Non-invasive collection and analysis of semen in wild macaques
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Assessments of primate male fertility via semen analyses are so far restricted to captivity. This study describes a non-invasive method to collect and analyse semen in wild primates, based on fieldwork with Yakushima macaques (Macaca fuscata yakui). Over nine mating seasons between 1993 and 2010, 128 masturbatory ejaculations were recorded in 21 males of 5 study troops, and in 11 non-troop males. In 55 %, ejaculate volume was directly estimated, and in 37 %, pH-value, sperm vitality, numbers, morphology and swimming velocity could also be determined. This approach of assessing semen production rates and individual male fertility can be applied to other primate taxa, in particular to largely terrestrial populations where males masturbate frequently, such as macaques and baboons. Furthermore, since explanations of male reproductive skew in non-human primate populations have until now ignored the potential role of semen quality, the method presented here will also help to answer this question.
KeywordsNon-invasive semen collection Fertility analysis Masturbation Macaques Macaca fuscata yakui Yakushima
The study was funded by a grant (HSP III-D/97/16290) from the German Academic Exchange Service (DAAD), a stipend from the City of Berlin (Berliner Programm zur Förderung der Chancengleichheit für Frauen in Forschung und Lehre, N-16/04), the Japanese Society for the Promotion of Science (JSPS; pilot-1994/96), Shimazu Kyoto (2009–2011), Suzuki Corp. (1999–2001), and a private donor (1997 and 2010). I thank Volker Sommer, Joseph Soltis, Mike Huffmann and Ute Radespiel for their encouragement during different stages of this project. Particular thanks go to Kiyoaki Matsubayashi, Juichi Yamagiwa, Hideki Sugiura, Sachiko Hayakawa, Miki Matsubara, Goro Hanya, and two field assistants as well as to all members of the Yakushima Research Group for support of my work in Japan and on Yakushima over the last two decades. I am grateful to Bettina Wachter and two anonymous reviewers for helpful comments on an earlier draft and to Anahita Kazem for proofreading the manuscript.
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