate the model’s stability. Extended uncertainty in intra-species competition for prey, although, is discovered to stabilize the system. In addition, increased consumption of juvenile predators by adult predators is observed to provide the system’s instability. [ABSTRACT FROM AUTHOR]

The Black Sea is a semi‐enclosed inland sea with an unevenly distributed extensive coastal shelf area and anoxic deep waters. It is inhabited by common and bottlenose dolphins, as well as harbour porpoises, all represented by local subspecies. Between September 2020 and October 2022, 19 F‐PODs deployed by research teams from Bulgaria, Georgia, Romania, Türkiye and Ukraine collected data on acoustic activity of Black Sea harbour porpoises. Strong seasonal and diel patterns were found, which varied in three regions. In the south‐eastern part of the Black Sea, harbour porpoise acoustic activity was higher from January to May, with a peak in April. This pattern agrees with the seasonal anchovy migration from the winter spawning grounds in warmer waters in the south‐eastern region to feeding grounds on the productive shallow north‐west shelf. The diel pattern showed strong nocturnal acoustic activity, which is consistent with anchovy vertical migration. Porpoises on the western side of the Black Sea exhibited a bimodal seasonal pattern in acoustic activity, with a larger peak in April and a smaller one in October. Diel activity was primarily nocturnal. On the north‐west shelf, harbour porpoise acoustic activity was mostly recorded during the warm period from April to October. The diel pattern showed activity mainly during daylight with two peaks: a smaller one approximately at dawn and a larger one at dusk. This pattern is similar to the vertical migrations of sprat. Overall, the results of the study were consistent with the prey being an important driver of seasonal and diel dynamics of harbour porpoise acoustic activity. [ABSTRACT FROM AUTHOR]

This article explores two recent texts – Stephen Graham Jones's (Blackfeet) 2021 novel My Heart Is a Chainsaw, and the 2022 Predator prequel Prey – as examples of Native American horror. While different in medium, narrative and style, both texts participate in and disrupt the traditional genre of the slasher and the trope of the final girl. The article concludes that Prey and Chainsaw create distinctive Native American horror aesthetics that unsettle the settler-colonial history of the United States. [ABSTRACT FROM AUTHOR]

To compare trophic properties in pelagic and benthic communities of the Kara Sea, isotopic composition of carbon and nitrogen (δ13C and δ15N) was examined in tissues of zooplankton, zoobenthos, and fish. The organisms exhibited rather low δ13C values in the surveyed area. Because of stable difference in isotopic composition of carbon for zooplankton and zoobenthos, the pelagic and benthic communities could be separated by the level δ13C = –21.5 ‰, on average. The δ15N values for these communities varied within their 3 trophic levels in the range from 6.4 ‰ (for bivalve Serripes groenlandicus) to 16.3 ‰ (for lycod Lycodes seminudus), reflecting the input of predation. The bottom and pelagic communities in the Kara Sea demonstrated trophic interdependence. Both pelagic and bottom fish species, more or less, consumed both pelagic and benthic prey. Taking into account the content of 13C isotope in tissues of zooplankton and zoobenthos, about 40 % of the bottom nekton species were linked mainly with the pelagic food web and bypassed the benthic one. Pelagic fish fed mainly on pelagic prey, though the portion of zoobenthos in food of the dominant species — arctic cod had increased with the fish size increasing. On the contrary, the portion of zoobenthos in food of ruffed flounder had decreases with their size.

Forelimb bones of the Jurassic theropod Allosaurus fragilis were digitally manipulated based on three-dimensional (3D) digital models. Bony articular surface margins were used as limits to determine the range of motion (ROM) for each forelimb joint, and to test functional hypotheses of forelimb usage. We discuss the effects of palaeopathology at the right shoulder joint on inferring ROM in the forelimb of Allosaurus. It is considered that the glenoid aberration of this sub-adult specimen occurred in early ontogeny and lasted for a long period of time, affecting to varying degrees the development of the whole right arm (but not the manus). The relatively large ranges of extension and flexion of manual joints indicate well grasping ability consistent with early-diverging theropods. The limited ROM of the shoulder joints of Allosaurus suggests that the forelimbs were predominantly prey-acquiring but could go no further forward, indicating that the first contact with prey was made by the mouth. The manus could assist in grasping prey on the chest or below the neck or hooking objects. [ABSTRACT FROM AUTHOR]

Riverine fishes face many challenges including habitat degradation and climate change, which alter the productivity of the riverscapes in which fish live, reproduce, and feed. Understanding the watershed portfolio of foraging and growth opportunities that sustain productive and resilient fish populations is important for prioritizing conservation and restoration. However, the spatiotemporal distribution and availability of fish food are poorly understood relative to other factors such as abiotic habitat quantity and quality (e.g., water temperature). In this paper, we build on the concept of “foodscapes,” and describe three components of food for fish, including abundance, accessibility, and quality. We then discuss methodological advances to help address three key questions: (1) Why is food availability hard to estimate? (2) What are the consequences of uncertainty in food availability estimates? and (3) What approaches are available or emerging for quantifying food available to fish? To address the first question, we characterize data acquisition and analytical challenges; for the second, we demonstrate the importance of evaluating and communicating potential consequences of uncertainty; and for the third, we posit opportunities for future work. Collectively, we highlight the need for greater appreciation of the role food plays in stream fish conservation, especially given its critical influence on responses to warming temperatures.This article is categorized under: Water and Life > Nature of Freshwater Ecosystems Water and Life > Conservation, Management, and Awareness Water and Life > Methods [ABSTRACT FROM AUTHOR]

Objectives Small copepods (<2 mm) compose an important constituent of the Arctic marine food web, but their trophic interactions remain largely unexplored, partly due to methodological limitations. Methods We here characterize the prey of the abundant cyclopoid Oithona similis , harpacticoid Microsetella norvegica and calanoid Microcalanus spp. from the Arctic Barents Sea and Nansen Basin during four seasons using brute force prey metabarcoding of the 18S rRNA gene. Key findings Chaetognaths were unexpectedly the most consistently identified taxa and composed 47% of all prey reads. Some taxa were seasonally important, including diatoms in April–May (43%), dinoflagellates in December (15%) and March (17%), and urochordates in August (20%). Compositional differences among species were also discernible, and the M. norvegica diet was significantly different from both O. similis and Microcalanus spp. The diets varied nevertheless more with season than species despite the inherent trophic traits that distinguish the ambush-predator O. similis , chemosensoric particle-chaser M. norvegica and current-feeding Microcalanus spp. Conclusions Our results thus indicate that dietary plasticity is common in small Arctic copepods, regardless of their behaviors or strategies for finding sustenance. We further hypothesize that such plasticity is an important adaptation in systems where prey availability is highly seasonal. [ABSTRACT FROM AUTHOR]

