Comunidades de carroñeros en el Neotrópico: patrones ecológicos y comportamentales

Programa de Doctorado Medio Ambiente y SostenibilidadUnderstanding the processes that allow several species depending on the same resource to coexist are fundamental in the maintenance of biodiversity, ultimately affecting ecosystem functions, and being a key issue in community ecology. The non-random structure of natural communities is driven by multiple biological, ecological, and evolutionary forces, and can be described by habitat utilization, resource availability, and the activity and interactions of the organisms that compose them. These interactions can be antagonistic (e.g., competition) or facilitative (e.g., mutualistic plant-pollinator). However, not all species within a network play the same ecological role or perform it with the same importance, since they will have different ecological traits. Competition between species that coexist within the same guild is particularly interesting because the similarity of their ecological niches increases competition strength. However, positive co-occurrence patterns within guilds may also emerge from facilitation processes, reducing competition and playing an important role in community structure. Carrion is an ephemeral and unpredictable resource in time and space. These characteristics allow a multitude of species to feed on the resource, even forming temporary mixed aggregations with high levels of competitive and facilitative interactions. Such dynamics make scavenger systems an ideal model for studying positive and negative processes across scales using diverse methodological approaches. This thesis focuses on describing the ecological factors and behavioral patterns that govern a scavenger community in the Neotropics, by the placement and monitoring of two carcass sizes in the field by using camera-trapping. Specifically this thesis aims to assess the following objectives: describe for the first time the scavenger community and identify the factors affecting scavenging efficiency in the Brazilian Cerrado (Chapter 3); infer interspecific processes of competition and facilitation through the study of species co-occurrence patterns in this Neotropical guild (Chapter 4); analyze possible information transmission cascades within this Neotropical scavenger community (Chapter 5); and determine factors driving temporal dynamics of scavenging successions (Chapter 6). In Chapter 3, we describe the vertebrate scavenger community composition of the Brazilian Cerrado, a biodiversity hotspot. In addition, we analyzed the effects of vegetation cover, time of carcass placement and carcass weight, on different variables related to community composition and efficiency. We documented a total of 19 vertebrate scavenging species, four species of vultures and 15 facultative scavengers. Carcass size was the most important factor affecting the scavenger assemblage and consumption patterns, while we did not find an effect of habitat or timing of carrion placement on scavenging patterns. The results show a highly diverse and efficient scavenging vertebrate community in the Brazilian Cerrado, and the need to preserve them in the face of the significant habitat transformations suffered by this biodiversity hotspot. In Chapter 4, we analyzed patterns of spatial and temporal co-occurrence between species, both qualitatively and quantitatively, and determined the activity patterns of the different scavenger species. 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. To clarify the processes that result in associations between vulture species with different foraging efficiencies, in Chapter 5, we apply a survival-modelling strategy to determine the transmission of social information among different species during carrion location. The use of different senses (smell and sight) within this guild facilitates carcass location through the transmission of social information between species with different carrion foraging efficiencies. Vultures with a highly developed sense of smell play a key role in this process, as they are the first ones to arrive at the carcasses and their presence seems to serve as a visual cue for other species to locate the resource. Our study supports the local enhancement hypothesis within scavengers, whereby individuals locate carcasses by following foraging heterospecifics, also suggesting the importance of the sense of smell in the maintenance of the community structure. In Chapter 6, we perform the