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The Morley Nelson Snake River Birds of Prey National Conservation Area (NCA), in southwestern Idaho, USA supports a large population of breeding Prairie Falcons (Falco mexicanus). Abundance of Prairie Falcons in the NCA was previously monitored in 1976–1978 and 1990–1994. That research indicated maximum counts for each period in 1976 and 1992 and a possible population decline across that time span. We assessed the abundance and nesting success of Prairie Falcons in the NCA in 2002–2003 and 2019–2021, and we compared results to data from before 2000 to assess possible population change. Number of nesting pairs increased over 45 years from peak counts of 206, 193, and 217 in the 1970s, 1990s, and early 2000s, respectively, to 257 in 2021. Increases were not concentrated in one region, but widely distributed across the study area. Rates of nesting success in 2002–2003 and 2019–2021 averaged 57 ± 11.8% (SD) at 49.8 ± 3.3 nests observed each year and did not differ from pre-2000 rates. Finally, our analysis showed that in all 10 years in which a full census was conducted, a sampling approach to surveys would have been effective at estimating the number of falcons nesting within the NCA. Prairie Falcons are of conservation concern because of possible population declines in parts of their range. These results illustrate an area with apparently increasing numbers of this important species and highlight the importance of long-term surveys for tracking population fluctuations and the value of a national conservation area for providing raptor breeding habitat. [ABSTRACT FROM AUTHOR]

Anthropogenic factors are accelerating species extinction, with small mammalian carnivores among the most affected. These species play vital ecological roles, yet their conservation needs are often overlooked. Our study focused on the plains spotted skunk (Spilogale interrupta (Rafinesque, 1820)), a small carnivore that has experienced population declines. We hypothesized that their resource selection was influenced by factors expected to influence prey availability, protection from predators, and human activity. We tracked 14 plains spotted skunks in east-central South Dakota, USA, over 2 years during spring and summer. Using mixed-effects logistic regression, we identified seasonal habitat associations. In spring, plains spotted skunks selected areas near farming structures and human development, avoiding high wetland density and crop cover. In summer, they continued to select areas near farming structures and low human development, but also high wetland density and pasture, while avoiding hay bales and crop cover. Our first analysis of the species' resource use in the Great Plains indicates that plains spotted skunks select habitats with permanent small-scale agricultural features and varying levels of human development across seasons. Our findings suggest that species' persistence in the region may depend on conservation strategies that account for seasonal planning, habitat heterogeneity, and key agricultural structures. [ABSTRACT FROM AUTHOR]

A Filippov–Gause predator–prey model is proposed, which suggests that cooperation and competition among predators depend on prey abundance. In this case, when the prey abundance is high, predators cooperate in hunting, but when the prey abundance decreases and falls below a critical level, predators compete for scarce food. The proposed model is analyzed in terms of the existence and stability of its equilibria and its pseudo-equilibrium, which is located on the differentiable curve separating the two vector fields. Given the conditions found which determine the existence of cycles and limit cycles, contrasted with a bifurcation diagram, we find that the proposed model can have an asymptotically stable limit cycle around the pseudo-equilibrium and two positive inner equilibria, together with an unstable limit cycle around the pseudo-equilibrium. Similarly, if the model has a pseudo-equilibrium and no positive inner equilibria, then we could have at least two limit cycles, one stable and one unstable, surrounding the pseudo-equilibrium. [ABSTRACT FROM AUTHOR]

The California sea lion (Zalophus californianus ; CSL) reflects environmental conditions of the Northeastern Pacific, where resource availability was importantly reduced for different taxa during climatic variations such as the North Pacific heatwave (The Blob 2014 to 2015) or El Niño 2015 to 2016 due to the effect of these anomalies on primary productivity. Our objective was to determine the abundance and foraging habits of CSLs from the San Benito Archipelago (Mexican Pacific) in a period (2013 to 2019) that involved warm anomalies. Annual counts were conducted by sex/age classes; scats were sampled to identify the main prey consumed; and pup fur (maternal foraging indicators) was collected for analysis of δ13C and δ15N. The prey importance index (PII) and trophic level were calculated and the Siber assessment in R was used to estimate isotopic niches. Colony abundance decreased by approximately 50% from 2013 to 2019. Values of δ13C showed significant interannual differences (P  < 0.001) with more negative values (−17.2‰ to −16.7‰) from 2015 onwards, indicating offshore foraging habits. Significant interannual differences (P  < 0.001) were found for δ15N, with a declining trend (20.4‰ to 19.07‰), and a difference of more than 1‰ between 2013 and 2019, evidencing a probable shift of foraging grounds toward higher latitudes. Based on the PII, Strongylura exilis (30%), Merluccius productus (24%), Ommastrephes bartramii (10%), and Sardinops sagax (10%) were the most important prey, showing significant interannual differences (P  < 0.001). CSLs had a mean trophic level of 4.89, with a slight increasing trend toward the end of the period. Dietary plasticity was found in CSLs, possibly caused by environmental changes that modified prey availability and led to variations in foraging grounds, and consequently in the colony abundance over time. [ABSTRACT FROM AUTHOR]

American martens (Martes americana) are often targeted by fur trappers across their distributional range; yet, there are few studies to assess the sustainability of harvest. In the absence of reliable information on abundance, data on the demographics of the harvested segment of populations can be used to provide insights on harvest sustainability. In response to concerns by some fur trappers that marten abundance was low in some areas, we collected 2,394 marten carcasses from three regions of Yukon, Canada, to investigate demographic trends in harvested martens among and within eight trapping seasons (1 November to 28 February; 2002/2003 to 2009/2010). We found consistently higher proportions of females in the harvest (42%) than recommended thresholds or previously reported for other localities. Juveniles made up approximately half of the overall harvest, and the proportion of juveniles varied significantly among trapping seasons (range = 2–90%). During trapping seasons with < 50% juveniles in the harvest, demographic harvest indicators showed signs of unsustainable harvest beginning in December. We also observed higher daily harvest rates (i.e., total number of animals harvested) in early winter and lowest harvest rates in February. Our results suggest that martens in a quota-free system were periodically vulnerable to local over-harvest. Much of the Yukon is remote with likely little trapping pressure, effectively providing harvest refugia for martens and allowing for continual over-harvest in areas with significant trapping pressure. As such, identifying and maintaining putative harvest refugia will be key to ensuring marten harvest is sustainable at broader temporal and spatial scales, especially in the absence of annually adjusted quotas. Regardless, ensuring sustainable harvest of this small carnivore in the future will require improvements to monitoring marten and the availability of their cyclic prey, continued stewardship by trappers, and possibly establishing quotas in areas of concern. Mandatory harvest reporting can aid in evaluating harvest sustainability at broad temporal and spatial scales. [ABSTRACT FROM AUTHOR]

Understanding predator-prey interactions is important to determine the inter-relationships between species. Optimal foraging theory states that predators balance out energy expended with the energy gained from their prey. In the Iberian Peninsula, the European rabbit (Oryctolagus cuniculus) is a key prey species for endangered Bonelli's eagle (Aquila fasciata). Thus, it is vital to understand how changes in rabbit abundance can influence habitat selection and territory use by Bonelli's eagle. We studied 11 radio-tagged Bonelli's eagles in their territories in Catalonia (NE Iberian Peninsula) and analysed the relationship between rabbit relative abundance, habitat selection and territory use of eagles. Rabbit relative abundance varied between territories, with shrublands hosting more rabbits, and eagles preferred shrublands and open areas for foraging and avoided dense forests. Spatial use by territorial eagles correlated positively with rabbit abundance in rabbit-rich territories, thereby supporting the idea that prey availability influences habitat selection. This result confirms optimal foraging strategies given that open habitats including shrublands tended to host more rabbits, thus providing better opportunities for prey detection and capture. Therefore, maintaining rabbit populations and their habitats (i.e., preserving open Mediterranean shrublands) would seem to be crucial for Bonelli's eagle conservation. Our findings improve our understanding of predator-prey interactions and highlight the relationship between habitat structure, prey abundance and predator behaviour. In addition, our results emphasize the need for targeted conservation strategies designed to safeguard endangered species such as Bonelli's eagle and maintain ecosystem integrity. [ABSTRACT FROM AUTHOR]

