Vultures and Hunting: Lead Poisoning, Carrion Ecology, and Conservation Challenges

This section looks at the relationship between human hunting of wildlife and vultures. This concerns both the provision of carcasses and possible externalities. Human hunting of wild animals may have both positive and negative effects on scavengers; it may provide carcasses and kill off predatory competitors, but may also kill off the species that provide the carcasses in the first place (Mateo-Tomas and Olea 2010). A major problem concerning hunting is lead poisoning. For vultures, exposure to lead from spent ammunition in large game carcasses may lead to lead toxicity (Garria-Fernandez et al. 2005; Cade 2007; Dobrowolska and Melosik 2008). This lead poisoning may have important effects at both individual and population levels (Gangoso et al. 2009).

Hunting of animals by people has a negative effect on biodiversity, which may impact vultures as well (Mateo-Tomas and Olea 2010). Impacts on predators may have serious impacts. Impacts may include the decimation of prey species (Lozano et al. 2007), the killing of predators and a consequent decline in carcasses they provide (Thirgood et al. 2000; Valkama et al. 2005) and animal behavior change (Casas et al. 2009). Nunez-Iturri et al. (2008) write that firearm hunting decimates primates that disperse the seeds of large-seeded trees; this reduction in primate affects the character of the forest in the case study in Peru. Effects on game species include overexploitation and possible extinction (Lindsey et al. 2007), threats to genetic diversity (Blanco-Aguiar et al. 2008) and possible modification of their behavior (Benhaiem et al. 2008). Mateo-Tomas and Olea (2010: 520) also point out that 'relatively few studies have examined positive effects of hunting on wildlife and/or ecosystem conservation' (see also Thirgood et al. 2000; Baker 1997; Lindsey et al. 2006, 2007; White et al. 2008).

In the United States, hunting remains an important attractant for obligate scavengers such as vultures and facultative scavengers such as coyotes (Smith 2013). In Alabama, where more than 447,000 hunters move into the woods annually for a deer kill, it is estimated the statewide average harvest is about 1.6 deer per hunter. Although most hunters dispose of the carcasses in a manner that limits odor, disease possibilities and environmental contamination, others do not do so. Unsuitable dumping pollutes water bodies, in fields and by roads (Smith et al. 2013).

Mateo-Tomas and Olea (2010: 520) further point out that although large animals are the principal food of Old World vultures and information on this topic is crucial for the current vulture population decline, 'To our knowledge, the influence that hunting could have in the ecology and conservation of this scavenger guild has not been assessed', with only passing references (see Sekercioglu et al. 2004; Garda-Fernandez et al. 2005; Cade 2007; Murn and Anderson 2008). Mateo-Tomas and Olea (2010) therefore argue that considering the food sources favored by vultures, hunting of the animals whose carcasses they eat might be relevant to vulture populations. Their case study was of the Griffon vulture and its relations with hunting in a part of Spain with no intensive farming or vulture-feeding stations. This allowed an examination of hunting as the main resource activity (Camina and Monteho 2006; Junta de Castilla y Leon 2006).

The study showed that Griffon vultures were highly dependent on shot ungulates, mainly red deer (Cervus elaphus Linnaeus, 1758) and wild boar (Sus scrofa Linnaeus, 1758). The vultures in the study area numbered about 350 breeding pairs and 1,100 others, and the results showed that the products of hunting could feed about 1,807 during the 5-6 hunting season. More vultures were recorded feeding of red deer and wild boar (69%) than on livestock (31%). Hunting could therefore play a role in maintaining the vulture population; as it would be the main food source during winter, outside the breeding season (Elosegui 1989; Olea and Mateo-Tomas 2009).

Vultures may also be hunted for food or religious use. For example, the decline of the Hooded vulture in East, West and Southern Africa, is mostly due to its over-exploitation for food and traditional medicines predominantly in West Africa (Anderson 1999; Sodeinde and Soewu 1999; Ogada and Buij 2011) ). It is now rare in the southwest of Burkina Faso (where it is commonly used for traditional medicines and sorcery is common and it is routine to see their body parts on sale at markets), Mali and Niger (Thiollay 2006a). In Nigeria, the Hooded vulture was the most frequently traded bird for traditional medicine (Sodeinde and Soewu 1999). The head is used to protect against witches and the whole body may be used for good fortune (Sodeinde and Soewu 1999). Large vultures are more desired but more difficult to obtain (Nikolaus 2001). They are also eaten (Rondeau and Thiollay 2004).