first in-depth analysis of the factors driving temporal dynamics of scavenging successions by using interspecific aggressions as a behavioral proxy of competition intensity. The results show that resource availability shapes behavioral interactions between species. Furthermore, facilitation was related to moments of higher tolerance (i.e., lower aggressiveness), thus reducing competition intensity and affecting community structure and dynamics. Our study highlights the importance of monitoring behaviors that are directly transferable to community function (e.g., those related to foraging and resource consumption), also considering the dynamics of succession over time. This novel framework evidences complex ephemeral successional processes characterized by a fluctuation in facilitation and competition intensity during the consumption of an unpredictable resource linked to key ecosystem processes. Finally, the general discussion (Chapter 7) addresses the implications of the findings obtained in the previous chapters, its contribution to the study of communities from a general perspective, and for scavenger assemblages, including conservation implications. Furthermore, we examine the limitations identified and outline avenues for future research aimed at comprehending the determinants of the balance between positive and negative processes among coexisting species.Comprender los procesos que permiten la coexistencia de varias especies que dependen de un mismo recurso es fundamental para el mantenimiento de la biodiversidad, lo que en última instancia afecta a las funciones ecosistémicas, siendo una cuestión clave en la ecología de comunidades. La estructura no aleatoria de las comunidades está impulsada por múltiples fuerzas biológicas, ecológicas y evolutivas, pudiendo describirse mediante la utilización del hábitat, la disponibilidad de recursos y la actividad e interacciones de los organismos que las componen. Estas interacciones pueden ser antagónicas (por ejemplo, competencia) o positivas (por ejemplo, mutualismo planta-polinizador). Sin embargo, no todas las especies de una red desempeñan el mismo papel ecológico, ni lo hacen con la misma importancia, ya que pueden tener rasgos ecológicos diferentes. La competencia entre especies que coexisten dentro del mismo gremio es especialmente interesante porque cuanto más similares son sus nichos ecológicos mayor es la competencia. Sin embargo, los patrones positivos de co-ocurrencia dentro de los gremios también pueden ser debidos a procesos de facilitación, reduciendo la competencia y desempeñando un papel fundamental en la estructura de la comunidad. La carroña es un recurso efímero e impredecible en el tiempo y el espacio. Estas características permiten que multitud de especies se alimenten de este recurso, llegando a formar agregaciones mixtas temporales con altos niveles de interacciones competitivas y de facilitación. Estas dinámicas hacen de los sistemas carroñeros un modelo ideal para estudiar procesos positivos y negativos a distintas escalas, y utilizando diversos enfoques metodológicos. Esta tesis se centra en describir los factores ecológicos y patrones de comportamiento que gobiernan una comunidad de carroñeros en el Neotrópico, mediante la colocación y seguimiento de carroñas de dos tamaños en el campo mediate fototrampeo. En concreto, esta tesis pretende evaluar los siguientes objetivos: describir por primera vez la comunidad de carroñeros e identificar los factores que afectan a la eficiencia carroñera en el Cerrado brasileño (Capítulo 3); inferir procesos interespecíficos de competencia y facilitación a través del estudio de los patrones de co-ocurrencia de especies en este gremio neotropical (Capítulo 4); analizar posibles cascadas de transmisión de información dentro de esta comunidad de carroñeros (Capítulo 5); y determinar los factores que impulsan la dinámica temporal de las sucesiones carroñeras (Capítulo 6). En el Capítulo 3 describimos la composición de la comunidad de vertebrados carroñeros del Cerrado brasileño, un punto caliente de biodiversidad. Además, analizamos los efectos de la cobertura vegetal, el momento de colocación de la carroña y su peso, sobre diferentes variables relacionadas con la composición y eficiencia de la comunidad. Documentamos un total de 19 especies de vertebrados carroñeros, cuatro especies de buitres y 15 carroñeros facultativos. El tamaño de las carroñas fue el factor más importante que afectó a la composición de la comunidad de carroñeros