Optimal foraging theory posits that foragers adjust their movements based on prey abundance to optimize food intake. While extensively studied in terrestrial and marine environments, aerial foraging has remained relatively unexplored due to technological limitations. This study, uniquely combining BirdScan-MR1 radar and the Advanced Tracking and Localization of Animals in Real-Life Systems biotelemetry system, investigates the foraging dynamics of Little Swifts (Apus affinis) in response to insect movements over Israel’s Hula Valley. Insect movement traffic rate (MoTR) substantially varied across days, strongly influencing swift movement. On days with high MoTR, swifts exhibited reduced flight distance, increased colony visit rate, and earlier arrivals at the breeding colony, reflecting a dynamic response to prey availability. However, no significant effects were observed in total foraging duration, flight speed, or daily route length. Notably, as insect abundance increased, inter-individual distances decreased. These findings suggest that Little Swifts optimize their foraging behavior in relation to aerial insect abundance, likely influencing reproductive success and population dynamics. The integration of radar technology and biotelemetry systems provides a unique perspective on the interactions between aerial insectivores and their prey, contributing to a comprehensive understanding of optimal foraging strategies in diverse environments. [ABSTRACT FROM AUTHOR]

Pacific fin whales (Balaenoptera physalus velifera), once the most abundant cetacean species in British Columbia (BC), were also one of the most heavily targeted by commercial whaling. Much of what we know about their phenology and ecology is from catch records, but their current status has not yet been summarized in Canadian waters. Here, we collated evidence from dedicated surveys, opportunistic sightings, and passive acoustic records that had not been reported before and reviewed them in the context of past data. This was to add new findings to what is known, and to establish if the population was showing signs of recovery. This is particularly relevant considering discussions of downlisting their population status in Canada from endangered to threatened. We then asked if this rebounding was consistent with what is known about pre-whaling presence and movement patterns, or if changes in whale distribution reflected altered oceanic regimes, prey availability, or increased anthropogenic pressures. The evidence suggested that fin whale populations in the northeast Pacific Ocean are repopulating areas along the BC coast recognized as part of their historic range. However, they are recovering in a different ocean than they were removed from, which makes them increasingly vulnerable to new anthropogenic threats. The sightings data suggested that, at least for the west coast of Vancouver Island, this repopulation has occurred over a relatively short period, with fin whales still absent from regular surveys as recent as the early 2000's. The recent acoustic recordings suggested their presence is not transitory, but that fin whales may be using locales along the BC coast for feeding and breeding activities. [ABSTRACT FROM AUTHOR]

Simple Summary: Reeve's muntjac (Muntiacus reevesi), a key prey species of the South China tiger (Panthera tigris amoyensis) in the Hupingshan National Nature Reserve, plays a crucial role in supporting tiger reintroduction efforts. We applied the MaxEnt model to assess Reeve's muntjac's current and future habitat distribution under two climate scenarios (SSP126 and SSP585) for the mid-century (2050s) and the late-century (2090s), respectively. The results showed that climate (35.2%) and human activities (49.4%) played a key role in the habitat distribution of Reeve's muntjac. Currently, the high, medium, and low suitability habitats were 150.9 km2, 290.9 km2, and 225.9 km2, respectively. The high and medium suitability habitat area will ascend to 658 km2 (2050s) but slightly descend to 651.3 km2 (2090s) under SSP126. The high and medium suitability habitat area will ascend to 540.7 km2 (2050s) but descend to 73.6 km2 (2090s) under SSP585. These findings suggest that while mid-century conditions may support the species, late-century climate conditions, particularly under SSP585, could cause severe habitat loss for Reeve's muntjac. Conservation measures such as establishing migration corridors and minimizing human activities are essential to mitigate these impacts and support both the survival of Reeve's muntjac and the success of the South China tiger reintroduction plan. Climate change and human disturbance are critical factors affecting the habitat distribution of wild animals, with implications for management strategies such as protecting migration corridors, habitat restoration, and species conservation. In the Hupingshan National Nature Reserve (NNR), Reeve's muntjac (Muntiacus reevesi) is a key prey species for the South China tiger (Panthera tigris amoyensis), which is extinct in the wild and targeted for reintroduction by the Chinese government. Thus, understanding the habitat distribution and abundance of Reeve's muntjac is essential to ensure the survival and sustainability of reintroduced tiger populations. Despite significant conservation efforts, the impacts of climate change and human disturbance on Reeve's muntjac habitat distribution in Hupingshan NNR remain unclear, though these factors could necessitate adaptive tiger management strategies due to shifts in prey abundance. In this study, we employed an optimized MaxEnt model to assess current habitat distribution and identify key environmental variables influencing the habitat distribution of Reeve's muntjac. Assuming non-climatic environmental factors will remain constant over the next century, we projected future habitat distribution under two shared socioeconomic pathways (SSP126 and SSP585) for the mid-century (2050s) and the late-century (2090s). Comparative analyses of current and projected habitat areas revealed potential impacts of climate change on this species. MaxEnt outputs classified habitat suitability into high, medium, and low levels. Results showed that climatic and human disturbance factors contributed 35.2% and 49.4% to habitat suitability, respectively. Under the SSP126 scenario, habitats with decreased suitability covered 0 km2 in the 2050s, expanding slightly to 4.2 km2 in the 2090s, while those with increased suitability spanned 491.1 km2 (2050s) and 463.2 km2 (2090s). Under the SSP585 scenario, habitats with decreased suitability covered 10.2 km2 in the 2050s and 431.8 km2 in the 2090s. Habitats with increased suitability were comparatively smaller under SSP585, covering 162.0 km2 (2050s) and 1.1 km2 (2090s). These findings suggest that while mid-century climate projections (SSP126 and SSP585) may support Reeve's muntjac's survival, habitat loss is projected by 2090s (SSP126). Thus, future climate change may lead to decreased habitat suitability and increased fragmentation, raising extinction risks for Reeves's muntjac. Mitigating these effects could involve establishing migration corridors, minimizing human disturbances, and potentially supplementing prey populations with captive-bred prey. Such measures are essential to support the South China tiger reintroduction plan and help ensure that prey availability remains sufficient for sustaining reintroduced tiger populations. [ABSTRACT FROM AUTHOR]

In the present study, we describe and compare the diet of two populations of Pleurodema diplolister from northeastern Brazil. We assessed whether diet composition varies between the different populations and whether the size of individuals is related to the composition, volume and the size of prey consumed. Stomach contents were retrieved through the stomach-flushing technique from specimens collected in two municipalities (Morro do Chapéu and Rio de Contas) in the semi-arid region of Bahia State. We captured a total of 163 individuals and 91 of them had some type of stomach contents. A total of 278 food items were classified and distributed among 10 prey categories. The main food items consumed include Hymenoptera (Formicidae), Isoptera and Coleoptera. The morphometric measurements (snout-vent length and mouth width) of P. diplolister were significantly correlated with the diet (total volume of prey and length of the largest prey ingested). Diet composition differed between the two localities, showing little overlap between populations. Part of the variation in diet composition may be attributed to differences in the size of P. diplolister individuals. However, many factors can be associated to these differences, such as prey availability, landscape structure or even anthropic influences on the local ecosystem. In order to unravel the intricacies behind these distinct patterns, a comprehensive examination of these factors and others becomes imperative. This detailed analysis is crucial for a more thorough understanding of the extent to which these elements influence the feeding habits of anurans. [ABSTRACT FROM AUTHOR]

Large carnivores such as leopards (Panthera pardus) experience continuing threats from habitat loss and fragmentation, depletion of prey populations, and retaliatory killing following conflicts with humans. We aimed to identify factors affecting leopard occupancy and temporal overlap between leopards and tigers (P. tigris), their major prey, and human activities in the Parsa‐Koshi Complex (PKC), Nepal. We deployed 154 cameras for 21 days each along wildlife trails throughout PKC during December 2022–March 2023. We found low leopard occupancy (0.17 ± 0.04) in PKC, with greater occupancy rates within protected areas, particularly in Parsa National Park and its buffer zone. Human (63.10 ± 23) and livestock (36.46 ± 102) detections were higher across the PKC. Leopard occupancy was positively associated with the presence of tigers and prey. Temporal overlap was moderately high between leopards and tigers, as well as between leopards and their prey. Our research suggests that coexistence between leopards and tigers is likely largely facilitated by higher prey availability, which may reduce competition. Further, we demonstrate that maintaining forest cohesion can improve habitat for leopards. Intensifying use of agricultural areas could reduce forest fragmentation and increase leopard habitat overall, in turn reducing leopard depredation of livestock and improving leopard‐human co‐existence and conservation. [ABSTRACT FROM AUTHOR]

