Birth intervention and non-maternal infant-handling during parturition in a nonhuman primate
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Direct intervention in infant delivery by non-parturient individuals is a rare phenomenon in nonhuman primates. In contrast, birth assistance by other individuals, or the practice of midwifery, is universal among human societies and generally believed to be a behavior unique to our species. It has been proposed that the enlarged head of the human fetus and the relatively narrow birth canal constrained by bipedalism has made human parturition more difficult than in nonhuman primates, and these anatomic challenges have led to the rotation of the fetus in the birth canal and an occiput anterior (i.e., backward-facing) orientation of emergence. These characteristics have hindered the mother’s ability to self-assist the delivery of the infant, therefore necessitating assistance by other individuals or midwives for successful birth. Here we report the first high-definition video recordings of birth intervention behavior in a wild nonhuman primate, the white-headed langur (Trachypithecus leucocephalus). We observed that while a primiparous female gave birth to an infant in an occiput posterior (i.e., forward-facing) orientation, a multiparous female intervened in the delivery by manually pulling the infant out of the birth canal and cared for it in the following hours. Our finding shows extensive social interactions throughout parturition, and presents an unequivocal case of non-maternal intervention with infant birth in a nonhuman primate.
KeywordsBirth mechanism Midwife behavior Allomaternal nursing Colobine Monkey
We are grateful to Xiangdong Zhang, Chao Zhang, Wenkui You, Xinyang Li, Meiying Huang, Yanping Yang, Meijiao Wei, Jiajia Tan, and Jintong Lu for their assistance with video recordings and field observations. We thank Dr. Sarah Hrdy and two anonymous reviewers for their valuable comments on the early versions of the manuscript. The project was supported by Natural Science Foundation of China (Grant No. 31272329) to M. Yao and the research grants of Peking University to W. Pan and M. Yao. W. Pan designed and carried out the long-term study. T. Gu, Y. Pan, C. Feng, Y. Long, Y. Zhao, H. Meng and Z. Liang conducted video recordings and helped with individual identification. M. Yao analyzed data and wrote the paper. This study complied with protocols approved by the Guangxi Forestry Administration of China and adhered to the legal requirements of China.
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