The social circumstances of the maternal experience and its biobehavioral associations, in rhesus macaques (Macaca mulatta) - PubMed (original) (raw)

The social circumstances of the maternal experience and its biobehavioral associations, in rhesus macaques (Macaca mulatta)

Alexander J Pritchard et al. Anim Reprod Sci. 2026 Jun.

Abstract

Motherhood is a physiologically and behaviorally demanding process. We sought to examine how such changes might be expected to alter a mother's social position within her group and whether there were physiological changes concomitant to these dynamics. We recorded contact-sitting, grooming, huddling, and proximity behavior over two birth and breeding seasons on 120 females across two mixed-sex groups of rhesus macaques (Macaca mulatta) at the California National Primate Research Center. We also collected blood samples (from all available females in the first birth season and n = 60, thereafter) for blood chemistry and cytokine assays. The reproductive stage of females exhibited a strong influence on the group's sociality. We observed meaningfully increased connectivity and investment for proximity and contact-sit beginning in late pregnancy continuing after birth, relative to non-mothers, while accounting for past offspring count. Grooming connectivity and investment meaningfully increased during pregnancy, compared to non-mothers, but decreased after the first 50 days postpartum. The number of infants in the group meaningfully increased social associations for all behaviors, except huddling, yet only in the first birth season. Maternal assortment increased, likely due to a higher number of mothers available as social partners; postpartum, however, kin assortativity did not dramatically change. Reproductive status predicted variation in biomarkers whereby pregnant females had meaningfully decreased blood chemistry measures but increased cytokines, relative to non-pregnant females. In summary, maternal social behavior exhibited marked differences across the phases of pregnancy and postpartum that exhibited distinct changes across behaviors, yet these changes in social behavior were not associated with physiological variation beyond that associated to shifts in maternal status.

Keywords: Allostatic load; Breeding season; Multifactorial; Primates; Shared motherhood.

Copyright © 2026 The Authors. Published by Elsevier B.V. All rights reserved.

PubMed Disclaimer

Conflict of interest statement

Declaration of Competing Interest The authors have nothing to declare.

Figures

Fig. 1.

Fig. 1.

Study timeline. Note that the dates of behavioral collection were similar between the two groups, though group B was dissolved before the last collection period.

Fig. 2.

Fig. 2.

Model posterior draws shown using half-eye and interval density plots for undirected behavioral counts (y-axes) across the categories of reproductive status (x-axis). Behavior are, clockwise from top-left: proximity, grooming, huddling, and contact-sit.

Fig. 3.

Fig. 3.

Posterior estimates for counts of each behavior. Behaviors are, clockwise from top-left: proximity, grooming, huddling, and contact-sit. Scaled infant count (x-axis) as a predictor of behavior count (y-axis) in each of the two birth seasons (panels). Note the change in association between seasons.

Fig. 4.

Fig. 4.

Boxplots of changes to motherhood assortativity with early (top row) or late infancy (bottom row) minus assortativity indices from the second (left column) or third trimester (right column) for three behaviors (x-axis and fill color). Note that equivalence between two periods is emphasized by 0 at the y-intercept.

Fig. 5.

Fig. 5.

Violin plots of Jaccard similarity indices (y-axes) for three of the behaviors (x-axes; fill color). Plots are organized for year one (top row) or two (bottom row) and compare breeding season associations to associations in the preceding pregnancy (left column) or early infancy (right column).

Fig. 6.

Fig. 6.

Posterior estimates for the univariate biomarker models. Points show the median estimate, with inner intervals extending to the 50 % credible interval, and outer intervals to the 95 % credible interval. Modelled fixed effect variables are on the y-axis.

References

    1. Altmann J., 1980. Social milieu. In: Baboon Mothers and Infants. Harvard University Press, Cambridge, MA, pp. 64–125.
    1. Atmospheric Science Program, Land Air and Water Resources, University of California Davis, 2025. Atmospheric Science:: UC Davis Weather & Climate Stations [WWW Document]. URL 〈https://atm.ucdavis.edu/weather/uc-davis-weather-climate-station/〉.
    1. Bakker J, Maaskant A, Wegman M, Zijlmans DGM, Hage P, Langermans JAM, Remarque EJ, 2023. Reference intervals and percentiles for hematologic and serum biochemical values in captive Bred Rhesus (Macaca mulatta) and Cynomolgus Macaques (Macaca fascicularis). Animals 13, 445. 10.3390/ani13030445. -DOI -PMC -PubMed
    1. Bardi M, Shimizu K, Barrett GM, Huffman MA, Borgognini-Tarli SM, 2003. Differences in the endocrine and behavioral profiles during the peripartum period in macaques. Physiol. Behav 80, 185–194. 10.1016/j.physbeh.2003.07.004. -DOI -PubMed
    1. Bardi M, Shimizu K, Fujita S, Borgognini-Tarli S, Huffman MA, 2001. Social behavior and hormonal correlates during the perinatal period in Japanese Macaques. Horm. Behav 39, 239–246. 10.1006/hbeh.2001.1651. -DOI -PubMed

MeSH terms

LinkOut - more resources