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Marine monitoring efforts are increasingly supported by opportunistic shipboard surveys. However, opportunistic survey methods often require adaptation to suit the vessel and the operations being conducted onboard. Whilst best-practice techniques for surveying marine wildlife on vessels of opportunity are yet to be established, testing and development of alternative methods can provide means for capturing ecological information in otherwise under-surveyed areas. Explicitly, survey methods can be improved while baseline ecological data for new regions are gathered simultaneously. Herein, we tested different survey approaches on a vessel of opportunity in a remote offshore area where little is known about the community composition of top-order marine vertebrate predators: western and south-western Tasmania, Australia. We found that continuous surveys provide greater species counts than structured "snapshot" surveys over the course of a voyage, but that structured surveys can be more practical when managing factors such as observer fatigue. Moreover, we provide a baseline dataset on the marine vertebrate community encountered in western and south-western Tasmania. This information will be critically important for industry and conservation management objectives, and is key to our understanding of the offshore ecosystem around Tasmania. [ABSTRACT FROM AUTHOR]

This article discusses the observation of the critically endangered soupfin shark in the Changing Salish Sea. The study confirms the presence of soupfin sharks in Hammersley Inlet through fishing efforts and sampling. The findings suggest that the presence of soupfin sharks may have implications for trophic dynamics and fisheries management in the region. The article also provides a list of references for further research on marine ecosystems in the Salish Sea and surrounding areas. [Extracted from the article]

Worldwide, lobsters are considered key predators that control urchin populations. It has been widely reported that lobster size plays a significant role in the size of urchins they feed on, as does the size of the urchin. Generally, it is thought that small palinurid "spiny" lobsters measuring less than 120 mm carapace length (CL) are morphologically incapable of eating urchins, while large lobsters are voracious predators. Urchin size is expected to affect predation with larger urchins of greater than 90 mm test diameter (TD) presenting the most difficult prey. These generalities, however, have not been quantitatively tested for the eastern spiny lobster Sagmariasus verreauxi and recently the accepted size paradigm for lobsters eating urchins has come into question. The aim of this study was to assess whether lobster predation on urchins would differ with urchin size or species, or the size of lobster. Our results indicate that S. verreauxi does not fit the common lobster patterns regarding urchin predation. There were generally low rates of predation and a significant negative relationship between feeding and both lobster size and urchin size. We found that small lobsters were capable urchin predators with a higher likelihood of eating urchins than larger lobsters, which were more reluctant predators. While we did find the expected effect of smaller urchins being significantly more vulnerable prey, there was none of the expected size limitations for small lobsters eating large urchins and predation did not differ between urchin species, indicating that this was a general pattern. Overall, we observed low rates of predation, suggesting that either S. verreauxi may not be a key urchin predator like other lobster species elsewhere, or that small lobsters are underestimated as urchin predators in temperate marine ecosystems. [ABSTRACT FROM AUTHOR]

Estimating the densities of marine prey observed in animal-borne video loggers when encountered by foraging predators represents an important challenge for understanding predator-prey interactions in the marine environment. We used video images collected during the foraging trip of one chinstrap penguin (Pygoscelis antarcticus) from Cape Shirreff, Livingston Island, Antarctica to develop a novel approach for estimating the density of Antarctic krill (Euphausia superba) encountered during foraging activities. Using the open-source Video and Image Analytics for a Marine Environment (VIAME), we trained a neural network model to identify video frames containing krill. Our image classifier has an overall accuracy of 73%, with a positive predictive value of 83% for prediction of frames containing krill. We then developed a method to estimate the volume of water imaged, thus the density (N·m-3) of krill, in the 2-dimensional images. The method is based on the maximum range from the camera where krill remain visibly resolvable and assumes that mean krill length is known, and that the distribution of orientation angles of krill is uniform. From 1,932 images identified as containing krill, we manually identified a subset of 124 images from across the video record that contained resolvable and unresolvable krill necessary to estimate the resolvable range and imaged volume for the video sensor. Krill swarm density encountered by the penguins ranged from 2 to 307 krill·m-3 and mean density of krill was 48 krill·m-3 (sd = 61 krill·m-3). Mean krill biomass density was 25 g·m-3. Our frame-level image classifier model and krill density estimation method provide a new approach to efficiently process video-logger data and estimate krill density from 2D imagery, providing key information on prey aggregations that may affect predator foraging performance. The approach should be directly applicable to other marine predators feeding on aggregations of prey. [ABSTRACT FROM AUTHOR]

Interspecific interactions, including predator–prey, intraguild predation (IGP) and competition, may drive distribution and habitat use of predator communities. However, elucidating the relative importance of these interactions in shaping predator distributions is challenging, especially in marine communities comprising highly mobile species.We used individual‐based models (IBMs) to predict the habitat distributions of apex predators, intraguild (IG) prey and prey. We then used passive acoustic telemetry to test these predictions in a subtropical marine predator community consisting of eight elasmobranch (i.e. shark and ray) species in Bimini, The Bahamas.IBMs predicted that prey and IG prey will preferentially select habitats based on safety over resources (food), with stronger selection for safe habitat by smaller prey. Elasmobranch space‐use patterns matched these predictions. Species with predator–prey and asymmetrical IGP (between apex and small mesopredators) interactions showed the clearest spatial separation, followed by asymmetrical IGP among apex and large mesopredators. Competitors showed greater spatial overlap although with finer‐scale differences in microhabitat use.Our study suggests space‐use patterns in elasmobranchs are at least partially driven by interspecific interactions, with stronger spatial separation occurring where interactions include predator–prey relationships or IGP. [ABSTRACT FROM AUTHOR]

Information on how the trophic ecology of predators shapes their movement patterns and space-use is fundamental to understanding ecological processes across organisational levels. Despite this, studies combining spatial and trophic ecology to determine how prey preference and/or resource availability shape space use are lacking in marine predators as these can occur at low density and are often difficult to track over extended periods. Furthermore, many exhibit behavioural variability within species and among closely related, sympatric species adding further complexity. We applied a context-focused, multimethod approach to the understudied great hammerhead shark (Sphyrna mokarran) to test if movement and home ranges relate to prey preference and availability. Movement data from satellite and acoustic telemetry in Queensland, Australia, were combined with stable-isotope analysis, drone surveys, and videos of hunting behaviour. Limited dispersal, and small home ranges in S. mokarran were linked to trophic specialisation on stingray prey. Drone surveys and videos showed predation events on stingrays and demonstrated high, year-round availability of this prey in shallow, inshore habitats, which may allow the majority of S. mokarran to remain resident. This affinity for inshore habitats suggests that critical life-history requirements are performed over local or regional scales, although some larger movements were evident. These results were interpreted in comparison to the well-studied bull shark (Carcharhinus leucas), which showed reliance on pelagic food webs. Carcharhinus leucas had high individual variability in movement, with both large-scale migrations and residency. This could indicate that only some individuals are locally sustained on dynamic, pelagic food webs, while others undergo large-scale excursions over distant habitats. The specialised foraging of S. mokarran indicates they play an apex predator role in shallow, inshore habitats, potentially shaping space-use, and foraging behaviour of batoids. As inshore habitats are disproportionately affected by anthropogenic stressors, S. mokarran's trophic specialisation and limited demographic connectivity may make the species particularly vulnerable to anthropogenic threats. [ABSTRACT FROM AUTHOR]

Despite global declines in the abundance and distribution of predators, conservation and reintroduction efforts are increasingly leading to predator recoveries. Unexpected species interactions and ecological consequences often arise when these predator recoveries occur. Here, we describe a novel species interaction in which coyotes (Canis latrans) kleptoparasitize North American river otters (Lontra canadensis) in a region of river otter recovery along the north‐central California coast, USA. We describe eight observations of coyotes scavenging otter‐killed waterbird carrion, including one observation in which river otters aggressively defended their prey from a coyote kleptoparasite. These observations highlight the importance of carrion provisioning as an overlooked pathway through which river otters facilitate nutrient subsidies to terrestrial scavengers. This behavior may have ecological implications including effects on the abundance, behavior, and health of scavengers as well as their interspecific interactions. We propose hypotheses and questions regarding these ecological consequences to guide further investigations into the cross‐ecosystem impacts of recovering river otter populations. [ABSTRACT FROM AUTHOR]

