The great Indian joint families of free-ranging dogs

Cooperative breeding is an excellent example of cooperation in social groups. Domestic dogs have evolved from cooperatively hunting and breeding ancestors but have adapted to a facultatively social scavenging lifestyle on streets, and solitary living in human homes. Pets typically breed and reproduce under human supervision, but free-ranging dogs can provide insights into the natural breeding ecology of dogs. We conducted a five year-long field based behavioural study on parental care of free-ranging dogs in India. 23 mother-litter units, belonging to 15 groups were observed, which revealed the presence of widespread allo-parenting by both adult males and females. While all the females were known to be related to the pups receiving care, the relatedness with the males could not be determined. Hence, we coined the term “putative father” for caregiving males. Allomothers provided significantly less care than the mothers, but the putative fathers showed comparable levels of care with the mothers. Mothers invested more effort in nursing and allogrooming, while the putative fathers played and protected more. Our observations provide support for both the “benefit-of-philopatry” and “assured fitness returns” hypotheses. Free-ranging dogs are not cooperative breeders like wolves but are rather communal breeders; their breeding biology bearing interesting similarities with the human joint family system. This breeding strategy is likely to have played an important role in increasing pup survival in a stochastic environment and helping to adapt to living among humans during the domestication of dogs.

合作繁殖（Cooperative breeding）是社会群体中合作行为的绝佳范例。家犬由以合作狩猎与繁殖为生存方式的祖先演化而来，但如今已适配两种生活模式：街头的兼性社会性食腐群体生活，以及人类家庭中的独居状态。宠物犬通常在人类监督下进行繁殖，但流浪犬（free-ranging dogs）能够为我们揭示犬类的自然繁殖生态学特征。我们在印度开展了一项为期五年的野外行为学研究，聚焦流浪犬的亲代抚育行为。研究共观测了隶属于15个群体的23个母犬-幼崽群，结果显示成年雌雄个体均存在广泛的异亲抚育（allo-parenting）行为。已知所有参与抚育的雌性个体均与受抚育幼崽存在亲缘关系，但无法确定其与雄性抚育者的亲缘关联。为此我们将提供抚育行为的雄性个体命名为‘推定父本（putative father）’。异亲雌性提供的抚育量显著少于母犬自身，但推定父本的抚育水平与母犬相当。母犬会投入更多精力进行哺乳与互理毛（allogrooming），而推定父本则更多参与幼崽玩耍互动与护卫行为。我们的观测结果同时支持‘亲缘留守收益（benefit-of-philopatry）’与‘确定适合度回报（assured fitness returns）’两大假说。流浪犬并非如狼那般属于合作繁殖类群，而是群体繁殖者；它们的繁殖生物学特征与人类的联合家庭制度存在有趣的相似之处。这种繁殖策略或在提升随机波动环境下幼崽存活率、以及助力家犬在驯化过程中适应与人类共处的生活方面发挥了关键作用。