Vultures and Livestock: The Where, When, and Why of Visits to Farms.

Marina García-Alfonso,José A Donázar,Laura Gangoso,Thijs Van Overveld,David Serrano

doi:10.3390/ani10112127

Abstract

Simple SummaryThe abandonment of carcasses around livestock farms has been recently legalized in Europe. Since little is known about how vultures use this kind of resource, we aimed to determine the main drivers of vultures’ visits to farms. We evaluated the effects of characteristics of both birds and farms regarding the way that vultures visit farms thanks to data collected from 45 GPS-tagged Egyptian Vultures and most farms on Fuerteventura Island, Spain (318 farms with >94% of insular livestock). We found that farms were more visited when they were located close to highly predictable feeding places, when they had more available food, and during the vulture breeding season, whereas farms located close to roads and vultures’ breeding territories received fewer visits. Younger territorial birds visited a farm more frequently than older territorial ones, whereas older non-territorial individuals concentrated those visits on farms closer to their main centers of activity compared with younger ones. Our findings indicate that visits to farms were determined by their spatial distribution regarding bird activity centers, availability of carcasses, seasonality, and vulture characteristics. Hence, these factors should be considered in vulture conservation, avoiding very general solutions that ignore population structure and that could be not enough to protect the biodiversity.Recent changes in European legislation have legalized the abandonment of carcasses around livestock farms, but our understanding of how vultures exploit these semi-predictable food sources is still very limited. For filling this gap, we determine the individual and ecological drivers influencing vulture visits to farms. We assessed the effects of individual characteristics of both birds and farms on the frequency of vultures’ visits to livestock facilities using data collected from 45 GPS-tagged Egyptian Vultures (Neophron percnopterus) and 318 farms (>94% of livestock) on Fuerteventura Island, Spain. Farms were more visited during the vultures’ breeding season. Farms located closer to highly predictable feeding places (i.e., vulture restaurants and garbage dumps) or with more available feeding resources were visited by more vultures, whereas those located close to roads and vultures’ breeding territories received fewer visits. Younger territorial birds visited a farm more frequently than older territorial ones, whereas older non-territorial individuals concentrated those visits on farms closer to their activity core areas compared with younger ones. Our findings indicate that visits to farms were determined by their spatial distribution in relation to the age-specific birds’ activity centers, the availability of carcasses, seasonality, and individual characteristics of vultures. These interacting factors should be considered in vulture conservation, avoiding very general solutions that ignore population structure.

Highlights

The abandonment of livestock carcasses near livestock facilities, as opposed to the use of feeding stations, is generally considered the more suitable strategy to preserve populations of endangered scavengers in traditional agro-grazing systems [1]
2020, 10, seasons in the number of farms included in Egyptian Vultures’ home ranges (N.farms HR) and in the number of farms visited by vultures (N.farms visited) accounting for their territorial status
U-tests assessing differences between sexes and breeding seasons in the number of farms included in Egyptian Vultures’ home ranges (N.farms HR) and in the number of farms visited by vultures (N.farms visited) accounting for theirN.farms territorial status

Summary

Introduction

The abandonment of livestock carcasses near livestock facilities, as opposed to the use of feeding stations, is generally considered the more suitable strategy to preserve populations of endangered scavengers in traditional agro-grazing systems [1]. Farms are more numerous and widely distributed than would be feasible for any network of feeding stations. Livestock deaths and food provision occurs sporadically, in contrast to the regular disposal of slaughterhouse remains. This pattern may reduce the spatiotemporal predictability of food sources (i.e., creating a semi-predictable resource), favoring less competitive (small-sized) and often more endangered species and populations of avian scavengers [2,3,4]. Carcass abandonment at farms has additional economic and environmental advantages, mainly through the ecosystem service provided by scavengers that may largely reduce costs for carcass removal while reducing associated pollution [5,6].

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