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[转载]33000年的“羁绊”:因为人,狗的眼神变了,承受的压力也大了

要问哪种动物是人类最好的朋友,被人类驯化了33000年的狗狗当仁不让。


我们常用 “忠诚”“能干”“伴侣”“善解人意”等词语来描述狗,说明这种动物与人关系紧密。然而仍有层出不穷的新证据显示,狗与人之间的纽带或许比我们已经知道的还要强


近期就有两篇与狗有关的新论文,分别证明在两个意义的“长时间”互动过程中,狗狗因为受到人的影响,发生了某些深刻的改变。


确认过,是爱你的眼神



一项研究发表在最新一期《美国科学院院刊》。英国朴次茅斯大学(University of Portsmouth)的Juliane Kaminski博士与其合作伙伴,详细比较了狗(Canis familiaris)和狼(Canis lupus)的面部肌肉组织特征。第一次发现,狗的眼睛上方比狼多出一条肌肉。而这条小小的肌肉,可以让狗扬起内眉、睁大眼睛。


狗和狼的面部肌肉组织非常相似,唯有眼睛上方不同(图片来源:参考资料[1])


研究者给狗狗这条新肌肉带动的动作命名为AU101。共同作者、美国杜肯大学(Duquesne University)的解剖学教授Anne Burrows说:“我们发现,在狼的面部,做抬眉动作的肌肉只是一些稀疏、不规则的纤维束。”


研究人员还分析了狗和狼的行为,观察到在与人接触的短短2分钟内,狗狗抬眉睁眼的动作比狼更多、幅度更大


▲注意箭头所指的变化(视频来源:参考资料[1])


“狗狗抬眉的表现力可能是人类在驯化过程中无意识偏好的选择结构。当狗做出这种动作时,似乎会让人更愿意照顾它们。这会让那些抬眉更厉害的狗拥有更多的选择优势。”Kaminski博士解释。


科学家分析,向上抬眼的动作会让狗的眼睛看起来更大、更像宝宝、更显得无辜,让人想养它们(图片来源:The University of Portsmouth)


在研究团队观察分析的多只狗狗当中,唯一没有AU101的是西伯利亚哈士奇。研究人员解释说,因为哈士奇属于比较古老的犬种。



心疼:人若压力大,狗也累趴下



另一项研究发表在Scientific Reports。瑞典林雪平大学(Linköping University)的Lina Roth博士和同事们发现,长时间压力大的养狗者,会把压力“传”给狗。这项研究第一次揭示了长期压力水平在不同物种之间的同步


研究者招募了33只喜乐蒂牧羊犬、25只边境牧羊犬以及它们的主人。分别在夏季和冬季测量了毛发/头发的皮质醇水平,来评估狗和人的长期压力


▲该研究主要作者Lina Roth博士和她的狗(图片来源:Linköping University实验室官网)


皮质醇常被称为“压力激素”,当我们处于应激状态时,肾上腺分泌皮质醇。测量血液或唾液内的皮质醇水平,可以了解短时间内的急性应激状态。由于皮质醇会被头发吸收并随着毛发的生长而累积,测量一段发丝中的皮质醇浓度可以了解较长时间段的慢性压力程度。


分析结果显示,当狗主人头发皮质醇水平高时,其狗狗的皮质醇水平也会上升,在母犬身上表现尤其明显。换言之,狗主人长期压力大,狗狗“感同身受”,压力水平同步上升。


这些科学研究提供的证据,真是让狗党看了流泪,猫党看了沉默啊……




论文

论文标题:Evolution of facial muscle anatomy in dogs
作者:Juliane Kaminski, Bridget M. Waller, Rui Diogo, Adam Hartstone-Rose, Anne M. Burrows
发表时间:2019/06/17
数字识别码:10.1073/pnas.1820653116
摘要:


Domestication shaped wolves into dogs and transformed both their behavior and their anatomy. Here we show that, in only 33,000 y, domestication transformed the facial muscle anatomy of dogs specifically for facial communication with humans. Based on dissections of dog and wolf heads, we show that the levator anguli oculi medialis, a muscle responsible for raising the inner eyebrow intensely, is uniformly present in dogs but not in wolves. Behavioral data, collected from dogs and wolves, show that dogs produce the eyebrow movement significantly more often and with higher intensity than wolves do, with highest-intensity movements produced exclusively by dogs. Interestingly, this movement increases paedomorphism and resembles an expression that humans produce when sad, so its production in dogs may trigger a nurturing response in humans. We hypothesize that dogs with expressive eyebrows had a selection advantage and that “puppy dog eyes” are the result of selection based on humans’ preferences.


论文


论文标题:Long-term stress levels are synchronized in dogs and their owners

作者:Ann-Sofie Sundman, Enya Van Poucke, Ann-Charlotte Svensson Holm, Åshild Faresjö, Elvar Theodorsson, Per Jensen, Lina S. V. Roth
发表时间:2019/06/06
数字识别码:10.1038/s41598-019-43851-x
摘要:This study reveals, for the first time, an interspecific synchronization in long-term stress levels. Previously, acute stress, has been shown to be highly contagious both among humans and between individuals of other species. Here, long-term stress synchronization in dogs and their owners was investigated. We studied 58 dog-human dyads and analyzed their hair cortisol concentrations (HCC) at two separate occasions, reflecting levels during previous summer and winter months. The personality traits of both dogs and their owners were determined through owner-completed Dog Personality Questionnaire (DPQ) and human Big Five Inventory (BFI) surveys. In addition, the dogs’ activity levels were continuously monitored with a remote cloud-based activity collar for one week. Shetland sheepdogs (N = 33) and border collies (N = 25), balanced for sex, participated, and both pet dogs and actively competing dogs (agility and obedience) were included to represent different lifestyles. The results showed significant interspecies correlations in long-term stress where human HCC from both summer and winter samplings correlated strongly with dog HCC (summer: N = 57, χ2 = 23.697, P < 0.001, β = 0.235; winter: N = 55, χ2 = 13.796, P < 0.001, β = 0.027). Interestingly, the dogs’ activity levels did not affect HCC, nor did the amount of training sessions per week, showing that the HCC levels were not related to general physical activity. Additionally, there was a seasonal effect in HCC. However, although dogs’ personalities had little effects on their HCC, the human personality traits neuroticism, conscientiousness, and openness significantly affected dog HCC. Hence, we suggest that dogs, to a great extent, mirror the stress level of their owners.



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