Obligate Scavengers Research Articles

Scavenger assemblages are structured by complex competition and facilitation processes among vultures

AbstractUnderstanding the factors that allow multiple species to coexist and share resources is an outstanding question in community ecology. Animals that share resources tend to use different strategies to decrease potential competition, through morphological adaptations, establishment of hierarchies, behavioral adaptations or spatial or temporal segregation. The main objective of this study was to infer interspecific processes of competition and facilitation through the study of species co‐occurrence patterns in a vertebrate scavenger guild in de Brazilian cerrado. We analyzed patterns of spatial and temporal co‐occurrence between species pairs, both qualitatively and quantitatively, and determined the activity patterns of the different scavenger species. For this purpose, we placed and monitored 11 large (i.e. goat) and 45 small (i.e. chicken) carcasses by camera‐trapping, obtaining a total of 27 448 images. Our results show complex competitive and facilitative relationships among scavenging species in the Brazilian cerrado that are influenced by carcass size and change depending on the spatial and temporal scale at which they are analyzed. The scavenger assemblages that consumed large and small carcasses were different, evidencing resource partitioning between obligate and facultative scavengers. Furthermore, as an alternative to reduce competition levels, most species showed differences in their scavenging patterns, in addition to a strong temporal segregation during carcass consumption. Regarding New World vultures, our results suggest a strong interference competition between species with clear differences in their ecological traits (e.g. size, social behavior). However, we also found evidence of facilitation processes between vulture species in the location and access to the interior of the carcasses. Our findings highlight the role of obligate scavengers both in competition and facilitation processes in this vertebrate scavenger community. Future research should focus on investigating which species play the most important role in the structure and dynamics of this community, also considering intraspecific and behavioral patterns.

Scavenging in changing environments: woody encroachment shapes rural scavenger assemblages in Europe

Rural abandonment and subsequent vegetation regeneration (‘passive rewilding') are expected to increase worldwide, producing cascades of dynamic socioeconomic, landscape and biological changes. Although landscape characteristics strongly influence the structure and functioning of scavengers, little is known about the ecological consequences of passive rewilding due to woody encroachment (i.e.‘landscape closure') on scavenging assemblages. We investigated differences in ‘scavenger assemblage composition' (species richness and abundances) and ‘scavenging efficiency' (scavenging frequency, detection and consumption times and consumption rates) in a mountain agroecosystem (Pyrenees) undergoing passive rewilding. We monitored 178 carcasses in three landscapes: ‘open', ‘shrubland' and ‘forest', and evaluated the effects of landscape type on ‘scavenger assemblage composition' and ‘scavenging efficiency' at the community and species levels, while accounting for the influences of carcass size, type and placement time. We also examined whether the locally most abundant and efficient scavenger (i.e. the griffon vultureGyps fulvus) affects scavenging patterns. We found that landscape type was the main factor governing scavenging dynamics. Overall and average scavenger richness were similar in open and shrubland landscapes, while forests contained the lowest number of scavengers, mainly comprising mammals. Unlike mammals, avian scavenging frequency decreased as vegetation cover increased, especially for obligate scavengers (i.e. vultures). Scavenger abundances were highest in open landscapes, and carcasses were detected and consumed more rapidly in these landscapes. Carcass size did not influence detection and consumption times, although it did affect average scavenger richness, abundances and consumption rates. Consumption rates were higher in open landscapes and were strongly associated with the presence of griffon vultures. Interestingly, we found that griffon vultures influenced scavenging dynamics via facilitation processes. However, woody encroachment could reduce the scavenging role of this species, while favoring mammalian facultative scavengers. Finally, our findings highlight the pivotal role of griffon vultures, mediated by landscape characteristics, in reducing carcass persistence.

A new look at an old Australian raptor places Taphaetus lacertosus de Vis 1905 in the Old World vultures (Accipitridae: Aegypiinae).

