Die soziale Organisation von frei lebenden Haushunden
Although nowadays most dogs in the world are living in a free-ranging state, relatively few studies have investigated the social organization of these animals. Pioneering studies suggested that domestication has greatly changed the social behaviour of free-ranging dogs relative to that of their wild ancestors. Actually, it is usually believed that, unlike wolves, free-ranging dogs have a limited capacity of forming stable family packs; moreover, their associations would lack a hierarchical structure affecting group activities, and they would be unable to effectively cooperate in territorial defence, in hunting and in raising puppies. These differences have often been interpreted as maladaptive consequences of artificial selection by humans. However, recent studies suggest that free-ranging (and free-breeding) dogs are genetically distinct from purebred dogs artificially selected by humans, being subjected to stronger natural selective pressures. Consequently, deviations of free-ranging dogs’ behaviour from the “wolf model” can be reasonably interpreted as natural adaptations of these animals to anthropic environments, in which dogs usually adopt the role of scavengers feeding mainly on human waste. Following this line of thought, I revise the scientific literature on free-ranging dogs’ behavioural ecology and propose an alternative interpretation of their social organization. First, I suggest that different accounts of the degree of social complexity of dogs can reflect differences in the methodological approaches employed by researchers. Moreover, I hypothesize that free-ranging dogs possess the potential to express several features of the wolf social organization indeed, although they do this to various degrees depending on how their behaviour is influenced by both humans and ecological conditions. Specifically, free-ranging pets (owned dogs who are allowed to roam free) tend to form mainly temporary associations with other dogs, whereas stray dogs (not-owned animals subsisting on human waste) can form stable packs under conditions of food abundance and low human interference. Recent ethological studies suggest that, contrary to previous belief, dog packs are often characterized by age-graded dominance hierarchies which affect several group activities: older dogs are usually dominant over younger group members, they lead collective movements and perform most breeding. Although the mating system of dogs is more promiscuous than that of wolves, both females and males exhibit mate choice, suggesting that sexual selection played an important, and neglected, role in dog evolution. Agonistic behavior in free-ranging dog packs appears much more ritualized than that reported for some pure breeds. Moreover, affiliative relationships between pack members seem to promote both coordination and formation of coalitions to defend resources against rival packs. Although intergroup competition seems to be less fierce in dogs than in wolves, cooperation is still functional since larger dog packs outcompete smaller ones in accessing food and space. It is suggested that the possibility to scavenge on humane refuse has decreased the importance of both cooperative breeding and hunting in dogs relative to wolves, although stray dogs are still flexible enough to express these behaviors to various degrees. Moreover, wild dogs (i.e. Australian and New Guinea dingoes that subsist mainly on natural prey) show a well developed cooperative breeding system similar to that of wolves. I conclude that the social behaviour of free-ranging dogs is much more flexible and complex than previously thought, and deserves further investigation.