y a los patrones de consumo, mientras que no se observó ningún efecto del hábitat o del momento de la deposición de la carroña. Los resultados muestran una comunidad de vertebrados carroñeros altamente diversa y eficiente en el Cerrado brasileño, y la necesidad de preservarlos frente a las significativas transformaciones del hábitat que se están dando en este punto caliente de biodiversidad. En el Capítulo 4, analizamos los patrones de co-ocurrencia espacial y temporal entre especies, tanto cualitativa como cuantitativamente, y determinamos los patrones de actividad de las diferentes especies carroñeras. Nuestros resultados muestran complejas relaciones competitivas y facilitadoras entre las especies carroñeras en el Cerrado brasileño que están influenciadas por el tamaño de la carroña, y cambian dependiendo de la escala espacial y temporal a la que se analicen. Los grupos de carroñeros que consumieron carroñas grandes y pequeñas fueron diferentes, evidenciando la partición de recursos entre carroñeros obligados y facultativos. Además, como alternativa para reducir los niveles de competencia, la mayoría de las especies mostraron diferencias en sus patrones de actividad, además de una fuerte segregación temporal durante el consumo de la carroña. En cuanto a los buitres del Nuevo Mundo, nuestros resultados sugieren una fuerte competencia por interferencia entre especies, con claras diferencias en base a sus rasgos ecológicos (p. ej., tamaño, comportamiento social). Sin embargo, también encontramos evidencias de procesos de facilitación entre especies de buitres en la localización y acceso al interior de las carroñas. Nuestros hallazgos destacan el papel de los carroñeros obligados tanto en los procesos de competencia como de facilitación en esta comunidad de vertebrados carroñeros. Para entender los procesos que dan lugar a asociaciones entre especies de buitres con distintas eficiencias de búsqueda de alimento, en el Capítulo 5 aplicamos una estrategia de modelado de supervivencia para determinar la transmisión de información social entre distintas especies durante la localización de la carroña. El uso de diferentes sentidos (olfato y vista) dentro de este gremio facilita la localización de las carroñas mediante la transmisión de información social entre especies con diferentes eficiencias de forrajeo. Los buitres con un sentido del olfato muy desarrollado desempeñan un papel clave en este proceso, ya que son los primeros en localizar y llegar a las carroñas y su presencia parece servir de pista visual para que otras especies localicen el recurso. Nuestro estudio apoya la hipótesis de la “mejora local” dentro de los carroñeros, según la cual los individuos localizan las carroñas siguiendo a los heteroespecíficos que buscan alimento, sugiriendo también la importancia del sentido del olfato en el mantenimiento de la estructura de la comunidad. En el Capítulo 6, realizamos el primer análisis en profundidad de los factores que determinan la dinámica temporal de las sucesiones de carroñeros utilizando las agresiones interespecíficas como indicador conductual de la intensidad de competencia. Los resultados muestran que la disponibilidad de recursos determina las interacciones conductuales entre especies. Además, la facilitación se relacionó con momentos de mayor tolerancia (es decir, menor agresividad), reduciendo así la intensidad de la competencia y afectando a la estructura y dinámica de la comunidad. Nuestro estudio destaca la importancia de monitorizar los comportamientos que son directamente transferibles a la función de la comunidad (por ejemplo, los relacionados con la búsqueda de alimento y el consumo de recursos), considerando también la dinámica de la sucesión a lo largo del tiempo. Este novedoso marco evidencia complejos procesos dinámicos caracterizados por una fluctuación en la facilitación y la intensidad de la competencia durante el consumo de un recurso impredecible vinculado a procesos ecosistémicos clave. Finalmente, la discusión general (Capítulo 7) aborda las implicaciones de los hallazgos obtenidos en los capítulos anteriores, su contribución al estudio de las comunidades desde una perspectiva general, y para el gremio de carroñeros en particular, incluyendo las implicaciones para la conservación. Además, se examinan las limitaciones identificadas y se esbozan vías para futuras investigaciones encaminadas a comprender los determinantes del equilibrio entre procesos positivos y negativos entre especies que coexisten