The Australian Pleistocene fossil record of the Accipitridae (hawks, eagles and Old World vultures) is sparse and poorly known. Only two extinct confirmed accipitrid species have been described for this time period; both have received little investigation since their description. One is Taphaetus lacertosus de Vis, 1905, described from a distal humerus and a quadrate from north-eastern South Australia. While this species was verified as an accipitrid in subsequent studies, its more precise taxonomic affinities have remained conjectural. In this study, a new analysis incorporating newly referred material and phylogenetic analyses using a wide range of accipitriforms reveals that the lectotype humerus of T. lacertosus is an Old World vulture in the subfamily Aegypiinae. The associated quadrate, one of two original syntypes from which de Vis named this species, is of an indeterminate species of ardeid. We erect the novel genus Cryptogyps, to accommodate the species lacertosus, as it cannot be placed in Taphaetus de Vis, 1891, because the type species of this genus, Uroaetus brachialis de Vis, 1889, was transferred back to the genus Uroaetus, a synonym of Aquila Brisson, by de Vis in 1905. Further, U. brachialis is now considered a synonym of Aquila audax (Latham, 1801). Moreover, Taphaetus de Vis, 1891 is a senior homonym of Taphaetus de Vis, 1905, type species Taphaetus lacertosus de Vis, 1905, making the 1905 version of the genus unavailable. Newly referred fossils from Wellington Caves (NSW) and the Nullarbor Plains (WA) reveal this taxon had a wide geographical range across Pleistocene Australia. The referred tarsometatarsus lacks hyper-developed trochleae, indicating that Cryptogyps lacertosus (de Vis, 1905) comb. nov., was probably a scavenger like other aegypiines. Identification of Cryptogyps lacertosus as an aegypiine significantly expands the palaeogeographical range of the Old World vultures, hitherto unknown in Australia. The avian guild of large, obligate scavenging birds of prey, is currently absent in the modern Australian biota, but its former presence is not surprising given the megafauna-rich communities of the Pleistocene.

Are white-rumped vultures (Gyps bengalensis) scavengers or predators at a vulture safe feeding site of Nepal?

Abstract. Gautan R, Baral N, Sharma HP. 2022. Are white-rumped vultures (Gyps bengalensis) scavengers or predators at a vulture safe feeding site of Nepal?. Biodiversitas 23: 3808-3812. Establishing safe feeding sites has been promoted as a strategy to conserve wild vultures following the population crash in South Asia due to the contamination of natural food by veterinary diclofenac. Several feeding sites have been established in the region, including Nepal and it is important to evaluate their effectiveness. One aspect that is not clear yet is whether such safe feeding sites change the behaviors of wild vultures in South Asia. Here, we report incidents of White-rumped Vultures Gyps bengalensis attacking live animals at the Vulture Safe Feeding Site in Ghachok village in central Nepal. Even though a carcass was available nearby to feed upon, three White-rumped Vultures attacked an adult cow and a calf at the feeding site. The vultures’ attack served as an ancillary cause of the calf’s death in this case. These two incidents of vultures’ attacking live animals at the safe feeding site may allude to changing behaviors and cast doubt on their status of being classified as an obligate scavengers. The findings suggest alteration of vulture behaviors at the safe feeding site. Further research is needed to test the hypothesis of vulture behavior change.

Eurasian griffon vultures carry widespread antimicrobial resistant Salmonella and Campylobacter of public health concern

The global emergence of antimicrobial-resistant (AMR) strains of Salmonella and Campylobacter is a serious public health concern. Both bacteria are leading causes of human gastrointestinal foodborne infections and the two most reported zoonoses in the European Union. By feeding on livestock carcasses, especially from intensive farming, as well as on landfill sites, obligate avian scavengers can become infected with zoonotic pathogens and AMR strains, and can be considered large-scale sentinels of the environmental burden. In this study, we assessed the occurrence and AMR of Salmonella spp. and Campylobacter spp. in 218 Eurasian griffon vultures (Gyps fulvus) captured in north-eastern Spain. We isolated Salmonella from 8.1 % of individuals and Campylobacter lari from 4.7 %. Among the 10 different Salmonella serovars found, monophasic S. Typhimurium was the most frequent. Genotyping analysis revealed same strains of monophasic S. Typhimurium shared by gulls, livestock and humans. Isolates from both bacterial species presented AMR to important antimicrobials (tetracyclines, fluoroquinolones and β-lactams). In conclusion, this study shows that Eurasian griffon vultures in north-eastern Spain are carriers of widespread AMR zoonotic Salmonella and Campylobacter. More comprehensive analyses are still needed to understand the potential risk of spill-over from those wild birds to humans.

