Prey Composition Research Articles

Stronger predation intensity and impact on prey communities in the tropics

The hypothesis that biotic interactions strengthen toward lower latitudes provides a framework for linking community-scale processes with the macroecological scales that define our biosphere. Despite the importance of this hypothesis for understanding community assembly and ecosystem functioning, the extent to which interaction strength varies across latitude and the effects of this variation on natural communities remain unresolved. Predation in particular is central to ecological and evolutionary dynamics across the globe, yet very few studies explore both community-scale causes and outcomes of predation across latitude. Here we expand beyond prior studies to examine two important components of predation strength: intensity of predation (including multiple dimensions of the predator guild) and impact on prey community biomass and structure, providing one of the most comprehensive examinations of predator-prey interactions across latitude. Using standardized experiments, we tested the hypothesis that predation intensity and impact on prey communities were stronger at lower latitudes. We further assessed prey recruitment to evaluate the potential for this process to mediate predation effects. We used sessile marine invertebrate communities and their fish predators in nearshore environments as a model system, with experiments conducted at 12 sites in four regions spanning the tropics to the subarctic. Our results show clear support for an increase in both predation intensity and impact at lower relative to higher latitudes. The predator guild was more diverse at low latitudes, with higher predation rates, longer interaction durations, and larger predator body sizes, suggesting stronger predation intensity in the tropics. Predation also reduced prey biomass and altered prey composition at low latitudes, with no effects at high latitudes. Although recruitment rates were up to three orders of magnitude higher in the tropics than the subarctic, prey replacement through this process was insufficient to dampen completely the strong impacts of predators in the tropics. Our study provides a novel perspective on the biotic interaction hypothesis, suggesting that multiple components of the predator community likely contribute to predation intensity at low latitudes, with important consequences for the structure of prey communities.

Prey Specialization by Cougars on Feral Horses in a Desert Environment

ABSTRACTNatural controls on the distribution, abundance, or growth rates of exotic species are a desirable mode of intervention because of lower costs compared to anthropogenic controls and greater social acceptance. In the Great Basin, cougars (Puma concolor) are the most widely distributed carnivore capable of killing large ungulate prey. Populations of feral horses (Equus ferus) are widely distributed throughout the Great Basin and can grow at rates up to 20%/year. Although cougars exhibit distributional overlap with horses, it has been assumed that predation is minimal because of differences in habitat use and body‐size limitations. To evaluate this hypothesis, we monitored the diets of 21 global positioning system (GPS)‐collared cougars in the western Great Basin (5 males, 8 females) and eastern Sierra Nevada (2 males, 6 females) from 2009–2012. We investigated 1,310 potential kill sites and located prey remains of 820 predation events. We compared prey composition and kill rates of cougars inhabiting the Sierra Nevada and Great Basin, and among male and female cougars across seasons. We used generalized linear mixed models (GLMMs) to examine the effects of prey availability and habitat characteristics on the probability of predation on horses by cougars. Mule deer (Odocoileus hemionus) comprised 91% of prey items killed on the Sierra Nevada reference site but only comprised 29% of prey items in the Great Basin study area. Average annual kill rates for deer differed between the Sierra Nevada ( = 0.85 deer/week, range = 0.44–1.3) and Great Basin ( = 0.21 deer/week, range = 0.00–0.43). Diets of cougars in the Great Basin were composed predominantly of horses (59.6%, n = 460 prey items; 13 individuals). Ten cougars regularly consumed horses, and horses were the most abundant prey in the diet of 8 additional individuals in the Great Basin. Cougars on average killed 0.38 horses/week in the Great Basin (range=0.00–0.94 horses/week). Differences in predation on horses between the sexes of cougars were striking; Great Basin females incorporated more horses across all age classes year‐round, whereas male cougars tended to exploit neonatal young during spring and summer before switching to deer during winter. Within GLMM models, the probability of predation on horses compared to other prey species increased with elevation, horse density, and decreasing density of mule deer on the landscape, and was more likely to occur in sagebrush (Artemesia spp.) than in pinyon (Pinus monophylla)–juniper (Juniperus osteosperma) forests. Behavior of individual cougars accounted for more than a third of the variation explained by our top models predicting predation on horses in the Great Basin. At landscape scales, cougar predation is unlikely to limit the growth of feral horse populations. In the Great Basin ecosystem, however, cougars of both sexes successfully preyed on horses of all age classes. Moreover, some reproductive, female cougars were almost entirely dependent on feral horses year‐round. Taken together, our data suggest that cougars may be an effective predator of feral horses, and that some of our previous assumptions about this relationship should be reevaluated and integrated into management and planning. © 2021 The Wildlife Society.

