Carrion Availability Research Articles

Seasonal variability of scavenger visitations is independent of carrion predictability

In temperate regions, larger mammalian carrion naturally occurs in terrestrial landscapes as a pulsed resource towards the end of the winter through enhanced ungulate mortality due to starvation or exhaustion. The return of large carnivores in Central Europe provides carrion more equally throughout the year and the active enhancement of carrion for biodiversity by game managers has increased, raising the question of how different scavengers respond to the temporal variation in carrion supply. To address this question, we experimentally deployed 106 cervid carcasses throughout the year in a temperate forest of south-eastern Germany on two types of plots: permanent (i.e., site with multiple subsequent deployments) or random (i.e., site with unique deployment), and reported vertebrate scavenger visitations by camera trapping. Deployment on random or permanent sites did not affect carrion use by any single species. Generalized additive modelling revealed that vertebrate scavenging peaked in the winter season and summer independent of carrion supply. Still, different scavenger species showed different temporal patterns. While wild boar as ungulate omnivores did not display any seasonal patterns, avian scavengers showed significant variation in visitation rates. The mesopredator red fox consumed carrion significantly more often from late winter to summer, while pine marten was present at carrion only during winter. Finally, the specialist large carnivore Eurasian lynx, visited carrion sites most frequently in late winter and early spring. Our results suggest that global warming might impact some groups of vertebrate scavengers more strongly than others by reducing carrion availability in late winter, while returning carnivores could mitigate these impacts.

Condors scavenge on fish at the land–water interface in the Andean foothill of southern Bolivia

AbstractThere is very little information on Andean condors scavenging on fish. Here we report five events of condors feeding on fish carrion in the Bolivian Chaco Serrano in three consecutive years. In 2019, 2020, and 2021, condors were observed feeding on discarded fish from local fishermen, 3 km west of Villa Montes, in the ‘El Angosto’ section of the Pilcomayo River. Fishing, mainly for sábalo (Prochilodus lineatus), is the most important economic activity in that part of the Pilcomayo basin and its discards explain fish carrion availability there, while driving scavengers to feed on this resource. We believe that fish carrion abundance, the intensity of intra‐ and interspecific competition for access to carrion, and overall carrion availability hierarchically influence the fact that condors feed on fish, something we will investigate later based on the observations reported here. From a conservation perspective, the main consequence of scavengers feeding on fish from the Pilcomayo is that they could be getting heavy metal poisoning. Heavy metal poisoning is a serious threat with widely known negative effects for wildlife. Our observations should serve to promote comprehensive bio‐monitoring of the Pilcomayo basin, using approaches such as One Health, and emphasizing the importance of coexistence between humans and the rest of biodiversity, with the Andean Condor as the flagship species.

A 2200-year record of Andean Condor diet and nest site usage reflects natural and anthropogenic stressors.

Understanding how animals respond to large-scale environmental changes is difficult to achieve because monitoring data are rarely available for more than the past few decades, if at all. Here, we demonstrate how a variety of palaeoecological proxies (e.g. isotopes, geochemistry and DNA) from an Andean Condor (Vultur gryphus) guano deposit from Argentina can be used to explore breeding site fidelity and the impacts of environmental changes on avian behaviour. We found that condors used the nesting site since at least approximately 2200 years ago, with an approximately 1000-year nesting frequency slowdown from ca 1650 to 650 years before the present (yr BP). We provide evidence that the nesting slowdown coincided with a period of increased volcanic activity in the nearby Southern Volcanic Zone, which resulted in decreased availability of carrion and deterred scavenging birds. After returning to the nest site ca 650 yr BP, condor diet shifted from the carrion of native species and beached marine animals to the carrion of livestock (e.g. sheep and cattle) and exotic herbivores (e.g. red deer and European hare) introduced by European settlers. Currently, Andean Condors have elevated lead concentrations in their guano compared to the past, which is associated with human persecution linked to the shift in diet.