Oceanic eddies are recognized as pivotal components in marine ecosystems, believed to concentrate a wide range of marine life spanning from phytoplankton to top predators. Previous studies have posited that marine predators are drawn to these eddies due to an aggregation of their forage fauna. In this study, we examine the response of forage fauna, detected by shipboard acoustics, across a broad sample of a thousand eddies across the world's oceans. While our findings show an impact of eddies on surface temperatures and phytoplankton in most cases, they reveal that only a minority (13%) exhibit significant effects on forage fauna, with only 6% demonstrating an oasis effect. We also show that an oasis effect can occur both in anticyclonic and cyclonic eddies, and that the few high-impact eddies are marked by high eddy amplitude and strong water-mass-trapping. Our study underscores the nuanced and complex nature of the aggregating role of oceanic eddies, highlighting the need for further research to elucidate how these structures attract marine predators. This study explores alternative stable states in microbial communities. Focusing on a respiratory tract community of 6 species, the authors identified four distinct stable states that are predicted to be driven by cooperative growth. The findings contrast with the common association between competitive interactions and multistability in microbial communities. Using a sample of a thousand eddies across the world's oceans, this study examines the response of forage fauna detected by shipboard acoustics. The findings show that a minority of eddies exhibit significant effects on forage fauna, but that an oasis effect can sometimes occur. This highlights the need for further research to elucidate how eddies might attract marine predators. [ABSTRACT FROM AUTHOR]

Species in one ecosystem can indirectly affect multiple biodiversity components and ecosystem functions of adjacent ecosystems. The magnitude of these cross‐ecosystem effects depends on the attributes of the organisms involved in the interactions, including traits of the predator, prey and basal resource. However, it is unclear how predators with cross‐ecosystem habitat interact with predators with single‐ecosystem habitat to affect their shared ecosystem. Also, unknown is how such complex top‐down effects may be mediated by the anti‐predatory traits of prey and quality of the basal resource.We used the aquatic invertebrate food webs in tank bromeliads as a model system to investigate these questions. We manipulated the presence of a strictly aquatic predator (damselfly larvae) and a predator with both terrestrial and aquatic habitats (spider), and examined effects on survival of prey (detritivores grouped by anti‐predator defence), detrital decomposition (of two plant species differing in litter quality), nitrogen flux and host plant growth. To evaluate the direct and indirect effects each predator type on multiple detritivore groups and ultimately on multiple ecosystem processes, we used piecewise structural equation models. For each response variable, we isolated the contribution of different detritivore groups to overall effects by comparing alternate model formulations.Alone, damselfly larvae and spiders each directly decreased survival of detritivores and caused multiple indirect negative effects on detritus decomposition, nutrient cycling and host plant growth. However, when predators co‐occurred, the spider caused a negative non‐consumptive effect on the damselfly larva, diminishing the net direct and indirect top‐down effects on the aquatic detritivore community and ecosystem functioning. Both detritivore traits and detritus quality modulated the strength and mechanism of these trophic cascades. Predator interference was mediated by undefended or partially defended detritivores as detritivores with anti‐predatory defences evaded consumption by damselfly larvae but not spiders. Predators and detritivores affected ecosystem decomposition and nutrient cycling only in the presence of high‐quality detritus, as the low‐quality detritus was consumed more by microbes than invertebrates.The complex responses of this system to predators from both recipient and adjacent ecosystems highlight the critical role of maintaining biodiversity components across multiple ecosystems. [ABSTRACT FROM AUTHOR]

In marine ecosystems, predators can affect community and ecosystem dynamics through a variety of processes such as foraging facilitation. Here, we report evidence of foraging facilitation between common bottlenose dolphins (Tursiops truncatus) and double-crested cormorants (Nannopterum auritum) in the Caribbean seagrass-dominated atoll of Turneffe, Belize using aerial drone observations conducted in 2015-2017. While dolphins exhibited occasional aggressive behaviours toward the cormorants, the latter frequently followed dolphin movements, suggesting opportunistic pursuit of dolphins for prey access during dolphin bottom foraging activity. Our observations underscore the intricate ecological relationships among marine predators and highlight the need to quantify the mutual benefits and costs of such interactions as coastal ecosystems are rapidly changing. [ABSTRACT FROM AUTHOR]

The Southern Ocean, its ecosystem, and inhabitants are vulnerable to climate‐mediated shifts in habitat conditions. These changes can affect marine predators in the long term through changes in the distribution, density, and quality of prey. To understand how these changes affect vital rates requires longitudinal studies integrating demography and environmental states. We analyzed 22 years of capture–mark–recapture data to quantify the influence of broad‐scale climate on the survival of male southern elephant seals from Macquarie Island, Tasmania, Australia. Weaning mass was incorporated as a quadratic predictor of survival to account for the known influence of maternal investment. First‐year survival was greatest for weaners weighing 160 kg. Subsequent developmental stages were grouped into juvenile, subordinate, and breeding adult states to reflect the known life history of individuals. We found increased juvenile and subordinate survival with positive values of the previous years' Southern Annular Mode. This is likely due to the northward shift of westerly winds increasing productivity and prey availability in the Sub‐Antarctic region. In contrast to females of this population, the Southern Oscillation Index did not affect male survival. In this highly polygynous mating system, sex‐dependent differences in foraging behavior may be causing the small number of successful breeding adult males to be less susceptible to external influences after reaching the minimum age and body size required to be socially competitive for mating. These extremely large bulls will breed with multiple females and thus make a disproportionate contribution to the gene pool of the next generation. Considering the susceptibility of males to climate influences is therefore highly relevant to assessing the future adaptive capability of the species. [ABSTRACT FROM AUTHOR]

Introduction: Eastern Boundary Upwelling Systems are some of the most productive marine ecosystems in the world. Little is known about habitat associations and spatial distributions of marine predators during seasonal periods of low productivity because there are few at-sea surveys during this period. During low productivity or prey scarcity, predators consuming similar prey in the same time and space may compete for limited resources, or they may avoid competition by exploiting different habitats or occupying separate spaces (i.e. niche partitioning). In this study, we examined habitat associations and niche partitioning of marine predators during the low-productivity winter downwelling season of the northern California Current Ecosystem (CCE). Methods: Seabird and marine mammal counts were continuously collected during systematic at-sea surveys during February--March/April in the northern California Current across four years (2006, 2008, 2009, and 2012). We examined seabird and marine mammal distributions in relation to seven habitat characteristics [i.e., sea surface temperature (°C), salinity, depth (m), seafloor slope (%), distance from shore (km), and distance from the 100 m and 200 m isobaths (km)]. We used a non-parametric multivariate analysis [i.e. canonical correspondence analysis (CCA)] to quantify species' habitat associations and directional distribution ellipses to explore overlap in species core winter habitat. Results: Results show 49 seabird and ten marine mammal species inhabit the CCE during this low productivity period, including endangered southern resident killer whales (Orcinus orca). Seabirds and marine mammals exhibited significant but low overlap in habitat associations (i.e. weak niche partitioning) and similar habitat associations to summer studies. Discussion: We also found that some species with similar foraging strategies showed asymmetrical spatial range overlap (i.e. common murre (Uria aalge) and parakeet auklet (Aethia psittacula)), which may mean that expected increased competition due to climate change can negatively affect some species more than others. Given that climate change is leading to increased frequencies, intensities, and durations of marine heat waves during winter months, addressing the winter ecology knowledge gap will be important to understanding how climate change is going to affect species that reside in or migrate through the northern California Current during the low productivity downwelling season. [ABSTRACT FROM AUTHOR]