Disturbance by invasive pathogenic fungus alters arthropod predator-prey food-webs in ash plantations.

According to the disturbance-succession theory, natural disturbances support biodiversity and are expected to increase the complexity of food-webs in forest ecosystems by opening canopies and creating a heterogeneous environment. However, a limited number of studies have investigated the impact of disturbance by invasive pathogenic species and succession on arthropod predator-prey food-webs in forest ecosystems. Hymenoscyphus fraxineus is a pathogenic fungus of ash trees that is invasive in Europe and causes massive dieback, mainly of the common ash Fraxinus excelsior across its native range. Here we investigated how this pathogenic fungus affects food-webs of web-building spiders and their prey in understorey vegetation of ash plantations. In 23 young and middle-aged ash plantations that were distributed along a gradient of infestation by H. fraxineus (29%-86% infestation), we measured the vegetation structure (canopy openness, shrub coverage, herb/grass coverage), the trait composition of local spider communities (web type, body size), the prey availability and the prey intercepted by spider webs. We then evaluated the multivariate prey composition (prey type, body size) and network properties. Hymenoscyphus fraxineus opened the ash tree canopy, which resulted in denser shrub coverage. The dense shrub vegetation changed the composition of web types in local spider communities and increasing fungus infestation resulted in reduced mean body size of spiders. Infestation by H. fraxineus reduced the availability of predaceous Coleoptera and increased the availability of herbivorous Coleoptera as potential prey. The mean body size of captured prey and the per capita capture rates of most prey groups decreased with increasing fungus infestation. Hymenoscyphus fraxineus infestation indirectly reduced the complexity in bipartite networks and the trophic functional complementarity in local web-building spider communities. The plantation age affected the vegetation structure but did not affect the studied food-webs. Forest disturbance by the invasive pathogen affected four trophic levels (plant-herbivore-coleopteran intermediate predator-top predator web-building spiders) and, contrary to the disturbance-succession theory, disturbance by the fungus simplified the web-building spider-prey food-webs. The results support the view that H. fraxineus represents a threat to the biodiversity and ecosystem functioning in the simplified ecosystems of ash plantations.

Predators override rainfall effects on tropical food webs

AbstractPredators alter ecological communities by inducing changes in prey abundance and phenotypes, including elemental and isotopic composition. Climatic factors are known to often moderate predator effects on prey abundance, but few studies consider the combined effects of climate and predators on prey phenotype. We examined how altered precipitation moderates the effects of predators on the abundance and the chemical composition of prey, as well as the indirect effects on the basal resource: leaf litter coated in biofilm. Using an experiment with an invertebrate food web module from tank bromeliads, we manipulated the presence of an odonate predator under scenarios of 10‐fold decreased, ambient, and threefold increased precipitation and measured responses of prey and their basal resource. Predators reduced prey abundance while precipitation did not. Both precipitation and predators, either singly or interactively, affected the elemental composition of prey. Predators increased C:N ratios of detritivorous beetles under high precipitation, but reduced the C:N ratio of the basal resource. Precipitation reduced the N content of filter‐feeding mosquitoes. The observed changes in chemical composition may reflect physiological or developmental responses to stress imposed by both predators and drought. This study demonstrates that the impact of predators and precipitation can vary substantially across a food web, including additive and synergistic effects, and numerical and phenotypic responses.Abstract in Spanish is available with online material.