Fishes use a variety of physical and biological resources that shift ontogenetically, seasonally and spatially. Quantifying what resources such as prey are required for persistence can improve understanding of ecological needs of fishes and riverine macrosystem functioning. Bowfin (Amia ocellicauda) and largemouth bass (Micropterus nigricans) cohabitate in their native range and potentially compete with one another. Yet, there have been no direct comparisons of their diets across spatial gradients to assess whether they partition resources or shift in prey use. We used multiple univariate and multivariate analyses to compare diet composition, diet overlap, feeding strategy, prey importance and diet partitioning between largemouth bass and bowfin across three reaches of the Upper Mississippi River. Largemouth bass ontogenetically shifted their diet from aquatic invertebrates to fishes and a more diverse assemblage of aquatic invertebrates. Bowfin and adult largemouth bass were top predators which consumed mostly crayfish and fish and overlapped in their diets. Despite overlapping diets, predators partitioned resources by consuming different lengths and abundances of prey, and largemouth bass had greater trophic plasticity. Within a predator group, few differences in diets existed spatially, underscoring the relative homogeneity in resource use potentially from similarities in the river's physical structure. Combined, prey use likely differed sufficiently to reduce potential competition between largemouth bass and bowfin, allowing long‐term coexistence in this system. Our results also highlighted the importance of crayfishes to riverine food webs and underscored the use of multiple prey and habitat types that sustain these predators. [ABSTRACT FROM AUTHOR]

Diets of fish larvae may vary within populations and among species and are affected by larval prey availability and foraging capacity. We aimed to describe the diet of fish larvae based on empirical field observations, emphasizing the interaction and organization of the predator–prey network using Auchenipterus osteomystax as a species model. The network showed few interactions (low connectance and modularity) but a nested structure (some items that had fewer records tended to occur together with the most frequent ones), low complementary specialization (the proportions of ingested items tended to be equivalent) and a pattern of segregation (some items tended not to be consumed together) in the use of resources among individuals. Robustness was low when the removal of prey with a higher consumption frequency occurred. The correlation between morphological variables and network attributes was significant and positive for abundance and strength, while the correlation with nested rank was negative. The availability of suitable dietary resources is likely to be the key factor for success and survival in the early stages of development. With changes in morphology during larval development, A. osteomystax showed a generalist position in the network as its predation capacity increased. A new approach to trophic ecology studies of fish larvae incorporating network analysis may help explain the individual characteristics of larvae and assess the pattern of interactions in the population. [ABSTRACT FROM AUTHOR]

As obligate nocturnal mammals, most bats spend the day hiding in dark shelters, sometimes as gregarious colonies. Roosting in such large colonies may have the advantage of reducing thermoregulatory costs, as the heat dissipated by thousands of bodies raises the temperature of the cave interior. However, bats in large aggregations may also suffer from increased predation risk. Here we studied the effect of a highly gregarious Palaeotropical bat, the wrinkle-lipped free-tailed bat (Mops plicatus), on cave temperature and the factors that influence its emergence behaviour. We studied cave temperature, prey abundance, emergence behaviour and attack rates by birds of prey during colony emergence. The study was made at Khao Wongkot Cave, counting more than one million individuals. In all seasons, we observed that the presence of M. plicatus caused relatively higher temperatures of around 30°C inside the cave, while temperatures outside were lower and more variable. This suggests that the body heat of aggregated bats raised the temperature inside the cave, presumably close to the thermo-neutral zone at the roosting sites of bats. Arthropod abundance was highest during late pregnancy/early lactation and lowest during late lactation/post lactation. Bats emerged earliest during the late wet season and latest during the hot season. During periods of high predation risk, bats always emerged as a column, whereas during periods of low predation risk (hot and early wet seasons), individual bats left first, before a column of bats formed, 10 to 20 min after the first individuals exited the cave. Our study highlights that large colonies may provide thermoregulatory benefits that could increase individual fitness. However, aggregations also increase predation costs during emergence. Bats form a column when aerial predator attacks are most frequent. Also, bats seem to adjust their emergence timing in response to seasonal changes in predation risk. [ABSTRACT FROM AUTHOR]

Prey abundance and quality are dynamic in time and space, impacting predator ecology. We examine variation in species-specific krill quantity and quality as prey for humpback whales in the Northern California Current region, using generalized additive models to assess metrics including biomass and energy density derived from an integrated dataset of concurrent active acoustics, net tows, and marine mammal observations (2018–2022). Overall, prey metrics were positively correlated with humpback whale presence, with increasing trends modified by seasonal (early versus late foraging season) and spatial (continental shelf versus offshore) variation (model deviance explained 36.3%–40.8%). Biomass and energy density had strong positive effects on humpback whale presence, suggesting whales target high-quality swarms that offer more energy per lunge. Elevated Thysanoessa spinifera abundance near humpback whales suggests that they target this species, particularly in the late season when they are energetically richer than Euphausia pacifica , the region's other abundant krill species. Environmental change may decrease krill abundance and quality, impacting humpback whales' ability to meet energetic requirements and potentially driving changes in their distributions and exposure to anthropogenic threats. Clarifying drivers of humpback whale krill patch selection can improve species distribution models and aid managers in mitigating risk to whales. [ABSTRACT FROM AUTHOR]

Experimental observations and field data demonstrated that predators adapt their hunting strategies in response to prey abundance. While previous studies explored the impact of predation risk on predator–prey interactions, the impact of symbiotic relationships between fear-affected prey and non-prey species on system dynamics remains unexplored. This study uses a mathematical approach to investigate how different symbiotic relationships govern system dynamics when predators adapt to prey availability. Our study illustrates that the mutualistic relationship between prey and partners extends predator survivability. However, the fear-affected symbiotic system may undergo regime shifts, which can be catastrophic or non-catastrophic, depending on symbiotic interaction patterns. The study demonstrates a hump-shaped relationship between the predator's optimal search rate and biomass and identifies an intermediate range of search rates where the system exhibits a "bubbling"phenomenon. Overall, our findings provide new insights into symbiotic relationships in community ecology, highlighting the complex interplay among predators, prey, and non-prey species. [ABSTRACT FROM AUTHOR]

The Bijagós Archipelago in West Africa is home to an ethnic group with a rich cultural heritage that is tightly linked to nature. The Bijagós people have a shared cultural identity, but management of natural resources varies between islands due to island-specific context with regards to socio-political organization and strength of cultural heritage. Across the archipelago, bivalves harvested manually from the mudflats are an important part of the Bijagós people's diet, economy, and culture. Migratory shorebirds share the use of these mudflats during their non-breeding season, consuming macrobenthos such as crustaceans and bivalves, including those harvested by local people. At the end of their stay in the Bijagós, just before taking off for their migratory flight, it is particularly important that shorebirds have access to undisturbed feeding areas with suitable food resources. In this study we start by exploring shellfishing patterns across different management regimes (via questionnaires to local shellfishers), then assess seasonal variation in the direct impact of shellfishing on shorebirds (through competition for resources and space), and finally quantify the indirect impact of sediment disturbance due to shellfishing upon shorebird prey availability with an experimental approach. Results indicate that bivalve resources are better managed in areas with formal protection, while traditional management based on cultural beliefs results in poorer stock conditions. Interestingly, the high density of shellfishers in mid-winter (14.4 ind. km-2) decreased markedly towards shorebirds' fuelling period, when they benefit the most from reduced disturbance on the mudflats. Regardless of the season, no direct competition for resources was detected due to differences in targeted sizes. Indirect impacts caused by sediment disturbance during shellfishing were also mostly absent, causing only a small reduction on shorebirds prey density but with no effect on the available biomass. [ABSTRACT FROM AUTHOR]

Predators may adjust their diets to match their energy needs and food availability, but these adjustments have not been explored for migratory aerial insectivores outside of the breeding grounds. We found that Chordeiles minor (Common Nighthawk), a long-distance migrant and member of the rapidly declining aerial insectivore guild, exhibited similar levels of diet richness, diet diversity, and prey selectivity on the breeding and nonbreeding grounds, despite large differences in prey abundance. We examined the diets and prey communities of C. minor during 2 breeding seasons in Florida, USA, and 2 nonbreeding seasons in Corrientes Province, Argentina (2020 to 2022). We used DNA metabarcoding to identify insect prey in C. minor fecal samples, and we employed Malaise and UV light traps to assess abundance and composition of aerial insect prey communities. Abundance and richness of available prey were significantly higher on the nonbreeding grounds than on the breeding grounds. Even so, C. minor exhibited similar within-sample and within-population diet richness, Shannon and Simpson diversities, and prey preferences at both sites. Adults differed in their consumption of Lepidoptera between sites: adults on the nonbreeding grounds preferred Lepidoptera over all other orders, whereas adults on the breeding grounds consumed Lepidoptera less frequently than expected. We suggest that breeding adult C. minor may deliver Lepidoptera to their young instead of consuming this prey. At both sites, C. minor showed preference for Hemiptera and Hymenoptera–both large-bodied, nutrient-rich prey–suggesting that these generalist predators exhibit less diet flexibility than previously thought and thus may be vulnerable to changes in prey communities at multiple points in the annual cycle. [ABSTRACT FROM AUTHOR]

