Abstract
Vultures constitute an important functional group in many ecosystems, providing crucial ecosystem services both in natural and humanized environments. These scavengers are facing massive declines worldwide, but in several African countries virtually nothing is known on populations’ status and threats, hampering the development of adequate conservation strategies. In Guinea-Bissau, globally important populations of Hooded Necrosyrtes monachus and African white-backed vultures Gyps africanus were recently reported. Using the country as a study area, we aim to characterize human-vulture interactions in West Africa applying a multidisciplinary approach. We assessed the status and distribution of vulture populations using data from 1711 km of roadside transects, examined predictors of their distribution, and produced a nationwide population estimate for the Hooded Vulture, using an innovative method based on the relationship between the size of human population in settlements and vulture numbers. We conducted 47 stakeholder interviews to assess perceived roles played by vultures, and to investigate potential anthropogenic threats. Hooded vultures were strongly associated with high human population densities, whereas no relation was found between African white-backed and Rüppell’s vultures and any of the tested predictors, which included cattle density, precipitation and Normalized Difference Vegetation Index, among others. We estimate a national population of 43347 Hooded vultures, the largest population reported in the species range. Respondents were generally aware of the services provided by vultures, especially waste and carcass removal, including in urban areas. Hunting for witchcraft and traditional medicine was the most frequently recognised threat, while poisoning was ranked as having the highest impact. We hypothesise that poisoning-related mortality may be affecting African white-backed and Rüppell’s vultures’ distribution and explain their scarcity in apparently highly suitable habitats. Our results suggest a mutualistic rather than a commensalistic relationship between vultures and humans, with important implications for designing and implementing conservation strategies.
Highlights
Scavenger vertebrates constitute an important functional group in many ecosystems, playing a critical role in many ecological processes [1]
This study confirms that Guinea-Bissau represents a stronghold for Hooded vultures and for African white-backed vultures, species which are present in large numbers and widely distributed across the country
Wild ungulates and other mammals have grown scarce in Guinea-Bissau, a general trend in most of West Africa [64,65], but vultures are still abundant in that country, apparently relying on domestic animals and human waste
Summary
Scavenger vertebrates constitute an important functional group in many ecosystems, playing a critical role in many ecological processes [1]. The importance of vultures on ecological processes is complex, but here we highlight two aspects: first, as nature’s most successful scavengers, they contribute greatly in the nutrient cycling dynamics by increasing the decomposition rate of carcasses and positively affecting transmission of nutrients to the soil [9,10]. This has a chain-effect that is important in maintaining biodiversity [11]. Some species provide important ecosystem services in humanised areas, like the disposal of organic waste, the control (through competition) of opportunistic mammalian scavengers and of disease transmission, among many others [12,13]
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