Seasonal and intra-populational diet variation in the Colombian Swamp frog Pseudopaludicola pusilla (Anura Leptodactylidae)

Diet is a fundamental aspect of the ecological niche of amphibians and usually varies intra-specifically in response to extrinsic environmental and intrinsic individual factors. Phenotypic variations among individuals can generate intrapopulation differences in trophic resource use, which could have important ecological and evolutionary implications in amphibian populations. Here, we studied the intrapopulation dietary variation of the frog Pseudopaludicola pusilla in an anthropic savanna of the Colombian Caribbean region, considering the effects of seasonality and sex on the size, amount, prey composition and dietary individual specialization. We collected 44 adult frogs during the dry season and 46 during the rainy season and analyzed their stomach contents to determine their dietary composition. Our results indicate that P. pusilla is a generalist and opportunist predator, feeding mainly on insects of the orders Orthoptera, Coleoptera and Hymenoptera, which were the most important prey categories due to their numeric, volumetric and frequency contributions. We observed seasonal variations regarding volumetric prey composition and the importance value of each prey category in the populational diet. Individuals of P. pusilla consume more prey items during the rainy season and bigger prey during the dry season, but the volume of stomach contents did not vary seasonally. Males and females of P. pusilla consumed a similar number of prey items, but females ingested more voluminous prey and had greater volumes of stomach contents than males. Additionally, we observed a pattern of dietary individual specialization, which was not related to morphological trade-offs and did not differ among seasons. These findings contribute to the understanding of the seasonal dynamics of the use of trophic resources by anurans and the effect of sex on dietary characteristics of P. pusilla, in environments strongly influenced by climatic seasonality.

Who's for dinner? Bird prey diversity and choice in the great evening bat, Ia io.

The mysterious predator–prey interaction between bats and nocturnally migrating birds is a very rare and incredible process in natural ecosystems. So far only three avivorous bat species, including two noctule bats (Nyctalus lasiopterus and Nyctalus aviator) and the great evening bat (Ia io), are known to regularly prey on songbirds during nocturnal avian migration. The information related to the diversity and the characteristics of the birds as prey and the hunting strategy in both species of noctule bats are already clear. However, the diversity of bird prey in the diet of I. io as confirmed by molecular identification remains unknown. Moreover, like hunting insects, it remains unclear whether the avivorous bats opportunistically prey on birds. Here, we used DNA metabarcoding to investigate the bird prey composition, diversity, and choice in diets of I. io. We found I. io consumed 22 species of seven families from Passeriformes with a body mass of 6–19 g, and preferentially selected small‐sized passerine birds for optimizing the benefit/risk trade‐off. Moreover, most of the species preyed upon were migratory birds, while four species were local resident birds, indicating that I. io may adopt both aerial‐hawking and gleaning strategies on songbirds as do the other two noctules. Further, I. io body mass did not influence in prey choice and predation richness on birds, suggesting I. io is an opportunistic avivorous predator. This study provides novel insights into the avian dietary ecology of I. io and completes the analysis of predator/prey interaction between three avivorous bats and nocturnally migrating birds. Our results also indicate bat predation on birds which occurs as an act of ecological opportunity may subject bats to intense natural selection pressure, causing them access to the new diet‐defined adaptive zones.

