Food Webs最新文献

Protected lands are an important source of food, shelter, and reproductive opportunities for wildlife, especially in urban landscapes. When urban development abuts the edges of undisturbed ecosystems, synanthropic species can alter their foraging behaviors and movement to utilize human-supplemented resources throughout the urban-wild interface. Therefore, urban development on the edges of protected lands can have pronounced effects on animal movement and ecosystem functions. Iconic urban adaptive mesopredators such as northern raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana) often benefit from human-supplemented food sources such as unsecured garbage, pet food, and fresh water when available. To investigate how urban edges affect the movements of urban-adapted omnivores within conservation lands, we estimated home ranges and third-order resource selection of 27 raccoons and 12 opossums with GPS collars throughout the protected areas of northern Key Largo, FL, USA between April 2022–October 2023. The proportion of urban development in an individual's home range was the most influential factor associated with home range size, followed by species and sex. Individuals with greater proportions of residential neighborhoods and commercial areas in their home ranges exhibited smaller home ranges. Third-order resource selection functions identified both mesopredator species using residential and commercial land use areas more than they were available on the landscape. These results indicate that urban areas attract urban-adapted mesopredators from protected areas and result in smaller home ranges in the face of abundant human-derived food. Reduced home ranges on edges can support higher densities of animals, which may increase rates of disease transmission, especially when the urban borders support populations of feral domestic species. Shifting foraging behaviors from the protected areas to urban edges could have cascading downward effects if seed-dispersing roles are diluted. As urbanization increases and the distance between wild lands and human disturbance decreases, it is increasingly important to study the mechanisms of how urban development on the edges of protected areas affect the movement of wildlife.

We observed a group of Groove-billed Anis (Crotophaga sulcirostris) foraging and following a walking Giant Anteater (Myrmecophaga tridactyla) in the Cojedes state (Central-western Venezuelan Llanos), using camera traps. We speculate that this behavior might be a mechanism to increase the birds’ foraging effectiveness since the number of prey caught when foraging along with the anteater tended to be high. Commensalism is relatively common in nature, but not easy to observe directly among Neotropical mammals and birds, due to their secretive and cryptic behaviors. Interactions between anis and anteaters had not been previously documented, so this is the first substantiated record of groove-billed anis foraging in association with an anteater. The expansion of camera trap networks in the tropics will likely increase our understanding and observations of commensal foraging behavior among diverse mammalian and avian taxa.

Most plant-bird interaction research employing complex ecological networks focuses on pollination and seed dispersal interactions. However, birds and plants are immersed in a great variety and complexity of direct and indirect relationships. Therefore, the use of multilayer networks (i.e., species interaction networks involving different types of interactions) could provide new insights into the ecological and coevolutionary dynamics of plant-bird relationships. Here, we used a multilayer network approach to determine how a bird-plant interaction network involving different types of interactions (i.e., foraging for invertebrates on plants, frugivory, nectarivory, and perching) is organized in a peri-urban Mexican cloud forest. Moreover, we added information about the interactive roles of the winter migratory and resident birds in the multilayer network. In general, we found that the bird-plant multilayer network exhibits modular but a non-nested structure. We also observed that interactions involving perching and foraging for invertebrates on plants are more frequent than frugivory and nectarivory. Moreover, just a small proportion of birds and plant species were important to the network organization and for connecting different interaction types. In this case, we observed that only two bird species, Cardellina pusilla (Parulidae) and Dumetella carolinesis (Mimidae), and the plant species Telanthophora grandifolia (Asteraceae) and Platanus mexicanus (Platanaceae) presented higher centrality values (i.e., an interactive role). Finally, we found that betweenness values (i.e., the number of times a species acts as a bridge along the shortest path between two species) and network structure's contributions are similar for both migratory and resident bird species. Our results highlight the importance of key interacting species that connect other interacting species for the preservation of community cohesion and to the persistence of species-rich assemblages.

Flies (Diptera) are among the most diverse groups of insects and are known to utilize various food resources, including plants, detritus, microbial tissues, and fresh and dead animal tissues. However, their feeding habits in the field remain poorly understood. We conducted a pilot study to apply stable nitrogen (N) and carbon (C) isotope techniques to examine the feeding habits of flies in a tropical rain forest in Sarawak, Malaysia. The fly samples comprised 13 families and >18 species. The results showed significant differences in nitrogen and carbon isotope ratios (δ¹⁵N and δ¹³C) among families and species within a family. The observed pattern is largely consistent with their known feeding habits; flies that use carcasses and carrion as diets (e.g., Sarcophagidae and Calliphoridae) have significantly higher δ¹⁵N values than those likely utilizing plant-based diets (e.g., Cecidomyiidae). There were significant differences in δ¹⁵N values among the six species of Calliphoridae, which is consistent with insect succession on carcasses. The differences in δ¹⁵N may be explained by the use of carrion at different stages of decomposition, because microbial decomposition can lead to the ¹⁵N enrichment. Tachinid flies had relatively low δ¹³C values, reflecting the use of lepidopterans as a host. This pilot study shows that the δ¹⁵N and δ¹³C values of flies provide insights into the diversity of feeding habits of fly communities, which could also serve as an indicator of resource availability in an entire ecosystem.