Insectivorous bats are an important group of natural enemies that use echolocation for communication, navigation, and foraging. While foraging, bats often eavesdrop on calls from other foraging individuals and are attracted to them as these indicate prey abundance. In addition, they use hedgerows such as tree lines in agroecosystems for commuting and foraging. In the present study, we employed two approaches to enhance the activity of desert-dwelling bats in fields of melon, pumpkin and onion in the hyper-arid Arava desert, Israel. We predicted that both approaches will enhance the activity of the bats in these agricultural fields. We broadcasted playbacks of echolocation calls of two common desert bats, Hypsugo ariel and Eptesicus bottae over the crop fields as a direct means and used gaps in windbreak lines made of planted trees Tamarix spp. as indirect means. Playback manipulation had differing results between the two species. The activity of H. ariel was initially higher in the control plot, but as broadcasting continued, the manipulated plot exhibited significantly higher activity over onion fields. In contrast, the activity of E. bottae declined over Cucurbit fields in the manipulated plots. These differences may reflect differences between the species in the level of sociality while foraging. The testing of the indirect approach showed that total bat activity and feeding buzzes ratio were significantly higher in small windbreak gaps compared to plots with continues tree line. Our results indicate the potential and the limitations of enhancing bat activity by broadcasting echolocation calls in open crop fields and the importance of landscape features which increase the heterogeneity of the crop fields to attract natural enemies in Conservation Biological Control. [ABSTRACT FROM AUTHOR]

Describing the habitat needs of endangered species is a major focus of applied conservation research. The blunt‐nosed leopard lizard (Gambelia sila (Stejneger, 1890)) is a flagship endangered species endemic to the San Joaquin Valley of California, USA. Arthropods are an important component of G. sila's diet and of many other listed vertebrate species in Californian drylands. We examined the drivers of abundance, richness, and composition across the current and extirpated ranges of the blunt‐nosed leopard lizard G. sila for four arthropod communities: ground‐active, shrub‐canopy active, open area active, and aerial. We found no evidence for lower arthropod abundance or species richness at sites from which G. sila has been extirpated. In contrast, the ground‐active arthropod and beetle communities were less abundant at sites with current populations of G. sila after accounting for environmental variation. Thus, prey availability—at least at the community level and for the taxonomic groups considered—would not likely be a factor constraining future repopulation efforts for G. sila into its historical range. Beta‐diversity partitioning analyses indicated that a regional approach to conservation is necessary to conserve arthropod biodiversity across the San Joaquin Valley. Increasing aridity lowered abundance and species richness at fine scales for most communities tested and was also related to spatial composition across the region. Thus, in terms of G. sila conservation and restoration, sites with the lowest current and projected future aridity should be prioritized to maximize the abundance and richness of co‐occurring ground‐active arthropod and beetle communities. [ABSTRACT FROM AUTHOR]

ABSTRACT Luciferidae (Decapoda) are an important component of mesozooplankton in pelagic food webs. This study investigated the spatiotemporal distribution and frequency of Luciferidae swarms along the Tamil Nadu coast, as observed during coastal monitoring cruises conducted between 2019 and 2022. Data were collected on various hydrobiological factors, including surface water temperature, salinity, chlorophyll a, zooplankton biomass, and the abundance of other mesozooplankton (such as copepods, cladocerans, and others) across eight locations in the coastal waters of Tamil Nadu, India. Salinity values were generally low (< 30 PSU) throughout the study period, except in September 2019. Microscopic analysis identified Belzebub hanseni Nobili, 1905, as the only organism responsible for swarm formation, with its occurrence peaking in January 2022. During this period, B. hanseni reached a maximum abundance of 3294 ind. m−3 for adults and 4056 ind. m−3 for larvae, together contributing approximately 27% of the total zooplankton abundance. Swarms of B. hanseni were observed a total of seven times over the course of the study, correlating with periods of low sea surface temperature and high food availability. Pearson's correlation analysis revealed a significant relationship between the abundance of copepods and B. hanseni (r = 0.84; p < 0.001), suggesting that both groups may be influenced by similar environmental factors, such as physical transport, food availability, and favorable conditions. This study indicates that the frequent swarming of B. hanseni in the nearshore waters of the Tamil Nadu coast is largely driven by food availability and optimal environmental conditions, including water temperature and monsoonal influences. The findings also suggest that geographical features, such as mangrove habitats, may contribute to the occurrence of B. hanseni swarms in this region. [ABSTRACT FROM AUTHOR]

ABSTRACT Spatiotemporal interactions between predators and prey are central to maintaining sustainable functioning ecosystems and community stability. For wild ungulates and their predators, livestock grazing is an important anthropogenic disturbance causing population declines and modifying their interactions over time and space. However, it is poorly understood how fine‐scale grazing affects the spatiotemporal responses of predators, prey, and their interactions. Two opposing hypotheses describe a dichotomy of possible effects. The human shield hypothesis states that people can protect prey because predators avoid areas with high human‐induced mortality risk, whereas in the human competitor hypothesis, humans compete for prey and negatively impact predators through reduced prey availability. We used camera‐trapping data from the Gansu Qilianshan National Nature Reserve in Northwest China to measure occupancy, daily activity patterns, and spatiotemporal interactions between snow leopards (Panthera uncia), the dominant predator, and their ungulate prey in areas with contrasting grazing intensities. The results of grazing were consistent with both the human‐shield and human‐competitor hypotheses, affecting spatiotemporal patterns and interactions of predators and prey. For the primary prey species, blue sheep (Pseudois nayaur), their spatial and temporal patterns were affected by grazing, which led to a reduction in interaction frequencies with snow leopards. For secondary prey, grazing led to reduced interaction frequencies with snow leopards for white‐lipped deer (Przewalskium albirostris) and red deer (Cervus yarkandensis), but increased frequencies for alpine musk deer (Moschus chrysogaster). Our results indicate how both competition among livestock and prey and predator or prey avoidance of grazed areas can impact populations and predator–prey interactions. Our findings are relevant to grazing management and snow leopard conservation. [ABSTRACT FROM AUTHOR]

Transferability of species distribution models (SDMs) is vital for guiding biological conversation in the changing marine ecosystems, whereas most SDMs have remained insufficiently tested in terms of transferences. Particularly, the roles of biotic interactions in shaping ecological niches had less been considered when predictive models are transferred into a new circumstance. Therefore, using silver croaker (Pennahia argentata) and slender lizardfish (Saurida elongata), two keystone predators in the coastal systems as examples, this study examined how the consideration of abiotic and biotic factors as well as spatial autocorrelation would improve the transferability of prevalent SDMs. We collected the data of species abundance and hydrological variables from coastal waters of Shandong Peninsula, China, and developed a framework to evaluate the interpolation performance and spatial transferability of SDMs with respect to different modelling algorithms and combinations of covariates. The covariates tested included (1) abiotic environmental variables only; (2) biotic variables of prey availability only; (3) both abiotic and biotic variables; and (4) spatial autocorrelation in addition to other variables. Generally, our results showed that including abiotic and biotic variables simultaneously could improve the model transferability, whereas biotic models exhibited greater uncertainty and overestimation in spatial transferences when delineating suitable habitats. Besides, models accounting for spatial autocorrelation yielded more accurate forecasts for slender lizardfish's abundance, and were less limited by geographic distance in transference. Regarding the model algorithms, GLM slightly outperformed GAM and RF overall, while RF showed more robust spatial extrapolations in many cases. Our transferability evaluations offer the opportunity to extend the use of biotic signals and spatial autocorrelation to improve the forecasts of habitat suitability, which would be informative for guiding marine conservation actions. [ABSTRACT FROM AUTHOR]

A species' diet is highly dependent on the availability of food resources in space and time, as well as on intrinsic factors such as sex or age. Accurate assessments of variations in the diet composition of bird populations across spatial scales, seasons and demographic groups are essential not only for understanding the basic ecology of species, but also for the conservation of endangered ones. However, our current knowledge about how birds' diet change according to spatio-temporal variations or intrinsic factors is very limited. Here, we used a multi-marker metabarcoding approach to characterize the diet of a declining shrub-steppe passerine, the Dupont's Lark (Chersophilus duponti), throughout a large part of its global distribution range. We also investigated spatial, phenological and sexual variations in its diet. Using markers from two genomic regions (18S and COI), we analyzed fecal samples from 303 adult Dupont's larks from Morocco and Spain during the breeding and non-breeding seasons. Overall, arthropods from the orders Coleoptera, Lepidoptera, Julida and Orthoptera were the main prey consumed by Dupont's Larks. We found that Dupont's Lark diet varied spatially, as well as temporally, reflecting dietary plasticity in response to changes in prey availability across landscapes and the species' phenological periods. High dietary overlap and no differences between sexes were observed, suggesting similar foraging behavior and nutritional requirements in both sexes. This is the first study providing detailed information on Dupont's Lark food ecology over much of its distribution, which is fundamental for the management and conservation of this declining steppe species. [ABSTRACT FROM AUTHOR]