Behavioral interactions are modulated by facilitation along a heterotrophic succession

Competition and facilitation drive ecological succession but are often hard to quantify. In this sense, behavioral data may be a key tool to analyze interaction networks, providing insights into temporal trends in facilitation and competition processes within animal heterotrophic succession. Here, we perform the first in-depth analysis of the factors driving temporal dynamics of carcass consumption by analyzing behavioral patterns (i.e., interactions) and community dynamics metrics (i.e., species richness, abundance, turnover, and diversity) in a Neotropical scavenger guild. For this purpose, we monitored goat carcasses using automatic cameras. From 573 reviewed videos, we registered 1784 intraspecific and 624 interspecific interactions, using intraspecific and interspecific aggressions (n = 2048) as a behavioral proxy of competition intensity. Our results show that resource availability shapes behavioral interactions between vultures, with a specific effect of the different species on behavioral and competition dynamics, showing the existence of a hierarchy between species. Furthermore, behavioral processes linked to carcass opening tended to be facilitative, related to moments of higher tolerance (i.e., lower aggressiveness), thus reducing competition intensity and also affecting community structure and dynamics. This novel framework demonstrates complex ephemeral successional processes characterized by a fluctuation in facilitation and competition intensity during the consumption of an unpredictable resource linked to key ecosystem processes.Lara Naves-Alegre, and Esther Sebastián-González were supported by the Generalitat Valenciana and the European Social Fund (ACIF/2019/056, SEJI/2018/024, respectively). Esther Sebastián-González also received the grant RYC2019-027216-I funded by MCIN/AEI/ 10.13039/501100011033 and by ESF Investing in Your Future

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

Understanding 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.LNA, ZMR and ESG were supported by the Generalitat Valenciana and the European Social Fund (ACIF/2019/056, APOSTD/2019/016, SEJI/2018/024, respectively), and JASZ by funds from the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund (RTI2018-099609-B-C21). ESG received the grant RYC2019-027216-I funded by MCIN/AEI/10.13039/501100011033 and by ESF Investing in your future. ZMR was also supported by a postdoctoral contract funded by the Junta de Andalucía (POSTDOC_21_00353)

Unravelling the vertebrate scavenger assemblage in the Gobi Desert, Mongolia

Despite the essential role that vertebrate scavengers play in ecosystems, most studies have been conducted in Europe and North America, and there is a lack of information on vertebrate scavengers in vast regions of the world. Our aim was to describe the functioning and composition of the unknown vertebrate scavenger assemblage in the Gobi Desert, Mongolia, and determine how carcass size and habitat type affect species composition and carrion use. We monitored carcasses with camera traps and we also conducted observation points to survey the raptor community and identify the proportion of raptor species making use of the carcasses. We recorded eight vertebrate scavenger species (five birds and three mammals) by camera trap and seven raptors at observation points. Over half of the raptor species recorded at the observation points were also found feeding on carrion. The two most threatened species were only recorded in the mountain habitat. Furthermore, scavenger abundance and consumption rates were higher at large carcasses. This study highlights the importance of scavenging by raptors and other vertebrate scavengers for carrion elimination in ecosystems with extreme climatic conditions.AOT, JMPG, ZMR, LNA and ESG were supported by Generalitat Valenciana (SEJI/2018/024), ZMR and LNA also by contracts co-funded by the Generalitat Valenciana and the European Social Fund (APOSTD/2019/016 and ACIF/2019/056, respectively), and JASZ by funds from the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund (RTI 2018-099609-B-C21)

Network Structure of Vertebrate Scavenger Assemblages at the Global Scale: Drivers and Ecosystem Functioning Implications