Individual diet specialization, where individuals within a population exhibit distinct dietary patterns, can be influenced by shifts in ecological opportunity. One underexplored avenue of research is in investigating whether individuals switch foraging strategies (e.g., shifting from herbivory to frugivory) when ecological opportunity provides a pulse of limiting resources, such as fleshy fruits. This study investigates the influence of seasonal frugivory on diet consistency and specialization among generalist herbivores, specifically the gopher tortoise (Gopherus polyphemus), in southeastern Florida, USA. We hypothesized that increased frugivory during the wet season (June through November), coinciding with a resource pulse of fleshy fruits, leads to more inconsistent and specialized diets. Using radio telemetry to track individual tortoises and analyzing dissected fecal samples grouped into functional food categories, we applied Bayesian hierarchical modeling to examine diet consistency and specialization. Our results indicated that higher frugivory levels in the wet season correlate with greater diet inconsistency and specialization compared to the dry season. This pattern suggests that gopher tortoises may switch foraging strategies to exploit seasonal resource pulses of fleshy fruit, thus adopting more inconsistent and specialized diets. Additionally, important activities in the life history of the gopher tortoise, such as copulation, home range defense, and burrow construction, coincide with periods of increased fruit consumption and dietary inconsistency/specialization. Increased intake of carbohydrates and digestible energy from fleshy fruits may allow for more time in the tortoise's activity budget for these activities. Finally, by elucidating the relationship between seasonal frugivory and diet consistency/specialization, this research enhances our understanding of the mechanisms shaping ecological dynamics at the intraspecific level which can subsequently influence community-level interactions such as animal-mediated seed dispersal.

Invasive species can achieve incredibly high densities in invaded ecosystems, introducing a novel resource base for willing consumers. Hyperabundant invaders in one ecosystem that spillover into adjacent ecosystems (e.g. terrestrial to aquatic) create new opportunities for multichannel omnivory, whereby generalist consumers feed on prey from different trophic levels and ecosystems. However, our understanding of how invasive organisms originating in one ecosystem are utilized by consumers in adjacent ecosystems remains poorly studied. The spongy moth (Lymantria dispar dispar; LDD) is an invasive invertebrate that exhibits cyclical hyperabundance, with larvae defoliating millions of hectares of deciduous forest during regular outbreaks in eastern North America. We sought to determine if larval LDD could represent an impactful spring and early summer resource for native fish species during years of high larval abundance. Here, we quantified the diets of pond-dwelling largemouth bass (Micropterus nigricans) and pumpkinseed sunfish (Lepomis gibbosus) during 2020 and 2021 respectively, two historic outbreak years for LDD in Ontario, Canada. Both pumpkinseed and largemouth bass failed to exhibit meaningful exploitation of LDD larvae, regardless of their overwhelming abundance. Of 315 pumpkinseed sampled across four pond populations from April to August of 2021, only two contained individual LDD larvae. Of the 82 largemouth bass sampled in June 2020, only 1 individual contained a single LDD larvae. Serendipitously, we discovered one pumpkinseed population relied heavily on a different invasive terrestrial invertebrate, the earthworm (60% of all pumpkinseed stomach contents by mass in early spring). Though hyperabundant LDD larvae appeared to be largely avoided by fish predators, a less well-defended invasive invertebrate (earthworms) acted as a terrestrial subsidy for a native fish. Despite LDD larvae not being consumed by fish, the replacement of leaf litter with the carcasses and frass of LDD larvae could represent an important modification to detrital food webs in ponds and lakes. Thus, understanding how invasive species impact both resident consumers and nutrient cycling will be critical for the appropriate management of invasive species and their resident food webs moving forward.