Marine top predators are expected to adjust their foraging behaviour at multiple time scales concomitantly with changes in forage fish availability. Rhinoceros auklets Cerorhinca monocerata rearing chicks at Teuri Island, Japan Sea, fed on anchovy Engraulis japonicus in 2012 and 2013 (anchovy regime) but switched to sand lance Ammodytes spp in 2019 and 2020 (sand lance regime). Here, we studied their at-sea behaviour using the GPS locations of 33 birds and the depth-acceleration records of 26 birds, and compared their foraging behaviour between these prey regimes. At the trip scale, auklets used offshore waters (> 50 m sea depth) and coastal waters in the anchovy regime but used mainland coastal waters (< 50 m sea depth) in the sand lance regime. In the sand lance regime, the birds also conducted more overnight 2- to 4-day trips in 2020 and spent more time flying during 1-day trips as they fed in further areas compared to the anchovy regime. At the dive scale, auklets frequently dove to both < 5 m and 20–30 m depths in the anchovy regime but mainly to < 5 m depth in the sand lance regime. Within each dive, auklets showed a greater number of fast/strong wing stroke events in the anchovy regime than in the sand lance regime. These changes in auklet behaviour reflected the different habitats, depth distribution, and swim speed of the targeted prey species. Our study shows the behavioural flexibility of a wing-propelled flying-diving seabird in response to the inter-annual shifts in the dominant forage fish community. It also indicates the ecological constraints on the mechanisms determining nest productivity in this day-foraging/night-provisioning seabird. [ABSTRACT FROM AUTHOR]

Introduction: Knowledge of the hunting strategies of top predators can provide insights into the cost-benefit trade-offs of their foraging activities. Air-breathing marine predators are constrained in their foraging activities due to their metabolic expenditure at depth being supported by limited body oxygen stores. Understanding how these species adapt their behaviours to maximise foraging success is of importance in view of the anticipated alterations to marine ecosystems in response to global change. The Australian fur seal (Arctocephalus pusillus doriferus), the largest fur seal species, has a distribution restricted to south-eastern Australia, which is one of the fastest warming oceanic regions and where the abundance, distribution and diversity of prey species is expected to change in coming decades. Methods: In the present study, combined IMU (acceleration, magnetometer, gyroscope), depth and GPS data logger information was used to reconstruct 3-dimensional tracks during diving, assess energy expenditure and quantify prey capture events in adult female Australian fur seals during benthic foraging. Results: The results revealed that individuals ascended at steeper pitches (to reduce transit time), remained for shorter durations and travelled shorter distances at the surface, and then descended at steeper pitches on subsequent dives after predatory events on the seafloor. Higher travel speeds and more directional changes during searching for prey along the seafloor, while requiring greater energy expenditure, were associated with more prey captures. Interestingly, individuals did not display conventional Area Restricted Search, with the heading between dives not influenced by prey encounters. Discussion: Together, these results suggest Australian fur seals undertake rapid searching along the seafloor to surprise cryptic prey and, if prey is encountered, undertake rapid surfacing (to reload body oxygen stores) and return to nearby seafloor habitat with a similar but undisturbed prey field. [ABSTRACT FROM AUTHOR]

Introduction: Human-induced environmental change is driving a global redistribution of biodiversity, resulting in shifting prey and predation landscapes. These shifting landscapes can lead to changes in behavior, health, and vital rates, with potential implications for population dynamics. Methods: In the present study, a state-dependent life-history theory model was developed to investigate the individual- and population-level responses of Australian fur seals (Arctocephalus pusillus doriferus) to changes in prey availability and at-sea mortality risk. Results: Rates of pregnancy, pup nursing, and abortion were unaffected by prey availability in the simulated population. Likewise, on-land and at-sea durations were largely unaffected by prey availability, with more pronounced affects for nonreproductive and pregnant females than for lactating females. There was a strong influence of prey availability on the proportion of females that were concurrently pregnant and lactating, largely due to an increase in pup abandonments under low prey availability scenarios. This effect on pup abandonments also had flow on effects for pup recruitment. Increasing at-sea mortality risk resulted in greater offspring losses due to maternal death. The combined impact of prey availability and at-sea mortality risk on the number of simulated female offspring reaching sexual maturity was substantial. Discussion: Consequently, our results suggest high vulnerability of the Australian fur seal population to shifting prey and predation landscapes. These results indicate a need for continued monitoring of Australian fur seal pup production and population dynamics in the face of rapid environmental change. [ABSTRACT FROM AUTHOR]

An animal's movement is influenced by a plethora of internal and external factors, leading to individual‐ and habitat‐specific movement characteristics. This plasticity is thought to allow individuals to exploit diverse environments efficiently. We tested whether the movement characteristics of white sharks Carcharodon carcharias differ across ontogeny and among habitats along the coast of Central California. In doing so, we elucidate how changes in internal state (physiological changes coinciding with body size) and external environments (differing seascapes and/or diel phases) shape the movement of this globally distributed predator. Twenty‐one white sharks, from small juveniles to large adults, were equipped with motion‐sensitive biologging tags at four contrasting seascapes: two islands, a headland, and an inshore cove. From multisensor biologging data, 20 metrics characterizing movement (i.e., depth use, vertical velocities, activity, turning rates, and bursting events) were derived and subjected to multivariate analyses. Movement characteristics were most different across seascapes, followed by ontogeny and diel phase. Juvenile sharks, which were only encountered at the cove, displayed the most distinct movement characteristics. Sharks at this seascape remained close to the shore traveling over smaller areas, shallower depth ranges, and with lower levels of tail beat frequencies, when corrected for size, than sub‐adult and adult sharks tagged elsewhere. Distinct tortuous daytime versus linear nighttime horizontal movements were recorded from sharks at island seascapes but not from those at the headland or inshore cove. At the offshore islands, the linear nighttime swimming patterns coincided with repeated dives to and from deeper water. The availability of prey and access to deeper water are likely drivers of the differences in movement characteristics described, with varying demographics of pinniped prey found at the subadult and adult aggregation areas and juvenile sharks being piscivorous and their habitat neither adjacent to pinniped haul out areas nor deeper water. This study demonstrates plasticity in the movements of a top predator, which adapts its routine to suit the habitat it forages within. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, the author conducted a comparative analysis of Greater lizardfish (Saurida tumbil) in the Beibu Gulf during two distinct periods (2010 and 2020), aiming to comprehend the variations in dietary strategies and trophic levels while investigating the driving factors influencing S. tumbil in the study area. Over the past decade, the main prey items of this species have been fishes, followed by cephalopods and crustaceans. However, changes in the community structure and primary prey resources have led the S. tumbil population to diversify their prey species, utilize alternative resources, and expand their foraging space. The timing and magnitude of ODSs varied between the two periods. In comparison to 2010, the proportion of population feeding on pelagic–neritic prey significantly increased, and the δ15N values decreased, indicating that the shift in the ecological types of preferred prey from demersal to pelagic–neritic was the primary cause of the decrease in trophic levels. Understanding dietary behavior during the individual development of marine predators and its temporal variations elucidates how species adapt to changes in marine resources. This is crucial for predicting marine predators' habitat selection and the natural population's responses to environmental changes. The authors conducted a comparative analysis of dietary shift strategies and trophic level variations in Greater lizardfish (Saurida tumbil) in the Beibu Gulf during two distinct periods (2010 and 2020) using stomach content and stable isotope analysis methods. Possible driving factors for these changes were also explored. Changes in the fishery community structure and the decline in the abundance of primary prey resources have led the S. tumbil population to diversify their prey species, utilize alternative resources, and expand their foraging space. However, the species' foraging strategy, characterized by chasing and preying on schooling and pelagic prey, promoted stability in their feeding behavior across spatial and temporal scales. The main prey items remained demersal and pelagic fish species, followed by cephalopods and crustaceans. Similar to other generalist fish species, ontogenetic dietary shifts (ODSs) indicated a partial transition towards larger prey items. However, the timing and magnitude of the ODSs varied between the two periods, reflecting life-history variations and adaptive adjustments to environmental changes. In comparison to 2010, the population's mean body length (BL) increased in 2020, and the proportion of the population feeding on pelagic–neritic prey significantly increased. However, the δ15N values were lower, indicating that the shift in the ecological niche of preferred prey from demersal to pelagic–neritic was the primary cause of the decrease in trophic levels. In the future, we will conduct further quantitative research integrating the spatiotemporal data of both predators and prey to clarify the relationships between marine predators' feeding behavior, trophic levels, and changes in prey community structure. [ABSTRACT FROM AUTHOR]

