Food Webs最新文献

The global loss of top predators has led to widespread changes in food webs. In Patagonia, it is hypothesized that local extirpations of terrestrial predators, including the puma (Puma concolor), has led to the expansion of Magellanic penguin (Spheniscus magellanicus) colonies across the Atlantic coast of Argentina. Interestingly, more recent wildlife conservation efforts in the region have led to an unexpected trophic link between pumas and penguins. Here, we used a camera trap array to assess this novel predator-prey relationship between pumas and penguins in Monte León National Park (MLNP) over a three-month period. Pumas were detected 12.5 times more than any other mammalian predator and were detected on 95% of the days during our study period. We also observed 28 individual events of pumas preying upon penguins. Our work demonstrates a strong linkage between the marine and terrestrial ecosystem at MLNP. Puma predation of penguins may have widespread ecological implications including effects on puma and penguin abundance, changes in puma social behavior, and interspecific competition among other prey items and carnivores in the park. We propose hypotheses and questions to investigate these potential outcomes.

We revisit the nature and extent of trophic cascades and quaking aspen (Populus tremuloides) recovery in the northern range of Yellowstone National Park, where studies have reported on Rocky Mountain elk (Cervus canadensis) browsing and young aspen heights following the 1995–96 reintroduction of gray wolves (Canis lupus). A recent study by Brice et al. (2021) expressed concerns about methodologies employed in earlier aspen studies and that results from those studies exaggerated the extent to which a trophic cascade has benefitted aspen, concerns such as: (a) the selection of aspen stands, (b) young aspen sampling and measurements within stands, (c) the upper browse level of elk, (d) cause of increased young aspen height growth, (e) interpretation of browsing and height data, and others. We individually address these concerns and conclude that earlier aspen studies have provided important insights regarding the recovery of aspen that is underway in northern Yellowstone and that they have not exaggerated the ongoing recovery. We found that Brice et al. (2021) misinterpreted or misrepresented various aspects of those earlier studies, while failing to address potential biases and shortcomings of their own 2007–2017 study, including; sampling aspen stands from only a portion of the park's northern range, not randomly selecting aspen stands across their study area, but only within identified treatments, varying sampling density (stands/km²) by more than an order of magnitude between treatments, and not sampling all stands in most years. Regardless of the research methodologies employed in various aspen studies, they have consistently shown that decreased browsing has resulted in greater young plant heights in the park's northern range, results consistent with an ongoing trophic cascade.

Animal dung holds an important role in the nutrient cycle of nearly every ecosystem on Earth. It also acts as an ephemeral resource for invertebrate communities and has facilitated the specialization of many life history strategies. Most ecosystem functions associated with dung are linked to burial - a process most often attributed to dung beetles. However, identifying other organisms that contribute to dung burial is important to understand how communities provide this ecosystem service. During a trail camera experiment intended to monitor dung beetle behavior, we observed an unidentified species of cricket burying dung pellets underground. We were unable to find previous documentation of dung-burying behavior for this animal group, raising questions of how common or extensive this behavior is. Particularly under the threat of global insect declines, understanding which species are responsible for key processes may be crucial to maintaining ecosystem function and resilience. Additionally, this experiment exemplifies how camera traps can be used in nontraditional applications to observe and monitor unique events, behaviors, and processes, such as the decay of ephemeral resource patches and insect behavior.

Predators are known to carry prey in their mouth for many purposes, including providing for dependent young or caching. Studying predator diet through the use of remote camera traps has seldom been explored, aside from natural history observations. We provide photographic evidence of prey carrying behavior of the elusive güiñas (Leopardus guigna) in two study sites in a temperate rainforest of Chilean Patagonia. We recorded 35 photographs and 12 events of güiñas carrying prey using camera traps across 57 sites between 2019 and 2022. All photographs show a rodent as prey except in one, where based on morphology, we conclude that it is a colocolo opossum, locally known as ‘Monito del Monte’ (Dromiciops gliroides). All events happened between 2000 and 0800 h, consistent with previous research documenting diel patterns of güiñas in Chile. We argue that camera traps may offer an alternative to help us understand the feeding ecology and diet, especially when collecting scat becomes difficult (e.g., rugged terrain, sites with heavy rainfall). This work discusses the use of camera traps to study predation events and predator diets. The observations here broaden our understanding of güiña predator-prey interactions and can help generate new ways to study diet.

Carrion is increasingly recognized as an important part of food web ecology that impacts multiple trophic levels and creates an arena for multiple species interactions. The pulsed nature of hunter-derived carrion, in the form of gut piles, is a form of carrion that has been overlooked in the study of food webs and scavenger interaction. The Offal Wildlife Watching project aims to better understand scavenger species that benefit from offal and how they interact with each other and this resource. Through citizen science efforts by hunters and Zooniverse volunteers, we have collected and analyzed over 230,000 images of scavengers at white-tailed deer gut piles. At some gut piles, we have observed barred owls and bobcats both scavenging at hunter provided gut piles and preying on rodents that were also attracted to the gut pile. This interaction, made possible by a food subsidy that is historically novel in time and space, may have implications for rodent populations, predator survival and fecundity, and the activity patterns of both. Continued research and investigation will shed light on the impacts of cascading carrion on species interaction.