Vertebrate and invertebrate competition for carrion in human‐impacted environments depends on abiotic factors

AbstractHuman altered landscapes have caused declines in the diversity of wildlife where behaviorally plastic species (i.e., mesocarnivores and invasive species) tend to monopolize these areas and consume predictable and readily accessible food resources, such as human food waste and carrion. Increased consumption of carrion by vertebrates and invasive invertebrate species can alter population dynamics of native necrophagous insects relying on these resources. We tested the hypothesis that vertebrate scavengers and invasive species reduce blow fly (1) ability to use carrion and (2) reproduction in human‐impacted environments in central Texas, USA, with season, habitat (field and wooded landscapes), and carrion type (species of carrion and coat color) acting synergistically. Vertebrate scavengers in this habitat, of which 75% of the documented species were mesocarnivores and obligate scavengers, consumed 100% of carrion during the winter and 62% during summer despite having low species richness (2–5 species). Of the remaining carcasses available for arthropod activity during summer, the invasive red imported fire ant, Solenopsis invicta (Hymenoptera: Formicidae), monopolized 34%, and blow flies (e.g., Lucilia eximia and Chrysomya rufifacies [Diptera: Calliphoridae]) were only able to colonize 25%. Approximately 90% of carrion that was utilized by blow flies was co‐colonized by fire ants, and subsequent production of adult blow flies experienced up to a ninefold reduction in production compared with carcasses that were not scavenged by vertebrates or fire ants. Our results demonstrate oviposition resources used by blow flies in environments altered by human activity are reduced significantly by vertebrate scavengers and an invasive ant species. Future research should determine whether competitive interactions between vertebrate and invasive ant competitors for access to carrion resources have population‐level impacts to blow flies in human‐mediated ecosystems, or whether blow flies are able to shift to other resources to maintain sustainable populations and continue providing ecosystem services, such as pollination.

Mitigating GHG emissions: A global ecosystem service provided by obligate scavenging birds

Dead animals release greenhouse gases to the atmosphere through natural decomposition or because they have to be processed by disposal methods such as composting or rendering. Obligate scavenging birds (vultures) consume dead animals and are among the most efficient terrestrial scavengers. They may therefore contribute to a considerable reduction in sources of greenhouse gases. Here, we quantify the global contribution of vultures in reducing greenhouse gas emissions by consuming organic material. First, we evaluated a scenario where all the dead animals that can be consumed by vultures every year have to be disposed of by composting, anaerobic decomposition (e.g., burial), anaerobic digestion or rendering. Second, we assessed a scenario in which dead animals are left to decompose in the environment. Current vulture populations (∼134–140 million individuals) may reduce emissions of 3.03–60.70 Tg CO2 eq. per year, depending on the disposal method implemented, without considering carcass transport to disposal plants. Alternatively, they may reduce emissions of 13.02 Tg CO2 per year if dead animals remain in the environment. Over recent years a decline in vulture populations worldwide has led to a decrease of a 30 % in their capacity to mitigate greenhouse gases emissions. A few abundant vulture species reduce almost 98 % of the maximum emissions potentially removed worldwide by all extant vulture species over one year. This ecosystem service contributed by vultures to humans and nature cannot easily be replaced by other species, including humans. Moreover, supplanting this contribution with alternative carcass disposal methods is expensive and harmful to the environment due to emissions generated in the process. Our results highlight an important service that vultures provide worldwide, which is relevant in the current context of global warming.

Old World Vultures Reflect Effects of Environmental Pollutants Through Human Encroachment.

