Predator–prey interactions can differ markedly in their frequency and energetic contribution, particularly when predators consume prey spanning a wide range of body sizes. Quantifying both dimensions may therefore provide complementary insights into the role of predators within food webs. We investigated the diet of the Lesser Horned Owl (Bubo magellanicus) in an agroecosystem of the Lower Chubut River Valley, Patagonia, Argentina, over almost five years, with the aim of assessing seasonal variation in prey composition and evaluating the relationship between numerical frequency and biomass contribution. We analyzed 128 pellets collected during breeding and non-breeding seasons and identified 1725 prey items, including arthropods and vertebrates. Arthropods dominated numerically (81% of prey), particularly Coleoptera and Scorpions, whereas vertebrates represented a smaller proportion of prey items but contributed most of the consumed biomass. Lagomorphs accounted for only a small fraction of prey items but represented 73.9% of total biomass. The contribution of prey categories also varied seasonally, with arthropods dominating numerically during the breeding season and vertebrates becoming relatively more important during the non-breeding season. These results reveal a pronounced decoupling between the frequency and biomass of prey consumed by B. magellanicus. Consequently, frequency-based representations of trophic interactions alone may emphasize numerous interactions with small-bodied prey while underrepresenting less frequent but biomass-dominant pathways involving larger prey. Our findings highlight the importance of integrating prey frequency and biomass when characterizing predator–prey interactions and interpreting the potential role of predators in food webs.
Many ecosystem functions and services that sustain biodiversity and human well-being are rooted in food-web processes, yet food-web studies often fail to integrate multiple ways of quantifying trophic links or to clearly distinguish top-down from bottom-up effects. To address these gaps in support of on-going Everglades restoration, we combined diet data with studies quantifying top-down effects to construct a high-resolution energetic food web for freshwater marshes. Our goal was to identify highly connected nodes relevant to restoration and to evaluate how bottom-up and top-down links interact to shape community structure and ecosystem function. Our review compiled diets for 107 consumers from 82 publications, revealing a food web reliant on detrital-based energy pathways, with notable exceptions for some invasive fishes. The detrital-energy pathway was characterized by highly connected consumer nodes including amphipods, grass shrimp (Palaemon paludosus), and cyprinodontid fishes. Most indicators of restoration success, like American alligators (Alligator mississippiensis), were highly connected. Comparisons of dynamic and energetic links indicated that strong top-down effects often occurred between consumer-resource pairs with weak energetic links; diet importance for predators failed to predict strength of population dynamic effects for prey. Further, top-down effects of some invasive fishes may limit bottom-up effects of Everglades restoration. Using both types of information and visualizing yielded a more complete, though still imperfect, food web, which can better inform ecological restoration strategies. In the Everglades, this means improving resolution for indicator species (higher predators) combined with understanding limitations of their prey and food-web responses to hydrologic and biogeochemical drivers.
Highways can alter the foraging behavior of top predators, such as raptors, by providing carcasses and attracting prey associated with human-modified environments or in areas preserved by set-aside areas along roads. However, exploiting these resources near roads increases the risk of collisions and poses additional conservation challenges. Here, we investigated the diet and individual specialization of Great Horned Owls (Bubo virginianus, n = 26) killed on highways in southern Brazil, integrating stomach content analysis with carbon and nitrogen stable isotope analysis (SIA) from multiple tissues. The species exhibited generalist feeding habits at the population level, with mammals (Prey-Specific Relative Importance Index, PSIRI% = 35.7) and insects (PSIRI% = 20.8) as the main prey items identified in stomach contents. SIA indicated a predominant assimilation of mammals in muscle (95% Credible Intervals CI = 20.4–48.2%), liver (95% CI = 25.9–58.4%), and feathers (95% CI = 30.7–60.2%), followed by amphibians (muscle: 95% CI = 3.5–38.9%; liver: 95% CI = 3.2–45.4%; feathers: 95% CI = 2.8–44.8%). Isotopic data also revealed high individual specialization, particularly reflected by carbon isotopic variation, suggesting consistent consumption of different prey groups or prey mixtures among individuals. Such specialization may lead to differential exposure to roadkill risk in anthropogenic landscapes, both by feeding on carcasses or preying in set-aside areas along roads. The integration of traditional dietary and isotopic approaches, unprecedented for this species, provides novel insights into the trophic ecology of the Great Horned Owl in highway-fragmented ecosystems of southern Brazil and underscores the importance of considering intraspecific variability in ecological and conservation studies.
