Food Webs最新文献

The diet of an organism is related to its intrinsic characteristics, such as morphology, physiology, and behavior, and those of the prey it consumes. For species occurring in sympatry, the knowledge of the mechanisms that favor the co-occurrence of morphologically and ecologically similar species may be important to understand the resource partition in the assemblage. In this study, we analyze the diet of small to large hylids (i.e., Scinax fuscomarginatus, Dendropsophus anataliasiasi, Boana caiapo, and B. raniceps) in an Amazonia-Cerrado transitional zone, verifying if the diet of species with different body sizes is similar and if species diet is explained by the availability of prey in the environment. We found that the dietary patterns of the studied hylids were not driven by prey availability in the environment, with species feeding preys in an opportunistic way. In addition, the diet composition was similar among species, however, the volume of consumed prey varied according to the body size, with large species feeding more prey volume than the small ones. This pattern is predicted by the optimal foraging theory, in which larger predators tend to maximize their energy intake by consuming large prey. Altogether, the segregation depending on the body size can play a key role in trophic resource partitioning, with small species feeding small prey and larger species consuming small to large prey, but preferring the larger ones when there is an option, avoiding interspecific competition.

Understanding complete ecological roles of species requires insight into various predator-prey relationships. Bald eagles (Haliaeetus leucocephalus) have been documented to consume a variety of species, including turtles. The ground beneath eight bald eagle nests located in Alabama and Tennessee were searched during the 2016, 2017, and 2018 nesting seasons for discarded turtle remains. Six turtle genera were documented, but the most abundant turtle genera observed were Graptemys and Sternotherus. Most remains were juveniles or adult males; however, the Sternotherus remains could have been adult males or females. The distance of the eagle nest to the nearest major waterway appeared to influence whether Graptemys or Sternotherus was the major turtle prey observed. The presence of different contaminants in these turtle species should be examined to determine if they potentially contribute to biomagnification in bald eagles.

Two-toed sloths (genus Choloepus) are almost exclusively arboreal. However, they often descend to the ground in places known as mineral licks or “saladeros” and feed from soil, which presumably enhances their digestion of toxins and helps them obtain minerals not readily available in their diet. Mineral licks are risky areas which may increase their visitors' vulnerability to predators. Here, we report a predation attempt on an adult Linnaeus two-toed sloth (Choloepus didactylus) by an adult ocelot (Leopardus pardalis) at a mineral lick at the Tiputini Biodiversity Station in the Ecuadorian Amazon. Predation events are rarely recorded in camera traps, and this particular predation event can be considered unusual, given that sloths usually come down to mineral licks during the night. Also, it is not clear how ocelots are able to capture sloths, and other arboreal animals and this record evidence that predation of arboreal vertebrates by ocelots may also take place in the ground. Finally, the anti-predatory behavior displayed by the two-toed sloth demonstrates that there are intrinsic risks for predators while attempting to capture prey.

The consumption of carrion is a key process in food web ecology and a common foraging strategy for facultative scavengers in the carnivore guild. As carrion represents a high-quality trophic resource, carcasses may be visited by multiple carnivore species and have the potential to act as hotspots for intraguild interactions. Mesocarnivores frequently consume carrion, yet the mechanisms used by these species to access carcasses and coexist with larger carnivores have been poorly studied. Here, we investigate the factors influencing carcass use by two understudied African mesocarnivores, the side-striped jackal (Canis adustus) and the African civet (Civettictis civetta). Using camera traps to monitor ungulate carcasses in Liwonde National Park (LNP), Malawi, we assess the influence of competing carnivores (spotted hyena; Crocuta crocuta), carcass size and carcass age on mesocarnivore detection rates. Jackals frequently consumed carrion and their detection at a carcass was positively associated with civet presence, increasing the potential for competitive interactions. Co-occurrence of jackals and civets, where both species were detected simultaneously, were mainly recorded at large (>200 kg) carcasses, suggesting competitive interactions were reduced when more abundant resources were available. Jackal and civet detection at a carcass was not influenced by the presence of spotted hyena, although we found evidence that civets use temporal partitioning to access carcasses at times of reduced spotted hyena activity. Continued monitoring of carcasses will be important to further understand carnivore coexistence dynamics, particularly as large carnivore populations recover in LNP.

Stream ecosystems are reliant on the reciprocal exchange of terrestrial and aquatic energy subsides to maintain a productive and stable food web. Land use around streams can have strong effects on the size and availability of resource subsidies for stream and riparian predators such as fish and spiders. A common forestry technique around streams is the establishment of forested buffers to protect aquatic and riparian ecosystems from upland disturbances. Buffer size may determine prey abundance, richness, and spatial extent of prey reach into both the aquatic and terrestrial systems. To test the effects of forested buffers subsidy direction, we explored the carbon and nitrogen stable isotope signatures of brown trout (Salmo trutta), Tetragnathidae and Lycosidae spiders, and their aquatic and terrestrial prey sources around twelve streams in southern Sweden. For both predator groups, buffer presence showed no effect on resource subsidy source. We found that both brown trout and spiders are significantly reliant on terrestrial sources of prey for their diets in the fall. To support the terrestrial subsidy into small streams it is vital to maintain ecologically functional riparian zones by conserving complex surrounding habitats that optimize habitat and both terrestrial and aquatic prey diversity.

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.

Understanding species (co)-occurrence patterns and how these are affected and mediated by humans is essential for the development of management plans to guide coexistence between humans and wildlife. Here, we evaluated two opposing hypotheses regarding the effects of humans on species occurrence: “humans as super-predators” and “humans as shield”, using an existing camera-trap dataset of mammal species occurrence collected in the coffee forests of southwestern of Ethiopia. We applied a multispecies occupancy modelling framework to explicitly examine co-occurrence patterns between humans, top-predators, prey, and crop-raiders, along a gradient of forest integrity (characterized by forest cover and fragmentation). We examined co-occurrence patterns during both coffee and non-coffee harvest seasons. Our results show partial support for the “humans as shield” hypothesis. We found (i) signs of co-occurrence between humans and prey in areas of low forest integrity during both survey seasons, and between humans and raiders during the coffee-season, (ii) signs of co-occurrence between prey and raiders during both seasons, (iii) no signs of negative or positive co-occurrence between humans and top-predators. Our findings indicate that a possible “shield effect” between humans and prey within a predator space, might be undergoing at the edges of coffee forests. Our findings suggest that incorporating humans as one more species in the ecological system can contribute to shed light into the effects of humans on species occurrence and ultimately contribute to inform management for coexistence.

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.