Research ArticleEVOLUTIONARY BIOLOGY

Postweaning maternal care increases male chimpanzee reproductive success

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Science Advances  18 Sep 2020:
Vol. 6, no. 38, eaaz5746
DOI: 10.1126/sciadv.aaz5746
  • Fig. 1 The impact of maternal loss on male chimpanzees’ reproductive careers.

    Impact of maternal loss on (A) alpha tenure, (B) age at first sire, and (C) likelihood of siring offspring. (D) Impact of alpha tenure on likelihood of siring offspring. Boxes show the median, 25th, and 75th percentiles, and whiskers are interquartile range × 1.5. (D) Model line (dashed) and 95% confidence intervals (gray), and larger points denote larger number of observations.

  • Fig. 2 Mother, Sumatra, grooming her 9 year old son, Solibra.

    Photograph by L.S.

  • Table 1 Models testing the impact of maternal loss on male chimpanzee alpha tenure, age at first siring and reproductive success.

    Bold, P < 0.05; italic, P < 0.01. Reference category of factors is in parenthesis. Asterisk (*) indicates test predictor. Full versus null model comparisons: (1) Gaussian: F3,19 = 3.718, P = 0.068; (2) Gaussian: df = 1, F3,19 = 15.454, P = 0.0008; and (3) Poisson: df = 1, χ2 = 5.871, P = 0.015. Offset terms: average number of males present per conception and number of conceptions resulting in viable births across reproductive years per male. Z transformed: all continuous predictor variables. Effect sizes = R2.

    TermEstimateSECIFPR2
    1. Alpha tenure
    Intercept2.4610.5052.121, 2.829
    Orphan (yes)*1.3550.702−1.707 to −1.0333.7180.0680.163
    Reproductive years1.5470.3621.191 to1.718 18.2400.00040.489
    Average males per conception−0.5720.360−0.797 to 0.3742.5190.1280.117
    2. Age at first siring
    Intercept13.4351.20512.292 to 13.849
    Orphan (yes)*3.0410.7732.763 to 3.44815.4530.00080.448
    Maximum dominance0.7250.3990.519 to 0.9043.2870.0850.147
    Average males per conception−0.0510.176−0.127 to 0.0650.0850.7720.004
    TermEstimateSECIχ2P
    3. Number of offspring
    Intercept−0.0100.234−0.133 to 0.237
    Orphan (yes)*−0.8630.367−1.103 to −0.7185.8720.0150.297
    Alpha tenure0.3370.1380.239 to 0.4006.1330.0130.329

Supplementary Materials

  • Supplementary Materials

    Postweaning maternal care increases male chimpanzee reproductive success

    Catherine Crockford, Liran Samuni, Linda Vigilant, Roman M. Wittig

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    • Tables S1 and S2
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