Understanding how habitat fragmentation affects trophic interactions is essential for guiding conservation strategies. However, studies on edge effects in nest predation are more common in temperate regions, with limited information available for tropical biomes such as the Cerrado. Here, we used artificial nests combined with camera traps to evaluate nest predation along an edge (25 m)–interior (100 m) gradient in 12 forest fragments embedded within an agricultural matrix in the Brazilian Cerrado. We tested whether predation dynamics differed between edge and interior habitats in terms of predation rates, time to predation, and predator assemblages, and whether these patterns varied seasonally. We recorded a diverse assemblage of avian and mammalian predators, with mammals accounting for most predation events. Rarefaction analyses showed that predator richness stabilized in fragment interiors but not at edges. Predator richness and overall predation rates did not differ between edge and interior habitats. Habitat position, vegetation quality, and season did not explain variation in time to predation. Predation was dominated by a few generalist species particularly Sapajus libidinosus, Cyanocorax cyanopogon, and Didelphis albiventris with some seasonal turnover in species composition. Capuchin monkeys were the main nest predators in interior habitats during the dry season. At the spatial scale evaluated, nest predation dynamics did not differ between edge and interior habitats.
Biological invasions can restructure food webs by introducing novel trophic resources. We reviewed publicly available iNaturalist observations to describe the vertical habitat use and feeding associations of the Tasmanian endemic Yellow Wattlebird (Anthochaera paradoxa), and document a previously undescribed nectar-feeding interaction with the invasive succulent African Pig's Ear (Cotyledon orbiculata). Of 879 iNaturalist observations that could be assigned to a vertical stratum, 79.5% occurred in the middle or upper canopy, whereas only 4.7% showed birds in a clearly terrestrial position. The focal Yellow Wattlebird foraged in a ground-level position continuously for 16 min across approximately 20 flowering clumps of C. orbiculata, comprising 167 flowering stalks across a ∼ 30 m2 patch. The observation combined with the habitat use context of the iNaturalist observations, demonstrates that dense C. orbiculata infestations can provide concentrated nectar resources capable of sustaining prolonged foraging by a native nectarivore that typically inhabits elevated canopy habitats. It also shows how invasive floral resources may draw consumers into unusual habitat settings, potentially altering exposure to predators, competitors and other interacting species. We discuss how invasive floral resources may influence foraging behaviour, risk exposure, and interaction structure of native wildlife, highlighting productive areas for future research.
Food webs are a key analytical tool for understanding the impact of disturbances and stressors on the structure and functioning of ecosystems. In the coral ecosystems of the Mexican Tropical Pacific (MTP), disturbances and local stressors mainly manifest as coral mortality and a reduction in the richness and abundance of fish and invertebrate communities. Therefore, in this study, the topological properties of food webs and their spatial variability were described and analyzed, their structure and function were compared, and the most important species or biological groups in each network were identified. Food webs were constructed from binary matrices (predator-prey), and topological, centrality, and keystone species indices were calculated. The results showed spatial changes in the structure and functioning of food webs, mainly associated with benthic variability and human disturbance. Isla Isabel and Cuastecomate-Punta Melaque had the highest number of nodes, links, and link density. They also exhibited more compartmentalized networks (modules). Punto B, Puerto Escondido, and Puerto Ángel had the lowest number of nodes but high connectance, which could be the result of the severe disturbances they face. The variation in modularity and centrality indices was low among sites, with higher values in Puerto Ángel. Most of the keystone species differed across each ecosystem; however, the species Lutjanus argentiventris, Pseudobatos productus, and P. glaucostigma were consistent through all food web models. This study represents the first attempt to understand the topological structure of MTP reefs and provides valuable insights into their structure and ecological functioning. Furthermore, it highlights the importance of this tool for studying complex ecosystems, as it enables rapid assessment of their structure and function for the purposes of managing these reefs.
Conservation biological control relies on native predators capable of suppressing pest populations through consumptive and non-consumptive effects. We experimentally evaluated the predatory potential of two sympatric spiders with contrasting hunting strategies, the web-building Ischnothele caudata and the cursorial Schizocosa sp., against the leaf-cutting ant Atta cephalotes. Both species showed similar prey acceptance and immobilisation times, despite differences in hunting mode. However, I. caudata induced stronger non-consumptive effects, significantly reducing plant damage. Our results suggest that behavioural plasticity and cues may play key roles in spider–ant interactions and highlight the potential of native spiders, particularly web-builders, for conservation biological control of leaf-cutting ants.
