Why do wolves eat livestock?: Factors influencing wolf diet in northern Italy
Graphical abstract
Introduction
The wolf (Canis lupus), because of its adaptability to different environments and its ability to re-colonize territories when no persecution occurs, has in just a few decades expanded its range in Europe (Balciauskas, 2008, Breitenmoser, 1998, Chapron et al., 2003, Chapron et al., 2014). The Russian wolf population is the largest in Europe, supporting those of Baltic and North-European countries, and it is contiguous with the populations of Eastern Europe from which wolves began the re-colonization of Central Europe (Ansorge et al., 2006, Linnell et al., 2005). The Spanish wolf Canis lupus signatus (2200–2300 individuals) is slowly extending its distribution (Mech and Boitani, 2003).
Wolves greatly declined in Italy, surviving in two small isolated subpopulations confined to the southern and central part of the Apennines. At their nadir in the early seventies of the last century, wolves in Italy numbered about 100 individuals (Zimen and Boitani, 1975). Since the late eighties, wolves have shown a spontaneous rapid recovery, re-colonizing all the Apennines and reaching the western Italian and French Alps (Boitani, 2000, Breitenmoser, 1998, Fabbri et al., 2007, Marucco and McIntire, 2010, Valière et al., 2003).
The re-colonization of the Alps would be a fundamental step for wolf conservation in Italy and Central Europe as well (Genovesi, 2002). Moreover, the early and ongoing wolf expansion from the eastern Alps will predictably increase chances to originate mixed packs and increase the local genetic diversity as has been already described (Fabbri et al., 2014, Randi, 2011).
The sub-population of wolves inhabiting the Liguria region thus plays a crucial role in assuring the linkage between the wolves of central Italy and those of the Western Alps (Fabbri et al., 2007). If this link should break, the wolf population of the Western Alps would be isolated, perhaps failing to recolonize the remaining part of the Alps.
The distribution of wolves is usually determined by the abundance of its preys, environmental characteristics, and the risk associated with the presence of humans (Eggermann et al., 2011, Jędrzejewski et al., 2004, Massolo and Meriggi, 1998). This last point is the key problem of wolf conservation because wolves can have a dramatic impact on livestock breeding, affecting human attitudes that can lead to illegal killing, increasing the risk of extinction (Behdarvand et al., 2014, Kovařík et al., 2014).
The impact of wolves on livestock is different according to geographical region. In regions with a very low abundance of wild ungulates, as in Portugal and Greece, wolves feed mainly on livestock (Migli et al., 2005, Papageorgiou et al., 1994, Vos, 2000). On the other hand, in Germany attacks on livestock are rare because shepherds equip the pastures with electric fences to protect their herds and because the wild ungulate availability is high (Ansorge et al., 2006).
In other new-recolonizing areas such as France or North Italy, wild ungulates are the main prey of wolves, but the use of livestock is still noticeable (MEEDDAT–MAP, 2008, Meriggi et al., 2011, Milanesi et al., 2012).
Systematic research on wolf feeding ecology has been carried out since 1987 in the Ligurian Apennines. These studies showed an increasing use of wild ungulates in the time but also a medium–high use of livestock species as prey (Meriggi et al., 1991, Meriggi et al., 1996, Meriggi et al., 2011, Schenone et al., 2004). Consequently, wolf presence in Liguria, as well as in other areas of natural re-colonization, causes a conflict with human populations that perceive predator presence as a negative element that can compromise a poor rural economy. Thus, wolves suffer a high mortality mainly due to illegal killing and accidents. This situation makes the population vulnerable and actions aimed at a greater protection of the species are required.
Usually wolf populations are structured in stable packs and lone wolves; packs are formed by a pair of adults, by their offspring and other related individuals (i.e. the offspring of previous years), and sometime by adopted individuals, whereas lone wolves are erratic individuals that can temporarily establish in an area without packs. In general lone wolves are young dispersing from packs but they can also be adults moving far from their original pack because of pack disruption or break off for several causes (killing by humans, low prey availability and related increasing aggressiveness, natural death of the dominant pair) (Mech and Boitani, 2003). Packs are established in areas with high prey availability, because only a high availability of preferred prey can dampen the aggressiveness of the pack members and avoid pack disruption (Thurber and Peterson, 1993). Dispersing and erratic individuals use the areas without wolf packs that can be considered suboptimal habitats because of the low prey availability, high human disturbance, and possibly potential problems with local people (Fritts and Mech, 1981). Illegal killing can break the packs, increasing erratic wolves and reproductive pairs that can have a greater impact in particular on livestock rearing (Wielgus and Peebles, 2014).
The objective of the present study was to determine which factors influence wolf diet, in particular, the choice of livestock as prey, which is the first step to find solutions for wolf conservation. With this aim, we determined wolf diet, by analyses of scats collected in the whole Liguria region from 2008 to 2013. We highlighted the factors influencing it, i.e. years, seasons, ungulate abundance, and social structure of wolves (packs or dispersing individuals). Then we related livestock consumption to environmental features, wild ungulate abundance and diversity, husbandry characteristics, wolf grouping and habitat occupancy behavior (stable packs or dispersing individuals).
Section snippets
Study area
This research was carried out in the Liguria region, north Italy (44°30′16″, 8°24′10″). The study area spreads over 5343 km2 including a part of the Northern Apennines and of the Western Italian Alps, until the border with France. The region is divided in four provinces, Imperia, Savona, Genoa and La Spezia, respectively from the western to the eastern part (Fig. 1). Altitude ranges from 0 to 2153 m a.s.l.; 36% of the area is between 0 and 400 m a.s.l., 35% between 400 and 800 m, 21% between 800 and
Genetic analysis
Genetic identifications of the 403 samples yield 205 (50.8%) reliable multilocus genotypes, corresponding to 58 wolves (31 males M and 27 females F), 5 dogs (4 M, 1 F), 9 wolf × dog hybrid individuals (8 M, 1 F). Wolf individuals were sampled from a minimum of 1 to a maximum of 10 times. The hybrids were sampled from 1 to 3 times while the 5 dogs once each.
Parentage analyses led to the assigning of 20–21 wolves to five distinct packs (Fig. 1, Table 1), respectively named: Imperia pack, Savona
Discussion
The diet of wolves in the Liguria region is characterized by a medium–high occurrence of wild ungulates and by an important part consisting of large domestic prey, the other food categories being a negligible fraction of the diet. This picture places the food habits of wolves in our study area between those of populations preying almost exclusively on wild herbivores and those of wolves living mainly at the expense of livestock and other food of human origin, that can be found in human altered
Conclusion
In Liguria, as in many countries of southern Europe, conflicts between wolf conservation and husbandry are far from being solved and they are an important threat to wolf conservation, as the high number of wolves found illegally killed demonstrates (12 individuals out of 16 confirmed dead between 2007 and 2014 in the whole region). Poaching by shooting and poisoning is the main mortality factor of wolves in the region and in Italy, and can be related to the damage to livestock farms (Lovari et
Acknowledgments
This research was supported by the Liguria Region, by the Regional Park “M. Antola” (Regional Operational Program — European Regional Development Fund 2007–2013 - CUP B37E12000040009). We thank F. Puopolo, L. Schenone, D. Signorelli, and M. Zanzottera for their help in field work as well as the personnel of the Forestry Corp and Provincial Police who helped in collecting data. V. Devictor, S. Lovari, and an anonymous referee provided helpful comments to an early draft of the manuscript.
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