To feed or not to feed? Evidence of the intended and unintended effects of feeding wild ungulates

Abstract

Storaas, T. (2014). To feed or not to feed? Evidence of the intended and unintended effects of feeding wild ungulates.Journal of Wildlife Management, 78(8) Large ungulates are keystone species in many ecosystems and are a highly valued natural 47 resource for social, cultural, and economic reasons (Gordon et al. 2004). Many populations have grown over recent decades, causing environmental and socio-economic 49 impacts on wider communities and conservation concerns, as well as density-dependent 50 changes in performance (Côté et al. 2004, Putman et al. 2011. Consequently, conflicts 51 arise between stakeholders who benefit economically from high ungulate numbers (e.g., 52hunters, outfitters, tourism operators) and those faced with the costs of their presence 53(e.g., land managers, conservationists, transport users and operators; Austin et al. 2010). 54Manipulating forage availability through the provision of additional food could 60Wildlife can be fed by humans in many different ways, intentionally (e.g., at 61 feeding stations) and unintentionally (e.g., unprotected agricultural crops and rubbish 62 dumps; Oro et al. 2013, Sorensen et al. 2014. In this review, we focus on the effects of 63 intentional feeding of ungulates, specifically considering supplementary feeding (often 64 called winter feeding) and diversionary, or intercept, feeding used to attract animals away 65 from vulnerable vegetation, livestock, or major traffic arteries (defined fully in 66 Supplemental Material). However, many of the issues raised also apply across a broad 67 range of unintentional but predictable anthropogenic food subsidies (Oro et al. 2013). 68Earlier reviews of the consequences of feeding large herbivores, published a decade or 77 METHODS 78We reviewed articles in the peer-reviewed and, to a lesser extent, grey literature that our search terms resulted in 232 articles. 86We identified 5 major management goals of supplementary and diversionary 87 feeding and considered the intended effects of feeding that would allow these goals to be 88 achieved (Table 1). We also identified commonly perceived unintended or secondary 89 consequences of feeding ( Table S1). 152Among adult females, an effect of feeding is complicated by the strong impact of 153 reproductive status on autumn mass (Cook et al. 2013 and higher neonatal growth rates (Jacobsen et al. 1981, Smith et al. 1997). 160The reproductive rate (number of offspring per adult female in summer or 161 autumn) of supplementally fed herbivores increased in 5/7 studies ( were used (Gundersen et al. 2004, Sahlsten et al. 2010 feeding site users and non-users (van Beest et al. 2010b). 282Of 16 controlled studies, 6 showed diversionary feeding to be effective in 283 reducing damage in the targeted areas, whereas 4 showed a significantly increased 284 impact, opposing the management goal ( we found no studies that formally addressed this ( 379In studies addressing the increased probability of browsing or grazing impacts in 380 response to feeding (4/4 studies; Table 2 and Supplem...

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“…However, there is limited evidence of the effectiveness of diversionary feeding to protect crops, forest regeneration and natural habitats, with any positive effects often being undermined by increases in ungulate density. The feeding of wild ungulates often has unintended effects, which are typically complex (Milner et al 2014). These may involve changes to vegetation composition and structure with consequent cascading effects on other trophic levels (Mathisen and Skarpe 2011), as well as exacerbating within-and between-species disease persistence and transmission risks (Sorensen et al 2014), browsing damage and competition between ungulate species (Felton et al 2017).…”

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