Age-graded dominance hierarchies and social tolerance in packs of free-ranging dogs

It is believed that domestic dogs rarely form packs with age-graded hierarchical structures similar to those found in wolves. Dog-wolf comparisons in captivity suggest that human control has reduced dog dependency on cooperation with conspecifics, resulting in a more despotic dominance order. However, free-ranging dogs are under stronger natural selection than purebred dogs. They are dependent on companions’ social support but usually exhibit lower reproductive skew than wolves, possibly because access to easily available human-derived food may have relaxed within-group competition. We investigated social dominance in 5 packs of mongrel dogs living in a free-ranging or semifree-ranging state. We aimed at replicating the findings of the few studies that detected a dominance hierarchy in dogs using a larger sample of packs. Additionally, we provided behavioral measures of social tolerance. We found that a linear hierarchy existed in all packs studied and that the rank order was positively related to age in all packs but one. In 2 packs in which testing was possible, age was a better predictor of dominance than body size. Potentially injurious aggression was very rare. Hierarchy steepness in dogs was similar to that found in wolves and in tolerant primates. Submissive reversals were more common in dogs than in wolves. These results suggest that age-graded hierarchies in dogs are more common than previously thought, that rank is not usually acquired through fighting because subordinates rely on the guidance of elders, and contradict the view that domestication has increased despotism in dog