Understanding trophic classifications (i.e., specialist/generalist) of predators is important as dietary selection can predict resilience to environmental change. Eastern hellbenders (Cryptobranchus alleganiensis) are large, fully-aquatic, and highly imperiled amphibians thought to specialize on crayfish. However, historical studies examining hellbender diet used visual analyses, potentially underestimating soft-tissue or fast-decaying prey. Thus, their specialist classification has been recently challenged and there is a need to understand hellbender dietary patterns and trophic classifications using contemporary techniques. The goal of this study was to use DNA metabarcoding, a genetic technique useful for identifying organic material, to examine diet and dietary selection of hellbenders across three streams in North Carolina, USA. We performed gastric lavage on 77 unique adult hellbenders to collect 81 stomach content samples across spring (n = 35) and summer (n = 46), then identified stomach contents using microscopy and DNA metabarcoding. We identified spring stomach contents prior to summer to identify the most commonly consumed prey orders. Then, we surveyed prey availability of those orders (Decapoda, Cypriniformes, Perciformes, Scorpaeniformes, Urodela) in the summer to determine summer dietary selection within a use-availability framework. We identified 394 individual prey items across seven classes, 19 orders, 35 families, 56 genera, and 55 species. We found that hellbenders significantly preferred Decapoda over other orders and consumed significantly more prey items (particularly Decapoda) in spring compared to summer. Our findings indicate that hellbenders preferentially consume crayfish, but opportunistically consume a wide variety of other prey, supporting a trophic classification of facultative specialists in our focal system.
Generalist predators often adjust their diets when environments are stressed by extreme climatic conditions. The American Kestrel (Falco sparverius) is a generalist raptor, and most studies have identified rodents and insects as its primary prey throughout its distribution. We examined prey capture rates of American Kestrels during the non-breeding and breeding seasons (2024–2025) in the southern Baja California Peninsula in a period of extreme drought. Overall prey capture rates did not differ significantly between the non-breeding (0.78 ± 0.23 prey·h−1) and breeding seasons (1.13 ± 0.24 prey·h−1). However, we detected significant seasonal differences in prey composition (ANOSIM, P = 0.005, R = 0.31). During the non-breeding season, diets consisted largely of insects, with vertebrates—primarily birds—being scarce. In.contrast, during the breeding season kestrels shifted markedly toward reptile prey. The limited consumption of rodents by kestrels was remarkable, particularly during the non-breeding season, and may have consequences for kestrels once the breeding season begins. Evidently, drought had important consequences for the diversity of prey consumed and subsequently impacted the breeding performance of kestrels in the area.
Tidal-dominated lagoons of the mid-Atlantic region serve as nursery habitats for summer flounder (Paralichthys dentatus), but information is scarce on the trophic ecology of the species in such systems. Summer flounder (3.8-25.2 cm TL) diet was assessed using samples collected seasonally (June 2011 to August 2014) from the Maryland Coastal Bays (MCBs). Summer flounder fed primarily on mysids, amphipods, annelids and isopods. Mysids contributed 53% by weight of P. dentatus stomach contents, and 52% of the stomachs contained mysids. About 63% of flounder consumed amphipods, which accounted for 36.3% by weight of the food consumed. In spring, amphipods contributed >50% of weight of flounder stomach contents in the Chincoteague Bay, whereas mysids (46.6%) were the most important prey in Newport Bay. Mysids (94.0%) and amphipods (98.5%) dominated the weight of stomach contents in Sinepuxent Bay and St. Martin River, respectively. Shrimp larvae (54.4%) and amphipods (30.0%) were the most important prey consumed in Assawoman Bay. In summer, flounder caught in St. Martin River, Assawoman Bay, and Sinepuxent Bay, consumed primarily mysids (>90% by weight); flounder from Newport (47.3%) and Chincoteague (15.6%) Bays consumed less mysids. Summer flounder diet in MCBs differs from the diet previously reported in the Chesapeake Bay, mainly because of the higher contribution of amphipods to, and negligible amounts of fish prey in the diets of, fish from the MCBs. These differences in diet probably result in a smaller mean size of fish at the end of their first year of residence in the MCBs.
Agroecosystems experiencing aphid outbreaks frequently attract diverse aphidophagous predators, which may lead to intraguild predation (IGP). IGP can interfere with food webs within aphidophagous guilds by altering predator-prey dynamics and may also affect ecosystem services, such as biological control. However, this complex and ephemeral interaction is difficult to detect and measure in the field. In this context, the present study aimed to document the unidirectional IGP of Allograpta aff. exotica Wiedemann, 1830 (Diptera: Syrphidae) larvae by the social wasp Polybia ignobilis (Haliday, 1836) (Hymenoptera: Vespidae) in an urban kale crop in southeastern Brazil. Although the ecological and management consequences of this interaction remain limited, we provide evidence of a previously undocumented IGP involving aphidophagous species (Vespidae vs. Syrphidae). Future research may clarify whether the release of aphids from intermediate predator (A. aff. exotica) pressure by the top predator (P. ignobilis) interferes with the biological control of these pests, as well as its effects on the population dynamics of food webs involving these insects.