The organization of ecological assemblages has important implications for ecosystem functioning, but little is known about how scavenger communities organize at the global scale. Here, we test four hypotheses on the factors affecting the network structure of terrestrial vertebrate scavenger assemblages and its implications on ecosystem functioning. We expect scavenger assemblages to be more nested (i.e. structured): 1) in species‐rich and productive regions, as nestedness has been linked to high competition for carrion resources, and 2) regions with low human impact, because the most efficient carrion consumers that promote nestedness are large vertebrate scavengers, which are especially sensitive to human persecution. 3) We also expect climatic conditions to affect assemblage structure, because some scavenger assemblages have been shown to be more nested in colder months. Finally, 4) we expect more organized assemblages to be more efficient in the consumption of the resource. We first analyzed the relationship between the nestedness of the scavenger assemblages and climatic variables (i.e. temperature, precipitation, temperature variability and precipitation variability), ecosystem productivity and biomass (i.e. NDVI) and degree of human impact (i.e. human footprint) using 53 study sites in 22 countries across five continents. Then, we related structure (i.e. nestedness) with its function (i.e. carrion consumption rate). We found a more nested structure for scavenger assemblages in regions with higher NDVI values and lower human footprint. Moreover, more organized assemblages were more efficient in the consumption of carrion. However, our results did not support the prediction that the structure of the scavenger assemblages is directly related to climate. Our findings suggest that the nested structure of vertebrate scavenger assemblages affects its functionality and is driven by anthropogenic disturbance and ecosystem productivity worldwide. Disarray of scavenger assemblage structure by anthropogenic disturbance may lead to decreases in functionality of the terrestrial ecosystems via loss of key species and trophic facilitation processes

Scavenging in the Anthropocene: Human impact drives vertebrate scavenger species richness at a global scale

Understanding the distribution of biodiversity across the Earth is one of the most challenging questions in biology. Much research has been directed at explaining the species latitudinal pattern showing that communities are richer in tropical areas; however, despite decades of research, a general consensus has not yet emerged. In addition, global biodiversity patterns are being rapidly altered by human activities. Here, we aim to describe large‐scale patterns of species richness and diversity in terrestrial vertebrate scavenger (carrion‐consuming) assemblages, which provide key ecosystem functions and services. We used a worldwide dataset comprising 43 sites, where vertebrate scavenger assemblages were identified using 2,485 carcasses monitored between 1991 and 2018. First, we evaluated how scavenger richness (number of species) and diversity (Shannon diversity index) varied among seasons (cold vs. warm, wet vs. dry). Then, we studied the potential effects of human impact and a set of macroecological variables related to climatic conditions on the scavenger assemblages. Vertebrate scavenger richness ranged from species‐poor to species rich assemblages (4–30 species). Both scavenger richness and diversity also showed some seasonal variation. However, in general, climatic variables did not drive latitudinal patterns, as scavenger richness and diversity were not affected by temperature or rainfall. Rainfall seasonality slightly increased the number of species in the community, but its effect was weak. Instead, the human impact index included in our study was the main predictor of scavenger richness. Scavenger assemblages in highly human‐impacted areas sustained the smallest number of scavenger species, suggesting human activity may be overriding other macroecological processes in shaping scavenger communities. Our results highlight the effect of human impact at a global scale. As speciesrich assemblages tend to be more functional, we warn about possible reductions in ecosystem functions and the services provided by scavengers in human‐dominated landscapes in the Anthropocene

Avian-power line interactions in the Gobi Desert of Mongolia: are mitigation actions effective?

Background: Electrocution and collisions on power lines are among the leading causes of non-natural mortality for birds. Power lines are exponentially increasing, particularly in developing countries, but mitigation strategies to prevent bird mortality are questionable. Mongolia combines a recently increased power line network, an abundant raptor population, a dangerous crossarm configuration and a habitat with no natural perches, producing many bird-power line interactions. Our aim is to assess the bird mortality caused by power lines in the Gobi Desert of Mongolia, to determine the factors increasing the risk of bird electrocution, and to evaluate the effectiveness of used retrofitting measures. Methods: In July 2019 we covered 132.9 km of 15 kV power lines checking 1092 poles. We also conducted bird transects to record raptor and corvid richness and abundance, to assess species vulnerability to electrocution. Results: We recorded 76 electrocuted birds of 7 species. Electrocution rate was 6.96 birds/100 poles. The most affected species were Common Raven (Corvus corax) and Upland Buzzard (Buteo hemilasius), highlighting the electrocution of 5 endangered Saker Falcons (Falco cherrug). By contrast, we only recorded 8 individuals of 5 species colliding with wires, the most affected being Pallas’s Sandgrouse (Syrrhaptes paradoxus). About 76.1% of sampled poles had some mitigation measure. Of these, 96.6% were brush perch deflectors and 3.4% rotating-mirrors perch deterrents. We found differences in electrocution rates among crossarm configurations, with the strain insulator with one jumper being the most lethal. Additionally, we found no correlation between bird abundance and electrocution rates, suggesting that some species are more sensitive to electrocution. Although no differences in total bird electrocution rates were detected between poles with and without perch deterrents, when bird size is considered, deterrents reduced the mortality rate of small birds, while they were ineffective for medium-sized birds. Conclusions: Despite the widespread use of perch deterrents in the Mongolian power line network, there is still an alarming electrocution rate. This strategy is ineffective and some mechanisms, such as brush perch deflectors, may increase the electrocution rate for some medium-sized birds. Finally, we propose strategies to minimize the avian electrocution rate in the Gobi Desert.This project was supported by Generalitat Valenciana (SEJI/2018/024). JMPG and ESG were supported by Spanish Ministry of Science, Innovation and Universities contracts (IJC-2019-038968 and RYC-2019-027216-I), ZMR and LNA by contracts cofunded by the Generalitat Valenciana and the European Social Fund (APOSTD/2019/016 and ACIF/2019/056, respectively)