Small mammal populations fluctuate significantly in abundance over time, affecting the entire food web. However, changes in their occupancy across a landscape receive less attention. While habitat features are relevant for some predators, diet specialization and prey distribution and abundance might play an important role in shaping predator populations. Using a multi‐season occupancy analysis, we examined the spatio‐temporal patterns of Mediterranean mesocarnivores—common genet, stone marten and red fox—focusing on the factors that influence their occupancy dynamics, particularly small mammal occupancy as a prey resource. Data was collected from December 2020 to May 2021 in the Sant Llorenç del Munt i l'Obac Natural Park using a camera‐trap grid. We analysed small mammal occupancy dynamics and used these as covariates in predator occupancy models to explore predator–prey relationships. Additionally, we included the occurrence of each carnivore as a predictor for interspecific analysis, and kernel density functions were used to assess daily activity overlaps. Results showed that interspecific competition significantly affected mesocarnivore occupancy, as genet occupancy was negatively correlated with the red fox occupancy. Although prey occurrence did not influence mesocarnivore occupancy, it did affect detectability, with genet and stone marten detectability being positively related to small mammal presence and high daily activity overlap between predators and prey. This suggests that mesopredators respond rapidly to prey abundance, highlighting the intricate temporal dependence between predator activity and prey occupancy. Dynamic occupancy and activity models provide a deeper understanding of predator–prey relationships at the local scale. [ABSTRACT FROM AUTHOR]

Ecosystem management requires an integrated understanding of ecological interactions. In the Gulf of Maine (GoM), trophic information pertaining to commercially important groundfishes and nearshore prey communities is lacking. We characterized nearshore communities and groundfish diets using data collected from nearshore surveys (864 bottom trawls and 3638 stomach samples of six groundfish species) conducted biannually (spring and fall) in Midcoast Maine and Penobscot Bay from 2012 to 2022. Groundfish diets were dominated by some of the most available nearshore prey (gadiform and clupeiform fishes and pandalid and crangonid shrimps). Shifts in relative prey availability over environmental gradients (e.g., depth and position along the coast), across seasons, and over years corresponded with parallel patterns in prey contributions to groundfish diets in specific predator–prey interactions. Negative trends in the relative availability and diet occurrence of signature GoM prey taxa (Northern shrimp Pandalus borealis, Atlantic herring Clupea harengus, and euphausiids) indicate that broader ecosystem changes, such as steady rises in water temperature and shifts in species distributions, are impacting nearshore trophic dynamics in the GoM. These observations provide timely information on mechanisms that underlie groundfish productivity and warrant inclusion of nearshore trophic dynamics in relevant ecosystem models. [ABSTRACT FROM AUTHOR]

In the context of the Persian leopard restoration program in the Russian Caucasus, an in-depth analysis was conducted to understand the hunting behaviors of rewilded Persian leopards and evaluate the program's effectiveness. From 2016 to 2023, GPS telemetry data from 14 leopards (8 males and 6 females) aged 20 months and older, released in the Western (WeC) and Central (CeC) Caucasus, were analyzed. Using cluster location analysis, we determined 243 kill sites categorized by prey-size into large, medium, and small classes. In the WeC, leopards exhibit a significantly higher proportion of large prey compared to the CeC (43%, N = 49 vs. 5.4%, N = 148, p < 0.01). There is no significant difference in the proportion of medium-sized prey, but there is a striking contrast in the proportion of small prey (WeC 16.2%, CeC 57.4% (p < 0.01)). No significant differences were found in the time spent on prey between male and female leopards, regardless of the region. Female leopards capture their next prey 215 ± 184 hours (Mean ± SD; N = 131) after leaving the previous one, covering a distance of 46 ± 40 km (Mean ± SD, max 191 km). Male leopards, in contrast, take 265 ± 246 hours (Mean ± SD, N = 110) between kills, with a distance of 59 ± 60 km (Mean ± SD, max 366 km) between them. In the WeC, the kill rate for leopards are lower than in the CeC, with averages of a prey every 264 ± 273 hours and 62 ± 64 km (N = 77) compared to 152 ± 172 hours and 47 ± 41 km (N = 165), respectively. Leopards in the CeC spend significantly more time on kill sites with large and medium-sized prey compared to small prey. In contrast, leopards in the WeC show no significant difference in the time spent on prey of different size classes. This disparity is explained by the fact that large and medium-sized prey are more challenging to conceal and defend from competitors whose populations densities are higher in the WeC than the CeC. 20% of large and medium-size prey kill sites of leopard in the Western Caucasus have been visited by bears or wolves. This suggests that environmental factors and attractive high ungulate population densities may also play a critical role in shaping predator-prey dynamics and interspecific competition in the region. It is imperative to evaluate the availability of potential prey across different size classes, alongside with moderate levels of competitor populations. These factors can play a decisive role during the crucial first year of the leopard's adaptation to life in the wild, ultimately determining the success of species restoration initiatives. [ABSTRACT FROM AUTHOR]

As an apex predator in arid steppe, saker falcon plays a crucial role in maintaining ecosystem balance. Understanding their movement patterns concerning conspecific competition and prey availability is important for their conservation. We aim to understand how movement pattern of breeding saker falcons relates to prey availability. Twelve adult sakers were tracked during the breeding seasons, using satellite transmitters. Throughout the breeding season, sakers exhibited territorial behavior, with minimal overlap in range use among neighboring conspecifics. Males occupied larger areas (mean = 2,397 ha, median = 1,221 ha), compared to females (mean = 1,241 ha, median = 554 ha), and it remained consistent throughout breeding season. Female home range size increased notably during a late nestling stage and post-fledging dependence periods, indicating release from brooding constraints. Notably, we found a negative relationship between male home range size and prey availability. In high rodent density areas, males occupied smaller areas (mean = 1,135 ha, median = 1,034 ha), contrasting with low rodent density areas (mean = 6,815 ha, median = 6,516 ha). However, no significant relationship was observed between female home range size and prey availability. We also noted instances of nest abandonment and early dispersal behavior in some females, potentially influenced by a handicapping effect of tagging. Our findings offer valuable insight into how prey availability shapes saker falcon space use and defines their spatial requirements for successful breeding. This knowledge is crucial for the conservation and management of globally endangered saker falcons, informing targeted habitat protection and resource management strategies. [ABSTRACT FROM AUTHOR]

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. KEY POLICY HIGHLIGHTS: Consistent, frequent monitoring accompanied by adequate laboratory processing is needed to evaluate seasonal changes in the timing of prey availability and subsequent predator response. 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. 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. Our results highlight the importance of monitoring metrics of prey size as indicated by prey size selection both during zooplanktivory and piscivory. [ABSTRACT FROM AUTHOR]

The Little Owl (Athene noctua) is a widespread nocturnal raptor whose diet has extensively been studied. In the Mediterranean, a tendency towards increased ingestion of insects has been highlighted, but this tendency still needs more empirical validation. Here, we provide data on the autumn diet of Little Owls in an arid area in southern Tunisia. We analyzed 621 pellets from 30 different territories and identified 4,267 prey items, with insects being by far the most ingested prey. However, based on biomass, the diet was more evenly distributed across the identified prey categories. Vertebrates accounted for 63% of the biomass ingested, while the remaining part of prey composition was almost equally shared between insects and arachnids. The importance of arachnids looks like a characteristic dietary trait of Little Owls in south Mediterranean deserts, where arachnids represent a main component of the community of potential prey. In summary, our findings highlight the great food opportunism of the Little Owl due to its capability of adapting its diet to the availability of potential prey. [ABSTRACT FROM AUTHOR]

Raptors are crucial indicators of ecosystem health, and thus, requires research attention. Despite an upsurge in Indian ornithology, raptors remain poorly studied, particularly in Northeast India. Here, we measured the taxonomic and functional diversity of raptors in Manas National Park, Assam. The study was conducted between 2018–2022. We surveyed 39 standard transects and recorded 776 individuals of raptors belonging to 30 species in different habitats: forest, open and mosaic. The taxonomic alpha diversity was highest in mosaic habitat and lowest in the forest habitat. Crested Serpent Eagle (Spilornis cheela) was the most abundant raptor in open and forest habitats, while Collared Falconet (Microhierax caerulescens) was dominating in mosaic habitats. Of the recorded raptor species, 66.67% were classified as residents, and 33.37% were winter migrants. We also measured the functional alpha diversity of raptors using the data collected from AVONET database. We used ten functional traits and evaluated the functional alpha diversity indices. The functional richness was the highest in open habitats and functional divergence was the highest in mosaic habitats, also functional evenness was the highest in open habitats and lowest in mosaic habitats. We suggest intensified research on raptors in the region, to identify and address critical research question which facilitates the conservation of these apex predators. [ABSTRACT FROM AUTHOR]