The cane toad Rhinella marina, introduced to Hawai'i in the 1930s, is now abundant across urban areas and forest remnants on O'ahu. To assess its trophic ecology and habitat-dependent resource use, we combined stomach-content analysis (current diet) with stable isotope ratios of carbon (delta C-13) and nitrogen (delta N-15) from liver (weeks) and muscle (months) samples. We examined stomachs of 93 adults (38 golf courses, 55 forest sites) and isotope values from 26 individuals (13 per habitat). Diets diverged strongly between habitats: forest toads showed a more even prey assemblage dominated by ants (Pheidole megacephala) and beetles (Sitophilus oryzae), while golf course toads were dominated by synanthropic cockroaches (>50% of dietary importance). Individuals from golf courses also exhibited higher prey richness, greater prey volume, and more food items per capita. Stable isotopes mirrored these trends: golf course toads were enriched in delta C-13 and delta N-15 and tended to show higher delta C-13 values, and occupied broader isotopic niches, whereas forest conspecifics showed narrower, Cs-based niches. Concordant liver-muscle isotopic values indicate consistent resource use across weeks to months, suggesting habitat fidelity rather than habitat switching. Morphometric and dietary data further reinforced habitat contrasts: golf course toads were larger and heavier, and snout-vent length was negatively correlated with prey richness and prey number. Overall, R. marina exhibited marked trophic plasticity, with resource subsidies in urban green spaces promoting larger body size and increased exploitation of available resources. This flexibility likely enhances the species' persistence and ecological impact across O'ahu's heterogeneous land-use mosaic, highlighting the role of anthropogenic resource pathways in shaping trophic interactions in invaded ecosystems.
Predator-prey interactions represent a fundamental regulatory mechanism governing energy flux and community structure across ecosystems. Characterizing these links is essential for understanding food web dynamics. Here, we documented two novel predatory interactions between Lycosidae spiders and nestlings of the Ibera Seedeater (Sporophila iberaensis) during reproductive monitoring across three breeding areas. Both predation events were visually recorded early in the morning during routine nest checks, and the parental behavior suggests that they occurred shortly before nest inspection. Although only 2% of nest predation events were attributed to lycosid spiders, their detection through direct observation indicates that such interactions may represent under-reported components of grassland trophic network. Predation is a primary cause of reproductive failure in grassland birds, yet invertebrate predators are rarely considered in this context. Our findings suggest that lycosids may opportunistically exploit vulnerable nestlings and could represent a previously overlooked sources of predation on small vertebrates, highlighting a potentially underestimated pathway of energy transfer in Neotropical grassland food webs. Furthermore, the apparent rarity of these events may reflect methodological biases that favor the detection of larger predators. These observations raise new questions regarding the ecological role of spiders in grassland trophic interactions and emphasize the need for future studies evaluating the frequency and ecological relevance of these interactions.
The introduction of managed western honeybees (Apis mellifera) is often assumed to disrupt native ecosystems by competitively displacing local pollinators and altering plant communities. However, the simultaneous impacts on pollinator community composition, and plant-pollinator network properties remain poorly integrated. This study investigated these effects in a Tibetan alpine meadow with a long history of apiculture by comparing sites close to and distant from apiaries. Using field surveys and pollen transport network analysis, we demonstrate that while Apis mellifera significantly reduced the abundance of native bees, it concurrently increased the abundance of dipterans (specifically Tachinidae and Syrphidae). This shift is driven by a cascading effect: honeybees facilitate the proliferation of specific preferred host plants, creating a resource pulse that supports increased fly populations. Regarding network topology, honeybee introduction increased modularity and functional complementarity but did not alter network nestedness or robustness in general. These findings suggest that rather than simply simplifying the ecosystem, introduced honeybees reorganize the pollination network. Although the compensatory surge in fly populations maintains network structural robustness to some extent, the lower pollination efficiency of these opportunistic visitors compared to the displaced specialized native bees implies a potential functional degradation. This shift may fail to guarantee plant reproductive success, thereby posing a threat to the long-term persistence of the plant community.