Predator–prey interactions in marine ecosystems are dynamically influenced by light, as demonstrated by diel vertical migrations of low-trophic level organisms. At high latitudes, the long winter nights can provide foraging opportunities for marine predators targeting vertically migrating prey closer to the surface at night. However, there is limited documentation of such diel patterns in marine predators under extreme light regimes. To address this, we recorded the diving behavior of 17 harbour porpoises just south of the Arctic circle in West Greenland, from summer to winter. Unlike classical diel vertical migration, the porpoises dove 24–37% deeper at night and the frequency of deep dives (> 100 m) increased tenfold as they entered the darkest months. The daily mean depth was negatively correlated with daylength, suggesting an increased diving activity when approaching the polar night. Our findings suggest a light-mediated strategy in which harbour porpoises would either target (i) benthic prey, (ii) pelagic prey migrating seasonally towards the seafloor, or (iii) vertically migrating prey that may be otherwise inaccessible in deeper waters at night, therefore maximizing feeding activity during extended periods of darkness. Extreme light regimes observed at high latitudes are therefore critical in structuring pelagic communities and food webs. [ABSTRACT FROM AUTHOR]

Trait-based frameworks are increasingly used for predicting how ecological communities respond to ongoing global change. As species range shifts result in novel encounters between predators and prey, identifying prey 'guilds', based on a suite of shared traits, can distill complex species interactions, and aid in predicting food web dynamics. To support advances in trait-based research in open-ocean systems, we present the Pelagic Species Trait Database, an extensive resource documenting functional traits of 529 pelagic fish and invertebrate species in a single, open-source repository. We synthesized literature sources and online resources, conducted morphometric analysis of species images, as well as laboratory analyses of trawl-captured specimens to collate traits describing 1) habitat use and behavior, 2) morphology, 3) nutritional quality, and 4) population status information. Species in the dataset primarily inhabit the California Current system and broader NE Pacific Ocean, but also includes pelagic species known to be consumed by top ocean predators from other ocean basins. The aim of this dataset is to enhance the use of trait-based approaches in marine ecosystems and for predator populations worldwide. [ABSTRACT FROM AUTHOR]

The relationship between aquatic and avian predators and prey is a fundamental process that influences the ecological dynamics of freshwater communities; a landscape of fear underpins spatial and temporal habitat use of prey, i.e., non‐consumptive predation effects. For example, complex marginal vegetation and other natural in‐river refuges are known to be important for prey to manage predation risk and predators must alter their behaviour in response to habitat patches prey occupy. However, it is unclear how prey respond to predators, and vice versa, in heavily modified degraded lowland rivers with a high degree of river maintenance measures; a component critical for flood risk management globally. Such modifications could lead to prey seeking refuge at hazardous anthropogenic infrastructure, but a robust quantification of predator–prey interactions in this context is required to develop this understanding.Using multi‐beam sonar (Dual‐Frequency Identification Sonar), we non‐invasively and simultaneously quantified the temporal rate of predator–prey interactions, the attack behaviour of predators, and the refuge seeking behaviour of prey at a pumping station intake during winter in a heavily modified lowland river.Prey fish experienced temporally dynamic, density‐dependant, and species‐specific predation risks from two dissimilar predators (i.e., aquatic vs. avian); pike (Esox lucius) and cormorant (Phalacrocorax carbo). Generalised linear modelling revealed that prey refuge use was positively associated with predator attack rate. Non‐consumptive effects were evidenced by quantified changes to shoal structure (density, area), shoaling (group aggregation), and schooling (coordinated directional movement), including diurnal migrations to and from the pumping station intake for refuge.Our results show that in the absence of natural refuge habitats the natural landscape of fear shifted and speculate that prey fish were paradoxically dependant on hazardous anthropogenic infrastructure, i.e., a pumping station intake, for refuge from predators in a degraded lowland river.These findings strongly enhance our understanding of the impact of anthropogenic infrastructure on predator–prey interactions by demonstrating how flood risk management, including river maintenance measures, and associated anthropogenic infrastructure can impact the behavioural game played between aquatic and avian predators and their prey. [ABSTRACT FROM AUTHOR]

The North American river otter Lontra canadensis was once widespread in North America but became extinct in the State of Indiana owing to habitat losses and unregulated trapping. However, following reintroduction, the population has expanded markedly since 1995, representing a notable conservation success story.The recent population growth has led to conflict with recreational angling groups who perceive otters as competitors. To investigate the extent of this competition, a DNA‐based study was conducted to determine whether material from the stomachs of trapper‐harvested otters could be used to identify fish prey species they had eaten.Representative specimens from 33 wild fish species were used as positive controls for DNA assays of otter prey. Mitochondrial DNA barcoding sequences generated from each fish species were used to develop a piscine barcoding assay to identify otter prey species.Fourteen otter carcasses were dissected, and multiple independent DNA extractions and mitochondrial sequencing reactions were performed on the prey bolus from each stomach. The sequences were analysed bioinformatically for taxonomic assignment to prey species.DNA evidence of nearly two dozen fish species, including species of recreational (e.g. bass) or conservation interest (darters) was found in the stomach material.This approach could help to determine the presence of prey species in otter diets, including those fish of conservation concern. That, in turn, would help to determine the best management options for conserving both otters and fish. [ABSTRACT FROM AUTHOR]

Information on how the trophic ecology of predators shapes their movement patterns and space-use is fundamental to understanding ecological processes across organisational levels. Despite this, studies combining spatial and trophic ecology to determine how prey preference and/or resource availability shape space use are lacking in marine predators as these can occur at low density and are often difficult to track over extended periods. Furthermore, many exhibit behavioural variability within species and among closely related, sympatric species adding further complexity. We applied a context-focused, multi-method approach to the understudied great hammerhead shark (Sphyrna mokarran) to test if movement and home ranges relate to prey preference and availability. Movement data from satellite and acoustic telemetry in Queensland, Australia, were combined with stable-isotope analysis, drone surveys, and videos of hunting behaviour. Limited dispersal, and small home ranges in S. mokarran were linked to trophic specialisation on stingray prey. Drone surveys and videos showed predation events on stingrays and demonstrated high, year-round availability of this prey in shallow, inshore habitats, which may allow the majority of S. mokarran to remain resident. This affinity for inshore habitats suggests that critical life-history requirements are performed over local or regional scales, although some larger movements were evident. These results were interpreted in comparison to the well-studied bull shark (Carcharhinus leucas), which showed reliance on pelagic food webs. Carcharhinus leucas had high individual variability in movement, with both large-scale migrations and residency. This could indicate that only some individuals are locally sustained on dynamic, pelagic food webs, while others undergo large-scale excursions over distant habitats. The specialised foraging of S. mokarran indicates they play an apex predator role in shallow, inshore habitats, potentially shaping space-use, and foraging behaviour of batoids. As inshore habitats are disproportionately affected by anthropogenic stressors, S. mokarran’s trophic specialisation and limited demographic connectivity may make the species particularly vulnerable to anthropogenic threats. [ABSTRACT FROM AUTHOR]