Understanding how animals maximize reproductive success in variable environments is important in determining how populations will respond to increasingly extreme weather events predicted in the face of changing climates. Although temperature is generally considered a key factor in reproductive decisions, rainfall is also an important predictor of prey availability in arid environments. Here, we test the impact of weather (i.e. rainfall and temperature) on female reproductive investment in an arid-dwelling bird (i.e. clutch size and egg volume) and tradeoffs between the two. We predicted that female chestnut-crowned babblers (Pomatostomus ruficeps), endemic to the arid region of Australia, would increase clutch size at the expense of egg volume in response to variation in rainfall and temperature. We found that over 14 breeding seasons, clutch size decreased with increasing temperature, but increased following more rain. Egg volume, on the other hand, became larger as temperatures increased and, although not related to the amount of rain, was related to the number of days since the last rainfall. Finally, egg size decreased as clutch size increased, indicating a tradeoff between the two reproductive parameters. Our results suggest that chestnut-crowned babblers breed reactively in response to variable environments. We expect that clutch size variation in response to rain may reflect the impact of rain on arthropod abundance, whereas the effect of temperature may represent an established decline in clutch size observed in other seasonal breeders. As the tradeoff between clutch size and egg volume was modest and clutch sizes were modified to a greater extent than egg volumes in response to rainfall, we suggest selection is more likely to increase offspring number than quality, at least in favorable years. Our results support the idea that reproductive investment is variable in fluctuating environments, which has implications for species living in habitats experiencing more extreme and less predictable weather as the global climate changes. [ABSTRACT FROM AUTHOR]

Climate heating has the potential to drive changes in ecosystems at multiple levels of biological organization. Temperature directly affects the inherent physiology of plants and animals, resulting in changes in rates of photosynthesis and respiration, and trophic interactions. Predicting temperature‐dependent changes in physiological and trophic processes, however, is challenging because environmental conditions and ecosystem structure vary across biogeographical regions of the globe. To realistically predict the effects of projected climate heating on wildlife populations, mechanistic tools are required to incorporate the inherent physiological effects of temperature changes, as well as the associated effects on food availability within and across comparable ecosystems. Here we applied an agent‐based bioenergetics model to explore the combined effects of projected temperature increases for 2100 (1.4, 2.7, and 4.4°C), and associated changes in prey availability, on three‐spined stickleback (Gasterosteus aculeatus) populations representing latitudes 50, 55, and 60°N. Our results showed a decline in population density after a simulated 1.4°C temperature increase at 50°N. In all other modeled scenarios there was an increase (inflation) in population density and biomass (per unit area) with climate heating, and this inflation increased with increasing latitude. We conclude that agent‐based bioenergetics models are valuable tools in discerning the impacts of climate change on wild fish populations, which play important roles in aquatic food webs. [ABSTRACT FROM AUTHOR]

Scorpions are diverse and abundant in tropical and subtropical regions worldwide, especially in arid ecosystems where they play a relevant role as predators. However, few studies have examined diet composition, use of alternative foraging strategies, prey selection, and predator-prey size relationships of scorpions in different microhabitats. This study provides an analysis of the diet of Buthus montanusLourenço & Vachon, 2004 in an arid area of SE Spain. Prey captured by scorpions were recorded during black-light censuses over the main activity season of B. montanus in the study area. Because scorpions were observed capturing prey on the ground surface, below ground, and in vegetation, prey availability was estimated using complementary methods for shrub- and ground-dwelling prey. Results show that B. montanus is a generalist predator that feeds on a diverse array of prey, although predatory arthropods and tenebrionid larvae comprised the highest proportion of its diet in both number of prey and biomass. Cannibalism was a major component of its diet, accounting for almost 25% of the biomass ingested, especially in large scorpions. The composition of the diet, prey-size variability, and predator-prey size relationship showed size-related differences. These size-related variations in the diet were also linked to habitat use, due to climbing vegetation by smaller scorpions. These results highlight the implications of ontogenetic shifts in the diet of B. montanus related to cannibalism by larger scorpions and climbing vegetation by smaller individuals, causing changes in the type of prey used by individuals of different size and predator-prey size relationships. [ABSTRACT FROM AUTHOR]

Although the Great crested newt (Triturus cristatus) is considered a generalist predator, there are few studies on its prey preferences across its wide range. Data on its feeding are virtually lacking for its southernmost populations; this study aims to fill this gap by analyzing the aquatic food spectrum and prey availability from three ponds in Stara Planina Mts., NW Bulgaria. Ponds were simultaneously sampled once per month; consumed prey items were collected using stomach flushing of captured newts, and hydrobiological samples were taken from each pond to establish potential prey diversity. Remains of ingested prey were found in 109 out of the 141 sampled adult newts (71 male and 70 female). Applying the widely used approach of "operational taxonomic units" (OTUs), prey items from stomach flushing were assigned to 27 OTUs (incl. plants and inorganic matter, and for females only - shed skin), while material from the hydrobiological samples - to 28 (20 of them were also found in the stomach content of the newts). The most frequent prey for both sexes were larvae from the family Chironomidae (found in 21% of the studied newts) and the most abundant superorder Cladocera (60% of the identified prey items). Male newts were more likely than females not to have eaten during the summer when the frequency of empty stomachs was higher compared to spring. For both sexes, prey diversity from stomach content was higher in the spring compared to the summer (Simpson's index values were respectively 0.76 vs. 0.12 for the males and 0.72 vs. 0.54 for the females), and females consumed more diverse prey during the summer, possibly as a result of their breeding behavior. [ABSTRACT FROM AUTHOR]

The estimation of foraging parameters is fundamental for understanding predator ecology. Predation and feeding can vary with multiple factors, such as prey availability, presence of kleptoparasites and human disturbance. However, our knowledge is mostly limited to local scales, which prevents studying effects of environmental factors across larger ecological gradients. Here, we compared inter‐kill intervals and handling times of Eurasian lynx (Lynx lynx) across a large latitudinal gradient, from subarctic to the Mediterranean ecosystems, using a standardised dataset of predicted adult ungulate kills from 107 GPS‐collared lynx from nine distinct populations in Europe. We analysed variations in these two foraging parameters in relation to proxies reflecting prey availability, scavengers' presence and human disturbance, to improve our understanding of lynx predation at a continental scale. We found that inter‐kill intervals and handling times varied between populations, social status and in different seasons within the year. We observed marked differences in inter‐kill intervals between populations, which do not appear to be driven by variation in handling time. Increases in habitat productivity (expressed by NDVI, used as a proxy for prey availability) resulted in reduced inter‐kill intervals (i.e. higher kill rates). We observed less variation in handling (i.e. feeding) times, although presence of dominant scavengers (wild boars and brown bears) and higher human impact led to significantly shorter handling times. This suggests that kleptoparasitism and human disturbance may limit the energetic input that lynx can obtain from their prey. We also observed that the human impact on foraging parameters can be consistent between some populations but context‐dependent for others, suggesting local adaptations by lynx. Our study highlights the value of large‐scale studies based on standardised datasets, which can aid the implementation of effective management measures, as patterns observed in one area might not be necessarily transferable to other regions. Our results also indicate the high degree of adaptability of these solitary felids, which enables them to meet their energy requirements and persist across a wide range of environmental conditions despite the constraints imposed by humans, dominant scavengers and variable prey availability. [ABSTRACT FROM AUTHOR]

In recent decades, the locally extinct sea otter (Enhydra lutris lutris) has been recolonizing the coast of eastern Hokkaido. Their diet includes benthic invertebrates such as bivalves, sea urchins, snails, and chitons. In the fall of 2021, a harmful algal bloom (HAB) of Karenia selliformis occurred across Hokkaido's northern and eastern coasts, leading to a massive mortality of sea urchins. This dinoflagellate produces a neurotoxin (gymnodimine) implicated in shellfish poisoning. To determine the effect of the HAB on the marine community, we conducted benthic surveys using SCUBA and visually monitored the prey items of the sea otters in the affected area from 2020 to 2023. Following the HAB, we observed an 82% decrease in benthic sea urchin density (number m2), leading to their complete absence from the diet of sea otters. Conversely, bivalve density increased six-fold, accompanied by a nearly two-fold rise in their percentage in the sea otters' diet. Minimal changes were observed in the density of chitons and snails, with no significant alteration in the sea otters' diet. Despite these changes, the impact of the HAB on otters' dietary preferences was temporary, as the percentage of dietary sea urchins began recovering one year later. Sea otters augmented their diet with bivalves to compensate for the reduced availability of sea urchins during the HAB with no apparent effects on the number of sea otters or their health. Our results highlight the adaptability of sea otters to adjust their diet according to prey availability. [ABSTRACT FROM AUTHOR]