Site Characteristics More Than Vegetation Type Influence Food Web Structure of Intertidal Salt Marshes

Salt marshes are under increasing anthropogenic pressures that have been reported to affect the diet of fish (e.g., change in prey composition and availability), eventually resulting in alterations in their nursery function. Most studies in Europe are based on fish gut content analysis, which only reflect a small proportion of pressures to salt marshes, and do not necessarily reflect long-term disturbances. In this study, we investigated the impact of salt-marsh vegetation type on trophic network structures (i.e., fish diet and trophic position). Primary producers (particulate organic matter, microphytobenthos, and dominant terrestrial plants), potential aquatic and terrestrial prey, and fish of two dominant species (sea bass and thinlip mullet) were sampled during the summer of 2010 in four creeks from two sites from Western France (the Mont-Saint-Michel Bay and the Seine Estuary). Analysis was undertaken using C and N stable-isotope compositions. Tested response variables (diet and trophic position) suggested a dominant site effect and a weaker effect of surrounding vegetation type. Site effect was attributed to differences in anthropogenic nitrogen inputs (with a steep increase in the Mont-Saint-Michel Bay) and tidal regime between the two bays, with more marine signatures associated with a higher frequency and duration of tidal flooding events in the Seine Estuary. A second hypothesis is that invasiveElytrigia acuta, which has recently replaced typical salt-marsh vegetation in Mont-Saint-Michel Bay, negatively impacted the native salt-marshes nursery function by modifying the access to terrestrial prey on this site. The trophic position of the sea bass and the thinlip mullet was unchanged by local salt-marsh vegetation, and considered consistent with their diet. This study highlights the relevance of stable-isotopes analyses for assessing long-term and integrative effects of changes in vegetation resulting from human disturbances in salt marshes.

Geographic variation in body size and plumage colour according to diet composition in a nocturnal raptor

Predator–prey interactions are amongst the strongest selective forces that promote the evolution of local phenotypes in both predators and prey. However, intraspecific spatial covariation in phenotypic traits between predators and prey has been rarely investigated, especially at a large geographic scale. Here, we studied the covariation between prey composition and some phenotypic traits, such as wing length, bill length and plumage colour, of a widely‐distributed nocturnal predator, the western barn owl Tyto alba. By using 3100 specimens collected across its entire range of distribution, spanning from Europe to Middle East and Africa, we showed that wing length positively covaries with prey size, but not with taxonomic composition. This finding suggests that larger prey might have selected for larger body size and/or that larger individuals might be more selective in hunting large prey. In addition, we also found that paler‐plumaged populations generally hunt larger prey. Paler barn owls might be thus better specialized in capturing averagely larger prey and/or mainly hunt in habitats where larger prey are more abundant. In addition, considering that paler individuals are generally larger than brownish ones, it is possible that paler plumage colour might have evolved as a by‐product of selection towards a large body size, which in turn have emerged in response to prey size composition. However, irrespectively of the direction of causality and the phenotypic target of selection, we showed that predator–prey interactions can affect spatial phenotypic variation by promoting the evolution of local adaptations.

Higher reversed sexual size dimorphism among nesting pairs of Northern Pygmy-Owls (Glaucidium gnoma) in northwestern Oregon than among specimens collected at the range-wide scale

