Data from: 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 dogs.学界普遍认为，家犬极少形成与灰狼类似的、按年龄分层的等级群体结构。圈养环境下的家犬-灰狼对比研究表明，人类的驯化管控已降低了家犬对同种个体合作的依赖，进而形成了更为威权的支配等级秩序。然而，相较于纯种犬，自由散养家犬面临更强的自然选择压力。它们依赖同伴的社会支持，但繁殖偏斜（reproductive skew）程度通常低于灰狼，这可能是因为易于获取人类提供的食物，缓解了群体内部的竞争。本研究对5群处于散养或半散养状态的混种家犬的社会支配等级展开了调查，旨在通过更大规模的群体样本，重现此前少数几项在家犬中检测到等级支配结构的研究结果；此外，本研究还提供了社会容忍度的行为测度指标。研究结果显示，所有被观测的犬群均存在线性等级结构，且除1个犬群外，其余所有犬群的等级顺位均与年龄呈正相关。在2个可开展测试的犬群中，年龄对支配等级的预测效果优于体型。具有潜在伤害性的攻击行为极为罕见。家犬的等级陡度（hierarchy steepness）与灰狼以及具有高社会容忍度的灵长类动物相似。顺从性反转行为在家犬中的出现频率高于灰狼。上述研究结果表明，家犬中按年龄分层的等级结构比此前人们认为的更为普遍；等级顺位通常并非通过打斗获得，因为低位个体依赖年长个体的指引；这一结果也与"驯化提升了家犬威权式等级特征"的观点相悖。