Scavenging patterns of generalist predators in forested areas: The potential implications of increase in carrion availability on a threatened capercaillie population

AbstractThe increases in ungulate populations and hunting bags throughout Europe and North America have resulted in higher carcass numbers available for mesocarnivore species in temperate and boreal forests. The increase in food resources can sustain denser predator populations, potentially affecting prey species such as the threatened western capercaillie Tetrao urogallus. We investigated the ungulate population trends in recent decades and the carrion use by facultative scavengers in areas of the Pyrenees occupied by capercaillie to assess the potential effects on predation of nests and adult birds, and on its population trend. We found a significant increase in the number of ungulates harvested during the period of sharp capercaillie population decline. Carrion was provided experimentally in forested areas occupied by capercaillie showing that remains were mainly consumed by red fox Vulpes vulpes, followed by wild boar Sus scrofa and marten species (Martes sp.). Season (cold or warm) was the most important factor determining scavenging activity in most species. Main predators of capercaillie nests and adults were martens and red fox, with no predation by wild boar. Our data show that main predators of capercaillie are the same species that mainly consume carrion, especially in winter, and that plentiful carrion resources could maintain higher populations of these species, potentially increasing predation pressure on the capercaillie population. This study shows that managing carrion arising from hunting activity in areas of capercaillie distribution is a necessary management action to reduce the available carrion biomass and so reduce the impact of mesocarnivores on capercaillie conservation.

Superb advantage from carrion‐associated arthropods?

Carcasses of adult African elephants (Loxodonta africana), as well as those of juveniles and subadults under certain conditions, often persist long enough to allow members of the blowfly family (Calliphoridae) to complete their life cycle en masse before the tissues are fully consumed and the skeletons disarticulated. The presence of tens of thousands of blowflies and other carrion-associated arthropods attracts species that are typically unaffiliated with carrion, such as the superb starlings (Lamprotornis superbus) shown here. This relationship may be more functionally important than it first appears. Each year, the availability of elephant carrion peaks during dry seasons, which bookend the wet seasons when superb starlings breed. The amount of seasonal rainfall influences insect population size, which in turn impacts the fitness of superb starlings (Rubenstein 2015; doi.org/10.1017/CBO9781107338357.012). Elephant carcasses may serve as reliable resource hotspots for superb starlings foraging during dry seasons. Given the persistence of carcasses and the presence of their accompanying arthropods, these hotspots may remain valuable to the starlings into the early portion of their breeding seasons. Although the arthropod-rich elephant carcasses likely provide fitness benefits to superb starlings and other insectivorous birds, these sites are not without peril. Predators (including Verreaux's eagle-owl [Bubo lacteus]) are also attracted by the concentration of prey at carcasses. Carrion ecology is a burgeoning field, and an improved, comprehensive understanding of the effects of carcasses within ecosystems is needed.

Evidence for seasonal cycles in deep-sea fish abundances: A great migration in the deep SE Atlantic?

Animal migrations are of global ecological significance, providing mechanisms for the transport of nutrients and energy between distant locations. In much of the deep sea (>200m water depth), the export of nutrients from the surface ocean provides a crucial but seasonally variable energy source to seafloor ecosystems. Seasonal faunal migrations have been hypothesized to occur on the deep seafloor as a result, but have not been documented. Here, we analyse a 7.5-year record of photographic data from the Deep-ocean Environmental Long-term Observatory Systems seafloor observatories to determine whether there was evidence of seasonal (intra-annual) migratory behaviours in a deep-sea fish assemblage on the West African margin and, if so, identify potential cues for the behaviour. Our findings demonstrate a correlation between intra-annual changes in demersal fish abundance at 1,400m depth and satellite-derived estimates of primary production off the coast of Angola. Highest fish abundances were observed in late November with a smaller peak in June, occurring approximately 4months after corresponding peaks in primary production. Observed changes in fish abundance occurred too rapidly to be explained by recruitment or mortality, and must therefore have a behavioural driver. Given the recurrent patterns observed, and the established importance of bottom-up trophic structuring in deep-sea ecosystems, we hypothesize that a large fraction of the fish assemblage may conduct seasonal migrations in this region, and propose seasonal variability in surface ocean primary production as a plausible cause. Such trophic control could lead to changes in the abundance of fishes across the seafloor by affecting secondary production of prey species and/or carrion availability for example. In summary, we present the first evidence for seasonally recurring patterns in deep-sea demersal fish abundances over a 7-year period, and demonstrate a previously unobserved level of dynamism in the deep sea, potentially mirroring the great migrations so well characterized in terrestrial systems.

