Old grandmothers provide essential care to their young granddaughters in a free-ranging group of Japanese monkeys (Macaca fuscata)
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This study reports 2 cases in which old grandmothers without dependent offspring provided essential care to their young granddaughters in a free-ranging group of Japanese monkeys (Macaca fuscata). In the first case, a 24-year-old grandmother provided essential care for the survival of her 2-month-old granddaughter for at least 6 days during which the mother had temporarily disappeared from the group for reasons unknown. In the second case, a 14-month-old granddaughter began sucking from her 23-year-old grandmother within 6 weeks after her mother gave birth to a younger sibling. For at least 6 months, the grandmother exhibited various patterns of maternal behavior toward her granddaughter. The behavioral data obtained in this study indicated that old yet healthy females without dependent offspring could contribute to the survival of their young grandchildren.
KeywordsGrandmother Granddaughter Japanese monkeys
Behavioral studies conducted on Katsuyama group of Japanese monkeys were approved by the Animal Research Committee of Graduate School of Human Sciences, Osaka University. We sincerely thank the park staff of Maniwa City for their help and encouragement throughout the study.
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