Research ArticleMATING BEHAVIOR

Why do some males choose to breed at home when most other males disperse?

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Science Advances  18 Mar 2016:
Vol. 2, no. 3, e1501236
DOI: 10.1126/sciadv.1501236
  • Fig. 1 Change in social rank of philopatric males and dispersers with time spent in the clan (tenure).

    Data are mean standardized social ranks (symbols) ± SDs (vertical bars). Standardized ranks were calculated at the start of each year of tenure by distributing ranks evenly between the highest (standardized rank +1) and lowest (standardized rank −1) rank in the hierarchy of sexually active males of a clan. Males with standardized ranks within the top, middle, and lower thirds of the total range (delimited by dashed horizontal lines) were high-ranking, medium-ranking, and low-ranking, respectively.

  • Fig. 2 Comparison of the reproductive rate of philopatric males and dispersers.

    Reproductive rate is the mean annual number of offspring sired during the first 6 years of tenure. Boxes indicate the interquartile range around the median (horizontal bar), vertical bars represent reproductive rates that lie within 1.5 times the interquartile range, and shaded areas represent the distribution (kernel density estimate) of the data.

  • Fig. 3 Influence of male origin and combined effect of male origin and social rank on male reproductive rate.

    (A to D) Reproductive rate is the mean annual number of offspring sired with high-ranking females (A and B) and medium-ranking and low-ranking females (C and D). Male origin refers to whether males grew up in the chosen breeding clan (native males) or in another clan (foreigners). Data are back-transformed predictions derived from GLMMs that considered the covariates male origin, male social rank, maternal social rank, number of breeding partners at clan choice, year of tenure, and interaction between male origin and year of tenure. Values for the influence of male origin are adjusted means considering all other covariates at their population mean. Values for the combined influence of male origin and social rank are adjusted means computed as for male origin but considering the mean social rank of native males and foreigners, respectively, at each year of tenure. Because male origin and social rank represent the two main traits characterizing philopatric males and dispersers, their combined effect shows the difference in reproductive rate between philopatric males and dispersers.

  • Fig. 4 Effect of clan quality on male clan choice and propensity of philopatry.

    (A) Distribution of natal and nonnatal clans across eight clan qualities as defined by the number of likely female breeding partners on the date a male chose a clan. Clan quality 1 corresponds to the clan with the highest number of likely breeding partners, and clan quality 8 corresponds to the clan with the lowest number of likely breeding partners. (B) Proportion of natal and nonnatal clans of each clan quality. (C) Distribution of clan choices by dispersers across the eight clan qualities. (D) Expected and observed number of philopatric males that chose each clan quality. (E) Expected and observed proportions of philopatric males across the eight clan qualities.

  • Fig. 5 Survivorship functions of the tenure of males in their first breeding clan.

    Curves correspond to the nonparametric Kaplan-Meier estimator of the proportion of philopatric males and dispersers with a total tenure longer than a given tenure. Data include complete tenures as exact values and tenures of males still alive at the end of the study as right-censored data (tick marks). Shaded areas represent 95% CIs.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/3/e1501236/DC1

    Table S1. The age at which male spotted hyenas chose their first breeding clan as a function of male origin (native or foreigner), maternal social rank, and identities of natal and chosen clans.

    Table S2. The tenure at which male spotted hyenas sired their first offspring as a function of male origin (native or foreigner), maternal social rank, the number of likely breeding partner at clan choice, and the identity of the chosen clan.

    Table S3. The total number of offspring sired each year by male spotted hyenas as a function of male origin (native or foreigner), male social rank, maternal rank, the number of likely breeding partners at clan choice, year of tenure, and the interaction between male origin and year of tenure.

    Table S4. The number of offspring of high-ranking females sired each year by male spotted hyenas as a function of male origin (native or foreigner), male social rank, maternal social rank, the number of likely breeding partners, year of tenure, and the interaction between male origin and year of tenure.

    Table S5. The number of offspring of medium- and low-ranking females sired each year by male spotted hyenas as a function of the combined effect of male origin and year of tenure, male social rank, maternal social rank, and the number of likely breeding partners.

  • Supplementary Materials

    This PDF file includes:

    • Table S1. The age at which male spotted hyenas chose their first breeding clan as a function of male origin (native or foreigner), maternal social rank, and identities of natal and chosen clans.
    • Table S2. The tenure at which male spotted hyenas sired their first offspring as a function of male origin (native or foreigner), maternal social rank, the number of likely breeding partner at clan choice, and the identity of the chosen clan.
    • Table S3. The total number of offspring sired each year by male spotted hyenas as a function of male origin (native or foreigner), male social rank, maternal rank, the number of likely breeding partners at clan choice, year of tenure, and the interaction between male origin and year of tenure.
    • Table S4. The number of offspring of high-ranking females sired each year by male spotted hyenas as a function of male origin (native or foreigner), male social rank, maternal social rank, the number of likely breeding partners, year of tenure, and the interaction between male origin and year of tenure.
    • Table S5. The number of offspring of medium- and low-ranking females sired each year by male spotted hyenas as a function of the combined effect of male origin and year of tenure, male social rank, maternal social rank, and the number of likely breeding partners.

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