Effects on carrion consumption in a mammalian scavenger community when dominant species are excluded

Carrion is a valuable resource exploited not only by obligate scavengers but also by a wide variety of facultative scavengers. These species provide several important ecosystem services which can suffer if the scavenger community composition is altered, thus reducing the ecosystem provided. We studied the response of the Mediterranean facultative scavenger community to the exclusion of larger scavenger species (red fox Vulpes vulpes, European badger Meles meles, and wild boar Sus scrofa) using an exclusion fence permeable to small scavenger species (mainly Egyptian mongoose Herpestes ichneumon, common genet Genetta genetta, and stone marten Martes foina). The exclusion of dominant facultative scavengers led to a significant reduction in the amount of carrion consumed and an increase in carrion available for smaller species and decomposers, over a longer period of time. Although carrion consumption by the non-excluded species increased inside the exclusion area relative to the control area, it was insufficient to compensate for the carrion not eaten by the dominant scavengers. Of the small scavenger species, only the Egyptian mongoose significantly increased its carrion consumption in the exclusion area, and was the main beneficiary of the exclusion of dominant facultative scavengers. Therefore, altering the facultative scavenger community in Mediterranean woodlands can reduce the efficiency of small carcass removal and benefit other opportunistic species, such as the Egyptian mongoose, by increasing the carrion available to them. This interaction could have substantial implications for disease transmission, nutrient cycling, and ecosystem function.

Population Viability and Conservation Strategies for the Eurasian Black Vulture (Aegypius monachus) in Southeast Europe

Simple Summary

Vultures have suffered dramatic declines worldwide. Using population viability models for the Eurasians Black Vulture population in Southeast Europe, we found that the current population is viable for a period of 100 years. However, high levels of poisoning, food reduction, and increase of wind farms make the population prone to extinction. With no supplementary feeding, the population showed an increased but low extinction risk. Our results suggest that removing and translocating juveniles from the extant population to a historic breeding area would not negatively affect the existing population. We suggest the establishment of more supplementary feeding sites and the reintroduction of the species to former breeding areas, along with the elimination of threats posed by poisoning and wind farms in order to increase the population and enhance the dispersal of the species across its historic range in Southeast Europe.

Abstract

The Eurasian Black Vulture is a globally threatened raptor that in Southeast Europe only occurs in an isolated population in Greece. We examined the population viability for the species under demographic fluctuations and conservation scenarios. The current population showed no possibility of extinction for the next 100 years. However, simulated scenarios showed that the most important factor affecting the viability of the species was medium and high poisoning, leading to 94.8% and 100% probability of extinction, respectively. Furthermore, high reduction of supplementary feeding highlighted an 18.6% extinction possibility. Also, a high increase of wind farms in the area may result in 17.4% extinction possibility. Additionally, the non-establishment of the feeding station in 1987 in the study area would have resulted in an extinction risk of 7%. The species can be translocated to the Olympus National Park by releasing 80 juveniles over 10 years. The implementation of the conservation scenarios concerning the establishment of a supplementary feeding site network, and the reintroduction of the Eurasian Black Vulture in its historic range, along with the elimination of threats posed by poisoning, low food availability, and wind farms would increase the probability of the species persistence and allow the population to become a source for dispersal across Southeast Europe.

Larger size and older age confer competitive advantage: dominance hierarchy within European vulture guild

Competition for limiting natural resources generates complex networks of relationships between individuals, both at the intra- and interspecific levels, establishing hierarchical scenarios among different population groups. Within obligate scavengers, and especially in vultures, the coevolutionary mechanisms operating during carrion exploitation are highly specialized and determined in part by agonistic behavior resulting in intra-guild hierarchies. This paper revisits the behavioral and hierarchical organization within the guild of European vultures, on the basis of their agonistic activities during carrion exploitation. We used a dataset distilled from high-quality videorecordings of competitive interactions among the four European vulture species during feeding events. We found a despotic dominance gradient from the larger species to smaller ones, and from the adults to subadults and juveniles, following an age and body size-based linear pattern. The four studied species, and to some extent age classes, show despotic dominance and organization of their guild exerting differential selection to different parts of the carrion. The abundance of these parts could ultimately condition the level of agonistic interactions. We discuss the behavioral organization and the relationship of hierarchies according to the feeding behavior and prey selection, by comparing with other scavenger guilds.