Deep-sea squids are presumably vital components of largely undescribed marine ecosystems, yet limited access to specimens has hampered efforts to detail their ecological roles as predators and preys. Biochemical techniques such as stable isotope analyses, fatty acid analyses, and bomb calorimetry are increasingly recognized for their ability to infer trophic ecology and dietary information from small quantities of tissue. This study used five opportunistically collected Taningia danae specimens and one Chiroteuthis aff. veranii specimen retrieved from the Great Australian Bight, South Australia, to detail the trophic ecology of these poorly understood squids. Four body tissue types (i.e., arm, buccal mass, mantle, and digestive gland) were assessed for their utility in stable isotope (SI) and fatty acid (FA) analyses, and we found that the arm, buccal mass, and mantle tissues had similar SI and FA profiles, suggesting that they can be used interchangeably when the entire specimen is unavailable. δ13C, δ15N, and fatty acid data suggests that the T. danae and C. aff. veranii specimens lived in the Southern Ocean and were high-trophic-level predators, feeding on deep-sea fishes and small squids, while also taking advantage of the summer upwelling region of the Great Australian Bight. The fatty acid analysis and bomb calorimetry results indicate that these squids might be important reservoirs of essential FAs (EPA and DHA) for Southern Ocean predators and that the whole-body energy content of T. danae individuals can reach up to 362,250 kJ. Our findings indicate that these squids may be contributing greatly to the transport of nutrients and energy between the Southern Ocean deep-sea and the Great Australian Bight shelf–slope environments. In addition to building our understanding of the trophic ecology of two poorly understood deep-sea squids, these findings also highlight the utility of partial specimens and demonstrate the important ecological information that can be obtained from few samples that may be opportunistically collected. [ABSTRACT FROM AUTHOR]

Between 1992 and 2018, the breeding population of Adélie penguins around Anvers Island, Antarctica declined by 98%. In this region, natural climate variability drives five‐year cycling in marine phytoplankton productivity, leading to phase‐offset five‐year cycling in the size of the krill population. We demonstrate that the rate of change of the Adélie breeding population also shows five‐year cycling. We link this population response to cyclical krill scarcity, a phenomenon which appears to have arisen from the interaction between climate variability and climate change trends. Modeling suggests that, since at least 1980, natural climate variability has driven cycling in this marine system. However, anthropogenic climate change has shifted conditions so that fewer years in each cycle now prompt strong krill recruitment, triggering intervals of krill scarcity that result in drastic declines in Adélie penguins. Our results imply that climate change can amplify the impacts of natural climate oscillations across trophic levels, driving cycling across species and disrupting food webs. The findings indicate that climate variability plays an integral role in driving ecosystem dynamics under climate change. [ABSTRACT FROM AUTHOR]

Freshwater salinization, due to road salt and other increased anthropogenic activities, has become a significant threat to freshwater organisms. However, whether freshwater salinization affects the response of aquatic organisms to their predators, especially prey that have been acclimated to salinity environments for a long time, remains unclear. In the present study, we investigated the changes in anti-predator defense of Daphnia magna with and without salinity acclimation at five different salinities (0, 0.6, 0.8, 0.10, and 0.12 M). Results showed that freshwater salinization weakened the induced defense response of D. magna, regardless of whether it had undergone long-term salinity acclimation. Specifically, induced defense traits such as smaller body size, higher relative spine length, more relative reproductive output, and smaller body size neonates disappeared at ≥ 0.08 M salinities. In addition, there were no significant differences in most traits of induced defense strength between D. magna with and without salinity acclimation at the same salinity. Importantly, the integrated induced defense response index decreased with increasing salinity. Our study showed that salinity-tolerant organisms do not recover their induced defense at high salinities, underlining the importance of incorporating interspecific interactions when estimating the effects of freshwater salinization on organisms. [ABSTRACT FROM AUTHOR]

As frogs undergo metamorphosis from tadpole to adult, they may be susceptible to decreases in locomotor performance and survival during stages in which the tail and limbs are both present. Because these alternative axial and appendicular propulsive systems might interfere with each other, performance might be better when only one or the other system predominates. This framework, termed the 'adaptive peak hypothesis' emerged from studies of generalist anuran taxa with biphasic life histories in which aquatic larvae transition to terrestrial adults. However, it is not clear that such patterns apply to taxa with different patterns of ontogenetic environmental transitions.We evaluated the relationship between morphology, locomotor performance and survival versus predators across metamorphic stages of a fully aquatic frog, the pipid Xenopus laevis. We measured escape performance from individuals of four developmental stages spanning possession of just a tail, the presence of both tail and legs and resorption of the tail, and then conducted selection trials in which equal numbers of individuals of all stages were exposed to an aquatic predator (cichlid fish). After collecting survivors from these trials, we calculated linear and nonlinear selection gradients for a suite of morphological traits.Unlike generalist frogs, we found that both locomotor performance and survival increased across metamorphic stages of X. laevis. Linear selection gradients favoured tadpoles with longer hindlimbs, longer and narrower bodies, and shorter tails—patterns that generally parallel trends during metamorphic growth. Nonlinear selection showed that longer hindlimbs were favoured as body length increased and the positive effect of forelimb length was reduced as tail length increased.The relationship between hindlimb and body length aligns with expected changes in growth postmetamorphosis where postmetamorphic individuals are expected to have greater survival. However, longer forelimbs are generally associated with decreased locomotor performance, suggesting that alternative mechanisms of selection may be acting on the forelimbs of Xenopus through development.Overall, our results indicate that the generality of the adaptive peak framework, as applied to amphibian metamorphosis, can be impacted by specifics of life history patterns across species. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The black caiman (Melanosuchus niger) is the largest aquatic predator in the Amazon freshwater bioregion. Their destruction of fishing gear, consumption of fish and turtles, and infrequent attacks on humans, pets, and livestock are drivers of conflict with riverine communities. Attitudes toward black caiman can motivate negative human–caiman interactions across their range. In this article, we explored the importance of understanding attitudes toward the presence of black caiman populations. We surveyed four villages situated along the Rupununi River in the North Rupununi Guyana. Analysis indicated that negative attitudes were influenced by seasonality, sex, and village. Results offered additional insights into human–wildlife interactions and the dynamics of living alongside a protected large predator in Guyana. We recommend further research into the linkage between black caiman behavioral ecology and incidences of conflict. [ABSTRACT FROM AUTHOR]

Consumptive effects (CEs) of predation have been well‐studied in most aquatic systems, but nonconsumptive effects (NCEs) on prey have only recently received limited attention. As aquatic consumers, tadpoles have traditionally been considered strict herbivores, leaving their predatory impacts via CEs and NCEs largely unexplored. We quantified omnivory among wood frog (Lithobates sylvaticus) tadpoles and characterized their CEs and NCEs on invertebrate communities. Tadpoles from natural ponds were dissected to quantify the frequency of omnivory generally, as well as specifically in relation to pond size and tadpole morphology. Additional tadpoles were employed in a mesocosm experiment that manipulated tadpole presence (absent, caged, or free‐swimming) to quantify CEs and NCEs on freshwater zooplankton and macroinvertebrate communities. Over 70% of tadpoles in natural ponds engaged in omnivory, primarily on zooplankton, and tadpoles with wider heads and deeper tails were more likely to be omnivorous. Tadpoles in mesocosms exhibited CEs and NCEs on invertebrate communities, with stronger effects exerted on zooplankton than macroinvertebrates. The NCEs of tadpoles on invertebrates likely included production of predatory chemical cues that influenced invertebrate behavior, abundance, and community composition. Because tadpoles are often the dominant vertebrate predators in ephemeral aquatic ecosystems, this study stresses their ecological importance in structuring aquatic communities. [ABSTRACT FROM AUTHOR]

Understanding the formation of feeding links provides insights into processes underlying food webs. Generally, predators feed on prey within a certain body‐size range, but a systematic quantification of such feeding niches is lacking. We developed a size‐constrained feeding‐niche (SCFN) model and parameterized it with information on both realized and non‐realized feeding links in 72 aquatic and 65 terrestrial food webs. Our analyses revealed profound differences in feeding niches between aquatic and terrestrial predators and variation along a temperature gradient. Specifically, the predator–prey body‐size ratio and the range in prey sizes increase with the size of aquatic predators, whereas they are nearly constant across gradients in terrestrial predator size. Overall, our SCFN model well reproduces the feeding relationships and predation architecture across 137 natural food webs (including 3878 species and 136,839 realized links). Our results illuminate the organisation of natural food webs and enables novel trait‐based and environment‐explicit modelling approaches. [ABSTRACT FROM AUTHOR]

