Cooperation improves the access of wild boars (Sus scrofa) to food sources

Wild boar is a highly polycotous ungulate species, characterized by a complex and dynamical social organization based on the maintenance of long-term bonds between mother and daughters. The roots of this social organization have to be researched at the individual level, considering adaptations that improve fitness in hostile environments. We used information collected by camera-traps at artificial feeding sites, in two contrasting environments in Bulgaria (mountain habitat) and Italy (sub-Mediterranean habitat). We recorded 417 and 885 distinct groups on 7 and 11 foraging sites in Bulgaria and Italy, respectively. We computed (controlling for time range, study area and supplementary feeding site) an index of effective foraging time of the different social groups. We observed a positive and significant effect of the number of conspecifics of the same social group on the effective foraging time. The impact of the other social classes on effective foraging time is also positive, and males, yearlings, and juveniles benefited more from the presence of other social classes, while females were less affected. The access of the different social groups to foraging sites is not random. Males and yearlings play producers (i.e., search for food) and are prone to attend foraging sites before adult females and subadults, so attaining a larger foraging efficiency with respect to a situation where other groups are already present on the feeding site. Wild boars exhibit a more complex social organisation than previously believed, where cooperation prevails largely on competition. A rough division of labour is also present: yearlings, males, and juveniles use to play producers and assume a significant amount of risk determined by the presence of predators or hunters.