African wildlife face challenges from many stressors including current and emerging contaminants, habitat and resource loss, poaching, intentional and unintentional poisoning, and climate-related environmental change. The plight of African vultures exemplifies these challenges due to environmental contaminants and other stressors acting on individuals and populations that are already threatened or endangered. Many of these threats emanate from increasing human population size and settlement density, habitat loss from changing land use for agriculture, residential areas, and industry, and climate-related changes in resource availability. Environmental chemicals that are hazardous include legacy chemicals, emerging chemicals of concern, and high-volume-use chemicals that are employed as weed killers and in other agricultural applications. Furthermore, there are differences in risk for species living in close proximity to humans or in areas affected by habitat loss, climate, and industry. Monitoring programs are essential to track the status of nesting pairs, offspring survival, longevity, and lifetime productivity. This is important for long-lived birds, such as vultures, that may be especially vulnerable to chronic exposure to chemicals as obligate scavengers. Furthermore, their position in the food web may increase risk due to biomagnification of chemicals. We review the primary chemical hazards to Old World vultures and the interacting stressors affecting these and other birds. Habitat is a major consideration for vultures, with tree-nesters and cliff-nesters potentially experiencing different risks of exposure to environmental chemicals. The present review provides information from long-term monitoring programs and discusses a range of these threats and their effects on vulture populations. Environ Toxicol Chem 2022;41:1586-1603. © 2022 SETAC.

A multivariate analysis of veterinary preferences for NSAIDs in Nigeria

Vultures are obligate scavengers known to accomplish incredible ecological feats unmatched by other birds of prey. However, the role of animal health specialists in vulture conservation is under-emphasized in Nigeria, despite vulture’s explicit dependence on the carcasses of domesticated livestock under the regime of veterinary caregivers. In our research, we evaluate the perception of animal health specialists on vultures and the veterinary use of Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) for livestock treatment in the study location. Data collated from a semi-structured questionnaire were analyzed using correspondence analysis to produce a simple visual display of the complex count data matrix. The prevalence of 10 NSAIDs was analyzed along 3 column attributes namely; Not-in-Use (NU), Rarely-Used (RU), and Frequently-Used (FU). The NSAIDs were statistically under the significant influence by the column attributes at 0.05 alpha-level (X2≤64.35;P<0.0000), with the principal axis accounting for 74.33% of the total inertia. Ketoprofen aggregated close to the centroid, while diclofenac and Ibuprofen were strongly associated with FU. Aspirin and Indomethacin inclined significantly towards the NU and RU axes, respectively. Despite the global consensus on the toxic influence of some NSAIDs on the vultures, about 90% of the research respondents were unaware of the hazards toxic NSAIDs are likely to impose on the vultures. Diclofenac has received less than enough focus, despite its extended use for livestock treatment in Nigeria. Future conservation interventions should therefore be designed to involve, engage and educate the veterinary practitioners in Nigeria.

Local ecological knowledge and education drive farmers' contrasting perceptions of scavengers and their function in Nepal

Abstract There is a long‐standing relationship between humans and vertebrate scavengers, as scavengers' contributions take on regulating (e.g. nutrient recycling and disease control), material (e.g. competition and livestock depredation) and non‐material (e.g. sky burials and ecotourism) roles in society. A social–ecological approach to studying biodiversity is increasingly needed, since the inclusion of local perceptions and knowledge has proven critical for effective conservation programs and ecosystem management. We examine livestock farmers' perceptions and knowledge related to vertebrate scavengers in the highly diverse Chitwan‐Annapurna Landscape (Nepal) and assess the socio‐demographic traits that influence their perceived value of scavengers' ecosystem service provisioning (ESP) index, and function via scavenging services (SS). Farmers' perceptions of functional importance (SS) showed species‐specific gradation, unlike ESP, where only avian scavengers were perceived as beneficial. Our results show that the perception of scavenging as a beneficial ecosystem service and its importance as a biological function are decoupled for facultative scavengers and coupled for obligate scavengers. Relatedly, we identify that affluence‐related traits drove positive perceptions of ESP, and local ecological knowledge‐based traits were linked to increased knowledge of function via SS. Thus, this increased awareness of functional importance based on close contact with nature does not guarantee positive valuations of scavengers' contributions, whereas formal education did influence positive perceptions despite reduced awareness of function. Additionally, our findings suggest that existing environmental education measures are targeting the right groups, as these respondents coincide with lower favourability of scavengers' ecosystem services, but may be unable to overcome existing human–wildlife conflict. For the first time in South Asia, we survey relevant community stakeholder's attitudes towards an entire scavenging guild and their associated benefits, detriments and functional importance. Our study illustrates the varied perceptions that exist for different scavenger species and closely examines a wide‐ranging set of socio‐demographic traits that show disparate influences on farmers' knowledge of ecological function and perceived ecosystem service benefits. Crucially, these findings can guide conservation and management priorities by considering the differences in public perception and awareness of scavenging, as well as the interpretation of nature's contribution to people. Read the free Plain Language Summary for this article on the Journal blog.