Many ectotherms are shifting their distributions polewards, which has been associated with the evolution of phenotypic traits and their thermal plasticity. Trophic interactions may determine the dynamics and ecological impact of range expansions. However, it is largely unknown how trait evolution in edge populations shapes trophic interactions.We studied evolutionary changes in the short‐term (functional response) and long‐term predator–prey interactions between an aquatic insect predator (the damselfly Ischnura elegans) and its prey (the water flea Daphnia magna) during the predator's ongoing poleward range expansion in northern Europe.Using a common‐garden warming experiment at 20 and 24°C we tested for differentiation between predator populations from edge and core regions in metabolic rate and functional response parameters, and used these empirical data to estimate the effects of range expansion on the short‐ and long‐term predator–prey interaction strengths.Metabolic rates did not differ between populations from edge and core regions nor between rearing temperatures. Functional response parameters and their thermal plasticity showed signals of evolution during the range expansion. Attack rates did not differ between predators from edge and core regions, but only decreased under warming in predators from the edge region. Handling times decreased under warming in predators from the edge region but increased under warming in predators from the core region. While handling times were shorter in predators from the core region at 20°C, these did not differ between regions at 24°C. As a result, the short‐term interaction strength was higher for predators from the core region at 20°C, but not different between regions at 24°C. The predator–prey system from the edge region showed lower long‐term system stability at 20°C, but this region difference disappeared under warming because the edge region stability then increased.Our results suggest that rapid evolution of functional response parameters during a predator's range expansion reduced the direct feeding impact on its prey and made the predator–prey system from the edge region more unstable, but not under warming. This provides rare evidence that functional responses can rapidly evolve during range expansions, potentially destabilizing food web dynamics. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Understanding the environmental effects of chemicals used in pest control on aquatic systems is crucial to ensure the conservation of beneficial non-target organisms. Mosquito larvicides are commonly applied to aquatic habitats; however, their non-target effects are not well understood. Our goal was to determine lethal and behavioral effects of insect growth regulators (IGRs) and surface films (SFs) on predaceous diving beetle adults and larvae, and damselfly and dragonfly nymphs in roadside ditch habitats. Behavioral effects were determined via bioassays quantifying predator movement, location, and larval mosquito predation. Using Principal Components Analyses, correlated behaviors were determined for each taxa, and compared within SF and IGR treatment levels. Surface films were lethal to beetle adults in the genus Laccophilus (Dytiscidae) at recommended and high concentrations. Laccophilus adult behavior changed in response to IGRs, those exposed to recommended and high concentrations were more active than controls. Larval Laccophilus mosquito consumption varied between SFs and IGRs. We conclude that SFs can harm aquatic organisms that require atmospheric oxygen, and both larvicides may have sublethal effects on hunting behaviors of aquatic insects. Future studies should focus on different larvicides, and a wider variety of aquatic taxa that interact with mosquito larvae. [ABSTRACT FROM AUTHOR]

The Red-fingered Bright-eyed Frog Boophis erythrodactylus is an endemic, range-restricted arboreal frog found only in the eastern rainforests of Madagascar. We report new localities for this species, along with locality records for its sister species B. tasymena, including localities where they occur in sympatry, which has never been reported before. We also document evidence for the existence of a colour variant of B. tasymena that is identical to B. erythrodactylus in appearance. We also observed never before documented breeding behaviour in the poorly known B. erythrodactylus, where the male and female in amplexus used a submerged site in a river potentially for oviposition. We also explore why this may be a predator-avoidance strategy considering the presence of aquatic invertebrate predators active near the surface and absence of fully aquatic vertebrate predators, such as fish in headwater stream habitats. Predator-avoidance strategies are a vital component of organismal survival, particularly for amphibians with complex life cycles. Natural history observations are key to revealing such strategies and behaviour, and they form the basis of evolutionary biology and is also fundamental for conservation management. [ABSTRACT FROM AUTHOR]

While aquatic invasive predators are among the most impactful trophic groups, we lack the understanding of whether alternative food resources mediate adverse predatory effects and stabilize native prey communities. Here, we use comparative functional responses to examine the influence of alternative food resources (Fucus sp.) on predator–prey interaction strengths from three gammarid crustaceans, with one native (Gammarus locusta) and two existing and emerging invasive (Gammarus tigrinus, Pontogammarus maeoticus, respectively) species, towards larval chironomid prey. All gammarids exhibited Type II functional responses, irrespective of the presence of alternative seaweed disks. Fucus sp. disks significantly reduced predation rates overall; however, significant reductions in maximum feeding rates (i.e., functional response magnitudes) were only evident in the native species and not for the two invaders. Our results thus may suggest that alternative resources dampen the predatory interaction strength of native but not invasive alien species, concerning these three study organisms. This potentially exacerbates the impacts of invasive predators relative to natives in diverse communities. Studies should increasingly consider alternative resources when quantifying ecological impacts of current and future invasive alien species compared with natives. [ABSTRACT FROM AUTHOR]

Natural lentic microhabitats are important for aquatic invertebrate communities in subtropical aquatic systems, which are usually dominated by mosquitoes, predators and zooplankton. Subtropical lentic microhabitats might be strongly affected by top‐down effects of predators. We evaluated the predator effects on aquatic macroinvertebrate and zooplankton communities by using black plastic buckets (10 L) to simulate lentic microhabitats, which were divided into four treatments: predator absence and presence, and initial (on experiment start) and final (on experiment end) community controls. Large top predators (Odonata) had a stronger effect on community structure by their sit‐and‐wait predatory behaviour. The richness of total macroinvertebrates, Culex genus (most abundant organism), and zooplankton was highest in predators' absence. On the other hand, the sit‐and‐wait behaviour increased the density of organisms by selective predation on macroinvertebrates that feed in the bottom of the system. Also, the sit‐and‐wait behaviour increased the density of gathering and filtering collectors (top swimmers) by differences in space preference. We observed a positive species‐specific relationship between Culex and predators. We concluded that predators' presence contributes to the balance of lentic microhabitat in subtropical lentic microhabitats by top‐down control. [ABSTRACT FROM AUTHOR]

Eyespots are taxonomically widespread color patterns consisting of large concentric rings that are commonly assumed to protect prey by influencing the behaviors of predators. Although there is ample experimental evidence supporting an anti‐predator function of eyespots in terrestrial animals, whether eyespots have a similar deterring function in aquatic animals remains unclear. Furthermore, studies in terrestrial systems suggest that the protective function of eyespots depends on ambient light conditions where predators encounter them, but this effect has never been tested in aquatic environments. Here, we examine how eyespots influence behavioral responses in an aquatic environment under different visual environments, using laboratory‐reared three‐spined sticklebacks (Gasterosteus aculeatus) as model predators. Specifically, we experimentally examined behavioral responses of sticklebacks toward artificial prey patterns (control vs. eyespots) under two different light environment treatments (low vs. high). We found that eyespots did not postpone attacks from sticklebacks. However, sticklebacks approaching eyespots stopped more frequently than sticklebacks approaching prey items with a control pattern. Sticklebacks were (marginally) slower to attack prey in the low‐light treatment, but the light level did not influence stickleback behavioral responses toward eyespots. We conclude that eyespots can modulate some behaviors of an aquatic predator, albeit with a different functional role from that previously demonstrated in terrestrial species. [ABSTRACT FROM AUTHOR]