Simple Summary: The South China tiger is a unique subspecies of tiger endemic to China and has become extinct in the wild. However, it is currently unclear whether there are still ideal habitats suitable for the survival of the South China tiger population in China at present and in the future. Our goal is to assess which areas will become the most suitable for the reintroduction of the South China tiger to China under the impact of climate change, and to estimate the number of tigers these areas can support. This study selects eight key prey species of the South China tiger, and predicts the potential suitable habitats for each prey under current and future climates. The study reveals that the core candidate sites for the reintroduction of the South China tiger cover a total area of 83,415 km2, with the largest core candidate site area totaling 10,000 km2, located in Tibet, which can ideally support the survival of 89 South China tigers in the wild. This study provides a research basis and strategy for the recovery of wild South China tiger populations. The South China tiger (Panthera tigris amoyensis) is a tiger subspecies unique to China and one of the top ten endangered species in the world. It used to play an important role in the overall function of the ecosystem. This study rationally screened out key prey species of the South China tiger—the Chinese serow, Chinese goral, tufted deer, water deer, Chinese muntjac, red muntjac, sambar deer, and wild boar. Candidate sites for the rewilding and reintroduction of the South China tiger were derived by exploring changes in suitable habitats for the prey using the MaxEnt model. The results show that: (1) by 2070, except for the high-suitability areas of water deer and Chinese muntjac, the areas of suitable habitats for the other six prey species would all have decreased significantly; (2) the location of the high-suitability area of the South China tiger obtained by superimposing the suitable areas of the eight prey species would be almost stable in 2050 and 2070, but the habitat index of some high- and medium-suitability areas would decrease and turn into low-suitability areas; (3) the core candidate sites were 83,415 km2 in total, of which 25,630 km2 overlapped with existing protected areas, accounting for 30.7% of the core candidate sites, and the remaining 69.3% of the core candidate sites were mostly distributed around the protected areas; (4) the maximum core candidate site area was projected to be 10,000 km2 by 2070, which could support a small population of 23 male tigers and 66 female tigers to survive and reproduce in the wild. This study revealed the core candidate sites for the rewilding of South China tigers and estimated the number of tigers that could be reintroduced to these areas, providing a preliminary research basis for promoting the rewilding of South China tigers in China. [ABSTRACT FROM AUTHOR]

Compound effects of anthropogenic disturbances on wildlife emerge through a complex network of direct responses and species interactions. Land‐use changes driven by energy and forestry industries are known to disrupt predator–prey dynamics in boreal ecosystems, yet how these disturbance effects propagate across mammal communities remains uncertain. Using structural equation modeling, we tested disturbance‐mediated pathways governing the spatial structure of multipredator multiprey boreal mammal networks across a landscape‐scale disturbance gradient within Canada's Athabasca oil sands region. Linear disturbances had pervasive direct effects, increasing site use for all focal species, except black bears and threatened caribou, in at least one landscape. Conversely, block (polygonal) disturbance effects were negative but less common. Indirect disturbance effects were widespread and mediated by caribou avoidance of wolves, tracking of primary prey by subordinate predators, and intraguild dependencies among predators and large prey. Context‐dependent responses to linear disturbances were most common among prey and within the landscape with intermediate disturbance. Our research suggests that industrial disturbances directly affect a suite of boreal mammals by altering forage availability and movement, leading to indirect effects across a range of interacting predators and prey, including the keystone snowshoe hare. The complexity of network‐level direct and indirect disturbance effects reinforces calls for increased investment in addressing habitat degradation as the root cause of threatened species declines and broader ecosystem change. [ABSTRACT FROM AUTHOR]

Jaguars are endangered in Mexico, with negative interactions with livestock producers being one of the main threats to their populations. We collared three jaguars with search Global Positioning System (GPS) clusters to document prey species eaten by them in the Sierra del Abra-Tanchipa Biosphere Reserve (RBSAT) and surrounding agrolandscape, in northeastern Mexico, to determine the relative use of natural prey and livestock. We detected, through examination of the carcasses (scavenging and predation events), 35 individual prey at feeding sites, primarily collared peccary (40% of sites), cattle (23%), and white-tailed deer (20%). Cattle comprised 64% and wild ungulates provided 34% of the estimated biomass in jaguar diets (biomass was calculated based on the estimated mass consumed and the assumption of an edible portion), with cattle consumed only during the dry season. Seasonal use apparently reflected increased encounters between jaguars and livestock during the dry season, probably due to the presence of limited permanent water sources concentrating livestock (and natural prey) along with jaguars taking advantage of the increased vulnerability of livestock during the dry season (either through predation or scavenging). [ABSTRACT FROM AUTHOR]

Sinosaurus from the Lufeng Basin, Yunnan Province, is the largest and most famous predatory dinosaur from the Early Jurassic in China. Although a number of specimens have been discovered in the past, no studies to date have focused exclusively on complete skeletal articulation, estimation of mass, or life strategies. Based on surface scans of a new well-preserved specimen, a digital skeleton of Sinosaurus was produced in two poses: osteologically neutral pose and extended pose. We estimated the possible living body mass by three volumetric-density methods, advocating the use of the expanding convex hulls method of 849.6 kg with the COM (0.41, 1.31, 0.00) as a more reliable result, which is greater than the mass of traditional regression formulas. The body shape and skull/body length suggested that Sinosaurus was a great runner, and this, combined with the weak crests and large forelimbs, further led to the conclusion that both the head and forelimbs were required to prey. This finding is also consistent with the finding that Sinosaurus has a moderate ability to metabolise body heat in the skin, as reflected by the surface/volume ratio. [ABSTRACT FROM AUTHOR]

The 'landscape of fear' concept offers valuable insights into wildlife behaviour, yet its practical integration into habitat management for conservation remains underexplored. In this study, conducted in the subtropical monsoon grasslands of Bardia National Park, Nepal, we aimed to bridge this gap through a multi‐year, landscape‐scale experimental investigation in Bardia National Park, Nepal. The park has the highest density of tigers (with an estimated density of ~7 individuals per 100 km2) in Nepal, allowing us to understand the effect of habitat management on predation risk and resource availability especially for three cervid species: chital (Axis axis), swamp deer (Rucervus duvaucelii) and hog deer (Axis porcinus). We used plots with varying mowing frequency (0–4 times per year), size (ranging from small: 49 m2 to large: 3600 m2) and artificial fertilisation type (none, phosphorus, nitrogen) to assess the trade‐offs between probable predation risk and resources for these cervid species, which constitute primary prey for tigers in Nepal. Our results showed distinct responses of these deer to perceived predation risk within grassland habitats. Notably, these deer exhibited heightened use of larger plots, indicative of a perceived sense of safety, as evidenced by the higher occurrence of pellet groups in the larger plots (mean = 0.1 pellet groups m−2 in 3600 m2 plots vs. 0.07 in 400 m2 and 0.05 in 49 m2 plots). Furthermore, the level of use by the deer was significantly higher in larger plots that received mowing and fertilisation treatments compared to smaller plots subjected to similar treatments. Of particular interest is the observation that chital and swamp deer exhibited greater utilisation of the centre (core) areas within the larger plots (mean = 0.21 pellet groups m−2 at the centre vs. 0.13 at the edge) despite the edge (periphery) also provided attractive resources to these deer. In contrast, hog deer did not display any discernible reaction to the experimental treatments, suggesting potential species‐specific variations in response to perceived predation risk arising from management interventions. Our findings emphasise the importance of a sense of security as a primary determinant of habitat selection for medium‐sized deer within managed grassland environments. These insights carry practical implications for park managers, providing a nuanced understanding of integrating the 'landscape of fear' into habitat management strategies. This study emphasises that the 'landscape of fear' concept can and should be integrated into habitat management to maintain delicate predator–prey dynamics within ecosystems. [ABSTRACT FROM AUTHOR]

Generally, competition excludes pairs of phylogenetically close species across the landscape. However, habitat, food and behaviour differentiation facilitate co‐occurrence of syntopic species. The taxa of frog‐biting midges Corethrella are assumed to be specialists on calling male frogs, but little is known about how habitat gradients and frog‐species composition influence their distribution and permit their coexistence in continuous landscapes.Our aims were to understand how environmental gradients in habitat, sound frequencies and frog‐species composition influence Corethrella spp. distributions and if habitat and sound frequencies segregate their occurrence across a landscape. We also investigated if habitat selection reduces co‐occurrence of species that share similar acoustic niches. The study was conducted in 20 permanent plots in Central Amazonia using different sound attractants as baits to capture Corethrella species.Habitat gradients, sound frequencies and frog‐species composition all influenced distributions of Corethrella spp. However, these factors do little to avoid Corethrella co‐occurrence, and habitat selection did not reduce co‐occurrence of species attracted to the same sound frequencies. These results suggest that competition is unlikely to affect the distribution of adults and that other aspects, such as competition in the larval phase, may be more important to permit their coexistence.The two most abundant species showed strong negative correlations in abundances, potentially indicating competition among these species, but larval habitat specialisation is likely to be the most important cause of this pattern. [ABSTRACT FROM AUTHOR]

