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Interbirth intervals in wild baboons: Environmental predictors and hormonal correlates
Laurence R Gesquiere1, Jeanne Altmann2,3, Elizabeth A Archie3,4
1Department of Biology, Duke University, Durham, North Carolina.
American Journal of Physical Anthropology
|February 9, 2018
Summary
Female baboons with better energy acquisition had shorter interbirth intervals (IBIs). Body fat changes and hormone levels during postpartum amenorrhea and cycling influence reproductive timing and readiness.
Area of Science:
- Primate reproductive ecology
- Animal physiology
- Behavioral endocrinology
Background:
- Interbirth intervals (IBIs) are crucial indicators of female reproductive success.
- Understanding factors influencing IBIs offers insight into female fitness variations.
Purpose of the Study:
- Investigate sources of variance in IBI duration and its phases (postpartum amenorrhea, sexual cycling, pregnancy) in wild baboons.
- Examine the relationship between body fat, hormone concentrations, and IBI phases.
Main Methods:
- Analyzed 36 years of reproductive data from 160 wild female baboons (490 IBIs).
- Monitored body fat and fecal hormone concentrations (glucocorticoids, progestogens, estrogens) across IBI phases.
Main Results:
- Shorter IBIs correlated with environmental and female traits favoring energy acquisition.
- Females lost body fat during postpartum amenorrhea, regaining it before cycling.
- Fecal glucocorticoids decreased during postpartum amenorrhea, indicating reduced energetic stress.
Conclusions:
- Female baboon reproduction is constrained by energy availability and physiological state.
- Body fat dynamics and hormone profiles signal reproductive readiness and energetic costs.
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