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108 results for “apex predation”

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Predation risk can modify the foraging behaviour of frugivorous carnivores: implications of rewilding apex predators for plant-animal mutualisms

Apex predators play key roles in food webs and their recovery can trigger trophic cascades in some ecosystems. Intra-guild competition can reduce the abundances of smaller predators and perceived predation risk can alter their foraging behaviour thereby limiting seed dispersal by frugivorous carnivores. However, little is known about how plant-frugivore mutualism could be disturbed in the presence of larger predators. We evaluated the top-down effect of the regional superpredator, the Iberian lynx (Lynx pardinus), on the number of visits and fruits consumed by medium-sized frugivorous carnivores, as well as the foraging behaviour of identified individuals, by examining the consumption likelihood and the foraging time. We carried out a field experiment in which we placed Iberian pear (Pyrus bourgaeana) fruits beneath fruiting trees and monitored pear removal by frugivorous carnivores, both inside and outside of lynx ranges. Using camera traps, we recorded the presence of the red fox (Vulpes vulpes), the Eurasian badger (Meles meles) and the stone marten (Martes foina), as well as the number of fruits they consumed and their time spent foraging. Red fox was the most frequent fruit consumer carnivore. We found there were fewer visits and less fruit consumed by foxes inside of lynx ranges, but lynx presence did not seem to affect badgers. We did not observe any stone marten visits inside of lynx territories. The foraging behaviour of red foxes was also altered when inside of lynx ranges whereby foxes were less efficient, consuming less fruit per unit of time and having shorter visits. Local availability of fruit resources, forest coverage and individual personality also were important variables to understand visitation and foraging in a landscape of fear. 5. Our results show a potential trophic cascade from apex predators to primary producers. The presence of lynx can reduce frugivorous carnivore numbers and induce shifts in their feeding behaviour that may modify the seed dispersal patterns with likely consequences for the demography of many fleshy-fruited plant species. We conclude that knowledge of the ecological interactions making up trophic webs is anasset to design effective conservation strategies, particularly in rewilding programs.

opencc-zeroMar 2022View details →

dryad36/100

Data from: Integrating isotopic and nutritional niches reveals multiple dimensions of individual diet specialisation in a marine apex predator

<ol> <li>Dietary specializations are important determinants of ecological structure, particularly in species with high per-capita trophic influence like marine apex predators. These species are, however, among the most challenging in which to establish spatiotemporally integrated diets.</li> <li>We introduce a novel integration of stable isotopes with a multidimensional nutritional niche framework that addresses the challenges of establishing spatiotemporally integrated nutritional niches in wild populations, and apply the framework to explore individual diet specialization in a marine apex predator, the white shark (Carcharodon carcharias).</li> <li>Sequential tooth files were sampled from juvenile white sharks to establish individual isotopic (δ-space; δ13C, δ15N, δ34S) niche specialization. Bayesian mixing models were then used to reveal individual-level prey (p-space) specialization, and further combined with nutritional geometry models to quantify the nutritional (N-space) dimensions of individual specialization and their relationships to prey use.</li> <li>Isotopic and mixing model analyses indicated juvenile white sharks as individual specialists within a broader, generalist, population niche. Individual sharks differed in their consumption of several important mesopredator species, which suggested among-individual variance in trophic roles in either pelagic or benthic food webs. However, variation in nutrient intakes was small and not consistently correlated with differences in prey use, suggesting white sharks as nutritional specialists and that individuals could use functionally and nutritionally different prey as complementary means to achieve a common nutritional goal.</li> <li>We identify how degrees of individual specialisation can differ between niche spaces (δ-, p- or N-space), the physiological and ecological implications of this, and argue that integrating nutrition can provide stronger, mechanistic links between diet specialisation and its intrinsic (fitness/performance) and extrinsic (ecological) outcomes. Our time-integrated framework is adaptable for examining the nutritional consequences and drivers of food use variation at the individual, population or species level.</li> </ol>

opencc-zeroOct 2022View details →

dryad36/100

Microgeographic divergence of functional responses among salamanders under antagonistic selection from apex predators