Wetlands serve as unique habitats that can support high biodiversity. Large-scale loss of wetland habitats can threaten important linkages between lake and wetland habitats that could affect diversity and growth of aquatic organisms. In this study, we compare prey diversity and abundance as well as Walleye (Sander vitreus) diets and condition in a large glacial lake (Lake Kampeska, South Dakota) with a connected wetland to better understand seasonal changes in the benefits provided by each habitat. We examined seasonal differences (spring, summer, and fall) through two years (summer 2021 through fall 2022) between the habitats using prey fish catch per unit effort, richness, Shannon diversity, and Bray–Curtis dissimilarity as well as Walleye relative weight, percent of empty stomachs, diet weight, stomach fullness, diet energy, and diet taxa importance. The prey fish community was more diverse and abundant in the wetland, and Walleye consumed more prey (by weight) in the wetland during all seasons except spring. Wetland reconnection can be a tool for managers to improve water quality while providing seasonal habitat needs for fish. Additionally, the diversity of prey resources provided by wetlands, many of which are unique, support resilience in the face of ecological change. Protection of wetlands may be critical for maintaining healthy and resilient fisheries into the future. [ABSTRACT FROM AUTHOR]

Although fires are common in Mediterranean ecosystems, there are substantial knowledge gaps regarding post-fire shifts in animal diets, especially for carnivores. Red fox Vulpes vulpes is a generalist medium-size carnivore known to have a positive post-fire response, probably due to increased prey availability or facility to hunt. As small mammals are often one of its primary food categories, and early successional visitors of post-fire habitats, we hypothesize a change in red fox diet composition in the warm season after a fire. Hair trapping and scat collection were used to investigate selection of small mammals in a typical Mediterranean region, 3 years after a fire. The diet composition of the fox was compared with that of the fox in the same area in 1992, and with other undisturbed Mediterranean areas. Diet selection was evaluated through the Forage ratio and single resource preference tests. Red fox diet was consistent with other Mediterranean areas, with fruits and seeds, invertebrates, and small mammals being the most consumed categories. However, small mammals were consumed significantly less than in 1992, while fruits and seeds significantly more. Resource selection analysis indicated avoidance for some ground-foraging small mammals, including Crocidura spp. house mouse Mus domesticus and voles, whereas Apodemus spp. were selected. Arboreal-foraging species, e.g. red squirrel Sciurus vulgaris and garden dormouse Eliomys quercinus were used in proportion to their availability. We concluded that this mesocarnivore had high feeding plasticity and exploited various resources according to their availability and catchability. Future studies are needed to further investigate red fox and other carnivores' food shifts after fire disturbance, including various seasons, other successional stages and competition within predator guilds. Fox mostly consumed fruits post-fire avoidance on 3 ground-foraging species Fox feeding follows both resource availability and catchability [ABSTRACT FROM AUTHOR]

Wireless Sensor Networks are essential for monitoring physical objects in smart systems powered by the Internet of Things. It gathers information by detecting the surroundings and transmits it to a central repository. In this study, an unknown domain was explored using multi-objective optimization. This proposed work employs Multi-objective Grey Wolf Optimization to form effective clustering among nodes and also for choosing the cluster head. Based on the multi-objective fitness function, the cluster heads are selected. For every iteration, the cluster heads are changed thereby saving the consumption of energy and also resulting in an increase in network lifespan. The suggested method divides the network into various optimal-sized clusters and chooses the best cluster heads. The performance of the multi-objective exploration is presented. The proposed method's key contributions are by utilizing MOGWO for efficient clustering and CH selection, ultimately enhancing network performance. It dynamically adjusts CHs, resulting in energy savings and an extended network lifespan. MOGWO takes into account multiple objectives simultaneously. Through network configuration optimization, MOGWO enhances resource utilization, resulting in lower energy consumption, extended network lifetime, and improved overall efficiency. [ABSTRACT FROM AUTHOR]

In the hypersaline lakes of Crimea, only 5–7 species of animals are common including Gammarus aequicauda (Amphipoda) and Eucypris mareotica (Ostracoda). Two experiments were carried out to characterize the trophic interactions between these species. In one, G. aequicauda were used freshly caught from the lake, and in the other, after they were starved for 2.5 days in the laboratory. The experimental options were one male or female G. aequicauda and either 10, 20, or 30 ostracods. The gammarids actively fed on the ostracods, and significant differences were between females and males. The feeding intensity of males was higher than that of females. However, ostracods are not passive prey, they can actively attack their predator and are capable of causing them harm. Ostracods attacked a Gammarus only if it had captured one of the ostracods. Sex differences in G. aequicauda were also evident in the reaction to the group's aggressive behavior of ostracods. Interactions between Ostracoda and Gammarids cannot be considered unidirectional; they both may be prey or predators depending on the situation. Research Highlights: Seagrass Ruppia influence on zooplankton in a hypersaline lake but direct or reverse to different species.From 2019 to 2023, the average number of Ruppia shoots gradually increased but the total abundance of zooplankton decreased. [ABSTRACT FROM AUTHOR]

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Establishing methods that allow for more focused management of wildlife under predator pressure may increase the efficiency of managing problematic predators. Non‐invasive dietary analysis and identification of conservation‐sensitive prey in the diet of 'culprit' predator individuals could help to facilitate this and is worthy of exploration. Recently on Phillip Island, Australia, Little Ravens Corvus mellori have emerged as a prominent predator on the clutches of burrow‐nesting Little Penguins Eudyptula minor. We tested the feasibility of using non‐invasive PCR approaches targeting the penguin mitochondrial 16S rRNA marker gene to establish whether penguin DNA could be detected in raven faecal samples, potentially enabling the identification of culprit ravens missed by extensive field observation. Using a metabarcoding approach, we examined the feasibility of non‐invasively establishing other dietary items via high‐throughput amplicon sequencing. We documented components of raven diet using the universal mitochondrial 16S rRNA, insect‐specific 'Chiar' 16S rRNA and plant ITS2. The assemblage of dietary items did not differ with raven culprit status (i.e. a raven previously observed preying upon penguin), sex or date. Penguin was detected in the diet of some individuals classified observationally as non‐culprits. Although some cases may conceivably have been false detections, other explanations include missed depredation events, consumption via scavenging or through secondary consumption (e.g. eating invertebrates that have consumed penguin). While this study found metabarcoding unreliable for unambiguous assigning of raven culprit status, at least as we implemented it, it may hold promise complementing observations if consumption via scavenging can be distinguished from direct depredation. [ABSTRACT FROM AUTHOR]