I report on the strength of reversed sexual size dimorphism (RSD) in a local sub-population of Northern Pygmy-Owls (Glaucidium gnoma) in northwestern Oregon (2007–2012) in comparison to range-wide museum specimens examined by Earhart and Johnson (1970). Using Storer's Dimorphism Index (DI), RSD was higher among local breeding pairs (DImass = 6.64, DIwing = 4.90, n = 20 pairs) and among all local specimens (DImass = 6.20, DIwing = 4.39, n = 31 females, n= 23 males) than for specimens range-wide (DImass = 5.45, DIwing = 4.30, n= 10 females, n= 42 males). RSD was also more distinct locally, because mass alone was diagnostic of the sexes at a threshold of 69 g and wing chord was nearly diagnostic, whereas range-wide there was greater intrasexual variation and intersexual overlap in both metrics. Locally, females weighed 75.3 ± 5.6 g (range 69.0–94.2 g), and males weighed 62.5 ± 2.5 g (range 58.5–68.5 g); all local males had wing chords <92 mm (89.2 ± 2.0 mm; range 85.0–91.5 mm), whereas for 90% of females wing chord was ≥92 mm (93.2 ± 1.3 mm; range 89.0–96.0 mm). Clutch size (F1,4 = 1.822, P= 0.248, n= 20) and the number of fledged young (F1,8 = 0.00, P= 0.619, n= 19) were independent of RSD among local breeding pairs. Vertebrate prey composition shifted seasonally and was similar at the 2 scales, with agile avian prey taken most frequently during the breeding season, when the evolutionary consequences of diet on RSD matter most. I found intersexual variation in prey composition at the local scale where males took avian prey more frequently than females. I concluded that RSD in pygmy-owls was stronger at the local scale and that intersexual differences in prey composition may be related to RSD in this species. This study highlights the value of examining multiple scales and seasonal variation in prey composition when evaluating the merits of RSD hypotheses. It also contributes to our understanding of one of the least studied owls in North America.

Broadbill swordfish (Xiphias gladius) foraging and vertical movements in the north‐west Atlantic

AbstractThe northern edge of Georges Bank is an important seasonal foraging habitat for swordfish (Xiphias gladius) in the North Atlantic, where aggregations support commercial pelagic longline and harpoon fisheries. Following a period of overfishing during the 1990s, the North Atlantic X. gladius stock underwent a period of recovery during the early 2000s and was considered rebuilt in 2009. We analysed stomach contents from X. gladius (n = 39) harvested by the Canadian harpoon fishery on Georges Bank in 2007 to characterize diet in this important foraging habitat. We used electronic tagging data from X. gladius (n = 6) on Georges Bank in 2005–2007 to assess vertical habitat preferences and associated prey composition within those zones. We also used stable isotope analysis (δ13C and δ15N) of X. gladius liver (n = 2) and common prey types (Paralepididae, Myctophidae, Merluccidae, Ommastrephidae) as a longer‐term record of feeding. Stomach contents were co‐dominated by Paralepididae [31.9% weight (W)] and Ommastrephidae (36.8%W) with secondary contributions from hake (Merluccidae, 6.5%W), Myctophidae (2.9%W) and Sebastidae (2.1%W). X. gladius displayed diel vertical migrations, descending to depths of 300–400 m during daytime followed by residence in surface waters at night. X. gladius liver δ15N values were similar to or lower than values of primary stomach contents, likely due to bias of diet consumed in southerly waters with lower nitrogen isotope baselines prior to arrival on Georges Bank. Diet data are similar to results from historical studies from the late 1950s to the early 1980s. This apparent temporal stability to the underlying food web in this region may explain the high X. gladius site fidelity observed in electronic tagging studies and the consistent aggregation of these fish to this region.

Using Regurgitated Pellets from White-Tailed Sea-Eagles as Noninvasive Samples to Assess Lead Exposure Caused by Hunting in Germany

ABSTRACT Anthropogenic lead intoxication is the most frequent cause of death of White-tailed Sea-Eagles (Haliaeetus albicilla) in Germany. Most lead fragments are ingested by eagles feeding on carcasses and viscera of game animals shot with lead-based ammunition left in the wild by hunters. We investigated how many regurgitated pellets contained metal fragments and hypothesized a correlation between the presence of metal fragments and (1) the hunting season, (2) the ban of lead in rifle ammunition, and (3) the frequency of specific prey animals in the pellets. We collected 273 regurgitated pellets, radiographed them for metal fragments, and analyzed the prey composition. The metal elements were identified using micro x-ray fluorescence. Metal particles were found in 9.2% of pellets; 24 fragments consisted of lead and one fragment was mostly copper. A higher proportion (14.3%) of contaminated pellets was detected during the hunting season from September through February. During the non-hunting season from March through August, 7.6% of the regurgitated pellets were contaminated. Furthermore, there was a significant positive correlation between the presence of mammalian remains in the pellets and metal contamination (general linear model, z = 2.16, P = 0.03). Our results indicate a correlation between the increased activity of hunters in winter and the occurrence of metal in regurgitated pellets of White-tailed Sea-Eagles.