Mass mortality events and declining obligate scavengers in the Anthropocene: Social feeders may be critical

A pervasive but understudied global change is occurring in the Anthropocene. Wildlife mass mortality events (MMEs) are increasing in frequency causing the abrupt entry of unusually large amounts of carrion into ecosystems, while most vertebrate obligate scavenger species are declining. We hypothesized that behavioral plasticity could still allow obligate-vertebrate scavengers to maintain carrion recycling with increasing carrion biomass as a result of relaxed competition, and that consumption is likely to be driven by those species less behaviorally constrained. We designed an experiment by establishing plots with increasing carrion biomass. The lowest carrion biomass represented a normal level of carrion with a single carcass, with each subsequent level of carrion biomass roughly doubling until reaching a carrion density similar to a recent MME. We monitored behavior of two obligate scavenger species: a social feeder (i.e., black vulture, Coragyps atratus) and a relatively solitary feeder (i.e., turkey vulture, Cathartes aura). In support of our hypothesis, group size and number of individuals feeding increased at the highest carrion biomass level for the more social feeder, while the less social increased solely the number of individuals feeding. Likewise, activity pattern overlap between the species increased with carrion biomass likely because both spent more of the day consuming larger carrion inputs. The effects of these behavioral changes resulted in an increase in estimated consumption with carrion biomass, which was primarily driven by the more social species. Our results indicate that vulture behavioral plasticity may be critical to maintain carrion recycling services in the Anthropocene.

More than just meat: Carcass decomposition shapes trophic identities in a terrestrial vertebrate

Abstract Most food web models fail to account for the full complexity of interactions within a community, particularly where microbes are involved. Carcasses are microbe‐rich resources and may represent a common nexus for the macrobiome and microbiome, effectively uniting autotrophs, consumers, predators and microbiota. We evaluated the role of carcasses as multitrophic resources and explored dietary partitioning for a sexually dimorphic obligate scavenger known for its hierarchical social system. This study was set in a well‐studied community of camelids Vicugna, Lama guanicoe, pumas Puma concolor and Andean condors Vultur gryphus in the Andes. We hypothesized that condors, by feeding on trophically distinct dietary substrates within any given carcass, would have highly variable trophic position (TP) values. Furthermore, we expected that the microbial consumers within the carcass would inflate TP values in both, the carrion and the condors. Thus, we expected that the trophic heterogeneity within a carcass could facilitate sex‐based dietary partitioning in condors. We used a multifaceted approach to assess the foraging of Andean condors, using regurgitated pellet and bulk isotopic analyses, and also quantified the TP of the entire community of graminoids, camelids, camelid carrion, pumas, and female and male condors employing compound‐specific stable isotopes analysis of amino acids. Our analysis of condor pellets and bulk isotopes revealed non‐trivial plant consumption, close to 10% of condor diet. Isotope analysis of amino acids revealed that condors had highly variable TPs (2.9 ± 0.3) compared to pumas (3.0 ± 0.0) and camelids (2.0 ± 0.1), likely representing ‘trophic omnivory’, wherein the condors consume plants (TP = 1.0 ± 0.1) and microbe‐colonized carrion (2.3 ± 0.1). Female condors exhibited a TP (2.8 ± 0.2) lower than strict carnivory, suggesting that they consume more plant biomass in a carcass, while males (TP = 3.1 ± 0.3) are likely consuming more of the microbe‐rich animal tissue. Our study highlights that carcasses represent a trophically heterogeneous resource and that vertebrate scavengers can feed across trophic groups within the carcass, from autotrophs to secondary consumers, and from both the macrobiome and microbiome. Thus, integration of microbes in macroecological contexts can help to resolve trophic identity, and better characterize the importance of microbes in detritivorous and omnivorous species. Read the free Plain Language Summary for this article on the Journal blog.