Compensatory recruitment can facilitate the persistence of populations experiencing high adult mortality. Because early life-stages of many taxa, including amphibians, are difficult to mark and recapture, sources of variation in survival at these stages often are unknown, which creates barriers to improving in situ recruitment rates. We leveraged count data and open N-mixture models to examine the environmental factors associated with the hatching of egg clutches, tadpole survival, and probability of metamorphosis in Boreal Toads (Anaxyrus boreas boreas) that inhabit pastures leased for cattle grazing in western Wyoming, USA. We conducted weekly surveys and measured a suite of environmental variables at 20 breeding ponds during May–September 2018. The hatching of egg clutches was most strongly related to pond surface area, as clutches often desiccated at smaller ponds. Weekly tadpole survival was lowest in ponds with high abundance of aquatic predators. Predation did not preclude metamorphosis, which was more strongly associated with higher dissolved oxygen and vegetation cover. Cattle grazing reduced vegetation cover in and around breeding ponds, which resulted in lower levels of dissolved oxygen. Grazing-induced habitat changes are therefore likely to negatively influence tadpole metamorphosis both via indirect effects on dissolved oxygen, and direct effects on vegetation cover, which also serves as feeding sites and escape cover from predators. We demonstrate the success of three critical phases in early life-stage development (egg hatching, tadpole survival, metamorphosis) was associated with different environmental factors. The inclusion of stage-specific responses in demographic analyses is therefore critical for a thorough understanding of what limits populations. [ABSTRACT FROM AUTHOR]

The interspecific interactions within and between adjacent ecosystems strongly depend on the changes in their abiotic and biotic components. However, little is known about how climate change and biodiversity loss in a specific ecosystem can impact the multiple trophic interactions of different biological groups within and across ecosystems.We used natural microecosystems (tank‐bromeliads) as a model system to investigate the main and interactive effects of aquatic warming and aquatic top predator loss (i.e. trophic downgrading) on trophic relationships in three integrated food web compartments: (a) aquatic micro‐organisms, (b) aquatic macro‐organisms and (c) terrestrial predators (i.e. via cross‐ecosystem effects).The aquatic top predator loss substantially impacted the three food web compartments. In the aquatic macrofauna compartment, trophic downgrading increased the filter feeder richness and abundance directly and indirectly via an increase in detritivore richness, likely through a facilitative interaction. For the microbiota compartment, aquatic top predator loss had a negative effect on algae richness, probably via decreasing the input of nutrients from predator biological activities. Furthermore, the more active terrestrial predators responded more to aquatic top predator loss, via an increase in some components of aquatic macrofauna, than more stationary terrestrial predators. The aquatic trophic downgrading indirectly altered the richness and abundance of cursorial terrestrial predators, but these effects had different direction according to the aquatic functional group, filter feeder or other detritivores. The web‐building predators were indirectly affected by aquatic trophic downgrading due to increased filter feeder richness. Aquatic warming did not affect the aquatic micro‐ or macro‐organisms but did positively affect the abundance of web‐building terrestrial predators.These results allow us to raise a predictive framework of how different anthropogenic changes predicted for the next decades, such as aquatic warming and top predator loss, could differentially affect multiple biological groups through interactions within and across ecosystems. [ABSTRACT FROM AUTHOR]

Predator-prey interactions influence prey traits through both consumptive and non-consumptive effects, and variation in these traits can shape vector-borne disease dynamics. Meta-analysis methods were employed to generate predation effect sizes by different categories of predators and mosquito prey. This analysis showed that multiple families of aquatic predators are effective in consumptively reducing mosquito survival, and that the survival of Aedes, Anopheles, and Culex mosquitoes is negatively impacted by consumptive effects of predators. Mosquito larval size was found to play a more important role in explaining the heterogeneity of consumptive effects from predators than mosquito genus. Mosquito survival and body size were reduced by non-consumptive effects of predators, but development time was not significantly impacted. In addition, Culex vectors demonstrated predator avoidance behavior during oviposition. The results of this meta-analysis suggest that predators limit disease transmission by reducing both vector survival and vector size, and that associations between drought and human West Nile virus cases could be driven by the vector behavior of predator avoidance during oviposition. These findings are likely to be useful to infectious disease modelers who rely on vector traits as predictors of transmission. [ABSTRACT FROM AUTHOR]

Selection may favor greater investment into sexual ornaments when opportunities for future reproduction are limited, for example, under high adult mortality. However, predation, a key driver of mortality, typically selects against elaborate sexual ornaments. Here, we examine the evolution of sexual ornaments in killifishes, which have marked contrasts in life‐history strategy among species and inhabit environments that differ in accessibility to aquatic predators. We first assessed if the size of sexual ornaments (unpaired fins) influenced swimming performance. Second, we investigated whether the evolution of larger ornamental fins is driven primarily by the pace of life‐history (investment into current vs. future reproduction) or habitat type (a proxy for predation risk). We found that larger fins negatively affected swimming performance. Further, males from species inhabiting ephemeral habitats, with lower predation risk, had larger fins and greater sexual dimorphism in fin size, compared to males from more accessible permanent habitats. We show that enlarged ornamental fins, which impair locomotion, evolve more frequently in environments that are less accessible to predators, without clear associations to life‐history strategy. Our results provide a rare link between the evolution of sexual ornaments, effects on locomotion performance, and natural selection on ornament size potentially through habitat differences in predation risk. [ABSTRACT FROM AUTHOR]

When navigating their lives through environments in which risks and rewards vary considerably in time and space, all biological organisms are continuously faced with uncertainty. The authors show that even though being distantly-related, prey species with shared predators may exchange information about the risk via mutually-recognized alarm signals, which in turn may lead to the emergence of taxonomically diverse information networks. [Extracted from the article]

Parasites are important players in ecological communities that can shape community structure and influence ecosystem energy flow. Yet beyond their effects on hosts, parasites can also function as an important prey resource for predators. Predators that consume infectious stages in the environment can benefit from a nutrient-rich prey item while concurrently reducing transmission to downstream hosts, highlighting the broad importance of this interaction. Less clear, however, are the specific characteristics of parasites and predators that increase the likelihood of consumption. Here, we determine what combination(s) of predator and parasite morphological traits lead to high parasite consumption. We exposed the infectious stages (cercariae) of five trematode (fluke) taxa to aquatic insect predators with varying foraging strategies and morphologies. Across the 19 predator—parasite combinations tested, damselfly predators in the family Coenagrionidae were, on average, the most effective predators of cercariae, consuming between 13 and 55% of administered cercariae. Large-bodied cercariae of Ribeiroia ondatrae had the highest average vulnerability to predation, with 37–48% of cercariae consumed. The interaction between predator head width and cercariae tail size strongly influenced the probability of consumption: small-bodied predators were the most effective consumers, particularly for larger tailed parasites. Thus, the likelihood of parasite consumption depended strongly on the relative size between predator and parasite. Our study helps establish that predation on free-living parasites largely follows a broader predator–prey framework. This will help to identify which predator and parasite combinations will likely have high consumptive interactions, potentially reducing parasite transmission in natural populations. [ABSTRACT FROM AUTHOR]

Running the gauntlet of predators consumes critical time and energy resources, as all species are vulnerable to one or, typically, more predators at some life stage. Prey employ a vast array of mechanisms to avoid predation, and predators, likewise, come in a bewildering variety. Thus, defensive adaptations are rarely one size fits all. Considerable work has addressed multi‐predator consumptive effects, but we now know that non‐consumptive effects of predators can dramatically impact individuals, (meta)populations, and (meta)communities. However, little is known regarding the community‐wide dynamics of non‐consumptive effects generated by multiple predators. Predator avoidance by choosing a patch that is free of a particular predator or predators can be the most effective strategy if conditions at colonization are a reliable predictor of absence, which is often true for fish in freshwater systems. We experimentally manipulated composition of the predator assemblage in aquatic mesocosms in a substitutive design, with zero, one, two, or three caged predatory fish species (one benthic, one pelagic, and one surface fish) at constant density and biomass, and assayed responses of naturally colonizing aquatic insects. We addressed three related questions; first, how do members of a diverse assemblage of colonizing aquatic insects respond to this variation in species and species combinations, second, do individual species (and higher taxa), respond differently to single vs. multiple predator species (species richness), and third how do any responses to fish species and species combinations, and effects on species richness, translate into community‐wide changes in the composition of colonists. Prey had varied responses to specific predators or combinations of predators, resulting in distinct community composition across treatments and higher β‐diversity with predators. Prey showed emergent multi‐predator effects, where certain species only responded to predator species combinations, but not to any individual predator, and stronger effects of multiple predator vs. single‐predator treatments, despite strong responses to individual predators in many taxa. Habitat selection effects can range from the individual to the metacommunity, and the dynamics of habitat selection in response to predators is a complex function of predator identity, density, richness, species composition, and patch spatial context. [ABSTRACT FROM AUTHOR]