Prey Composition of Post-denning Dhole (Cuon alpinus) in South Wayanad Forest Division, Kerala, India

Dhole (Cuon alpinus) prey composition in South Wayanad Forest Division, Kerala was investigated from May 2017 to July 2017. Dhole scats were collected from 28 selected forest trails and roads, a total distance of 138.94 km was surveyed in the study area. Encounter rate of Dhole scats across habitat varied, with higher encounter rate in the Shola Grassland (1.76/km), followed by Tea and Cardamom plantation. The average encounter rate of Dhole scats for the study area was 2.74 scats/km. A total of 80 Dhole scats were analysed microscopically by comparing hair samples with standard key and reference slides of known species. A total of 12 prey species were identified belonging to different size classes and 25% of the scats samples were found to be having multiple prey species. The relative contribution of each prey species was stabilized in the diets of Dhole at 65th scat sample. Brillouin’s index of the diversity of prey species was 0.55. The most common and the largest ungulate species, Sambar was constituted 69.68%, followed by Wild Pig (15.48%). Dholes occasionally prey on domestic cattle, constituted 2.81%. The lesser percent of livestock in the diet of Dhole indicating a lower level of conflict in the study area during the study period. Land-use changes and conversion of revenue forest areas into human habitation are threats to Dhole and its prey species in South Wayanad Forest Division.

Changes in the Montagu's Harrier Circus pygargus diet in Eastern Poland across decades promote insects and reptilians, but not birds and rodents.

We investigated temporal changes in diet composition of the Montagu's Harrier Circus pygargus breeding in natural habitat (calcareous peat bog) in SE Poland. We characterized diet composition in a three‐year period (2007–2009), based on pellet analyses. We investigated whether diet composition was affected by years or stage of breeding. We compared diet of the studied population between 2000s and 1990s and with other populations. We found that the food of the studied population was dominated by insects and mammals (by number) and mammals and birds (by biomass). Biomass and abundance of main prey items differed between studied years because of different air temperatures. We found some interannual differences in contribution of some prey items including higher number of thermophilic prey (insects and amphibians) in warmer years. Comparison of pellet composition in the 1990s and 2000s revealed significant increase in the abundance of thermophilic prey (insects and reptiles) and decrease of mammals including Microtus voles and birds. Those changes may be linked to habitat changes in areas neighboring peat bogs and climate change‐induced changes in prey communities. The studied population was able to respond to changes in foraging habitats and prey composition by opportunistic foraging on easily available prey. The diet of the studied population is the most similar to the geographically closest populations foraging in similar habitats and characterized by high contribution of insects.

Zooplanktivore fish body growth responses to browning‐induced light limitation vary over ontogeny, but not with fish density

AbstractOngoing climate change is leading to browning of many lakes and coastal areas, which can impair fish body growth and biomass production. However, whether and how effects of light limitation caused by browning on fish body growth vary over early ontogeny is unknown. In this study, we set up a mesocosm experiment to test whether roach (Rutilus rutilus) body growth responses to browning depend on body size, and if findings are robust over roach densities. We also studied a potential mechanism for size‐specific responses by conducting an aquaria experiment to test if size‐specific prey selectivity in roach changes with browning. We found that roach body growth responses to browning‐induced light limitation vary over ontogeny (independent of roach density), negatively affecting body growth of young‐of‐the‐year (YOY) but not of 1‐year‐old individuals. We also show that this difference in growth response is likely a consequence of browning‐induced alterations in zooplankton community composition and variation in prey selectivity between YOY and 1‐year‐old fish. This suggests that we should account for the diverse effects of browning over fish ontogeny, mediated via altered prey composition and ontogenetic changes in prey preference, when assessing overall impacts of browning on aquatic ecosystems.