Adult sharks often exert fear-based effects on prey, including producing antipredator behaviors in reef fishes, which may result in altered community and ecosystem dynamics over time. However, little information is available on the role that juvenile sharks play in driving antipredator behavior of reef fishes within nursery habitats. Here, we used baited remote underwater video surveys (BRUVS) with different bait types to attract sharks and turtles to observe how reef fishes in a nursery habitat would respond to the presence of a potentially risky predator in comparison to a similarly sized, but non-risky animal. We quantified abundance of reef fishes at the moment of each shark or turtle sighting, and measured the maximum abundance of reef fishes (MaxN) within 30-s video timesteps for five minutes before and after each sighting. We detected a significant reduction in reef-fish abundance at the initial sighting of juvenile sharks in comparison to turtles. However, this effect was short-lived, and neither sharks nor turtles influenced MaxN within any 30-s timestep beyond normal baseline variability. These results suggest that reef fishes displayed a brief antipredator response at the moment of predator arrival, but this behavior did not persist over longer time scales. This ephemeral antipredator response aligns with existing evidence of shark-induced risk effects on behavior of reef fishes, and highlights the need for further investigation into predator-prey dynamics within nursery habitats.
Omnivorous carnivores can alter their trophic role across human-modified landscapes by shifting the diversity and composition of resources they consume. Such changes may influence how these consumers are embedded in local food webs, particularly in fragmented tropical ecosystems where resource availability is strongly shaped by landscape structure. We investigated diet composition of the maned wolf (Chrysocyon brachyurus) across three Atlantic Forest landscapes in southeastern Brazil that differed in forest cover, fragmentation, and anthropogenic disturbance. A total of 77 fecal samples were collected from latrine sites between May and December 2025, and food items were identified to the lowest possible taxonomic level. We tested whether diet composition differed among landscapes and evaluated how trophic links varied along with the disturbance gradient. Diet composition differed significantly among landscapes and was dominated overall by fruits and small mammals. However, more anthropized landscapes showed a broader set of consumed resources, including insects, exotic fruits, and disturbance-tolerant plant species, whereas the less disturbed landscape was characterized by stronger use of native fruits and vertebrate prey. These results suggest that landscape anthropization can modify the trophic role of a generalist carnivore by expanding or concentrating on the set of trophic interactions it establishes. In fragmented Atlantic Forest mosaics, the maned wolf may function as a flexible trophic connector, linking native and anthropogenic resources across landscapes. Our findings highlight how landscape context can reshape trophic interaction patterns of a mobile omnivore, with implications for seed dispersal and predator-prey dynamics in human-modified food webs.
The sunflower sea star (Pycnopodia helianthoides) is a large predator and scavenger which was historically abundant along the west coast of North America until a sea star wasting disease (SSWD) outbreak starting in 2013 caused precipitous population declines throughout its range. P. helianthoides feeds on a variety of benthic invertebrates, in diverse habitats, spanning from subtidal to intertidal depths, in both sedimentary and rocky substrates. Assessment of P. helianthoides diet and role in food webs has previously been based solely on analysis of stomach contents, and there are no studies of its trophic ecology using fatty acids as trophic biomarkers. To investigate the trophic ecology of wild P. helianthoides, fatty acids were extracted and identified from arm-snip tissues of n = 119 individuals, ranging in size from 2.6 to 46 cm in diameter, collected from shallow subtidal benthos of different sites and habitats near Calvert Island, BC, Canada. Because of the loss of large individuals following SSWD, our sampling was restricted to smaller stars (76% of individuals were < 20 cm diameter). The multivariate fatty acid signatures of P. helianthoides differed significantly among sites, indicating diet variation at the relatively small scale similar to 750 km(2). We identified the key individual fatty acids in driving differences in P. helianthoides among sites (in order) as 20:4 omega 6, 20:5 omega 3, 18:0, a-17:0, 18:1 omega 13, 21:5 omega 3, 22:6 omega 3, 18:2 omega 3, 20:3 omega 9, and 20:1 omega 9, and show that bacterially-derived fatty acids are important for separating one fjord site which has been known to be a refuge to P. helianthoides throughout SSWD
This record documents a previously unreported trophic interaction linking aquatic and terrestrial components of Andean stream ecosystems. The natural history of Micrurus dumerilii remains poorly known, particularly regarding its predators. Predation on the related species M. mipartitus has been attributed only to birds, and no confirmed predators have been reported for M. dumerilii. Here we describe a predation event in which the freshwater crab Hypolobocera bouvieri captured and consumed the snake. The observation represents the first evidence of a pseudothelphusid crab preying on an elapid snake, and illustrates the trophic flexibility of H. bouvieri. Species of Hypolobocera, widely distributed in Andean streams of Colombia, are key components of Neotropical lotic ecosystems and play an important role in organic matter processing and energy transfer. The ability of H. bouvieri to exploit such specialized vertebrate prey expands current knowledge of its ecological interactions and its functional role within Andean freshwater systems.