Anthropogenic disturbances, including habitat changes, climate change, and pesticides, contribute significantly to species declines and extinctions worldwide. These disturbances also hinder conservation efforts like species reintroductions by creating novel ecosystems that no longer support the species that is being reintroduced. Using camera traps, we observed Great Horned Owls (Bubo virginianus), which are a dominant avian predator, perching on the nests of Northern Aplomado Falcons (Falco femoralis septentrionalis), a federally endangered species reintroduced to coastal Texas with a current breeding population of 23 pairs. The presence of Great Horned Owls on five of the twenty cameras placed on Northern Aplomado Falcon nest structures led us to consider the impact this interaction may have on occupancy and productivity of the nests. Throughout the study system, fast-growing tree and shrub species have become more prominent, which could be facilitating the interaction. We hypothesize that encroachment of woody vegetation is drawing Great Horned Owls into the open coastal grassland habitat of Northern Aplomado Falcons, which may limit the occupancy and productivity of falcon nests. Based on this hypothesis from the camera trap observations and anecdotal evidence of habitat encroachment, quantifying this relationship is a key next step in the recovery process. This will enable us to define priority areas for targeted restoration to push back woody vegetation, as well as areas best suited to release Northern Aplomado Falcons that will minimize the likelihood of predation by Great Horned Owls.

The marine-terrestrial interface provides consumers with access to nutrient rich ocean-based resource subsidies. Coyotes, omnivorous generalists with large ranges that can span many landscape types including the coastal ecotone, might be a critical component of the intertidal food web, contributing to resource subsidy movement into the less productive adjacent coastal scrub habitat. This study utilized an array of camera traps along identified coastal game trails in two protected coastal properties in California to assess the consumption of marine fauna by coyotes in intertidal habitats. We captured coyotes consuming a variety of marine resources, including marine mammals, fish, and intertidal invertebrates. We therefore suggest that coyotes are a more consistent consumer in intertidal habitats than previously thought. We highlight the need for further research into the role of coyotes as a marine to terrestrial subsidy vector, especially under the pressure of anthropogenic change in coastal systems.

Coyote (Canis latrans) are a generalist carnivore that are presumed to be a facultative scavenger. However, we observed feeding behavior that calls into question the simplicity of this interaction. During a carcass deployment experiment, we recorded 105 potential coyote feeding observations, of which 44 included information regarding the food item being consumed. Adult necrophagous flies accounted for these detailed observations as often as carrion (21% of all potential feeding events). Most observations of necrophagous fly consumption occurred at a single block during a restricted window of time, which could reveal individual variation in coyote diet. Our finding highlights the importance of characterizing indirect food web interactions at carcasses. In our case, coyotes likely encountered necrophagous flies in the process of scavenging at carcasses. Food webs may thus include dependencies (e.g., necrophagous flies reproducing on decomposing organic matter) that can generate spatiotemporally limited interactions involving facultative consumers. Moving forward, researchers can advance knowledge regarding food webs by defining the complete suite of consumer interactions at resource pulses.

We present evidence for the first documentation of consumption of a water oak (Quercus nigra) acorn by an eastern screech owl (Megascops asio). A screech owl diet typically consists of small mammals, small birds, and arthropods. In our study, we had a 1-m x 1-m sand pad under observation from a game camera that was set on a 1-min time-lapse delay. On this sand pad, we placed five water oak acorns. In a series of six images over six minutes, we observed an eastern screech owl land near the sand pad, walk to an acorn, and appear to consume the acorn. Although there could be other plausible explanations and events that transpired between 1-min image intervals, we believe this acorn was consumed by the eastern screech owl. The importance of this addition of food type to the diet of a raptor is largely unexplored and undocumented.

Emergent multiple predator effects can result in either risk enhancement or reduction for prey populations. However, whether emergent multiple predator effects influence survival of entire prey assemblages is unknown, which could alter community diversity. We tested whether emergent multiple predator effects would lead to changes in survival of multiple prey species that would subsequently alter prey diversity. We experimentally tested whether larval ringed (Ambystoma annulatum) and marbled salamanders (A. opacum) had additive or multiplicative effects on hatchlings of an assemblage of five amphibian prey species using outdoor mesocosms. We also examined this question using data from a previously published experiment. We extended the multiplicative risk model to estimate prey diversity based on individual prey survival probabilities from each mesocosm. We found that predators generally had additive effects on all prey species, as the expected survival of prey was not different from the observed data, indicating a lack of emergent multiple predator effects. Consistent with this result, observed diversity was not different from expected diversity based on our extension of the multiplicative risk model, further indicating predator species had additive effects. Re-analysis of previously published data showed that when emergent multiple predator effects resulted in risk reduction, diversity changed in a manner consistent that outcome. Overall, we found that additive and multiplicative effects of multiple predators contributed to structuring entire prey communities, including influencing community metrics like diversity. Future work should consider further under what conditions diversity enhancement or reduction would occur.