Trophic interactions at avian carcasses: Do scavengers feed on vulture carrion?

Scavenging is a pervasive foraging strategy among vertebrates, yet researchers have only recently begun to reveal the complex implications of scavenging dynamics. Scavenging studies have predominantly used lower trophic level (i.e., herbivore) species as carrion bait, and the few studies that have used higher trophic level (i.e., carnivore) carrion have found these carcass types are generally avoided by vertebrates or scavenged by fewer species than similarly sized herbivore carcasses. No studies have assessed the fate of carcasses of obligate scavengers. To investigate potential differences in scavenging dynamics among avian carrion representing different guilds and trophic levels, we conducted scavenging trials using 20 replicates of two obligate scavenger species (i.e. black vulture, Coragyps atratus; turkey vulture, Cathartes aura) and two lower trophic level species, chicken (Gallus gallus domesticus), and mallard (Anas platyrhynchos). Carcass trials were conducted at the Savannah River Site, SC, USA, and monitored with remote cameras. We hypothesized carcasses of vultures would persist longer and have a distinct scavenging community compared to lower trophic level carcasses (mallard and chicken). As expected, turkey and black vulture carcasses persisted in the environment longer, were less likely to be entirely consumed by vertebrate scavengers, and had a different scavenging community than mallard and chicken carcasses. These results contribute to the growing body of evidence suggesting higher trophic level carrion is exploited differently by vertebrate scavengers. Our findings suggest nutrients derived from vulture carcasses are likely largely reincorporated into lower trophic levels.

A Global Review of Causes of Morbidity and Mortality in Free-Living Vultures.

Vulture species worldwide play a key role in ecosystems as obligate scavengers, and several populations have had precipitous declines. Research on vulture health is critical to conservation efforts including free-living vultures and captive breeding programs, but is limited to date. In this systematic review, we determined the reported causes of free-living vulture species morbidity and mortality worldwide. The most commonly reported cause of mortality was from toxins (60%), especially lead and pesticides, followed by traumatic injury (49%), including collisions with urban infrastructure and gunshot. Neglected areas of research in free-living vulture health include infectious diseases (16%), endocrine and nutritional disorders (6%), and neoplasia (< 1%). Almost half of the studies included in the review were conducted in either Spain or the USA, with a paucity of studies conducted in South America and sub-Saharan Africa. The highest number of studies was on Griffon (Gyps fulvus) (24%) and Egyptian vultures (Neophron percnopterus) (19%), while half of all vulture species had five or fewer studies. Future investigations on free-living vulture health should focus on neglected areas of research, such as infectious diseases, and areas with gaps in the current literature, such as South America, sub-Saharan Africa, and under-studied vulture species.

Competition between obligate and facultative scavengers and infection: vulture-jackal-anthrax dynamics in Etosha National Park

Different species of scavengers may compete for the same food in an ecosystem. This case study considers the competition between jackals and vultures in Etosha National Park in Namibia. While jackals are facultative scavengers, able to hunt for food if necessary, vultures are obligate scavengers wholly dependent on carcasses of animals like zebras for persistence. This competition may be further affected by outbreaks of infections such as anthrax, which temporarily increase the number of carcasses but lower the zebra population, acting in some ways as a third competitor. We use a dynamical system to model the interplay between competition dynamics and infection dynamics, and how it is affected by the nature of the competition: indirect (exploitative) or direct (interference). A bifurcation analysis using reproduction numbers shows how vultures’ survival may depend on their direct competitive edge in reaching carcasses faster than jackals, and how the infection and the scavengers complicate each other’s persistence. Vultures’ interference causes a backward bifurcation which enables them to persist. One possible outcome is a “strange bedfellows” bistability in which anthrax and vultures persist only together, not apart, despite being competitors.