ABSTRACT Bigeye tuna (Thunnus obesus; BET) and yellowfin tuna (Thunnus albacares; YFT) are commercially and ecologically important Atlantic Ocean species. Numerous studies have examined interacting species with clearly synchronous or asynchronous dynamics, but few have investigated interactions among tuna species. This study investigated the effects of climate indices on the standardized catch per unit effort (CPUE) and habitat preferences of BET and YFT in the Atlantic Ocean. The indicators for both tuna species were found to be influenced by the Atlantic Multidecadal Oscillation (AMO) and Tropical North Atlantic index. The AMO had the strongest effect on standardized CPUE for the two species, and habitat suitability also reflected AMO trends. We compared CPUE trends in overlapping suitable habitat areas and estimated variations in primary prey abundance for between BET and YFT to evaluate their species' competition for limited prey and habitat area resources. The standardized CPUE, habitat suitability index (HSI), and primary prey levels (squid and crustaceans) of BET all increased following the change to the positive AMO phase after the 1990s. Although the HSI value for YFT also increased in an area of habitat overlap, the corresponding standardized CPUE decreased. We suggest that this pattern of a decreasing‐standardized CPUE for YFT may have been caused by competition for limited prey and habitat area resources in the overlap area. [ABSTRACT FROM AUTHOR]

Many seabirds congregate in large colonies for breeding, a time when they are central place foragers. An influential idea in seabird ecology posits that competition during breeding results in an area of reduced prey availability around colonies, a phenomenon known as Ashmole's halo, and that this limits colony size. This idea has gained empirical support, including the finding that species coexisting within a colony might be able to do so by foraging on a single prey species but at different distances. Here, we provide a comprehensive mathematical model for central place foragers exploiting a single prey in a two-dimensional environment, where the prey distribution is the result of intrinsic birth and death, movement in space, and mortality due to foraging birds (we also consider a variant tailored toward colonial social insects). Bird predation at different distances occurs according to an ideal free foraging distribution that maximizes prey delivery under flight and search costs. We fully characterize the birds' ideal free distribution and the prey distribution it generates. Our results show that prey depletion halos around breeding colonies are a robust phenomenon and that the birds' ideal free distribution is sensitive to prey movement. Furthermore, coexistence of several seabird species on a single prey easily emerges through behavioral niche partitioning whenever trait differences between species entail trade-offs between efficiently exploiting a scarce prey close to the colony and a more abundant prey far away. Such behavioral-based coexistence-inducing mechanism should generalize to other habitat and diet choice scenarios. [ABSTRACT FROM AUTHOR]

ABSTRACT Sardine (Sardinops sagax) in the southern Benguela has shown substantial changes in population size over the past 70 years. Heavy fishing pressure in the 1950s to early 1970s caused the collapse of sardine stocks in South Africa. A fishery collapse happens because of significant alterations in the marine community, hindering the recovery of valuable commercial species and leading to cascading effects across multiple trophic levels in marine food webs. In this study, a robust 58‐year biochronology (1962–2019) was developed using archived sardine otoliths from the West of Cape Agulhas in South Africa. Sequential t‐test analysis of regime shifts (STARS) performed on the biochronology of fish growth indicated four regimes with three alteration points in 1986, 2006 and 2015 that correspond with periods of low, high, average and low biomass, respectively; that is, high growth rates occurred during the high biomass period and vice versa. A series of mixed effects models was developed to determine increment width response to selected environmental, prey availability and sardine biomass factors based on the assumption that otolith increment growth is a proxy for somatic growth. Predicted sardine growth positively correlated with sardine biomass, sea surface temperature and copepod abundance estimates. This observation suggests that sardine population dynamics exhibit a depensation mechanism, potentially destabilizing populations after the fishery collapse. Sea surface temperature and copepod abundance have been primary factors influencing sardine growth, partly because of depensatory population dynamics. Furthermore, the study improves understanding of how different factors have affected sardine growth following the collapse of the sardine fishery. [ABSTRACT FROM AUTHOR]

ABSTRACT In stream ecosystems, invertebrates are a principal source of prey for many fishes, but their abundance as a food source depends on the predator's ability to exploit them in time and space. Although salmonid fishes are commonly thought of as daytime drift‐feeding predators of invertebrates in streams, they exhibit great flexibility in foraging behaviour and may also consume prey from the benthos and at night. Char species, (Salvelinus sp.), in particular, may be better adapted to forage under low light conditions due to greater scotopic sensitivity than other salmonids. In this study, we used in situ or in place videography to quantify the foraging behaviour of bull trout (Salvelinus confluentus) and determine when and where they capture prey. We found that bull trout were primarily daytime predators of invertebrates drifting in the water column, and that they rarely captured prey from the benthos or foraged at night. We did observe size‐related differences and seasonal declines in foraging rate from summer to fall months. A modelled estimate of energy intake indicates that daytime drift‐feeding by small size classes of bull trout was above that needed for a maximum daily ration under a range of assumptions about prey size and prey retention rates. Energy intake rates for larger fish were more dependent on assumptions of preferred prey size and prey retention rates. Our data indicate that daytime measures of invertebrate drift abundance and size are the most inclusive measure of food abundance for stream‐dwelling bull trout. [ABSTRACT FROM AUTHOR]

Dinophysis is an obligate mixotroph that relies on consumption of the ciliate, Mesodinium rubrum, to grow and form harmful algal blooms (HABs). In this study, blooms of Dinophysis acuminata in two NY, USA, estuaries were studied over the course of 3 yr (2019–2021) using discrete samples and an Imaging FlowCytobot (IFCB) to capture images of plankton 20–150 μm. The darkness of Dinophysis images on the IFCB was used to quantify the "fullness" or feeding state of Dinophysis cells. Culture experiments performed to ground truth this approach revealed a highly significant correlation (R = 0.98; p < 0.001) between the darkness of Dinophysis cells and the abundance of Mesodinium. With a quantitative scale developed to track the fullness of Dinophysis cells, ecosystem observations revealed the percentage of "full" Dinophysis cells increased during blooms of a large‐morphotype Mesodinium that preceded the initiation of Dinophysis blooms. A smaller morphotype Mesodinium appeared during Dinophysis bloom peaks suggesting they supported bloom maintenance. While the relative abundance of diatoms was elevated before Dinophysis blooms, other dinoflagellates and tintinnids increased in abundance during these HABs indicating they emerged within a consortium of heterotrophs and mixotrophs that may have collectively filled the same open niche as Dinophysis. This study reveals the manner in which different Mesodinium populations co‐bloom with Dinophysis to support plastid acquisition, bloom initiation, and bloom maintenance and contextualizes these changes within the larger plankton community succession associated with these HABs. [ABSTRACT FROM AUTHOR]

Grazing and mowing constitute two important ways of reducing vegetation structure, which causes mechanical injuries in plants. In response to these injuries, plants emit herbivore-induced plant volatiles (HIPVs) that can act as recruitment signals for arthropod predators. Among these arthropods, spiders have been suggested to respond to HIPVs. It is unknown, however, if spiders make microhabitat choice based on the detection of those HIPVs or based solely on the availability of vegetal structure. In this study, we investigated microhabitat choice of the orb-weaver spider Argiope trifasciata (Forsskål, 1775) and its potential relationship with impacted and not impacted vegetation structure availability. Our major results corroborate other findings that microhabitat choice in orb-weaver spiders is driven not by HIPVs, but rather by vegetation structure. Habitat structure influences a variety of ecological factors such as predation risk, prey availability, and mate finding in orb-weavers. The mechanisms underlying assessment by A. trifasciata of the vegetative structure remains unknown, and future studies might investigate their capacity to perceive light and shade and/or their assessment of vertical positioning. Practically, our results can be useful in evaluating the impact of land management on spider populations and their resilience to these impacts. [ABSTRACT FROM AUTHOR]

The knowledge regarding the feeding ecology of the greater amberjack remains limited despite its ecological and economic importance. Therefore, this study investigated the feeding dynamics of the greater amberjack and its key prey species in Taiwanese waters. Samples were collected from the Taiwan Bank (22.5° N–24.5° N, 118.5° E–121.5° E) and Northern Taiwan waters (25° N–26° N, 121° E–123.5° E). Analysis of samples obtained between June 2020 and June 2022 indicates that environmental factors influenced the availability of prey species, thereby affecting dietary preferences. The prey-specific index of relative importance indicated that the predominant prey species were pelagic species (52.81%), followed by demersal species and unidentified teleosts (18.74% and 16.58%, respectively); squid and crustaceans were the least frequently consumed prey species (6.11% and 5.76%, respectively). Although no difference was discovered between males and females in terms of diet, seasonal and size-related variations were noted in the feeding patterns, as evident from the substantial ontogenetic shift observed in the dietary composition of the samples during the study period. The findings of this study improve the understanding of the feeding dynamics of the greater amberjack and the association between oceanographic factors, such as sea surface temperature (SST), sea surface salinity (SSS), sea surface height (SSH), mixed-layer depth (MLD), and eddy kinetic energy (EKE), and prey availability in the coastal waters of Taiwan. [ABSTRACT FROM AUTHOR]