Reforestations of Tropical Forests Alter Interactions Between Web-Building Spiders and Their Prey

Immense effort has been devoted to mitigating the negative effect of deforestation, one of the main factors causing global change. However, the effect of reforestation management on food-webs has been rarely studied and no study so far has investigated the effect on predator–prey interactions in forest understories. We studied predator–prey interactions in forest understories using web-building spiders in four forest types: dry evergreen forest representing a natural control and three 20–30-year-old reforestation types, namely secondary naturally regenerating dry evergreen forest, monoculture reforestation dominated by Eucalyptus camaldulensis, and mixture reforestation dominated by Acacia mangium and E. camaldulensis. We collected spiders with their prey and measured the availability of potential prey. We also measured different spider traits (web type, body size) that can be selected by various forest types and consequently affect the predator–prey interactions. The forest type influenced the predator–prey interaction in a complex way, interactively affecting spider density and prey-specific capture efficacy of spider community. The forest type also influenced the web-type and body-size distributions of spiders. Surprisingly, the prey composition caught by spider webs was related only to the web-type but not to the spider mean body size. None of the studied reforestations have yet restored the natural predator–prey interactions, which indicates that conservation management in the tropics should focus on establishing protected areas in pristine regions instead of relying on reforestation. Moreover, the food-web models need to incorporate not only body sizes but also hunting strategies of predators to improve their predictive abilities.

Hey, That's My Fish – Overlap in Prey Composition between European Shag and Local Fisheries in Portugal

Hey, That's My Fish – Overlap in Prey Composition between European Shag and Local Fisheries in Portugal

GPSeqClus: An R package for sequential clustering of animal location data for model building, model application and field site investigations

Abstract Evaluating the concentration of animal locations, in space and time, provides insight regarding animal activity and behaviour. Most commonly collected via global positioning system technology, these concentrations are identified using rule sets resulting in location ‘clusters’. Cluster algorithms provide a framework for modelling and predicting behavioural states when paired with field data to evaluate habitat characteristics and validate results. We provide a sequential clustering algorithm package (GPSeqClus) to process location datasets based on user‐defined parameters. GPSeqClus also calculates an array of movement attributes commonly applied as covariates to develop cluster‐based models. Our package maps locations and clusters, with additional functions to assess specific clusters for site investigations and to export GPS Exchange format (.gpx) files for navigation. We highlight the ability of GPSeqClus to modify existing cluster attributes or to append additional attributes, and the flexibility to accommodate archived or near real‐time (satellite‐driven) datasets. Although spatio‐temporal clustering is widely used in animal ecology, clustering routines are commonly applied to assess carnivore movement patterns to predict denning or feeding locations, evaluate prey composition and estimate kill rates and handling times. We demonstrate the applicability of GPSeqClus by constructing clusters using mountain lion Puma concolor location data. Our package provides an efficient data processing routine to build, characterize, visualize and navigate to clusters. Attributes provided within GPSeqClus can be used when developing predictive cluster models, or can be applied to other modelling procedures to advance understandings of animal behaviour.

High gene flow in polar cod (Boreogadus saida) from West-Svalbard and the Eurasian Basin.

The current and projected environmental change of the Arctic Ocean contrasts sharply with the limited knowledge of its genetic biodiversity. Polar cod Boreogadus saida (Lepechin, 1774) is an abundant circumpolar marine fish and ecological key species. The central role of polar cod in the Arctic marine food web warrants a better understanding of its population structure and connectivity. In this study, the genetic population structure of 171 juveniles, collected from several fjords off West-Svalbard (Billefjorden, Hornsund and Kongsfjorden), the northern Sophia Basin and the Eurasian Basin of the Arctic Ocean, was analysed using nine DNA microsatellite loci. Genetic analyses indicated moderate to high genetic diversity, but absence of spatial population structure and isolation-by-distance, suggesting ongoing gene flow between the studied sampling regions. High levels of connectivity may be key for polar cod to maintain populations across wide spatial scales. The adaptive capacity of the species will be increasingly important to face challenges such as habitat fragmentation, ocean warming and changes in prey composition. In view of a limited understanding of the population dynamics and evolution of polar cod, a valuable next step to predict future developments should be an integrated biological evaluation, including population genomics, a life-history approach, and habitat and biophysical dispersal modelling.