Development of a QuEChERS method for simultaneous analysis of antibiotics in carcasses for supplementary feeding of endangered vultures

Antibiotics have been beneficial for human and animal health. However, an excessive use in livestock and a deficient management of the carcasses can lead to adverse effects in the scavengers that ingest them, especially in "supplementary feeding sites" (SFS). The aim of this study was to assess the potential risk of exposure to antibiotics for an endangered population of Cinereous vultures (Aegypius monachus) from southeastern Portugal. Hence, a multi-residue method based on QuEChERs was adapted and validated to analyse, in small volumes of tissues, the most frequent antibiotics used in livestock. The method was applied to 87 samples of liver, muscle and kidney from 7 goats and 25 sheep disposed in SFS. According to questionnaires to farmers, the animals had not been treated with antibiotics, but analyses showed residues in 29% of the samples. Antibiotics were more frequent in goats (42.9%) than in sheep (24.2%), and oxytetracycline and trimethoprim were the most common (both 13.8%). Oxytetracycline, the most common antibiotic for livestock in Portugal, showed the highest concentration (1452.68 ng g^-1). To our knowledge, this is the first study of presence of antibiotics in carrion from SFS. The concentrations of antibiotics in carrion do not seem to pose a risk of acute intoxication for adult Cinereous vultures. However, subtle and likely chronic exposure with unknown health consequences may occur, which requires more research. Moreover, the results of this first study can be used in future studies to assess the risk for avian scavengers.

Effects of trophy hunting leftovers on the ranging behaviour of large carnivores: a case study on spotted hyenas

Human-related food resources such as garbage dumps and feeding sites have been shown to significantly influence space use, breeding success and population dynamics in a variety of animal species. In contrast, relatively little is known on the effects of unpredictable sources of food, such as carcasses discarded by hunters, on carnivore species. We evaluated the effect of elephant carcasses, mainly deriving from trophy hunting, on the ranging and feeding behavior of spotted hyenas (Crocuta crocuta) in the Okavango Delta, Botswana. Using data from hyenas monitored before and during carcass availability via GPS radio-collars and camera traps, we investigated changes in ranging and feeding behavior over time. Carcass availability influenced hyenas' ranging behavior for an average of 10-12 days, after which their movements returned to patterns observed before carcass availability. In particular, we observed an increased spatial clustering of locations and reduced speeds (up to 15% less) between successive locations with carcass availability. Consistent feeding at carcasses during the first two weeks was typical, and some individuals fed from elephant carcasses for as long as 50 days. The impact and conservation value of hunting are often assessed based solely on the effects on the hunted species. Our results show that hunting remains can influence other species and suggest that such extra food could have important effects on critical life history processes and ultimately population dynamics. We recommend conservationists and wildlife managers evaluate management strategies and hunting practices regarding carcass disposal in order to incorporate the potential collateral impacts of hunting on non-hunted species in the same community.

An experimental study of vertebrate scavenging behavior in a Northwest European woodland context

Vertebrate scavengers can modify surface deposited human remains which can hinder forensic investigations. The effects of such scavenging vary between species and regions. Published research into the effects of the scavenging of human remains is dominated by work from North America with few studies covering Northwestern Europe. Forensic scientists, investigators, and police search officers in Northwestern Europe are often left questioning on a basic level as to which scavengers are active and how they might affect human remains. This paper presents the results of a field study utilizing deer (Cervus nippon; Capreolus capreolus) as surface deposits observed by motion detection cameras in a British woodland. The most common avian and rodent scavenger species recorded included the buzzard (Buteo buteo), carrion crow (Corvus corone), wood mouse (Apodemus sylvaticus), and gray squirrel (Sciurus carolinensis). The scavenging behaviors observed were affected by seasonality, rates of decomposition, and insect activity. Scavenging by buzzards, unlike carrion crows, was most frequent during fall to winter and prior to insect activity. Overall, avian scavengers modified and scavenged soft tissue. Rodents scavenged both fresh and skeletonized remains with gray squirrels only scavenging skeletal remains. Wood mice were most active in winter and scavenged both soft tissue and bone.