Direct and indirect effects of carrion subsidies in an arid rangeland: Carrion has positive effects on facultative scavengers and negative effects on a small songbird

In the absence of top-down regulation by predators, herbivore populations irrupt. In irrupting populations of large herbivores deaths are frequent and availability of carrion from carcasses is high, potentially subsidising facultative scavengers such as crows and ravens. Increases in facultative scavengers could amplify perceived and real predation risk for small prey. We provisioned large-herbivore carcasses over 2 weeks at three sites (400 ha/site) in the Australian arid zone and monitored detection rates of facultative scavenger birds and low-nesting small passerines at these sites and at three control sites of the same size. We found that provisioning large herbivore carcasses rapidly increased local abundances of scavenging corvids Corvus coronoides and C. bennetti by 50% and decreased relative detection rates of a predation-sensitive small passerine, white-winged fairywren Malurus leucopterus by 50%. White-winged fairywren detection rates were inversely correlated with corvid abundances. Our study indicates that increases in carrion availability associated with herbivore irruptions subsidise facultative scavengers, and thus may indirectly affect co-occurring prey species.

Effect of mammalian mesopredator exclusion on vertebrate scavenging communities

Carrion is a valuable resource used by facultative scavengers across the globe. Due to conflicts with humans, many vertebrate scavengers have experienced population declines due to direct persecution or indirect effects of human activities. However, little is known about the implications of altered scavenger community composition on the fate and efficiency of carrion removal within ecosystems. In particular, mammalian mesopredators are efficient scavengers that are often subjected to control, thus, it is important to understand how the reduction of this scavenger guild influences the fate of carrion resources and efficiency of carrion removal within ecosystems. We evaluated the influence of the absence of mammalian mesopredators on vertebrate scavenging dynamics by comparing the efficiency of carrion removal and species composition at carrion between sites where we experimentally manipulated mesopredator abundance and paired control sites. Overall scavenging rates were high, even within our mesopredator exclusion sites (79% of carcasses). Despite the exclusion of an entire guild of dominant scavengers, we saw little effect on scavenging dynamics due to the extensive acquisition of carrion by avian scavengers. However, we observed a slight reduction in vertebrate scavenging efficiency in sites where mesopredators were excluded. Our results suggest vertebrate communities are highly efficient at carrion removal, as we saw a functional response by avian scavengers to increased carrion availability. These data provide insights into the impact of mesopredator control on food web dynamics, and build upon the growing body of knowledge investigating the role of vertebrate scavengers on ecosystem services provided through carrion removal.

Rewilding with large herbivores: Positive direct and delayed effects of carrion on plant and arthropod communities.