A predator's functional response determines predator–prey interactions by describing the relationship between the number of prey available and the number eaten. Its shape and parameters fundamentally govern the dynamic equilibrium of predator–prey interactions and their joint abundances. Yet, estimates of these key parameters generally assume stasis in space and time and ignore the potential for local adaptation to alter feeding responses and the stability of trophic dynamics. Here, we evaluate if functional responses diverge among populations of spotted salamander ( Ambystoma maculatum ) larvae that face antagonistic selection on feeding strategies based on their own risk of predation. Common garden experiments revealed that spotted salamander from ponds with varying predation risks differed in their functional responses, suggesting an evolutionary response. Applying mechanistic equations, we discovered that the combined changes in attack rates, handling times and shape of the functional response enhanced feeding rate in environments with high densities of gape-limited predators. We suggest how these parameter changes could alter community equilibria and other emergent properties of food webs. Community ecologists might often need to consider how local evolution at fine scales alters key relationships in ways that alter local diversity patterns, food web dynamics, resource gradients and community responses to disturbance.

opencc-zeroJul 2021View details →

dryad36/100

Mesocarnivore community structuring in the presence of Africa's apex predator

Apex predator reintroductions have proliferated across southern Africa, yet their ecological effects and proposed umbrella benefits of associated management lack empirical evaluations. Despite a rich theory on top-down ecosystem regulation via mesopredator (<20kg) suppression, a knowledge gap exists relating to the influence of lions (Panthera leo) over Africa's diverse mesocarnivore communities. We investigate how geographical variation in mesocarnivore community richness and occupancy across South African reserves is associated with the presence of lions. An interesting duality emerged: lion reserves held more mesocarnivore-rich communities, yet mesocarnivore occupancy rates and evenness-weighted diversity were lower in the presence of lions. Human population density in the reserve surroundings had a similarly ubiquitous negative effect on mesocarnivore occupancy. The positive association between species richness and lion presence corroborated the umbrella species concept but translated into small differences in community size. Distributional contractions of mesocarnivore species within lion reserves, and potentially corresponding numerical reductions, suggest within-community mesopredator suppression by lions, likely as a result of lethal encounters and responses to a landscape of fear. Our findings offer empirical support for theoretical understanding of processes underpinning carnivore community assembly and are of conservation relevance under current large-predator orientated management and conservation paradigms.

opencc-zeroAug 2021View details →

dryad36/100

Of wolves and bears: Seasonal drivers of interference and exploitation competition between apex predators

Competition between apex predators can alter the strength of top-down forcing, yet we know little about the behavioral mechanisms that drive competition in multipredator ecosystems. Interactions between predators can be synergistic (facilitative) or antagonistic (inhibitive), both of which are widespread in nature, vary in strength between species and across space and time, and affect predation patterns and predator-prey dynamics. Recent research suggests gray wolf (Canis lupus) kill rates decrease where they are sympatric with brown bears (Ursus arctos), however, the mechanisms behind this pattern remain unknown. We used data from two long-term research projects in Scandinavia (Europe) and Yellowstone National Park (North America) to test the role of interference and exploitation competition from bears on wolf predatory behavior, where altered wolf handling and search time of prey in the presence of bears are indicative of interference and exploitation competition, respectively. Our results suggest the mechanisms driving competition between bears and wolves were dependent on the season and study system. During spring in Scandinavia, interference competition was the primary mechanism driving decreased kill rates for wolves sympatric with bears; handling time increased, but search time did not. In summer, however, when both bear and wolf predation focused on neonate moose, the behavioral mechanism switched to exploitation competition; search time increased, but handling time did not. Interference competition, however, did affect wolf predation dynamics in Yellowstone during summer, where wolves prey more evenly on neonate and adult ungulates. Here, bear presence at a carcass increased the amount of time wolves spent at carcasses of all sizes and wolf handling time for small prey, but decreased handling time for the largest prey. Wolves facilitate scavenging opportunities for bears, however, bears alter wolf predatory behavior via multiple pathways and are primarily antagonistic to wolves. Our study helps clarify the behavioral mechanisms driving competition between apex predators, illustrating how interspecific interactions can manifest into population-level predation patterns.

opencc-zeroOct 2021View details →

dryad36/100

Data from: Whiskers provide time-series of toxic and essential trace elements, Se:Hg molar ratios, and stable isotope values of an apex Antarctic predator, the leopard seal