Non‐native species can affect ecosystems by influencing native predator‐prey dynamics. Therefore, management interventions designed to remove non‐natives may inadvertently lead to increased predation on native species. Feral horses are widely distributed throughout the arid parts of western North America. A growing body of research indicates that horses can be an important prey species to mountain lions in ecosystems where they overlap. In December 2020, the Bureau of Land Management removed 455 horses from the Delamar Mountains, Nevada, USA. We leveraged this management intervention to implement a before–after–control–impact study to test hypotheses about predation on horses and native ungulates. We predicted (1) that horses would comprise an important part of the diet in this mixed‐prey community, (2) following removal, the proportion of horses in the diet would decrease and native ungulates would increase, and (3) mountain lion home ranges overlapping the treatment areas would increase in response to decreased prey availability. From 2018 to 2022, we investigated 1360 clusters from 29 GPS‐collared lions and identified 1056 prey items. To model the probability of a predation event (a kill), we fit a mixed‐effects logistic regression model for ungulate prey as a function of lion sex, treatment area (in/out), and treatment period (pre‐/post‐removal). We used a log‐linear regression model to evaluate changes in home range size. The most common prey were mule deer (55%), feral horses (32%), and coyotes (4%). Twenty‐two of 29 lions consumed horses, although the rate of horse consumption was highly variable across individuals. Horses of both sexes and all age classes were predated. In contrast to predictions, our models detected no effect of removals on diet composition (βinteraction = 0.30 ± 1.1), nor did the removal influence home range size (βinteraction = 0.02 ± 0.02). Despite a 46% reduction in horse abundance, we found no evidence for prey‐switching following the horse removal treatment. Removal magnitude, rapid horse immigration, and/or behavioral specialization of individual mountain lions may help explain these results. Our findings have important implications for mountain lion and feral horse management in arid environments characterized by high prey diversity, but low prey abundance. [ABSTRACT FROM AUTHOR]

Juvenile North Pacific Albacore tuna (Thunnus alalunga) support commercial and recreational fisheries in the California Current Large Marine Ecosystem (CCLME), where they forage during summer and fall. The distributions of the commercial and recreational fisheries and estimates of forage availability have varied substantially over the past century. Time-series quantifying Albacore diet can help link forage composition to variability in Albacore abundance and distribution and, consequently, their availability to fishers. Previous diet studies in the CCLME are of relatively short duration, and long-term variability in Albacore diet remains poorly understood. We describe the diets of juvenile Albacore from three regions in the CCLME from 2007 to 2019 and use classification and regression tree analysis to explore environmental drivers of variability. Important prey include Northern Anchovy (Engraulis mordax), rockfishes (Sebastes spp.), Boreal Clubhook Squid (Onychoteuthis borealijaponica), euphausiids (Order: Euphausiidae), and amphipods (Order: Amphipoda), each contributing >5% mean proportional abundance. Most prey items were short lived species or young-of-the-year smaller than 10 cm. Diet variability was related to environmental conditions over the first 6 months of the year (PDO, sea surface temperature, and NPGO) and conditions concurrent with Albacore capture (region and surface nitrate flux). We describe foraging flexibility over regional and annual scales associated with these environmental influences. Continuous, long-term studies offer the opportunity to identify flexibility in Albacore foraging behavior and begin to make a predictive link between environmental conditions early in the year and Albacore foraging during summer and fall.

Prey abundance and size vary seasonally, creating a dynamic connection between predator and prey. The natural complexity related to consuming multiple prey types as fish undergo ontogenetic diet shifts combined with the frequent sampling and substantial laboratory time investment required to investigate seasonal predator-prey dynamics limits understanding of seasonal prey availability and age-0 prey taxa and size selection. Our study used frequent prey sampling spanning a four-year period to understand which prey taxa and sizes are seasonally available to age-0 walleye Sander vitreus, which were sampled from May to November across all four years of this study to document food habits and prey sizes. Consumed prey were then compared to available prey within the reservoir to evaluate prey taxa and size selection. Age-0 walleye seasonal food habits were consistently simplistic as age-0 walleye in this study largely consumed a single zooplankton taxa (calanoida) and then shifted directly to piscivory where they again focused consumption on a single taxa, and age group (age-0 gizzard shad Dorosoma cepedianum) while passing over available benthic macroinvertebrates. The ontogenetic shift to larval gizzard shad coincided with peak larval shad availability. Interestingly, age-0 walleye were size selective for both prey types, selecting the largest calanoida available when zooplanktivorous but consuming some of the smallest age-0 gizzard shad despite increasing gape size that would have allowed for consumption of larger shad.

This study investigated the feeding behavior of the generalist predator Nabis ferus (Heteroptera: Nabidae) toward various Aphididae species as prey in a laboratory setting. Data were obtained on the predatory behavior of N. ferus, including a ranking of the most preferred species for feed. Eight representatives of the Aphididae family were used as prey: Schizaphis graminum, Rhopalosiphum padi, Aphis fabae, Megoura viciae, Brevicoryne brassicae, Aphis pomi, Myzus cerasi and Aphis urticata. The average number of prey ranged from 11.2±1.18 in the case of bird cherry-oat aphid to 13.7±0.38 in case of the apple aphid. The consumption of M. viciae individuals was significantly lower, averaging 6.6±1.03 aphids per predator. These studies have implications for the biological control of phytophagous pests in agriculture. These findings highlight the potential of N. ferus as a sustainable and effective control agent to organic farming.

The trophic niche is one of the most important ecological traits for any species, providing information about trophic position in the food web, habitat preferences, and interspecific interactions. In this study, we describe the autumn diet of two sympatric species of salamander from central Italy—Italian Cave Salamanders (Speleomantes italicus) and Fire Salamanders (Salamandra salamandra), assessing whether competition for the same prey occurs. Furthermore, we combine our data with those obtained for the same population during a different season (spring) and assess potential seasonal variation in the diet of these two salamander species. The overlap of the trophic niche between the two species was limited, with S. italicus consuming smaller and fast-moving prey (e.g., Diptera, Collembola), and S. salamandra consuming slow and often elongated prey (e.g., Gastropoda, Haplotaxida, Diplopoda). Seasonal differences in diet composition were observed in both species between spring and autumn; in autumn, both species narrowed their trophic niche breadth. This seasonal divergence is likely due to the variation of prey phenology and availability. The consumption of prey of different size was likely the main factor allowing the coexistence of these two salamander species. In both species we observed a general increase in the proportion of generalist individuals in autumn, most likely because of a reduction in prey availability. In addition to providing information on the trophic niche of these species, our study represented a further step that helps unravel the dynamics promoting the coexistence of potentially competing species. [ABSTRACT FROM AUTHOR]

Riparian ecosystems are valuable habitats for bats, due to high densities of emergent aquatic invertebrates that provide high-quality feeding areas. Throughout Europe, decline and extirpation of European beaver (Castor fiber) has been a key driver in the decline of the extent and quality of riparian habitat, and thus recolonisation has considerable potential to restore degraded areas. Previous research has shown that beaver-modified ecosystems can support more bats, but the assumed causal link (an increase in invertebrate prey) has not been tested. Here, we study bat activity and richness/abundance of aquatic macroinvertebrates at a site where free-roaming beavers have colonised naturally from a nearby (unofficial) release location versus a nearby control site with very similar hydrology and habitat matrix. Bat activity was recorded using walked activity transects and fixed-point acoustic detectors. Although bat species richness was similar, bat activity was substantially and significantly higher at the beaver site versus the control site overall (42.7%) and for four specific taxa: soprano pipistrelle (Pipistrellus pygmaeus; 8.4%), Daubenton's (Myotis daubentonii; 46.5%), common pipistrelle (Pipistrellus pipistrellus; 110.4%) and common noctule (Nyctalus noctula; 170.9%). Richness of the larvae/nymphs of emergent aquatic macroinvertebrate species known to form an important part of bat diet was 205.5% higher at the beaver site compared to the control site, while abundance was 817.4% higher. Overall bat activity was also linked to habitat (lotic > lentic), survey method (transect > fixed-point), and season (May–July peak). This is the first evidence of a likely causal link between beaver recolonisation and bat activity via an increase in abundance of key aquatic invertebrate prey and we recommended that benefits of beaver reintroduction on bats be considered in future feasibility studies. [ABSTRACT FROM AUTHOR]

