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Consequences of maternal loss before and after weaning in male and female wild chimpanzees

Abstract

The mother-offspring relationship is paramount in most mammals and infant survival often depends on maternal investment. In species with prolonged periods of development or co-residence, mothers may continue to influence their offspring’s outcomes beyond nutritional independence with benefits biased towards the philopatric sex. Chimpanzees (Pan troglodytes) are long-lived mammals with a protracted period of immaturity during which offspring continue to travel with their mothers. In contrast to most mammals, chimpanzees are also typically male philopatric. Here, we use over 50 years of demographic data from two communities in Gombe National Park, Tanzania, to examine the survival and longevity of both male and female chimpanzees that experienced maternal loss during three different age categories. Males who were orphaned between the ages of 0–4.99 years, 5–9.99 years, and 10–14.99 years all faced significantly lower survival than non-orphans and died earlier than expected. Females faced similarly reduced survival probabilities when orphaned between 0–4.99 and 5–9.99 years of age; however, females who experienced maternal loss between 10 and 14.99 years of age were no more likely to die than non-orphans. Females orphaned in this later age class also lived significantly longer beyond maternal loss than their male counterparts. As observed in other mammals, philopatric male chimpanzees may continue to benefit from their mother’s ecological knowledge, whereas maternal influence on female offspring likely fades as they prepare to emigrate. These results emphasize how maternal influence on offspring outcomes can extend well beyond weaning, particularly for the philopatric sex.

Significance statement

Mammalian mothers are crucial to their infant’s survival and in species where offspring continue to live with their mothers after weaning, maternal influence may extend beyond dependence on mother’s milk. While in most group-living mammals females remain in their natal group, chimpanzees typically display the opposite pattern with males residing alongside their mothers into adulthood. Using over 50 years of data on wild chimpanzees, we investigated the consequences of maternal loss both before and after weaning. We found that both males and females orphaned up to 10 years of age were less likely to survive than non-orphans; however, only males orphaned between 10 and 15 years also faced lower survival. These results emphasize how chimpanzee mothers continue to matter for offspring beyond infancy and provide novel data on reduced maternal influence on survival for daughters compared to sons.

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Data availability

The data analyzed during the current study are available in supplementary material: Online Resource 2.

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Acknowledgments

We thank the Jane Goodall Institute for their continued support of research at Gombe with special thanks to Dr. Jane Goodall for initiating research at Gombe. We are also extremely grateful to the Gombe Stream Research Centre staff, the Government of Tanzania, Tanzania National Parks, Tanzania Commission for Science and Technology, and Tanzania Wildlife Research Institute for their continued support of and permission to conduct this project. We also thank the numerous researchers and assistants who participated in long-term data entry and maintenance, as well as the associate editor and three anonymous reviewers for their comments on this manuscript.

Funding

This research was supported by the Jane Goodall Institute funding of data collection at Gombe. Additional funding support was provided by the National Science Foundation grants DBS-9021946, SBR-9319909, BCS-0452315, IOS-LTREB-1052693, the National Institutes of Health grant R01 AI 058715, Harris Steel, University of Minnesota, and Duke University.

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Correspondence to Margaret A. Stanton.

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The authors declare that they have no conflicts of interest.

Ethical approval

All applicable international, national, and institutional guidelines for the use of animals were followed. Permission to conduct data collection at Gombe National Park was granted and approved by all applicable governing bodies in Tanzania, including Tanzania National Parks, the Tanzanian Wildlife Research Institute, and the Tanzanian Commission for Science and Technology.

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Communicated by M. A van Noordwijk

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Stanton, M.A., Lonsdorf, E.V., Murray, C.M. et al. Consequences of maternal loss before and after weaning in male and female wild chimpanzees. Behav Ecol Sociobiol 74, 22 (2020). https://doi.org/10.1007/s00265-020-2804-7

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  • DOI: https://doi.org/10.1007/s00265-020-2804-7

Keywords

  • Maternal absence
  • Orphan
  • Survival
  • Female dispersal