Temporal variation in the diet of Yangtze finless porpoise calls for conservation of semi‐migratory fish

AbstractIdentifying the feeding patterns of large‐bodied predators is necessary to predict their potential effects on food‐web dynamics and to inform species conservation. In contrast to diet information from stomach contents, diet estimates obtained using stable isotopes in blood and muscle can reveal temporal variation in diets.Here, we used an extensive stable isotope dataset and Bayesian stable isotope mixing model to evaluate the trophic role of the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), a critically endangered species distributed in the middle and lower catchments of the Yangtze River. We analysed blood samples from 24 individuals captured during March 2017 in Poyang Lake (which adjoins the Yangtze River), and muscle samples from 8 individuals stranded in the lake over a 1‐year period (2012–2013). We additionally genotyped prey from faecal samples taken from 13 individuals captured in March 2017.We found that as a generalist apex predator, this finless porpoise consumes semi‐migratory and non‐migratory fish prey. However, relative proportions of these two prey resources were different between dietary analyses based on blood samples compared to muscle samples, reflecting recent and longer‐term consumption patterns, respectively.Non‐migratory fish contributed mainly to the diet of predators in the early and middle of March. In contrast, semi‐migratory fish comprised the majority of the prey composition over a more extended period (e.g. 2–3 months), and the difference may be linked to changes in the fish abundance influenced by seasonal factors.Our findings provide insights into the trophic role of this critically imperilled but little studied species, demonstrate how stable isotope analyses can elucidate finless porpoise feeding ecology, and emphasise the importance of semi‐migratory fish to conserving this porpoise population.

Feeding Hotspots and Distribution of Fin and Humpback Whales in the Norwegian Sea From 2013 to 2018

Fin whales (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) are commonly found in the Norwegian Sea during the summer months. Records from around 1995 to 2004 show that their distribution patterns were mainly associated with those of macro-zooplankton. More recent studies conducted from 2009 to 2012 demonstrate marked shifts, with fin whale distribution related to pelagic fish distribution, decreasing densities of humpbacks, and increased densities of toothed whales. During the same period, historically large abundances of pelagic planktivorous fish in the Norwegian Sea were reported. The goals of this study were to examine the summer distribution of fin and humpback whales from 2013 to 2018 and to assess the potential association between distribution and environmental impact factors. Results suggest a pronounced northerly shift in distribution for both species, a feeding hotspot for fin whales at the shelf area between Svalbard and Norway, and one near Bear Island for humpback whales. Fin whale distribution was associated with that of blue whiting (Micromesistius poutassou) and capelin (Mallotus villosus), whereas humpback whale distribution was associated with that of euphausiids (Meganyctiphanes norvegica, Thysanoessa longicaudata, andThysanoessa inermis), capelin, and herring (Clupea harengus). However, a significant negative spatial correlation was found between whale occurrence and the widely expanding population of northeast Atlantic mackerel (Scomber scombrus). The results of this study suggest that the prey composition of fin and humpback whales in recent years contain a large proportion of fish. The apparent northerly shift in the distribution of these whale species is largely determined by the availability of prey, but it likely is also impacted by direct or indirect interspecific interactions, especially with killer whales (Orcinus orca). Such large-scale pronounced changes in distribution seem to confirm a high degree of plasticity in fin and humpback whale feeding in the Norwegian Sea.