Dogs are exceptionally well adapted to life close to humans, and alterations in their endocrine system during the domestication process may be an underlying mechanism. In particular, it has been suggested that low circulating cortisol concentrations in conjunction with simultaneously high oxytocin concentrations may have resulted in dogs' increased docility (‘selection for tameness’ hypothesis) and heightened propensity to interact and form relationships with humans (‘hypersociability’ hypothesis) compared to wolves. To investigate this, we analyzed cortisol and oxytocin metabolite concentrations from urine samples of hand-raised, pack-living domestic dogs and their non-domestic relatives, grey wolves. Based on the hypotheses outlined above, we predicted lower cortisol but higher oxytocin concentrations in dogs than wolves. In contrast to our prediction, we found higher cortisol concentrations in dogs than wolves. However, oxytocin concentrations were higher in dogs compared to wolves although the effect was relatively small. Indeed, male dogs had the highest oxytocin concentrations while female dogs' oxytocin concentrations were comparable to wolves'. Feeding status, reproductive phase, and conspecific social interactions also significantly affected cortisol and oxytocin concentrations. Furthermore, we compared two methods of correcting for variable water content of urine samples. We discuss our results in light of physiological and behavioral changes during domestication and highlight the importance of accounting for confounding variables in future studies.

狗非常适应接近人类的生活，驯化过程中内分泌系统的改变可能是一个潜在的机制。特别是，有人提出，低循环皮质醇浓度与同时高浓度催产素可能导致狗的温顺性增加（“驯服选择”假说）和与人类互动和建立关系的倾向增加（“超社交性”假说） ) 与狼相比。为了研究这一点，我们分析了手工饲养的、群居的家犬及其非家养亲属灰狼的尿液样本中的皮质醇和催产素代谢物浓度。基于上述假设，我们预测狗的皮质醇含量低于狼，但催产素浓度高于狼。与我们的预测相反，我们发现狗的皮质醇浓度高于狼。然而，与狼相比，狗的催产素浓度更高，尽管影响相对较小。事实上，公狗的催产素浓度最高，而母狗的催产素浓度与狼相当。喂养状态、生殖阶段和同种社会互动也显着影响皮质醇和催产素浓度。此外，我们比较了两种校正尿液样本中可变水含量的方法。我们根据驯化过程中的生理和行为变化来讨论我们的结果，并强调在未来研究中考虑混杂变量的重要性。与狼相比，狗的催产素浓度更高，尽管影响相对较小。事实上，公狗的催产素浓度最高，而母狗的催产素浓度与狼相当。喂养状态、生殖阶段和同种社会互动也显着影响皮质醇和催产素浓度。此外，我们比较了两种校正尿液样本中可变水含量的方法。我们根据驯化过程中的生理和行为变化来讨论我们的结果，并强调在未来研究中考虑混杂变量的重要性。与狼相比，狗的催产素浓度更高，尽管影响相对较小。事实上，公狗的催产素浓度最高，而母狗的催产素浓度与狼相当。喂养状态、生殖阶段和同种社会互动也显着影响皮质醇和催产素浓度。此外，我们比较了两种校正尿液样本中可变水含量的方法。我们根据驯化过程中的生理和行为变化来讨论我们的结果，并强调在未来研究中考虑混杂变量的重要性。催产素浓度与狼相当。喂养状态、生殖阶段和同种社会互动也显着影响皮质醇和催产素浓度。此外，我们比较了两种校正尿液样本中可变水含量的方法。我们根据驯化过程中的生理和行为变化来讨论我们的结果，并强调在未来研究中考虑混杂变量的重要性。催产素浓度与狼相当。喂养状态、生殖阶段和同种社会互动也显着影响皮质醇和催产素浓度。此外，我们比较了两种校正尿液样本中可变水含量的方法。我们根据驯化过程中的生理和行为变化来讨论我们的结果，并强调在未来研究中考虑混杂变量的重要性。