Novel interactions between invaders and native species that have evolved in their absence may impose strong selective pressures that drive species to extinction or prompt rapid co-evolution and learning. Here, we report on the effects that invasive cane toads, a toxic prey species, have had on freshwater crocodile populations in 7 waterholes of the Victoria River, Australia, before and up to 14 years after toads invaded. We recorded observations of crocodiles attacking toads, dissected dead crocodiles to determine if they had eaten toads and indexed the abundances of cane toads, live crocodiles and dead crocodiles. Following toad-invasion we observed crocodiles attacking cane toads. Dead crocodiles were only observed following the invasion of toads and 62% of the 71 dead crocodiles we dissected had toads in their stomachs. Counts of dead crocodiles showed a humped relationship with time since toad invasion and declined markedly after 3 years post-toad invasion. Live crocodile abundance declined sharply following toad-invasion, but this decline attenuated approximately 4 years post-invasion. The pulse of crocodile mortality and attenuation of the rate of crocodile population decline suggests that crocodiles have evolved or learned to enable co-existence with toads. However, crocodile populations have shown no sign of recovery in the 8–14 years post toad invasion. Our findings highlight that adaptation by native species to the presence of invaders may be imperfect and thus may not necessarily entail numerical recovery of populations to pre-invasion levels, but instead downward shifts to new equilibria due to ongoing interactions with invaders. [ABSTRACT FROM AUTHOR]

Context: Predators typically select prey on the basis of their availability and traits such as body size, speed, camouflage and behaviour that influence ease of capture. Such selectivity, particularly by invasive predators, can disproportionately affect the conservation status of prey. Control of top-order predators can also trigger trophic cascades if subordinate predators have different prey preference. Aims: We aimed to document prey selectivity of feral cats by comparing their diet with prey availability over a 27-year study in an Australian desert. Methods: Stomach-content and demographic data were recorded from 2293 feral cats, showing 3939 vertebrate prey. These were compared with vertebrate-prey availability estimated from 224,472 pitfall-trap nights, 9791 Elliott-trap nights and opportunistic sampling that accumulated 9247 small mammal and 32,053 herptile records. Potential bird availability was assessed through 2072 quantitative counts amounting to 29,832 bird records. We compared cat selectivity among species, guilds, and physical and behavioural traits of potential prey. Key results: Prey guild selectivity from two quantitative subsets of these data indicated that cats preferentially selected medium-sized rodents, snakes and ground-nesting birds over other prey guilds, and also preyed extensively on rabbits, for which selectivity could not be assessed. Species that froze or responded defensively to predators were less favoured than were prey that fled, including fast-evading species. Species inhabiting dunes were hunted more frequently relative to their abundance than were closely related species on stony plains. Conclusions: The size, habitat preference and response to predators of potential prey species affect their targeting by feral cats. Implications: Our results assist assessment of risk to wildlife species from cat predation and suggest that cat control will trigger changes in the relative abundance of prey species depending on their size, habitat use and behaviour. Cat hunting selectivity has the potential to influence trophic cascades and conservation status of wildlife, including many species threatened by cat predation. Analyses of a 27-year dataset of over 2000 cats and 4000 prey items identified species and guilds disproportionately hunted by cats relative to their availability. Implications of prey selectivity for conservation planning are described. Photograph by John Read. [ABSTRACT FROM AUTHOR]

Context: In the vicinity of the western Rajaji Tiger Reserve, a significant rise in conflicts between humans and leopards has occurred. These conflicts have resulted in a substantial number of human deaths, with 60% attacks resulting in deaths over a 4-year period. Aims: This study aims to examine any potential connection among the non-breeding tigers, leopards, prey, humans and the increased occurrence of conflicts. Methods: To address this objective, we conducted an analysis to evaluate the density of leopards, as well as their spatial and temporal behaviour with respect to tigers, prey and humans through on-site habitat use, circular statistics, diel-overlap as well spatial niche breadth and spatial-niche overlap. Key results: Our findings showed one of the highest leopard-density estimates (excluding cubs) (mean ± s.e.) of 23.7 ± 4.8 per 100 km2. When examining on-site habitat use by leopards, we found three variables that had a negative influence, namely, human presence, slope, and the presence of tigers. The presence of a large prey (sambar) had a positive influence. Leopards, exhibiting the highest spatial-niche breadth, demonstrated a small overlap with both tigers and humans, while displaying a significant diel overlap with sambar. The niche overlap was notably high with sambar, but very low with humans and tigers. Conclusions: Although tigers locally created a zone of spatial and temporal avoidance, at the population level the leopards experienced a surge in numbers in response to the reduced tiger numbers, indicated by their high density. This could be a cause of high leopard movement into nearby human settlements. This unique scenario could have contributed to conflict. Implications: Understanding the coexistence among different species and the impact of transient animals is crucial to develop effective management strategies to mitigate conflict. This approach would facilitate and ensure the long-term survival of diverse large carnivores in the tropical forests of southern Asia through sustained support for conservation from local communities. The larger carnivores often influence a top–down regulation on mesopredator behaviour. This study aimed to assess the response of the leopards to non-breeding tigers and its probable link with the conflict with humans, and showed that leopards avoided tigers and increased in substantial numbers, with transient individuals likely to be dispersing and causing conflict. We make recommendations to study the coexistence of copredators and transient animals. Photograph by Wildlife Institute of India. [ABSTRACT FROM AUTHOR]

The behavioural responses of predator-naïve (laboratory-born), predator-experienced (laboratory-born but with short-term experience with predators), and wild-caught (with long-term experience with predators in natural settings) tadpoles of Sphaerotheca breviceps to carnivorous predatory tadpoles of Hoplobatrachus tigerinus was studied in the laboratory. The predator's stimulus solution (kairomones) was used to simulate predation threat. All S. breviceps tadpoles (i.e., predatornaïve, predator-experienced and wild-caught) exhibited behavioural antipredator responses, i.e., reduced swimming activity and time spent swimming, and had a higher burst speed in response to water-borne kairomonal cues of predators. Wildcaught tadpoles showed stronger responses than predator-naïve and predator-experienced tadpoles and the latter exhibited stronger responses than predator-naïve tadpoles. Our study thus suggests that antipredator behaviour in these tadpoles is basically innate. Furthermore, the enhanced antipredator behaviour of wild-caught tadpoles indicates that learning is involved. [ABSTRACT FROM AUTHOR]

Northwest Atlantic harbor (Phoca vitulina vitulina) and gray (Halichoerus grypus atlantica) seal populations are recovering from early to mid-20th century exploitation, increasing their biological interactions and bycatch in Northeastern US commercial fisheries. We evaluated the seals' diet composition and compared their prey to commercial catches to assess trophic overlap and potential competition with commercial fisherman target catches. We obtained 148 harbor and 178 gray seal stomach samples from bycatch events that occurred between 2004 and 2018. We learned from the hard part remains that the majority of seals bycaught are young-of-the-year (≤12 months old) that consume a wide breadth of prey across three trophic groups. There was a general dichotomy in extrinsic factors associated with seal diet in which 45% trophic niche separation was explained by non-overlapping harbor and gray seal phenology and pup haul-out locations that are adjacent to active fishing areas. Prey size estimated from fish otoliths and squid beaks recovered from stomach contents showed that gray seals consumed larger prey than harbor seals and prey sizes from both seals showed limited overlap with prey sizes caught by commercial gillnet fishermen. The most important prey to both seals included large (>20 cm) and small (≤20 cm) silver hake (Merluccius bilinearis), (≤40 cm) red hake (Urophycis chuss), gulf stream flounder (Citharichthys arctifrons), medium (21-40 cm) white hake (Urophycis tenuis), and (<50 cm) Atlantic cod (Gadus morhua). Important prey to harbor seals that did not overlap with gray seals were Acadian redfish (Sebastes fasciatus), Atlantic herring (Clupea harengus), longfin (Doryteuthis pealeii), and shortfin squid (Illex illecebrosus). They contrasted with prey important to gray seals that did not overlap with harbor seals: yellowtail flounder (Limanda ferruginea), sand lance (Ammodytes spp.), Urophycis spp., and fourspot flounder (Hippoglossina oblonga). Despite the potential bias associated with opportunistic bycatch sampling, this study demonstrates the importance and value of utilizing carcasses retained from bycatch events, is complimentary to newer methodologies (i.e., DNA meta-barcoding), and fills data gaps in our understanding of the role recovering harbor and gray seal populations have on Northeastern US regional food webs. [ABSTRACT FROM AUTHOR]

