A Bruce Effect in Wild Geladas

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Science  09 Mar 2012:
Vol. 335, Issue 6073, pp. 1222-1225
DOI: 10.1126/science.1213600
  1. Fig. 1

    Number of births for groups with and without male replacements. Sum of births from groups with a male replacement (light gray) as compared with a similar-sized group at the same time that did not experience a male replacement (black). Paired groups were compared (Wilcoxon signed-ranks test) 0 to 6 months before male replacement, 0 to 6 months after male replacement, and 7 to 12 months after male replacement.

  2. Fig. 2

    (A) Hormonally determined pregnancy failures. Hormone (fE ng/g) profiles of three representative females that aborted after male replacement. Each black diamond represents one hormone sample from a given female. Dark vertical lines [for both (A) and (B)] indicate the time of male replacement. (B) Composite comparison between hormone (fE ng/g) profiles of successful (“successful,” black circles) and aborted (“failed,” gray squares) pregnancies across each trimester (±SEM). Estrogens of successful and aborted pregnancies show no significant differences before male replacement. After male replacement (vertical line), aborted pregnancy estrogen profiles drop well below pregnancy levels. Sample size (number of pregnancies) is indicated in italics above the x axis. One female that aborted was not included in the figure because we were unable to obtain a hormone sample from her immediately after male replacement; she is known to have aborted because she expelled a poorly developed fetus (23) the day after a male replacement.

  3. Fig. 3

    Boxplot of interbirth intervals between successfully weaned infants (whiskers represent highest and lowest values). Interbirth intervals (in years) for females experiencing different events between infants. None: two successive infants; pregnancy termination: an abortion between surviving infants; infant death: an infant death between surviving infants. Sample size (number of interbirth intervals) is indicated in italics above the x axis.