Effect of methodological and ecological approaches on heterogeneity of nest-site selection of a long-lived vulture

The application of scientific-based conservation measures requires that sampling methodologies in studies modelling similar ecological aspects produce comparable results making easier their interpretation. We aimed to show how the choice of different methodological and ecological approaches can affect conclusions in nest-site selection studies along different Palearctic meta-populations of an indicator species. First, a multivariate analysis of the variables affecting nest-site selection in a breeding colony of cinereous vulture (Aegypius monachus) in central Spain was performed. Then, a meta-analysis was applied to establish how methodological and habitat-type factors determine differences and similarities in the results obtained by previous studies that have modelled the forest breeding habitat of the species. Our results revealed patterns in nesting-habitat modelling by the cinereous vulture throughout its whole range: steep and south-facing slopes, great cover of large trees and distance to human activities were generally selected. The ratio and situation of the studied plots (nests/random), the use of plots vs. polygons as sampling units and the number of years of data set determined the variability explained by the model. Moreover, a greater size of the breeding colony implied that ecological and geomorphological variables at landscape level were more influential. Additionally, human activities affected in greater proportion to colonies situated in Mediterranean forests. For the first time, a meta-analysis regarding the factors determining nest-site selection heterogeneity for a single species at broad scale was achieved. It is essential to homogenize and coordinate experimental design in modelling the selection of species' ecological requirements in order to avoid that differences in results among studies would be due to methodological heterogeneity. This would optimize best conservation and management practices for habitats and species in a global context.

Post-mortem volatiles of vertebrate tissue

Volatile emission during vertebrate decay is a complex process that is understood incompletely. It depends on many factors. The main factor is the metabolism of the microbial species present inside and on the vertebrate. In this review, we combine the results from studies on volatile organic compounds (VOCs) detected during this decay process and those on the biochemical formation of VOCs in order to improve our understanding of the decay process. Micro-organisms are the main producers of VOCs, which are by- or end-products of microbial metabolism. Many microbes are already present inside and on a vertebrate, and these can initiate microbial decay. In addition, micro-organisms from the environment colonize the cadaver. The composition of microbial communities is complex, and communities of different species interact with each other in succession. In comparison to the complexity of the decay process, the resulting volatile pattern does show some consistency. Therefore, the possibility of an existence of a time-dependent core volatile pattern, which could be used for applications in areas such as forensics or food science, is discussed. Possible microbial interactions that might alter the process of decay are highlighted.

Can wild ungulate carcasses provide enough biomass to maintain avian scavenger populations? An empirical assessment using a bio-inspired computational model

Background

The reduction in the amount of food available for European avian scavengers as a consequence of restrictive public health policies is a concern for managers and conservationists. Since 2002, the application of several sanitary regulations has limited the availability of feeding resources provided by domestic carcasses, but theoretical studies assessing whether the availability of food resources provided by wild ungulates are enough to cover energetic requirements are lacking.

Methodology/Findings

We assessed food provided by a wild ungulate population in two areas of NE Spain inhabited by three vulture species and developed a P System computational model to assess the effects of the carrion resources provided on their population dynamics. We compared the real population trend with to a hypothetical scenario in which only food provided by wild ungulates was available. Simulation testing of the model suggests that wild ungulates constitute an important food resource in the Pyrenees and the vulture population inhabiting this area could grow if only the food provided by wild ungulates would be available. On the contrary, in the Pre-Pyrenees there is insufficient food to cover the energy requirements of avian scavenger guilds, declining sharply if biomass from domestic animals would not be available.

Conclusions/Significance

Our results suggest that public health legislation can modify scavenger population trends if a large number of domestic ungulate carcasses disappear from the mountains. In this case, food provided by wild ungulates could be not enough and supplementary feeding could be necessary if other alternative food resources are not available (i.e. the reintroduction of wild ungulates), preferably in European Mediterranean scenarios sharing similar and socio-economic conditions where there are low densities of wild ungulates. Managers should anticipate the conservation actions required by assessing food availability and the possible scenarios in order to make the most suitable decisions.