Carrion of large animals is an extremely nutrient rich, ephemeral resource that is essential for many species, but is scarce in the anthropogenic Western-European landscape due to legislative restrictions. Rewilding, a novel conservation strategy that aims at restoring natural processes with minimal human intervention, is increasing in popularity and could lead to increased carrion availability in the landscape. It is therefore important to understand the effects of carrion on biodiversity. We investigated the direct and delayed (five months) effects of red deer (Cervus elaphus) carcasses on plants and arthropods in the Oostvaardersplassen, the Netherlands, one of the oldest rewilding sites in Europe. Specifically, we tested whether carrion has a positive direct effect on the abundances and diversity of various arthropod functional groups, as well as a delayed effect on the vegetation and arthropods through the increased nutrient availability. During the active decomposition stage in spring, we, not surprisingly, observed higher abundances of carrion associated species (scavengers and their specialized predators) at the carrion sites than at control sites without carrion, but no higher abundances of predators or detritivores. In late summer, after near-complete decomposition, plant biomass was five times higher, and nutritional plant quality (C:N ratio) was higher at the carrion sites than at the control sites. Arthropod abundance and diversity were also manifold higher, owing to higher numbers of herbivorous and predatory species. Regression analysis showed that abundances of herbivores and detritivores were positively related to plant biomass, and predator abundances were positively related to abundances of herbivores and detritivores, suggesting bottom-up effects propagating through the food chain. Our results show that even in a naturally nutrient-rich ecosystem like the Oostvaardersplassen, carrion can have strong positive effects on local plant biomass and nutritional quality and arthropod abundances, lasting the whole growing season. We found evidence that these effects were first directly caused by the presence of carrion, and later by the enhanced nutrient availability in the soil. This highlights the importance of the indirect pathways by which carrion can structure arthropod communities.

Pre-eradication assessment of feral cat density and population size across Kangaroo Island, South Australia

Abstract Context Feral cats (Felis catus) are a significant threat to wildlife in Australia and globally. In Australia, densities of feral cats vary across the continent and also between the mainland and offshore islands. Densities on small islands may be at least an order of magnitude higher than those in adjacent mainland areas. To provide cat-free havens for biodiversity, cat-control and eradication programs are increasingly occurring on Australian offshore islands. However, planning such eradications is difficult, particularly on large islands where cat densities could vary considerably. Aims In the present study, we examined how feral cat densities vary among three habitats on Kangaroo Island, a large Australian offshore island for which feral cat eradication is planned. Methods Densities were compared among the following three broad habitat types: forest, forest–farmland boundaries and farmland. To detect cats, three remote-camera arrays were deployed in each habitat type, and density around each array was calculated using a spatially explicit capture–recapture framework. Key results The average feral cat density on Kangaroo Island (0.37 cats km−2) was slightly higher than that on the Australian mainland. Densities varied from 0.06 to 3.27 cats km−2 and were inconsistent within broad habitat types. Densities were highest on farms that had a high availability of macropod and sheep carcasses. The relationship between cat density and the proportion of cleared land in the surrounding area was weak. The total feral cat population of Kangaroo Island was estimated at 1629±661 (mean±s.e.) individuals. Conclusions Cat densities on Kangaroo Island are highly variable and may be locally affected by factors such as prey and carrion availability. Implications For cat eradication to be successful, resources must be sufficient to control at least the average cat density (0.37 cats km−2), with additional effort around areas of high carcass availability (where cats are likely to be at a higher density) potentially also being required.

Sex-specific effects of fisheries and climate on the demography of sexually dimorphic seabirds.

Many animal taxa exhibit sex-specific variation in ecological traits, such as foraging and distribution. These differences could result in sex-specific responses to change, but such demographic effects are poorly understood. Here, we test for sex-specific differences in the demography of northern (NGP, Macronectes halli) and southern (SGP, M.giganteus) giant petrels - strongly sexually size-dimorphic birds that breed sympatrically at South Georgia, South Atlantic Ocean. Both species feed at sea or on carrion on land, but larger males (30% heavier) are more reliant on terrestrial foraging than the more pelagic females. Using multi-event mark-recapture models, we examine the impacts of long-term changes in environmental conditions and commercial fishing on annual adult survival and use two-sex matrix population models to forecast future trends. As expected, survival of male NGP was positively affected by carrion availability, but negatively affected by zonal winds. Female survival was positively affected by meridional winds and El Niño-Southern Oscillation (ENSO), and negatively affected by sea ice concentration and pelagic longline effort. Survival of SGPs did not differ between sexes; however, survival of males only was positively correlated with the Southern Annular Mode (SAM). Two-sex population projections indicate that future environmental conditions are likely to benefit giant petrels. However, any potential increase in pelagic longline fisheries could reduce female survival and population growth. Our study reveals that sex-specific ecological differences can lead to divergent responses to environmental drivers (i.e. climate and fisheries). Moreover, because such effects may not be apparent when all individuals are considered together, ignoring sex differences could underestimate the relative influence of a changing environment on demography.