Effects of red imported fire ant (Solenopsis invicta) control on carrion use by vertebrate scavengers

Carrion is an important resource, and competition for carrion by microbial, invertebrate, and vertebrate scavenging communities is great. In particular, carrion is important to facultative and obligate vertebrate scavengers globally, and these species provide an irreplaceable ecological service by efficiently removing carcasses, which potentially harbor pathogens, from the environment. Although vertebrates efficiently acquire carcasses, they compete intensively with invertebrate and microbial communities, especially during warmer months when invertebrate and microbial activity peaks. The presence of invasive invertebrates may further exacerbate competition among scavenging groups; however, little is known about how invasive invertebrates can influence invertebrate scavenger dynamics and ultimately competition with vertebrate scavengers. The red imported fire ant (Solenopsis invicta; RIFA) is an invasive species of particular interest in North America, as it is a dominant predator and decomposer throughout much their range. We hypothesized that in areas where abundant, RIFA can outcompete vertebrates for carrion resources, altering nutrient cycling and food web dynamics. We tested this hypothesis by experimentally excluding RIFA from rabbit carcasses and found strong seasonal effects in our data; however, surprisingly, we found no effect of RIFA control on vertebrate scavenging efficiency, rates of carcass detection, carcass persistence, or the richness of local scavengers. Rather, we observed a highly efficient vertebrate scavenging community that assimilated 87.4% of carcasses during our study. This high rate of vertebrate scavenging efficiency was maintained in both control (93.0%) and RIFA treatment (81.8%) sites, suggesting presence of abundant RIFA populations did not limit vertebrate acquisition of carrion. Future research should focus on the interactions of RIFA with the remaining invertebrate scavenging community to further investigate whether RIFA impact the assimilation of carrion resources within invertebrate communities.

Emerging Pathogenic Gammaproteobacteria Wohlfahrtiimonas chitiniclastica and Ignatzschineria Species in a Turkey Vulture (Cathartes aura).

New World vultures, such as turkey vultures (Cathartes aura), are obligate scavengers with large geographic ranges. In a preliminary characterization of the turkey vulture (TV) gastrointestinal microbiome in Southern California, we identified 2 recently described emerging bacterial pathogens not previously known to be associated with this avian species. High-throughput sequencing of broad-range 16S rRNA gene amplicons revealed sequences from TV cloacal swabs that were related closest to Wohlfahrtiimonas chitiniclastica and Ignatzschineria species, both Gammaproteobacteria considered by the United States Centers for Disease Control and Prevention as emerging zoonotic pathogens. None of these bacterial sequence types have been previously identified from samples obtained from the turkey vulture gastrointestinal microbiome. With the use of bioinformatics workflows previously established by our research group, we designed specific and sensitive polymerase chain reaction primer sets that represent novel diagnostic assays for the genera Wohlfahrtiimonas and Ignatzschineria. These primer sets were validated by Sanger sequence confirmation from complex TV samples. Because the genera Wohlfahrtiimonas and Ignatzschineria are both known to have dipteran hosts, the molecular diagnostic tools we present here should be useful for better understanding the role of flies, vultures, and other scavengers in the ecology and epidemiology of the genera Wohlfahrtiimonas and Ignatzschineria from a One Health perspective.

Habitat preferences of the Eurasian Griffon Vulture (Gyps fulvus) in Bulgaria to support species management

The Eurasian Griffon Vulture (Gyps fulvus) is a large scavenger with a population ranging between Portugal and India. The species is an obligate scavenger with a narrow ecological niche and is therefore particularly dependent on, and limited by habitat availability. The study aimed, for the first time in Eastern Europe, to identify the habitat preferences of the Griffon Vulture at landscape and cliff scales. We used long-term monitoring data between 1987–2018 to analyze habitat preferences of the natal Griffon Vulture population in the Eastern Rhodope Mountains, Bulgaria. We employed single explanatory variable tests to reveal the species habitat preferences at two spatial scales. The results revealed Griffon Vultures’ high preferences towards rocky habitats at the landscape level. At a cliff scale, the height and length of the cliff, the distance to the nearest conspecific colony and the distance to the nearest feeding site were the best predictors for the species habitat preferences. We stress the importance of these findings considering the current status of the species within the region. Our results are useful to support the future conservation of the Griffon Vulture population in Bulgaria and provide a starting point for future research in the Balkans and Eastern Europe.

