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Data from: Sex bias in mortality risk changes over the lifespan of bottlenose dolphins

McEntee, Molly1; Foroughirad, Vivienne1; Krzyszczyk, Ewa2; Mann, Janet1

Published Feb 11, 2025 on Dryad. https://doi.org/10.5061/dryad.dz08kps30

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Feb 11, 2025 version files 140.51 KB
Feb 11, 2025 version files 138.36 KB

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Abstract

Research on sex biases in longevity in mammals often assumes that male investment in competition results in a female survival advantage that is constant throughout life. We use 35 years of longitudinal data on 1,003 wild bottlenose dolphins (Tursiops aduncus) to examine age-specific mortality, demonstrating a crossover effect of sex on mortality hazard over the five-decade lifespan of a social mammal. Males are at higher risk of mortality than females during the juvenile period, but female mortality hazard begins to exceed male mortality hazard in the mid-teens, coincident with the onset of female reproduction. Female mortality hazard remains higher than male hazard throughout most of adulthood. Bottlenose dolphins have an intensely male-competitive mating system, and juvenile male mortality has been linked to social competition. Contrary to predictions from classical sexual selection theory, however, male-male competition does not result in sustained male-biased mortality. As female dolphins experience high costs of sexual coercion in addition to long and energetically expensive periods of gestation and lactation, this suggests that substantial female investment in reproduction can elevate female mortality risk relative to males in adulthood.