Indirect Influence of African Swine Fever Outbreak on the Raven (Corvus corax) Population.

Simple SummaryThe persecution of ravens ceased in the middle of the 20th century, and consequently their abundance started to rise in most European countries. Ravens are food opportunists that can eat plants, prey on animals, and feed on garbage dumps. However, carrion plays a crucial role in their diet. In Central Poland, the carrion of farm animals (disposed of illegally) was thought to be the main food source for ravens. This changed radically in February 2014, after the first case of African swine fever (ASF) in Poland, and the introduction of strict procedures for the utilization of pig and wild boar carcasses to stop the spread of the virus. This decrease in carrion availability influenced the raven population; ravens changed their diet, i.e., instead of feeding on the carrion of pigs (previously their main dietary component), they ate (among others) the carrion of domestic dogs and cats, and also preyed on small vertebrates. Consequently, the number of breeding raven pairs decreased, and birds produced fewer fledglings. This research showed how certain human activities influence wildlife. The illegal disposal of dead animals, motivated by the desire to save money, resulted in abundant food sources for ravens and an increase in population size.Carrion plays a crucial role in the raven’s diet. In the past, domestic pig carrion was widely available in Poland. This changed with an African swine fever (ASF) outbreak and the introduction of strict procedures aimed at stopping the virus from spreading. We compared data from Central Poland (field and forest mosaic, study area of 105 km2) for two periods, i.e., before (2011–2014) and after the ASF outbreak (2015–2018). In breeding seasons, nests of ravens were found, juveniles were counted, and the time when juveniles left their nests was recorded. Diet composition data were based on pellet analysis and direct observations of feeding birds. The number of breeding pairs dropped from 12.3 to 7.5 in the second period. Breeding parameters were similar. However, birds in the second period had fewer fledglings per successful pair. Domestic pig carrion was found to be an important food item, and with its limited supply, ravens changed their diet, i.e., they fed on the carrion of dogs and cats or preyed on small vertebrates more often. Overall, our study points to a crucial role of the availability of the carrion of big farm animals (i.e., domestic pig) in maintaining the high density of breeding raven populations.

Livestock farming practices modulate vulture diet-disease interactions

Low- and high-intensity farming exert different direct and indirect effects on vulture populations by driving the availability, exploitation and characteristics of carrion. This is especially true for the levels of pharmaceuticals in wild and domestic animal carcasses. However, the impact of farming systems on the diet-related health of avian scavengers remains unclear. Here, we evaluate diet and disease signs in nestlings of three European species of vultures (Cinereous, Aegypius monachus, Griffon, Gyps fulvus, and Egyptian, Neophron percnopterus), living in different regions of Spain under contrasting farming schemes. We test the hypothesis that disease (oral mucosal lesions caused by mixed fungal and bacterial infections) in vultures is influenced by features of food and foraging conditions derived from farming systems, especially due to the expected chronic and irregular ingestion of pharmaceuticals under intensive (factory farms) compared to extensive systems. A large proportion of nestlings of the three vulture species in central Spain (high-intensity farming area) continue to be affected by oral lesions (cinereous: 75%, n = 16; griffon: 61%, n = 28; Egyptian: 46%, n = 13). The same type of lesions, at a much lower frequency, was found in nestling of the three vulture species in each of the selected areas corresponding to low-intensity farming areas in southern and northern Spain (Cinereous: 39%, n = 13; Griffon: 7%, n = 14; Egyptian: 6%, n = 17). As predicted, a positive relationship was found between the proportion of nestlings with lesions and the frequency of intensive livestock from factory farms (swine and poultry) in the diet. The intensive medication in factory farms deserves further research to assess its implications in vulture diet-disease interactions at large geographical scales. Assessing the presence of oral lesions as an indicator of physiological alterations is encouraged along with pharmacovigilance in surveillance programs aimed at evaluating the direct and indirect effects of livestock farming practices on vulture health. Given the increasing exploitation of domestic instead of wild animals by vultures, the growth in high-intensity farming and the medication practices in free-ranging and semi-extensive farming systems, this assessment would help to characterize the risks associated with different farming operations for wildlife. This evaluation is crucial to avoid exacerbating the detrimental consequences of supplementary feeding programs contrary to their primary aim of the conservation of endangered species.

