Vultures and Humans: An Unstable Alliance
Top scavengers (“true” vultures, Accipitridae) have been evolutionarily dependent on carcasses of large animals, mainly ungulates, grazing in open areas of southern Europe, Africa and central and southern Asia (Houston 1974, 1979; Donázar 1993). They have in common extreme adaptations and skills aimed to locate scarce and unpredictable sources of food (Houston 1979; Cortés-Avizanda et al. 2014). However, because of the rampant humanization of ecosystems, this natural scenario no longer exists, apart from some strictly protected areas, especially in African countries where large herds of ungulates subsist (Cortés-Avizanda et al. 2011; Fig. 5.2). Thus, following the progressive eradication of most native populations of wild ungulates (e.g. Chap. 8), guilds of avian scavengers have become largely dependent on livestock carcasses associated with human activities (Mundy et al. 1992; Donázar 1993). This scenario has likely remained almost unchanged since the so-called “Neolitic revolution” (i.e., a process in which agrarian societies began to substitute hunting around 8500 BC with agricultural practices including the domestication of the herbivores) in many regions of the Old World, and certainly in southern Europe, where the agro-grazing traditional economies remained unchanged (Donázar et al. 1996a, 2009; Olea and Mateo-Tomas 2009; Fig. 5.3).
Fig. 5.2 a Egyptian vulture ( Neophron percnopterus) and b Black kite ( Milvus migrans) in the Mauritanian Sahel. In Africa the availability of trophic resources is not limiting and therefore scavengers show a homogeneous spatial distribution. (Cortés-Avizanda et al. 2011; Photo credit: Jose Ramón Benitez)
After the industrial revolution this scenario changed dramatically. During the 19th and the first half of the 20th century, a utilitarian view of nature became common. “Harmful” species were more efficiently prosecuted and raptor populations, including scavengers, declined steeply across Europe and in many regions to full extinction (Bijleveld 1974). In parallel, a key resource for carrion-eaters, the wild ungulates, were
Fig. 5.3 Avian scavengers and traditional extensive grazing. After the eradication of native populations of wild ungulates, avian scavengers have become dependent of traditional livestock carcasses. (Photo credit: Iosu Anton)
also decimated by hunting and poaching (the main decline of ungulate populations in Europe took place during the last centuries after the generalized use of firearms), disappearing from most of the European landscapes (see e.g. Chapman and Buck 1910; Deinet et al. 2013 and references therein). Carcasses of domestic ungulates were probably still plentiful until well into the 20th century but the transformation of farming to intensive practices and the abandonment of extensive grazing reduced their availability in the last decades (Donázar et al. 1996a). This dramatic scenario began to improve from the 1960s onwards. Given the high public profile of many large avian scavengers, local administrations and conservationist groups created a number of feeding stations (also known as “vulture restaurants”; Fig. 5.4) to supply food and help re-establish the decimated populations of these species (Bijleveld 1974 and see below; Fig. 5.4). But perhaps much more importantly, legal protection curbed non-natural mortality allowing scavenger populations to quickly recover, mainly in the Iberian Peninsula and Southern France (Donázar and Fernández 1990; Donázar et al. 1996a, b; Slotta-Bachmayr et al. 2004). The griffon vulture ( Gyps fulvus) was the most favoured species, its populations having dramatically increased in numbers in the Iberian Peninsula and France (BirdLife International 2004). Populations of Cinereous vulture ( Aegypius monachus) and Bearded vulture ( Gypaetus barbatus) have also increased in numbers, albeit more moderately, in some European regions (Margalida and Heredia 2005; Moreno-Opo 2007; Dobado et al. 2012). By contrast, the numbers of small-sized scavengers such as Egyptian vultures ( Neophron percnopterus) and Red ( Milvus milvus) and Black ( Milvus migrans) kites continue to decline (Viñuela et al. 1999; Del Moral and Martí 2001, 2002).
Fig. 5.4 Supplementary feeding stations devoted for vultures. The supplementary feeding stations are a worldwide conservation tool to recover endangered populations of avian scavengers. Usually they are fenced sites where local farmers and rangers dispose the carcasses. a A vulture restaurant devoted to Egyptian vulture in Fuerteventura (Canary Island) where the dominant griffons are not presented. b A group of Egyptian vulture feeding at a vulture restaurant also in Fuerteventura. (Photo credit : a) José Antonio Donázar and b) Manuel de la Riva)
A decade ago the appearance of the Bovine Spongiform Encephalopatie (BSE) changed the picture abruptly. New sanitary regulations driven by the European Union banned the abandonment of livestock carcasses in the field, and consequently, the availability of food resources declined in some regions by more than 80 %. The consequences for vulture populations are still being evaluated, but spatial distribution, breeding success and survival seem to have been affected. This is particularly noticeable in those species with greater dependence on carcasses of large animals such as griffon vultures (see reviews in Donázar et al. 2009a). To complicate things even more, after these sanitary measures a conflict between farmers and vultures developed in Mediterranean regions (particularly Spain and southern France). Griffon vultures are known to occasionally kill and consume diminished livestock but the number of cases reported increased sharply after the implementation of sanitary regulations (Margalida et al. 2014). No doubt that this trend was largely the result of a social contagion driven by misinformed media, but regardless, a true conflict arose compromising decades of conservation measures aimed to restore avian scavenger populations. The consequence was that hundreds of individuals of griffon and other species of vultures and facultative scavengers perished by poison, while public opinion called for a quick fix consisting of artificially feeding vultures to distract their attention from live prey (Margalida et al. 2010).
After these events and due to the widespread pressures coming from researchers, policy conservation managers and farmers, recent European regulations have increasingly allowed the disposal of livestock carcasses for consumption by vultures (Donázar et al. 2009a, b; Margalida et al. 2010). The adoption of this new legislation takes time, especially for the transposition of EU laws to individual country governments and then in many cases from the country level to local government departments. In general, the legal framework is cumbersome such that administrations are faced with complex and time-intensive processes. Consequently, the European regional governments (e.g. in Spain), have adopted a common strategy whereby just a few widespread sites -in theory under strict veterinary controlare supplied with carcasses for scavengers. Thus, vultures have access to restaurant networks with large amounts of food (Cortés-Avizanda et al. 2010, 2012). The effects of this conservation strategy, which is not new and has now become widespread, may be substantial from both population and ecological points of view.