Scavenging in the realm of senses : smell and vision drive recruitment at carcasses in Neotropical ecosystems

Social information, acquired through the observation of other individuals, is especially relevant among species belonging to the same guild. The unpredictable and ephemeral nature of carrion implies that social mechanisms may be selected among scavenger species to facilitate carcass location and consumption. Here, we apply a survival-modelling strategy to data obtained through the placement and monitoring of carcasses in the field to analyse possible information transmission cascades within a Neotropical scavenger community. Our study highlights how the use of different senses (smell and sight) within this guild facilitates carcass location through the transmission of social information between species with different carrion foraging efficiencies. Vultures with a highly developed sense of smell play a key role in this process, as they are the first to arrive at the carcasses and their presence seems to serve as a visual cue for other species to locate the resource. Our study supports the local enhancement hypothesis within scavengers, whereby individuals locate carcasses by following foraging heterospecifics, also suggesting the importance of the sense of smell in the maintenance of the community structure.peerReviewe

Uncovering the vertebrate scavenger guild composition and functioning in the Cerrado biodiversity hotspot

Scavenging is widespread among vertebrates, being very important for maintaining certain ecosystem functions. Despite this, the scavenger communities remain poorly known in some biomes, especially in the Neotropics. Our main objective was to describe for the first time the scavenger community and identify the factors affecting scavenging efficiency in the Brazilian Cerrado. We analyzed the effects of vegetation cover, time of carcass placement and carcass weight, on scavenger species richness, individual abundances, carcass detection and consumption times, and carcass consumption rate. We monitored 11 large and 45 small carcasses using automatic cameras. We documented a total of 19 vertebrate scavenging species, four species of vultures and 15 facultative scavengers. We found that carcass size was the most important factor affecting the scavenger assemblage and consumption patterns. Large carcasses were dominated by vultures, whereas small carcasses were consumed mainly by facultative scavengers. We also found differences between large and small carcasses in all carcass consumption variables except for detection time. However, we did not find an effect of vegetation cover or time of carcass placement on scavenging patterns. The negligible role of mammals and non-raptor birds in large carcasses is also noteworthy, probably due to the consumption and foraging efficiency of the vultures, and the more frugivorous habits of the mesocarnivores. Our results show a highly diverse and efficient scavenging vertebrate community in the Brazilian Cerrado, and the need to preserve them in the face of the significant habitat transformations suffered by this biodiversity hotspot.LNA, ZMR, and ESG were supported by the Generalitat Valenciana and the European Social Fund (ACIF/2019/056, APOSTD/2019/016, SEJI/2018/024, respectively) and JASZ by funds from the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund (RTI2018-099609-B-C21). ESG was also funded by the Spanish Ministry of Science and Innovation (RYC-2019-027216-I)

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