Top carnivore decline has cascading effects on scavengers and carrion persistence.

Top carnivores have suffered widespread global declines, with well-documented effects on mesopredators and herbivores. We know less about how carnivores affect ecosystems through scavenging. Tasmania's top carnivore, the Tasmanian devil (Sarcophilus harrisii), has suffered severe disease-induced population declines, providing a natural experiment on the role of scavenging in structuring communities. Using remote cameras and experimentally placed carcasses, we show that mesopredators consume more carrion in areas where devils have declined. Carcass consumption by the two native mesopredators was best predicted by competition for carrion, whereas consumption by the invasive mesopredator, the feral cat (Felis catus), was better predicted by the landscape-level abundance of devils, suggesting a relaxed landscape of fear where devils are suppressed. Reduced discovery of carcasses by devils was balanced by the increased discovery by mesopredators. Nonetheless, carcasses persisted approximately 2.6-fold longer where devils have declined, highlighting their importance for rapid carrion removal. The major beneficiary of increased carrion availability was the forest raven (Corvus tasmanicus). Population trends of ravens increased 2.2-fold from 1998 to 2017, the period of devil decline, but this increase occurred Tasmania-wide, making the cause unclear. This case study provides a little-studied potential mechanism for mesopredator release, with broad relevance to the vast areas of the world that have suffered carnivore declines.

Different criteria for implementing sanitary regulations lead to disparate outcomes for scavenger conservation

Abstract Integrating environmental concerns into sectoral policies is a priority for sustainable development. Despite environmental policy integration being established in Europe in 1998, major weaknesses still limit its effectiveness, such as poor coordination at national and subnational levels. We use the integration of scavenger conservation into sanitary European regulations to illustrate how the adoption of different criteria when implementing the same legislation affects the effectiveness of the environmental policy integration process. We focus on the implementation across Spanish autonomous regions of Regulation EU 142/2011 allowing dead livestock to be left in situ for feeding scavengers. Using Asturias (NW Spain) as a case study, we provide spatially explicit estimates of two key factors guiding the implementation of the legislation, the estimates of scavenger feeding requirements, and the area designated as scavenger feeding zones, based on different criteria used across Spanish regions. We detected a remarkable variation in both scavenger feeding requirements (up to 452%; ranging from 108 to 596 t/year) and scavenger feeding zones (up to 72% in size) depending on the implementation criteria used. The concentration of scavenger feeding requirements per km2 within scavenger feeding zones (i.e., carrion demand) varied up to 167%. Similarly, the concentration of carrion supply from livestock within scavenger feeding zones (i.e., carrion availability) changed up to 33%. Policy implications. Our results support the need for systematic evaluations to choose the best criteria for implementing sanitary regulations concerning scavenger conservation. Interregional coordination in implementing the agreed criteria emerges as a relevant issue to improve the effectiveness of environmental policy integration for transboundary conservation of European scavengers.