Calanus finmarchicus is an abundant calanoid copepod in the New York Bight (NYB) that has energy-dense lipid stores. This study measured C. finmarchicus abundance, lipid storage and energy density and compared it to two other abundant calanoid species in the region. We compared the NYB C. finmarchicus preyfield characteristics with data from two other NW Atlantic coastal ecosystems, the Gulf of Maine (GoM) and Cape Cod Bay (CCB). Copepods from net tows were identified, enumerated, photographed and measured. These data were used to calculate animal biovolume and lipid content as well as the volumetric energy density of the copepod preyfield. C. finmarchicus were most abundant in spring and summer and the mean lipid storage of C. finmarchicus remained largely constant regardless of season and location within the NYB. Centropages typicus were abundant enough in the winter to be more energy-rich than C. finmarchicus. Temora longicornis, while also abundant, never surpassed the energy density of C. finmarchicus. C. finmarchicus in the NYB were comparably lipid-rich to those from the GoM and CCB. C. finmarchicus in the NYB can be a reliable energy source for local predators due to their high spring and summer abundances and year-round storage of high-energy wax esters. [ABSTRACT FROM AUTHOR]

Since the closure of fishing in the Yangtze River, the population of ferocious fish in Poyang Lake has been steadily increasing. In order to investigate whether the Predatory activity of ferocious fish impact the population of Procambarus clarkii, we employed Silurus asotus and Channa argus as predators, using eight different types of bait organisms in this study. Three sizes of P. clarkii larvae (small: 39.20±1.30 mm; medium: 49.82±2.13 mm; large: 58.99±1.16 mm), along with Cyprinus carpio, Carassius auratu, Squaliobarbus curriculus, Mosquitofish, Hypoph-thalmichthys molitrix, Pseudorasbora parva and Macrobrachium nipponense, were used as prey to examine the species selectivity of S. asotus and C. argus and the size selectivity of P. clarkii larvae. The results revealed that: (1) S. asotus and C. argus exhibited a preference for nocturnal predation, with their peak predation occurring between 20:00--8:00; (2) In the presence of various food organisms simultaneously, S. asotus and C. argus did not prey on P. clarkii larvae, displaying clear predation preference for C. carpio, mosquitofish and M. nipponense. (3) When presented with P. clarkii larvae of the same size, S. asotus exhibited a pronounced predation preference for small size P. clarkii larvae, while C. argus preyed significantly more on small-sized P. clarkii larvae than on large-sized ones (P<0.05). (4) In the equal polyculture combination of various sizes of P. clarkii larvae, both S. asotus and C. argus displayed a clear preference for small size P. clarkii larvae, and this preference intensified with increasing size gap among the P. clarkii larvae. In summary, when multiple food organisms coexist, P. clarkii is not the preferred prey for ferocious fish, however, when the variety and quantity of other food organisms are limited, smaller-sized P. clarkii larvae remain at a high risk of predation. [ABSTRACT FROM AUTHOR]

The Psychedelic Rock Gecko (Cnemaspis psychedelica), is a species endemic to southernmost Vietnam. It was recently assessed as Endangered in the IUCN Red List and also included in the CITES Appendix I, due to anthropogenic threats such as habitat degradation and over-collection for the pet trade. To protect wild populations and the natural habitat of this species, knowledge of its demography and ecology is essential to implement fitting conservation measures. In this study, we conducted field surveys on Hon Khoai Island, Ca Mau Province, southern Vietnam in both dry and wet seasons, and obtained food contents of 114 individuals of C. psychedelica by water-flushing the stomach without sacrificing them. Consequently, 685 invertebrate items were identified, belonging to 24 different prey types of 20 invertebrate orders, as well as flatworms, snails and plant parts. Araneae, Blattodea, Hymenoptera and Isoptera were identified as the most important prey of C. psychedelica , among which Araneae accounted for the highest percentage, and thus the highest importance index, during the dry season and Hymenoptera during the wet season. There was a large overlap in the trophic niche between the two seasons, and between males and females of C. psychedelica. This study shows that not only suitable habitat but also a particular food spectrum is a requirement for the species and this, in addition, is important to optimize conservation breeding programs. [ABSTRACT FROM AUTHOR]

Abstract The ‘landscape of fear’ concept offers valuable insights into wildlife behaviour, yet its practical integration into habitat management for conservation remains underexplored. In this study, conducted in the subtropical monsoon grasslands of Bardia National Park, Nepal, we aimed to bridge this gap through a multi‐year, landscape‐scale experimental investigation in Bardia National Park, Nepal. The park has the highest density of tigers (with an estimated density of ~7 individuals per 100 km2) in Nepal, allowing us to understand the effect of habitat management on predation risk and resource availability especially for three cervid species: chital (Axis axis), swamp deer (Rucervus duvaucelii) and hog deer (Axis porcinus). We used plots with varying mowing frequency (0–4 times per year), size (ranging from small: 49 m2 to large: 3600 m2) and artificial fertilisation type (none, phosphorus, nitrogen) to assess the trade‐offs between probable predation risk and resources for these cervid species, which constitute primary prey for tigers in Nepal. Our results showed distinct responses of these deer to perceived predation risk within grassland habitats. Notably, these deer exhibited heightened use of larger plots, indicative of a perceived sense of safety, as evidenced by the higher occurrence of pellet groups in the larger plots (mean = 0.1 pellet groups m−2 in 3600 m2 plots vs. 0.07 in 400 m2 and 0.05 in 49 m2 plots). Furthermore, the level of use by the deer was significantly higher in larger plots that received mowing and fertilisation treatments compared to smaller plots subjected to similar treatments. Of particular interest is the observation that chital and swamp deer exhibited greater utilisation of the centre (core) areas within the larger plots (mean = 0.21 pellet groups m−2 at the centre vs. 0.13 at the edge) despite the edge (periphery) also provided attractive resources to these deer. In contrast, hog deer did not display any discernible reaction to the experimental treatments, suggesting potential species‐specific variations in response to perceived predation risk arising from management interventions. Our findings emphasise the importance of a sense of security as a primary determinant of habitat selection for medium‐sized deer within managed grassland environments. These insights carry practical implications for park managers, providing a nuanced understanding of integrating the ‘landscape of fear’ into habitat management strategies. This study emphasises that the ‘landscape of fear’ concept can and should be integrated into habitat management to maintain delicate predator–prey dynamics within ecosystems.

ABSTRACT DNA metabarcoding is a rapidly advancing tool for diet assessment in wildlife ecology. Studies have used a variety of field collection methods to evaluate diet; however, there is a pressing need to understand the differences among sampling methods and the downstream inferential consequences they may have on our ability to document diet accurately and efficiently. We evaluated seven DNA metabarcoding sampling methods to assess the diet of a large avian predator: Buteo lagopus (rough‐legged hawk). We collected beak swabs, talon swabs, cheek (buccal) swabs, cloacal swabs, and cloacal loops from captured birds, and collected fecal samples from both captured and uncaptured birds. We described and compared variation in prey recovery within and among the seven sampling methods and identified appropriate analytical methods to compare diet among individuals sampled via different methods. Beak and talon swabs produced the highest prey detection rates, yielded the greatest prey richness per sample, and contributed the most to an individual's total prey richness per sampling occasion compared to other sampling methods. Within individuals sampled using five methods during a single capture occasion, cloacal swabs and cheek swabs positively predicted prey richness and average prey mass, respectively, from fecal samples. While all methods identified similar dominant prey taxa that were consistent with prior diet studies, beak and talon swabs detected greater prey richness at both the individual and population levels. We propose a food residue duration hypothesis whereby methods which sample areas containing food DNA consumed from longer and more continuous pre‐sampling time intervals explain variation among sampling methods in observed prey richness. Choice of sampling method can influence predator diet characterization and is particularly important if researchers wish to quantify uncommon diet items or compare diet metrics using samples collected via different methods.