Functional traits driving species role in the structure of terrestrial vertebrate scavenger networks.

Species assemblages often have a non-random nested organization, which in vertebrate scavenger (carrion-consuming) assemblages is thought to be driven by facilitation in competitive environments. However, not all scavenger species play the same role in maintaining assemblage structure, as some species are obligate scavengers (i.e., vultures) and others are facultative, scavenging opportunistically. We used a database with 177 vertebrate scavenger species from 53 assemblages in 22 countries across five continents to identify which functional traits of scavenger species are key to maintaining the scavenging network structure. We used network analyses to relate ten traits hypothesized to affect assemblage structure with the "role" of each species in the scavenging assemblage in which it appeared. We characterized the role of a species in terms of both the proportion of monitored carcasses on which that species scavenged, or scavenging breadth (i.e., the species "normalized degree"), and the role of that species in the nested structure of the assemblage (i.e., the species "paired nested degree"), therefore identifying possible facilitative interactions among species. We found that species with high olfactory acuity, social foragers, and obligate scavengers had the widest scavenging breadth. We also found that social foragers had a large paired nested degree in scavenger assemblages, probably because their presence is easier to detect by other species to signal carcass occurrence. Our study highlights differences in the functional roles of scavenger species and can be used to identify key species for targeted conservation to maintain the ecological function of scavenger assemblages.

Diurnal and nocturnal scavenger communities differ at two shallow-water depths in an Irish marine lough

We report on still/video photographic studies in 2018/9 of diurnal and nocturnal benthic scavenging on carrion in shallow water (2 m and 12 m depths) within Lough Hyne (a biodiverse Irish sea lough) using natural light during replicated 6 h daytime deployments and dim red light (630 nm) during 6 h deployments at night. In 2018 at 2 m depth in the North Basin, bait was present throughout day-time deployments, showing little evidence of scavenging; scavenger species' richness and abundance were low. At night, baits disappeared or were skeletonised; they were scavenged by a significantly more abundant and species-rich scavenger guild. At 12 m depth in the same basin, baits were removed or skeletonised during day and night. This confirmed our hypothesis that scavengers avoid well-lit very shallow water during the day, probably to avoid predation. Multivariate analysis of 2018/19 still photo data (12 m depth) revealed pronounced and statistically significant separate clustering of day, night and basin abundance/species data, although overall species' richness values did not differ significantly. These analyses together reflected differences in species’ compositions associated with contrasting sediments, flow regimes and night/day. Nephrops norvegicus, Pagurus bernhardus and Crangon crangon were only found in the low flow rate North Basin; Homarus gammarus, Trigla sp., Callionymus lyra, Agonus, Tritia reticulata and Marthasterias glacialis were only found in the high flow rate South Basin. Most scavenger species foraged in both day and night (though in different proportions). However, prawns (Palaemon serratus) only appeared at night. Small mobile scavenging fish, small crabs and prawns arrived at baits within seconds to minutes, as did locally-abundant slow movers (e.g. anemones (Anthopleura ballii), whelks (T. reticulata)). These times are shorter than recorded in earlier studies in deeper water. Larger crustaceans (e.g. Cancer pagurus, H. gammarus) took tens of minutes to hours before arrival; similar times have previously been recorded in deeper water. Large crustacean scavengers (C. pagurus, Maja squinado, H. gammarus) took substantial quantities of bait during long feeding bouts, but catsharks (Scyliorhinus canicula) often took similar quantities in a few seconds. All of the dominant scavenger species are broad-spectrum omnivores; only one obligate scavenger species (Tritia reticulata) was present (only in South Basin) and consumed negligible quantities of bait.