Understanding the response of marine organisms to temperature is crucial for predicting climate change impacts. Fundamental physiological thermal performance curves (TPCs), determined under controlled conditions, are commonly used to project future species spatial distributions or physiological performances. Yet, real‐world performances may deviate due to extrinsic factors covarying with temperature (food, oxygen, etc.). Using a bioenergetic marine ecosystem model, we evaluate the differences between fundamental and realised TPCs for fish species with contrasted ecology and thermal preferences. Food limitation is the primary cause of differences, decreasing throughout ontogeny and across trophic levels due to spatio‐temporal variability of low‐trophic level prey availability with temperature. Deoxygenation has moderate impact, despite increasing during ontogeny. This highlights the lower sensitivity of early life stages to hypoxia, which is mechanistically explained by lower mass‐specific ingestion at older stages. Understanding the emergence of realised thermal niches offers crucial insights to better determine population's persistence under climate warming. [ABSTRACT FROM AUTHOR]

Decades of persecution has resulted in the long‐term absence of grey wolves Canis lupus from most European countries. However, recent changes in both legislation and public attitudes toward wolves has eased the pressure, allowing wolves to rapidly re‐establish territories in their previous central European habitats over the last 20 years. Unfortunately, these habitats are now heavily altered by humans. Understanding the spatial ecology of wolves in such highly modified environments is crucial, given the high potential for conflict and the need to reconcile their return with multiple human concerns. We equipped 20 wolves, originating from seven packs in six central European regions, with GPS collars, allowing us to calculate monthly average home range sizes for 14 of the animals of 213.3 km2 using autocorrelated kernel density estimation. We then used ESA WorldCover data to assess the mosaic of available habitats used within each home range. Our data confirmed a general seasonal pattern for breeding individuals, with smaller apparent home ranges during the reproduction phase, and no specific pattern for non‐breeders. Predictably, our wolves showed a general preference for remote areas, and especially forests, though some wolves within military training areas also showed a broader preference for grassland, possibly influenced by local land use and high availability of prey. Our results provide a comprehensive insight into the ecology of wolves during their re‐colonisation of central Europe. Though wolves are spreading relatively quickly across central European landscapes, their permanent reoccupation remains uncertain due to conflicts with the human population. To secure the restoration of European wolf populations, further robust biological data, including data on spatial ecology, will be needed to clearly identify any management implications. [ABSTRACT FROM AUTHOR]

Evaluating methods used to capture and mark neonates is necessary for ensuring research methods are ethical, follow best practices, and do not have long‐term unintended impacts on neonates or populations. We used a quasi‐experimental approach (reference versus treatment) to determine whether visiting wolf dens and marking wolf Canis lupus pups affects important wolf population metrics. Specifically, we examined whether pup recruitment and pack size differed between packs where we visited dens and handled pups ('disturbed packs' = treatment group) and those where we did not visit dens ('undisturbed packs' = reference group). During 2019–2023, we studied 43 wolf packs and litters, 19 of which were disturbed packs and 24 of which were undisturbed. We found no difference in recruitment or pack size between disturbed and undisturbed wolf packs. However, we did observe substantial annual variation in recruitment and pack size, which indicated that other ecological factors (e.g. prey abundance) were likely responsible for annual changes in recruitment and pack size. Our findings are consistent with several other studies, and together this research indicates that wolf dens can be visited once and wolf pups handled briefly for research purposes without having a measurable effect on recruitment and pack size. [ABSTRACT FROM AUTHOR]

Aim: Mobulid rays are a group of threatened batoid fishes susceptible to population decline from targeted fisheries and accidental capture. Spatial distributions of mobulid rays remain poorly known. Prior studies found commonalities between favourable environments and prey among various mobulid species, yet most were conducted in tropical waters. To explore the habitat use and distribution of mobulid rays in a temperate environment we model the habitat suitability of two mobulid rays (Mobula mobular and Mobula birostris) in Aotearoa New Zealand using fisheries and citizen science occurrence data spanning almost two decades. Location: Northeastern coast of Aotearoa, New Zealand. Methods: Boosted Regression Tree models were used to predict the annual habitat suitability and favourable environmental conditions of the two species based on available sightings records in conjunction with high resolution (1 km2) environmental data. Results: The sympatric study species had contrasting habitat requirements. We found a separation in their spatial distribution defined by the 200 m isobath – the onshore extent for M. birostris and the offshore extent for M. mobular. While there were only subtle variations in relative habitat suitability for M. mobular over the study period, M. birostris exhibited greater interannual variability. Despite differing interannual patterns, spatial separation, as a function of environmental properties, persisted regardless of the year. Main Conclusions: Our results suggest that associations between mobulid species may differ from tropical regions due to regional adaptations to prey availability or local environmental conditions unique to colder and more productive temperate waters. Our findings highlight the importance of multi‐species surveys and the inclusion of temporal variability in support of separate species‐specific management plans to account for differing stressors impacting each species. [ABSTRACT FROM AUTHOR]

Understanding diets of aquatic fauna is crucial to interpretation of their ecological roles and contributions to ecosystem function. The Kanawha darter (Etheostoma kanawhae) is a vibrantly colored, endemic fish found only in the New River (Kanawha Basin, USA) and its tributaries. In this study, the diet of the Kanawha darter was determined by analyzing gut contents from museum specimens. A total of 75 Kanawha darter stomachs were dissected and prey items were identified and enumerated. Additionally, gut contents of 40 fantail darters (Etheostoma flabellare) were also quantified to compare diets of these sympatric species. Numerical and presence-absence methods were used to calculate total prey abundances, percent prey abundances, prey-specific abundance, and frequencies of occurrence. Kanawha darter diets were composed of aquatic dipteran and ephemeropteran larvae. Standard length and meteorological season affected Kanawha darter gut contents with few differences seen among males and females. Dietary comparisons revealed that Kanawha darters incorporate greater proportions of ephemeropteran prey while fantail darters prey upon trichopterans more often. Additionally, Costello-Amundsen plots displayed considerable overlap in dietary composition among these sympatric congeners. Results provide novel insight with regard to Kanawha darter natural history and their ecological role in stream communities. Moreover, interspecific comparisons may indicate that niche partitioning is occurring between the two species. Subsequent investigations should attempt to reveal potential ontogenetic shifts in dietary composition, determine Kanawha darter trophic position, and examine their influence on ecosystem processes. Conservation stakeholders should also consider how the absence of this environmentally sensitive species might impact stream communities. [ABSTRACT FROM AUTHOR]

Alternative ecological theories make divergent predictions about the relationship between predators and their prey. If predators exert top‐down ecosystem control, increases in predation should diminish prey abundance and could either diminish or enhance community diversity of prey species. However, if bottom‐up ecosystem controls predominate, predator populations should track underlying variation in prey diversity and abundance, which ultimately should reflect available energy. Past research, both across islands and comparing islands with the mainland, has frequently invoked the importance of predation in regulating lizard abundance and diversity, suggesting an important role of top‐down control when predators are present. However, others have posited a stronger role of food limitation, via competition or bottom‐up forces. If top‐down control predominates, then negative correlations between prey abundance and predator occurrence should emerge within and among islands. Using data from eBird, we inferred landscape‐level presence data for bird species on the islands of Jamaica and Hispaniola. By summing occurrence probabilities of all known anole‐predator birds, we estimated total avian predation pressure and combined these estimates with anole community data from a mark‐recapture study that spanned spatial and climatic gradients on both islands. Avian predators and anole lizards were both affected by climate, with total predator occurrence, anole abundance and anole species richness increasing with mean annual temperature. Anole abundance and predator occurrence showed a curvilinear relationship, where abundance and predator occurrence increased together until predator occurrence became sufficiently high that anole abundance was negatively impacted. This indicates that bottom‐up ecosystem controls drive richness of both anoles and their predators, mitigating the negative effects predators might have on their prey, at least until predator occurrence reaches a threshold. We did not detect consistent evidence of predator occurrence reducing anole community richness. These findings support past research showing that islands with more predators tend to have lower prey abundances, but it does not seem that these top‐down forces are strongly limiting species coexistence. Instead, bottom‐up forces linked with climate may be more important drivers of diversity in both lizards and their avian predators on these islands. [ABSTRACT FROM AUTHOR]