Black ruff (Centrolophus niger) is a rare and poorly studied species found in both the Atlantic and Pacific Oceans and also in the Mediterranean Sea. It is sporadically caught south of Iceland during the annual International Ecosystem Summer Survey of the Nordic Seas. In total, 43 specimens were caught from 2009 to 2021, of which 41 specimens were caught during 2017–2021. All specimens, except one, were caught using a pelagic trawl (cod‐end mesh‐size: 50 mm) close to the surface (trawl depth: 0–35 m) with in situ temperature ranging from 9 to 13°C. The area south of Iceland is characterized by having warmer temperatures than other areas around the island, which might be indicative of a northern limit for the distribution of black ruff. The fish were primarily in the range of 29–46 cm with a few larger individuals up to 71 cm. Fourteen fish, caught in 2017 and 2021, were dissected to gather biological information on this species. These fish were all juveniles with no obvious sign of gonad development. Correlations between total length, fork length, and standard length are presented. Otoliths were thin and delicate with a length of ~13–16 mm, and otolith size (length, width, and area) was correlated with fish size. Much of the stomach content was at an advanced stage of digestion, but some contents could be identified and consisted of invertebrates, primarily of the orders Amphipoda and Calanoida with some unidentified fish also present. [ABSTRACT FROM AUTHOR]

Nonbreeding raptors are vulnerable to many anthropogenic changes such as habitat fragmentation and increasing risk of collision (e.g., with wind turbines, powerlines, or vehicles). One aspect of habitat quality for raptors during winter has received comparably less attention: the role of colonial burrowing rodents such as prairie dogs (Cynomys spp.) as a reliable food source, and the effects of widespread reduction in prairie dog abundance and availability to nonbreeding raptors. We used a historical dataset (1998–2002) of roadside surveys for raptors and prairie dogs in the Southern and Central Great Plains, including Arizona, Colorado, New Mexico, and Texas, USA, and the Mexican state of Chihuahua, to provide the most spatially and temporally expansive analysis to date of the potential role of prairie dogs in influencing presence and abundance of raptors. We assessed patterns of co-occurrence among raptors and prairie dogs and modeled the response of selected species to weather, latitude, grassland cover, and prairie dog presence and abundance at multiple spatial scales. During the study period, we detected 19 species of raptors and identified nine raptor species that co-occurred with prairie dogs more than expected by chance. We also found evidence that occurrence of prairie dogs was related to presence and/or abundance of Ferruginous Hawks (Buteo regalis), Golden Eagles (Aquila chrysaetos), Bald Eagles (Haliaeetus leucocephalus), and Rough-legged Hawks (B. lagopus). Our work underscores the association of prairie dogs with many wintering raptor species, especially Ferruginous Hawks and Golden Eagles, and indicates that prairie dogs may also be an important resource for Rough-legged Hawks and Bald Eagles during the nonbreeding season. Las rapaces no reproductoras son vulnerables a muchos cambios antropogénicos, como la fragmentación del hábitat y el aumento del riesgo de colisión (por ejemplo, con aerogeneradores, líneas eléctricas o vehículos). Un aspecto de la calidad del hábitat para las rapaces durante el invierno ha recibido comparativamente menos atención: el papel de roedores coloniales que excavan madrigueras, como los perritos de las praderas (Cynomys spp.), como una fuente confiable de alimento, y los efectos de la reducción generalizada en la abundancia y disponibilidad de perritos de las praderas para las rapaces no reproductoras. Utilizamos una serie de datos histórica (1998–2002) de censos en carreteras de rapaces y perritos de las praderas en las Grandes Llanuras del sur, que incluyen Arizona, Colorado, Nuevo México y Texas, EEUU, y el estado mexicano de Chihuahua, para proporcionar el análisis espacial y temporal más amplio hasta la fecha sobre el papel potencial de los perritos de las praderas en la influencia de la presencia y abundancia de rapaces. Evaluamos patrones de coocurrencia entre rapaces y perritos de las praderas y modelamos la respuesta de especies seleccionadas a factores como el clima, la latitud, la cobertura de pastizales y la presencia y abundancia de perritos de las praderas considerando múltiples escalas espaciales. Durante el período de estudio, detectamos 19 especies de rapaces e identificamos nueve especies de rapaces que coocurrieron con perritos de las praderas más de lo esperado por azar. También encontramos evidencia de que la presencia de perritos de las praderas estaba relacionada con la presencia y/o abundancia de Buteo regalis, Aquila chrysaetos, Haliaeetus leucocephalus, y B. lagopus. Nuestro trabajo destaca la asociación de los perritos de las praderas con muchas especies de rapaces invernantes, especialmente con B. regalis y A. chrysaetos, e indica que los perritos de las praderas también pueden ser un recurso importante para B. lagopus y H. leucocephalus durante la temporada no reproductiva. [Traducción del equipo editorial] [ABSTRACT FROM AUTHOR]

With about 8000 marine benthic species, the amphipod crustaceans form one of the richest animal groups of the worldwide Ocean. They have colonized a wide range of soft- and hard-bottom natural and artificial habitats extending from the intertidal to hadal zones. Moreover, they show a broad size spectrum, with numerous giant species exceeding 20 cm in length and some species smaller than 2 mm. When biofouling artificial hard surfaces, some tube-building species can form very dense populations comprising up to 100,000 individuals per square meter. Amphipods are important prey for fish and mammals. Along with cephalopod juveniles, they are also included in the trophic diet of shorebirds that consume amphipods mostly during the low tide on tidal flats. They display diel migration, which reinforces the predation by demersal fish in the suprabenthic zone just above the sea bed, as well as by pelagic fish in the water column. Despite their importance in terms of biodiversity and trophic transfer, no general overview is available on the role of benthic amphipods in marine ecosystem food webs. Various methods, including laboratory and field experiments, as well as the analysis of stomach contents and DNA extraction, have been used to identify the prey/predator trophic links. Based on an extensive literature review, this study discusses the role of marine benthic amphipods as potential food for higher trophic levels in natural and artificial hard-bottom communities created via the construction of offshore wind farms. [ABSTRACT FROM AUTHOR]