Disturbance foraging, the behavior for obtaining food at a disturbance created by another organism, is a widespread form of commensalism interaction observed across the animal kingdom. In the Shiretoko World Heritage site in northern Japan, brown bears (Ursus arctos) dig for cicada nymphs, causing soil physical disturbance. Other predators of cicada nymphs may exploit the soil disturbances caused by brown bears to gain easier access to soil prey, including cicada nymphs. Here, I observed the foraging association among cicada nymph predators, especially brown bears, red foxes (Vulpes vulpes), and crows (Corvus macrorhynchos and C. corone) using camera traps. Notably, the camera traps captured 14 instances of crows and brown bears cooccurring, with the crows engaging in disturbance foraging. In contrast, foxes were never captured alongside brown bears. In addition, the interspecific foraging association between the crows and brown bears was more frequently observed before the cicada emergence season than during it. This suggests that crows predominantly engage in the interspecific foraging association with brown bear digging to facilitate easier predation on the soil-dwelling cicada nymphs prior to the cicada emergence season. During the emergence season, cicada nymphs emerge aboveground, and crows can easily prey upon them without the disturbance of the brown bear digging. The strength of the disturbance foraging association between brown bears and crows is affected by seasonal variations in the life history of prey.

Heterospecific coprophagy. i.e., the consumption of excreta of other species, is reported and documented for the first time for Iberian wild goat Capra pyrenaica Schinz, 1838 and is discussed in light of the nutritional composition of the excreta. Two adult female goats were observed consuming guano of rock dove Columba livia Gmelin, 1789 in March 2021 in the Natural Park of Guara. The chemical composition and feed value of the dove guano consumed by goats was analyzed using standard methods of food analysis. The guano had moderate energy content and high concentrations of nitrogen-compounds that are convertible into protein. It was also rich in macronutrients such as calcium, phosphorus, sodium and sulfur, some of which (namely phosphorus) may be deficient for goats in calcareous environments such as the study area. High levels of sodium and possibly of guanine can cause hedonistic responses to salty and umami flavors that may contribute and reinforce this feeding habit. The guano was affected by desiccation and aging resulting from outdoor exposure, which might have also decreased its degree of pathogenicity. We hypothesize that female Iberian wild goats could be stimulated by guano in the second half of their pregnancy period, when their protein requirements increase. Heterospecific coprophagy has been documented in a wide range of mammals indicating it may be an important feeding activity, but it is still poorly described and understood. Its causes, consequences and relevance should deserve more attention to better understand their feeding ecology. This has to be faced under a multidisciplinary approach.

Climate-induced changes in marine ecosystems have been documented worldwide. As one of the main consequences, a shift in the distribution of species is observable in many marine areas, resulting in the formation of new species communities and new interactions. In the North Sea, the squid community has changed considerably over the last 100 years. Some species have disapeared while new species have established and are now living in coexistence in a new community. Although squids are considered to be predators that feed rather non-selectively, we aimed to answer the question of whether their diet differs nevertheless. Therefore, we analysed the fatty acids of three squid species whose distribution substantially overlaps. We were able to recognise a dependence between the size of the squid and the composition of fatty acids and are able to demonstrate the already known ontogenetic shift in food composition on the basis of fatty acid composition. Furthermore, we illustrate that the fatty acid composition differs significantly between squid species, which points to different prey of the analysed squid species and which may be one reason for their successful coexistence.

Over the last half-century, cities across the southeastern United States have experienced consistent human population growth, which has increased the rate of urban sprawl and subsequent habitat fragmentation with resource subsidies from development. The northern raccoon (Procyon lotor) and Virginia opossum (Didelphis virginiana) are mesopredators commonly associated with and benefiting from urbanized areas. We conducted a small-scale study of raccoons and opossums within the Nacogdoches, Texas, in January 2014. We captured and marked individual raccoons and opossums and used occupancy and spatial-capture-recapture models to examine habitat use, detection, and population density in high- and low-density urban study areas. We predicted to find high densities of each mesopredator, relative to other studies in larger metropolitan areas. We also expected to find a response to landscape features in the high-development study area to be closely associated with anthropogenic features and proximity to water, but less pronounced in the low-development study area. Contrary to our predictions, the detectability of each species in the high-development study area had a positive association with areas further from buildings, and raccoon habitat use had a positive association farther from natural water. Similarly, in the low-development study area, we found raccoon detectability had a positive association with areas farther from the urban edge and opossums had a positive association with areas with smaller forest patches (i.e., edge habitat). We were able to estimate 13.66 raccoons/km² (95% CI 7.10–26.30) in the high-development study area and 12.55 opossums/km² (95% CI 04.36–36.15) in the low-development study area. Our results indicate high densities of each species, and the first urban density of Virginia opossum using spatial-capture-recapture methods which further supports that these mesopredators are adapted to and benefit from urban-derived resources in urban areas. This study highlights the adaptability of these small mesopredators and the need for managers to consider adaptive strategies across different urban intensities as the ecology of these species may differ as compared to larger cities.