Bioinspired models for assessing the importance of transhumance and transboundary management in the conservation of European avian scavengers

The assessment of temporal and spatial availability of food resources is an important prerequisite in developing improved management tools for effective conservation action. It is especially useful in the conservation of avian scavengers inhabiting regions where livestock move on a regular basis (transhumance). Important management decisions can be taken on the basis of theoretical analyses that need to be regularly checked. In this case study, we consider models of Griffon vulture Gyps fulvus, Egyptian vulture Neophron percnopterus and bearded vulture Gypaetus barbatus populations in a part of Spain with one of the highest densities of scavenging birds, and where traditional farming practices remain. We applied bioinspired Population Dynamic P System models (PDP) to assess these species' population trends against the distribution, quantity and availability of carrion for food. We show asymmetries in the availability of food resources, which are substantially higher in summer due to transhumant movements. In the study area, a lack of food resources in winter leads to a seasonal reduction in food supplies to levels unable to meet the energetic requirements of the most abundant vulture species, the Griffon vulture. Our results suggest that regardless of active management (e.g. supplementary feeding sites) and the birds’ use of other potential food resources not included in the model, Griffon vultures are able to find important alternative food resources in more remote areas. We show the importance of variations at spatio-temporal scales in the objective forecasting of population trends, and in the correct application of management actions. Because of the importance of robust assessments for management applications, we discuss the advantages and limitations of ecological modelling for avian scavengers, highlighting the importance of transhumance processes and transboundary approaches.

Roads do not increase carrion use by a vertebrate scavenging community

Wildlife-vehicle collisions introduce a considerable amount of carrion into the environment, but scavenger use of this resource has not been extensively investigated. Scavengers may use roads for reliable foraging opportunities, but might also use roads for other purposes and encounter carrion opportunistically. We examined scavenging of carrion along linear features by placing 52 rabbit carcasses in each of three treatments in forested habitat during winter (Dec 2016-Mar 2017) in South Carolina, USA: roads, power line clearings (linear feature with fewer carcasses than roads due to lack of road kill), and forest interior. We used motion-activated cameras to compare arrival times and presence of vertebrate scavengers among treatments. There was no difference in proportion of carcasses scavenged or scavenger arrival time across treatments. No species arrived at roads quicker than other treatments. Turkey vultures (Cathartes aura) and coyotes (Canis latrans) scavenged equally across treatments, whereas gray foxes (Urocyon cinereoargenteus) scavenged along roads and power lines, but not in forests. We suggest that scavenger use of carrion near roads at this location during winter relates to factors other than carrion availability. Because some scavengers readily consumed carrion on roads, this resource has the potential to influence the ecology of these species.

Supplementary feeding stations for conservation of vultures could be an important source of monophasic Salmonella typhimurium 1,4,[5],12:i:-

Vultures are nature's most successful scavengers, feeding on the carcasses of dead animals present in the field. Availability of domestic carrion has been unstable due to rapidly changing agro-grazing economies and increasing sanitary regulations that may require burial or burning of livestock carcasses. Thus, several griffon vulture (Gyps fulvus) recoveries are based on European legislation that guarantees the animals' welfare, avoids intense persecution of the vultures and allows the feeding of threatened wildlife in supplementary feeding stations (SFS). However, in recent years, many studies have speculated on the likelihood that avian scavengers may be infected by feeding on pig carcasses at SFS from intensive livestock. In this context, the present study evaluated whether free-living griffon vultures and pig farms share zoonotic Salmonella strains to test the hypothesis that vulture are infected during consumption of carcasses provided at SFS. Here, the occurrence, serotypes and genomic DNA fingerprinting (phage typing and pulsed-field gel electrophoresis) of isolated strains were carried out in griffon vultures and pig farms authorised to provided carcasses at SFS in Castellón province (eastern Spain). The bacteriological analyses revealed that 21.1% of vultures and 14.5% for pig farms samples tested were Salmonella-positive. Monophasic S. typhimurium 1,4,[5],12:i:- was the most frequently isolated serovar. Comparison of Salmonella strains isolated from vultures and pig farms revealed that monophasic S. typhimurium 1,4,[5],12:i:-, S. Derby and S. Rissen strains were highly genetically homogeneous (similar DNA fingerprint). In conclusion, the current study indicates that free-living griffon vultures and pig farms that provide the carcasses at SFS share several zoonotic Salmonella strains. On this basis, and although transmission could be bidirectional, our result seems to corroborate the pig carcasses-to-vulture transmission and cross-infection at SFS. As an immediate Salmonella control strategy in wild avian scavengers, we suggest the implementation of a programme to guarantee that solely pig carcasses from Salmonella-free farms arrive at SFS.