In an era of rapid environmental change and increasing human presence, researchers need efficient tools for tracking contaminants to monitor the health of Antarctic flora and fauna. Here, we examined the utility of leopard seal whiskers as a biomonitoring tool that reconstructs time-series of significant ecological and physiological biomarkers. Leopard seals (Hydrurga leptonyx) are a sentinel species in the Western Antarctic Peninsula due to their apex predator status and top-down effects on several Antarctic species. However, there are few data on their contaminant loads. We analyzed leopard seal whiskers (n = 18 individuals, n = 981 segments) collected during 2018–2019 field seasons to acquire longitudinal profiles of non-essential (Hg, Pb, and Cd) and essential (Se, Cu, and Zn) trace elements, stable isotope (ẟ15N and ẟ13C) values and to assess Hg risk with Se:Hg molar ratios. Whiskers provided between 46 and 286 cumulative days of growth with a mean ~125 days per whisker (n = 18). Adult whiskers showed variability in non-essential trace elements over time that could partly be explained by changes in diet. Whisker Hg levels were insufficient (<20 ppm) to consider most seals being at "high" risk for Hg toxicity. Nevertheless, maximum Hg concentrations observed in this study were greater than that of leopard seal hair measured two decades ago. However, variation in the Se:Hg molar ratios over time suggest that Se may detoxify Hg burden in leopard seals. Overall, we provide evidence that the analysis of leopard seal whiskers allows for the reconstruction of time-series ecological and physiological data and can be valuable for opportunistically monitoring the health of the leopard seal population and their Antarctic ecosystem during climate change.

opencc-zeroDec 2022View details →

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Data for: Prey resources are equally important as climatic conditions for predicting the distribution of a broad-ranged apex predator

Aim: A current biogeographic paradigm states that climate regulates species distributions at continental scales and that biotic interactions are undetectable at coarse-grain extents. However, advances in spatial modelling show that incorporating food resource distributions are important for improving model predictions at large distribution scales. This is particularly relevant to understand the factors limiting distribution of widespread apex predators whose diets are likely to vary across their range. Location: Neotropical Central and South America Methods: The harpy eagle (Harpia harpyja) is a large raptor, whose diet is largely comprised of arboreal mammals, all with broad distributions across Neotropical lowland forest. Here, we used a hierarchical modelling approach to determine the relative importance of abiotic factors and prey resource distribution on harpy eagle range limits. Our hierarchical approach consisted of the following modelling sequence of explanatory variables: (a) abiotic covariates, (b) prey resource distributions predicted by an equivalent modelling for each prey, (c) the combination of (a) and (b), and (d) as in (c) but with prey resources considered as a single prediction equivalent to prey species richness. Results: Incorporating prey distributions improved model predictions but using solely biotic covariates still resulted in a high performing model. In the Abiotic model, Climatic Moisture Index (CMI) was the most important predictor, contributing 76 % to model prediction. Three-toed sloth (Bradypus spp.) was the most important prey resource, contributing 64 % in a combined Abiotic-Biotic model, followed by CMI contributing 30 %. Harpy eagle distribution had high environmental overlap across all individual prey distributions, with highest coincidence through Central America, eastern Colombia, and across the Guiana Shield into northern Amazonia. Main conclusions: With strong reliance on prey distributions across its range, harpy eagle conservation programs must therefore consider its most important food resources as a key element in the protection of this threatened raptor.

opencc-zeroFeb 2023View details →

dryad36/100

The essential habitat role of a unique coastal inlet for a widely distributed apex predator

Essential habitats support specific functions for species, such as reproduction, feeding or refuge. For highly-mobile aquatic species, identifying essential habitats within the wider distribution range is central to understanding species ecology, and underpinning effective management plans. This study examined the movement and space use patterns of sevengill sharks (Notorynchus cepedianus) in Caleta Valdés, a unique coastal habitat in northern Patagonia, Argentina. Seasonal residency patterns of sharks were evident, with higher detectability in late spring and early summer and lower during autumn and winter. The overlap between the residency patterns of sharks and their prey, elephant seals, suggests that Caleta Valdés functions as a seasonal feeding aggregation site for N. cepedianus. The study also found sexual differences in movement behavior, with males performing abrupt departures from Caleta Valdés and showing increased roaming with the presence of more sharks, and maximum detection probability at high tide. These movements could be related to different feeding strategies between sexes or mate-searching behavior, suggesting that Caleta Valdés may also be essential for reproduction. Overall, this study highlights the importance of coastal sites as essential habitats for N. cepedianus and deepens our understanding of the ecological role of this apex predator in marine ecosystems.

opencc-zeroSep 2023View details →

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