Because littoral cladocerans are common prey for odonate larvae, they are ideal organisms to examine prey and predator interactions in aquatic habitats. Although death‐feigning behaviour observed in littoral cladocerans is viewed as a trait to reduce predation risk, no study has examined the effectiveness of death‐feigning at reducing mortality. We studied the effectiveness of death‐feigning behaviour by two littoral cladocerans, Chydorus sphaericus and Oxyurella tenuicaudis, against the odonate larvae of Sympetrum frequens.We first examined how the odonate larvae detected the prey and found that the larvae consumed active cladocerans, even under dark conditions, but they did not consume anaesthetised cladocerans, indicating that the larvae detect the prey using mechanical cues such as vibrational currents created by the prey individuals.We then observed behavioural events of odonate larvae and prey cladocerans using a video‐recording system to count the number of cladocerans that showed death‐feigning behaviours when odonate larvae attacked and those that were not consumed when they showed death‐feigning behaviours.We observed a total of 1,099 behavioural events in prey–predator interactions. On average, the odonate larvae pursued 63% of the cladocerans encountered, attacked 89% of the cladocerans pursued, and successfully captured only 29% of the cladocerans with the first attack. Among the cladocerans that were not captured, 38% of the individuals continually swam, but 62% ceased to move and exhibited death‐feigning behaviours. The odonate larvae's capture rate for cladocerans exhibiting the death‐feigning behaviours fell significantly short of that for cladocerans that were continually swimming.The experiments clearly showed that the littoral cladocerans' death‐feigning behaviour effectively decreased predation rate by odonate larvae. The results suggest that the death feigning serves as an adaptive behaviour to reduce mortality risk in littoral cladocerans under predation by such predators that can detect prey using mechanical cues such as those of vibrational currents. [ABSTRACT FROM AUTHOR]

This document is an erratum for an article titled "Trophic ecology shapes spatial ecology of two sympatric predators, the great hammerhead shark (Sphyrna mokarran) and bull shark (Carcharhinus leucas)." The erratum acknowledges a production error in which Data Sheet 1 and Supplementary videos 1-7 and 10-13 were not included in the supplementary materials section of the article. The publisher apologizes for the mistake and states that the original version of the article has been updated. The article is open access and distributed under the terms of the Creative Commons Attribution License. [Extracted from the article]

The extent to which prey traits combine to influence the abundance of predators is still poorly understood, particularly for mixed predators in sympatry and in aquatic ecosystems. In this study, we characterise prey use and distribution in iconic bird (grey wagtails and Eurasian dippers) and fish species (brown trout and Atlantic salmon) to assess whether prey traits could predict populations of these four riverine predators. Specifically, we hypothesised that: 1) prey key traits would predict predator populations more effectively than 2) diversity of prey traits, 3) the taxonomic abundance or richness of prey (known as traditional or mass‐effect types of biodiversity) or 4) the prevailing environmental conditions. Combined predator population sizes were predicted better by a few key traits – specifically those revealing prey habitat use, size and drifting behaviour – than by prey diversity or prey trait diversity or environmental conditions. Our findings demonstrate that the complex relationships between prey assemblages and multiple predator species can be represented mechanistically when the key prey traits that govern encounter and consumption rates are identified. Given their apparent potential to reveal trophic relationships, and to complement more traditional measures of prey abundance, we advocate further development of trait‐based approaches in predator–prey research. [ABSTRACT FROM AUTHOR]

Predators are a particularly critical component of habitat quality, as they affect survival, morphology, behavior, population size, and community structure through both consumptive and non‐consumptive effects. Non‐consumptive effects can often exceed consumptive effects, but their relative importance is undetermined in many systems. Our objective was to determine the consumptive and non‐consumptive effects of a predaceous aquatic insect, Notonecta irrorata, on colonizing aquatic beetles. We tested how N. irrorata affected survival and habitat selection of colonizing aquatic beetles, how beetle traits contributed to their vulnerability to predation by N. irrorata, and how combined consumptive and non‐consumptive effects affected populations and community structure. Predation vulnerabilities ranged from 0% to 95% mortality, with size, swimming, and exoskeleton traits generating species‐specific vulnerabilities. Habitat selection ranged from predator avoidance to preferentially colonizing predator patches. Attraction of Dytiscidae to N. irrorata may be a natural ecological trap given similar cues produced by these taxa. Hence, species‐specific habitat selection by prey can be either predator‐avoidance responses that reduce consumptive effects, or responses that magnify predator effects. Notonecta irrorata had both strong consumptive and non‐consumptive effects on populations and communities, while combined effects predicted even more distinct communities and populations across patches with or without predators. Our results illustrate that an aquatic invertebrate predator can have functionally unique consumptive effects on prey, attracting and repelling prey, while prey have functionally unique responses to predators. Determining species‐specific consumptive and non‐consumptive effects is important to understand patterns of species diversity across landscapes. [ABSTRACT FROM AUTHOR]

We performed a multiyear monitoring study to compare amphibian habitat quality among four natural, four restored, and six created pools. We used successful reproduction and metamorphosis of two vernal pool indicator species, the wood frog and spotted salamander, to represent desired outcomes. Ordination techniques were used to identify the aspects of habitat quality that were most correlated with desired outcomes. Previously published results indicated that pool depth, volume, and hydroperiod were among the best predictors of success, regardless of pool type. Observations in the first few years of monitoring also suggested that pools with longer hydroperiods had a greater abundance of aquatic predators of eggs and larvae of indicator species. This follow‐up study further explores and compares predator–prey relationships among pool types. We quantified within‐pool predator and prey abundance and diversity and collected another year of data on the reproductive success of indicator species. Our results confirmed that mean predator abundance was eight times higher in pools with longer hydroperiods. We documented a 96% decrease in wood frog survival rates in a semi‐permanent, natural pool following a 41% decrease in overhead canopy cover and an increase in green frog abundance. At the same time, wood frog reproductive success increased in nearby restored pools with lower predator abundance. Pools with the highest mean survival rates for the two indicator species combined were short‐ or long‐cycle pools (i.e. hydroperiod of 12–35 weeks) with low predator abundance (i.e. <1 organism L−1) and greater proportions of arthropod prey relative to other food items. [ABSTRACT FROM AUTHOR]

Turbidity plays an important role in aquatic predator–prey interactions. Increases in turbidity are expected to reduce prey capture rates, especially for visually oriented predators. However, there is also evidence indicating that turbidity may have little or no effect on predation rates.Here, we conducted a systematic review and meta‐analysis of the relationship between turbidity and capture rate. We explored possible sources of heterogeneity in the effect sizes (capture strategy, predator's body size, relative eye size and turbidity range in the experiments) while controlling for the dependence among effects sizes and phylogenetic relationships among predator species.We found a consistent negative effect of turbidity on prey capture and that turbidity range (manipulated in the experiments) was the main factor accounting for between‐study variation in effect sizes. Also, capture rates of both visually and non‐visually oriented predators decreased with an increase in turbidity. In addition, for visually oriented fish predators, the relative eye size did not influence the effect sizes.Despite the paucity of studies for some groups of aquatic predators (mainly in tropical regions), we provide corroborative evidence that turbidity is a critical environmental factor controlling predator–prey interactions. This result is especially relevant considering that changes in turbidity is a human‐induced pervasive environmental alteration resulted from, among other mechanisms, runoff after deforestation, eutrophication or oligotrophication in reservoir cascades, which imply changes in predator–prey interactions. [ABSTRACT FROM AUTHOR]