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Pregnancy rate and conception date in a wild population of Japanese monkeys
Shin-ichi Hayama1, Sachie Nakiri, Fumiharu Konno
1Laboratory of Wildlife Medicine, Nippon Veterinary and Life Science University, Musashino, Tokyo 180–8602, Japan. hayama@nvlu.ac.jp
Abstract:
This study is the first to determine the conception dates of specific individuals and estimate the pregnancy rate of a wild population in Japanese monkeys. The conception dates estimated from the embryonic ages of 37 fetuses were distributed over 128 days between September 17 and January 23, with a mean conception date of November 19 (SD=29.2 days). A comparison of the mean conception dates among age groups showed a significantly delayed conception in the subadult animals (aged 4 to 5 years; December 5, n=8) than in the adult animals (aged 6 or more years; November 15, n=29; P<0.03). The mean pregnancy rate among animals aged 4 years or more in this local population was estimated to be 48.5% (32/66).
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