Simple Summary: Masu salmon (Oncorhynchus masou), a commercially important fish endemic to the North Pacific Ocean, received national second-level protected animal status in China in 2021. Employing gastrointestinal tract environmental DNA (GITeDNA) metabarcoding and traditional morphology, this study explored the diet of fluviatile Masu salmon. The results showed a diverse prey composition, with larger fish exhibiting a significant preference for terrestrial invertebrates. The fluviatile Masu salmon acts as a crucial link between aquatic and terrestrial food webs, emphasizing the need for conservation efforts in riparian habitats. This study recommends combining GITeDNA metabarcoding and morphological observation for a comprehensive understanding of fish diet diversity. Masu salmon, Oncorhynchus masou (Brevoort 1856), a commercially important fish species endemic to the North Pacific Ocean, attained national second-level protected animal status in China in 2021. Despite this recognition, knowledge about the trophic ecology of this fish remains limited. This study investigated the diet diversity of fluviatile Masu salmon in the Mijiang River, China, utilizing the gastrointestinal tract environmental DNA (GITeDNA) metabarcoding and morphological identification. The results revealed a diverse prey composition, ranging from terrestrial and aquatic invertebrates to small fishes. The fluviatile Masu salmon in general consumed noteworthily more aquatic prey than terrestrial prey. There were much more prey taxa and a higher diet diversity detected by GITeDNA metabarcoding than by morphological identification. GITeDNA metabarcoding showed that larger and older Masu salmon consumed significantly more terrestrial insects than aquatic prey species did, with 7366 verses 5012 sequences in the group of ≥20 cm, 9098 verses 4743 sequences in the group of ≥100 g and 11,540 verses 729 sequences in the group of age 3+. GITeDNA metabarcoding also showed size- and age-related diet diversity, indicating that the dietary niche breadth and trophic diversity of larger and older Masu salmon increased with food resources expanding to more terrestrial prey. Terrestrial invertebrates of riparian habitats play a vital role in the diet of fluviatile Masu salmon, especially larger individuals, highlighting their importance in connecting aquatic and terrestrial food webs. Conservation plans should prioritize the protection and restoration of riparian habitats. This study advocates the combined use of GITeDNA metabarcoding and morphological observation for a comprehensive understanding of fish diet diversity. [ABSTRACT FROM AUTHOR]

The dynamic interactions between predators and their prey have two fundamental processes: numerical and functional responses. Numerical response is defined as predator growth rate as a function of prey density or both prey and predator densities [dP/dt = f(N, P)]. Functional response is defined as the kill rate by an individual predator being a function of prey density or prey and predator densities combined. Although there are relatively many studies on the functional response in mammalian predators, the numerical response remains poorly documented. We studied the numerical response of Eurasian lynx (Lynx lynx) to various densities of its primary prey species, roe deer (Capreolus capreolus), and to itself (lynx). We exploited an unusual natural situation, spanning three decades where lynx, after a period of absence in central and southern Sweden, during which roe deer populations had grown to high densities, subsequently recolonized region after region, from north to south. We divided the study area into seven regions, with increasing productivity from north to south. We found strong effects of both roe deer density and lynx density on lynx numerical response. Thus, both resources and intraspecific competition for these resources are important to understanding the lynx population dynamic. We built a series of deterministic lynx–roe deer models, and applied them to the seven regions. We found a very good fit between these Lotka–Volterra type models and the data. The deterministic models produced almost cyclic dynamics or dampened cycles in five of the seven regions. Thus, we documented population cycles in this large predator–large herbivore system, which is rarely done. The amplitudes in the dampened cycles decreased toward the south. Thus, the dynamics between lynx and roe deer became more stable with increasing carrying capacity for roe deer, which is related to higher productivity in the environment. This increased stability could be explained by variation in predation risk, where human presence can act as prey refugia, and by a more diverse prey guild that will weaken the direct interaction between lynx and roe deer. [ABSTRACT FROM AUTHOR]

Predation is a crucial ecosystem function, transferring nutrients and shaping the abundance and diversity of animals within communities. On coral reefs, fish-fish predation (i.e., piscivory) is arguably one of the best known ecosystem functions, yet is also one of the least well quantified. Recent work has suggested that the prey capture performance of piscivorous fishes may differ when feeding on actively swimming vs. cryptobenthic fish prey. However, the extent of this difference remains unquantified. Our goal, therefore, was to conduct performance-based experiments comparing piscivorous fishes feeding on two different fish prey types, namely, actively swimming vs. cryptobenthic prey (i.e., prey sitting on the benthos). While predators were able to immediately detect actively swimming prey, when feeding on cryptobenthic prey, predators were generally unable to detect the prey until it moved. Both focal predators, the grabber Pseudochromis fuscus and the engulfer Pterois volitans were less successful at capturing cryptobenthic prey (mean 28% probability of capture), compared to actively swimming prey (85%). Overall, our study demonstrates the heterogeneous nature of fish predation on coral reefs, and the challenges of feeding on different prey functional groups. [ABSTRACT FROM AUTHOR]

Species assemblages are influenced by trophic and intraguild interactions, which may be competitive, facilitative, or neutral. These interactions vary in relative importance depending on resource availability. We assessed the nature of interactions among six carnivore species (Ursus arctos, Panthera uncia, Vulpes vulpes, Mustela altaica, and Martes foina) and their prey (Capra sibirica, Pseudois nayaur, Hemitragus jemlahicus, Moschus leucogaster, Ochotona sp., and Rodentia sp.) by examining their spatial–temporal overlaps using camera‐trap data gathered between 2016 and 2019 from the resource‐limited landscapes of the high Himalayas. We examined fine scale pairwise spatial interaction using multi‐species occupancy method and temporal overlap using time activity kernel densities function. Carnivore species showed relatively high spatio‐temporal overlap. We found spatial avoidance between two pairs and temporal avoidance between four out of 15 pairs. Contrary to our expectation that carnivore species would segregate due to competition in a resource‐poor environment, our results showed that they generally showed significant co‐occurrence and appeared to track their prey's activity. Our findings highlight the potentially overriding role of prey availability in influencing carnivore species occurrence in resource‐poor landscapes. [ABSTRACT FROM AUTHOR]

We report for the first time multitrophic interaction among Thamnophis sumichrasti (Squamata, Natricidae), Isthmura gigantea (Caudata, Plethodontidae), and Megacormus gerstchi (Scorpiones, Euscorpiidae), three endemic, rare and endangered species that inhabit cloud forests and pine-oak forests from Sierra Madre Oriental in México, which provides novel data on their natural history and distribution.

Northwest Atlantic harbor (Phoca vitulina vitulina) and gray (Halichoerus grypus atlantica) seal populations are recovering from early to mid-20th century exploitation, increasing their biological interactions and bycatch in Northeastern US commercial fisheries. We evaluated the seals’ diet composition and compared their prey to commercial catches to assess trophic overlap and potential competition with commercial fisherman target catches. We obtained 148 harbor and 178 gray seal stomach samples from bycatch events that occurred between 2004 and 2018. We learned from the hard part remains that the majority of seals bycaught are young-of-the-year (≤12 months old) that consume a wide breadth of prey across three trophic groups. There was a general dichotomy in extrinsic factors associated with seal diet in which 45% trophic niche separation was explained by non-overlapping harbor and gray seal phenology and pup haul-out locations that are adjacent to active fishing areas. Prey size estimated from fish otoliths and squid beaks recovered from stomach contents showed that gray seals consumed larger prey than harbor seals and prey sizes from both seals showed limited overlap with prey sizes caught by commercial gillnet fishermen. The most important prey to both seals included large (>20 cm) and small (≤20 cm) silver hake (Merluccius bilinearis), (≤40 cm) red hake (Urophycis chuss), gulf stream flounder (Citharichthys arctifrons), medium (21–40 cm) white hake (Urophycis tenuis), and (

To compare the trophic characteristics of pelagic- and bottom-dwelling fish in the western Chukchi Sea, isotopic composition of carbon and nitrogen (δ13С and δ15N) is considered separately for the Subarctic water mass (invaded from the Bering Sea) and local Arctic water mass. In summer of 2018 and 2019, the proper water mass occupied mostly the area southward from 71оN and the latter one – northward from this latitude. The isotopic composition of both pelagic and bottom nekton in the southern area was characterized by higher values of δ13C (up to 2 % higher) and low values of δ15N (up to 1 % lower) in comparison with those in the northern area. That was interpreted that in the southern area, within the water from the Bering Sea, more than 90 % of the sampled bottom fish species were linked with prey from the bottom community. In the northern area, within the Arctic water, all samples of bottom fish were characterized by minimal content of heavy carbon δ13C isotope, comparable with the values in samples of pelagic fish that indicated a significant role of pelagic prey in nutrition of the bottom nekton.