Effects of vulture exclusion on carrion consumption by facultative scavengers.

Vultures provide an essential ecosystem service through removal of carrion, but globally, many populations are collapsing and several species are threatened with extinction. Widespread declines in vulture populations could increase the availability of carrion to other organisms, but the ways facultative scavengers might respond to this increase have not been thoroughly explored. We aimed to determine whether facultative scavengers increase carrion consumption in the absence of vulture competition and whether they are capable of functionally replacing vultures in the removal of carrion biomass from the landscape. We experimentally excluded 65 rabbit carcasses from vultures during daylight hours and placed an additional 65 carcasses that were accessible to vultures in forested habitat in South Carolina, USA during summer (June–August). We used motion‐activated cameras to compare carrion use by facultative scavenging species between the experimental and control carcasses. Scavenging by facultative scavengers did not increase in the absence of competition with vultures. We found no difference in scavenger presence between control carcasses and those from which vultures were excluded. Eighty percent of carcasses from which vultures were excluded were not scavenged by vertebrates, compared to 5% of carcasses that were accessible to vultures. At the end of the 7‐day trials, there was a 10.1‐fold increase in the number of experimental carcasses that were not fully scavenged compared to controls. Facultative scavengers did not functionally replace vultures during summer in our study. This finding may have been influenced by the time of the year in which the study took place, the duration of the trials, and the spacing of carcass sites. Our results suggest that under the warm and humid conditions of our study, facultative scavengers would not compensate for loss of vultures. Carcasses would persist longer in the environment and consumption of carrion would likely shift from vertebrates to decomposers. Such changes could have substantial implications for disease transmission, nutrient cycling, and ecosystem functioning.

Spatial complexity of carcass location influences vertebrate scavenger efficiency and species composition

Scavenging plays an important role in shaping communities through inter- and intra-specific interactions. Although vertebrate scavenger efficiency and species composition is likely influenced by the spatial complexity of environments, heterogeneity in carrion distribution has largely been disregarded in scavenging studies. We tested this hypothesis by experimentally placing juvenile bird carcasses on the ground and in nests in trees to simulate scenarios of nestling bird carrion availability. We used cameras to record scavengers removing carcasses and elapsed time to removal. Carrion placed on the ground was scavenged by a greater diversity of vertebrates and at > 2 times the rate of arboreal carcasses, suggesting arboreal carrion may represent an important resource to invertebrate scavengers, particularly in landscapes with efficient vertebrate scavenging communities. Nonetheless, six vertebrate species scavenged arboreal carcasses. Rat snakes (Elaphe obsolete), which exclusively scavenged from trees, and turkey vultures (Cathartes aura) were the primary scavengers of arboreal carrion, suggesting such resources are potentially an important pathway of nutrient acquisition for some volant and scansorial vertebrates. Our results highlight the intricacy of carrion-derived food web linkages, and how consideration of spatial complexity in carcass distribution (i.e., arboreal) may reveal important pathways of nutrient acquisition by invertebrate and vertebrate scavenging guilds.