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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 species‐rich 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.

No abstract

Limited mapping of migrations hampers conservation

Interspecific social information transfer can play a key role in many aspects of animal ecology from foraging to habitat selection to predator avoidance. Within scavenging communities, avian scavengers often act as producers and mammalian scavengers act as scroungers, but we predict that species-specific cueing will allow for mammalian scavengers to utilize particular avian scavenger species using preferred food sources similar to their own preferences. We use empirical and theoretic approaches to assess interactions between mammalian and avian scavengers in one of the most diverse scavenging guilds in Masai Mara National Reserve, Kenya. Using a spatially explicit model and data from experimental carcasses, we found evidence that mammals benefit from local enhancement provided by vultures and that mammalian-avian following patterns are consistent with the idea that species-specific cueing is occurring. Results suggest that ongoing population declines in avian scavengers may have significant impacts on mammalian scavengers and potentially create trophic cascades.

The ongoing global decline in vulture populations raises major conservation concerns, but little is known about the factors that mediate scavenger habitat use, in particular the importance of abundance of live prey versus prey mortality. We test this using data from the Serengeti-Mara ecosystem in East Africa. The two hypotheses that prey abundance or prey mortality are the main drivers of vulture habitat use provide alternative predictions. If vultures select areas based only on prey abundance, we expect tracked vultures to remain close to herds of migratory wildebeest regardless of season. However, if vultures select areas where mortality rates are greatest then we expect vultures to select the driest regions, where animals are more likely to die of starvation, and to be attracted to migratory wildebeest only during the dry season when wildebeest mortality is greatest. We used data from GSM-GPS transmitters to assess the relationship between three vulture species and migratory wildebeest in the Mara-Serengeti ecosystem. Results indicate that vultures preferentially cluster around migratory herds only during the dry season, when herds experience their highest mortality. Additionally during the wet season, Ruppell’s and Lappet-faced vultures select relatively dry areas, based on Normalized Difference Vegetation Index, whereas White-backed vultures preferred wetter areas during the wet season. Differences in habitat use among species may mediate coexistence in this scavenger guild. In general, our results suggest that prey abundance is not the primary driver of avian scavenger habitat use. The apparent reliance of vultures on non-migratory ungulates during the wet season has important conservation implications for vultures in light of on-going declines in non-migratory ungulate species and use of poisons in unprotected areas.

Categorized as Vulnerable on the IUCN Red List, the common hippopotamus Hippopotamus amphibius is under considerable pressure from habitat degradation and hunting. Although human–hippopotamus conflict is known to increase retaliatory killing and culling of hippopotamuses, the issue has been little examined. Using interviews I investigated various spatial, ecological and agricultural factors that influence the vulnerability of farms to crop raiding by hippopotamuses in three villages to the south-east of Ruaha National Park, Tanzania. There was a positive correlation between these crop-raiding events and a farm’s proximity to the river and to hippopotamus access points (places where hippopotamuses leave and enter the river). Results from this study provide insights for management and conservation of hippopotamuses, including a need to identify key habitat areas to mitigate future conflict.

Temporal segregation is known to be an important mechanism of coexistence in many foraging guilds but has not been examined in avian scavengers. Given that carrion availability is higher in the morning than in the afternoon and that differences in wing-loading and nesting behavior may limit morning activity in some species, there is potential for temporal segregation in resource use to play an important role in the coexistence of avian scavengers. I predicted that Lappet-faced Vultures (Torgos tracheliotos), which have lower wing-loading and lower competitive abilities, would have higher abundance at carrion resources in the morning than White-backed Vultures (Gyps africanus) and Rüppell's Vultures (G. rueppellii). In addition, I predicted that differences in activity patterns among vulture species would affect foraging success. Using experimental carcasses, I examined the effect of time of day on foraging behavior. I quantified foraging success in roosting birds, measured as the proportion of individuals with a full crop. Contrary to predictions, during the dry season White-backed and Rüppell's Vultures were more abundant at carcasses in the morning and Lappet-faced Vultures were more abundant in the afternoon. In the afternoon a large proportion of the Gyps individuals appeared to be satiated and densities were lower at carcasses, perhaps creating a temporal competitive refugium in the afternoon during which Lappet-faced Vultures could feed. However, Lappet-faced Vultures have lower foraging success than White-backed and Rüppell's Vultures. These results demonstrate that temporal segregation occurs, but may not reduce competition, in this scavenging guild.El ave que madruga consigue el cadá ver: Segregación temporal y sus efectos sobre eléxito de forrajeo en aves carroñeras RESUMEN La segregación temporal es reconocida por su importancia como mecanismo de coexistencia en muchos gremios de forrajeo, pero no ha sido examinado en aves carroñeras. Ya que la disponibilidad de carroña es mayor en la mañana que en la tarde, y diferencias en carga alar y comportamiento de nidificación pueden limitar la actividad matinal de algunas especies, existe la posibilidad de que la segregación temporal en el uso de recursos juegue un rol importante en la coexistencia de aves carroñeras. Predigo que Torgos tracheliotos, el cual tiene una carga alar menor y abilidades competitivas inferiores, sería más abundante que miembros del género Gyps en recursos de carroña durante la mañana. Además, predigo que las diferencias en patrones de actividad entre especies de buitres afectará eléxito de forrajeo. Utilizando cadáveres experimentales, examiné el efecto de hora del día sobre el comportamiento de forrajeo. Cuantifiqué eléxito de forrajeo de aves en dormideros midiendo la proporción de individuos con el buche lleno. Contrario a mis predicciones, durante laépoca seca, Gyps africanus y Gyps rueppelli fueron más abundantes en cadáveres en la mañana y Torgos tracheliotos fue más abundante en la tarde. En la tarde, una proporción importante...