Data_Sheet_1_Context-Specific Arousal During Resting in Wolves and Dogs: Effects of Domestication?.docx

Due to domestication, dogs differ from wolves in the way they respond to their environment, including to humans. Selection for tameness and the associated changes to the autonomic nervous system (ANS) regulation have been proposed as the primary mechanisms of domestication. To test this idea, we compared two low-arousal states in equally raised and kept wolves and dogs: resting, a state close to being asleep, and inactive wakefulness, which together take up an important part in the time budgets of wolves and dogs. We measured arousal via cardiac output in three conditions: alone, with a familiar human partner, or with pack members (i.e., conspecifics). Specifically, we compared heart rate (HR) and heart rate variability (HRV) of six wolves and seven dogs. As patterns of resting can vary adaptively, even between closely related species, we predicted that dogs would be generally more aroused than wolves, because living with humans may come with less predictable contexts than living with conspecifics; hence, dogs would need to be responsive at all times. Furthermore, we predicted that due to the effects of domestication, emotional social support by familiar people would reduce arousal more in dogs than in equally human-socialized wolves, leading to more relaxed dogs than wolves when away from the pack. Overall, we found a clear effect of the interactions between species (i.e., wolf versus dog), arousal state (i.e., resting or awake inactive) and test conditions, on both HR and HRV. Wolves and dogs were more aroused when alone (i.e., higher HR and lower HRV) than when in the presence of conspecifics or a familiar human partner. Dogs were more relaxed than wolves when at rest and close to a familiar human but this difference disappeared when awake. In conclusion, instead of the expected distinct overall differences between wolves and dogs in ANS regulation, we rather found subtle context-specific responses, suggesting that such details are important in understanding the domestication process.

鉴于驯化过程，犬类与狼在应对环境方面存在差异，包括对人类的反应。选择驯顺性及其相关的自主神经系统（ANS）调节变化被提出作为驯化的主要机制。为验证此观点，我们比较了在同等养育和饲养条件下，狼和犬类在两种低唤醒状态下的表现：休息状态，一种接近睡眠的状态，以及非活跃觉醒状态，这两种状态共同构成了狼和犬类时间预算中的重要部分。我们通过三种条件下的心输出量来测量唤醒水平：独自一人、与熟悉的人类伙伴在一起或与群体成员（即同种个体）在一起。具体而言，我们比较了六只狼和七只犬的心率（HR）和心率变异性（HRV）。鉴于休息状态的模式可能因适应性而异，甚至在密切相关的物种之间，我们预测犬类相较于狼类普遍具有更高的唤醒水平，因为与人类生活可能伴随更不可预测的情境，因此犬类需要时刻保持警觉。此外，我们预测由于驯化效应的影响，熟悉的人的情感社会支持在犬类中比同等人类社会化程度的狼类中更能减少唤醒水平，导致犬类在离开群体时比狼类更为放松。总体而言，我们发现物种间互动（即狼与犬）、唤醒状态（即休息或非活跃觉醒）和测试条件对心率（HR）和心率变异性（HRV）均产生了显著影响。狼和犬在独自一人时（即心率更高、心率变异性更低）比在同类个体或熟悉的人类伙伴在场时更为唤醒。当犬类在休息状态且靠近熟悉的人类时，其放松程度高于狼类，但这种差异在清醒状态下消失。总之，与预期的狼与犬在自主神经系统调节方面的整体显著差异相反，我们发现了微妙且情境特定的反应，这表明这些细节对于理解驯化过程至关重要。