Journal Article Developmental changes in feeding behaviors of infant chimpanzees at Mahale, Tanzania: Implications for nutritional independence long before cessation of nipple contact

Matsumoto, Takuya

163 ( 2 )  , pp.356 - 366 , 2017-06 , Wiley-Blackwell
Objectives: Weaning of chimpanzees is considered to occur at 4-5-years-old with completecessation of nipple contact and timing of reconception calculated by inter-birth interval minus ges-tation length. This is also the basis of “early weaning” in humans (i.e., approximately 2.5-years-old).However, recent studies of the survival of orphans and the first molar (M1) eruption in wild chim-panzees have predicted that infants move toward nutritional independence at 3-years-old.Therefore, this study aimed to investigate ontogeny of feeding behavior at around 3-years-old inwild infant chimpanzees.Materials and methods: I studied 19 infants aged 1-60 months in the M group in MahaleMountains National Park, Tanzania. The total observation time was 518 h, 25 min.Results: At around 3-years-old, infant chimpanzees spent more total feeding time, and timefeeding on leaves, and food physically difficult to process without food transfer from other individ-uals. These results suggest that infant chimpanzees significantly reduced their dependence on milkfor nutrition at around 3-years-old, that is, before cessation of nipple contact.Discussion: This study suggests that M1 eruption in wild Eastern Chimpanzees is an index of theperiod when infants move toward nutritional independence with a key dietary transition. This isthe first study to provide behavioral evidence of the large temporal gap between nutritional inde-pendence of infants and reconception of mothers in great apes, and clarify the unique feature ofhuman life history whereby mothers can reconceive before an infant reaches nutritionalindependence.

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