DOI: 10.5061/dryad.gd788
title: Data from: Interbirth intervals in wild baboons: environmental predictors and hormonal correlates

description: Objectives: Interbirth intervals (IBIs) are a key metric of female
 reproductive success; understanding how they are regulated by
 environmental, social, and demographic factors can provide insight into
 sources of variance in female fitness. Materials and Methods: Using 36
 years of reproductive data on 490 IBIs for 160 wild female baboons, we
 identified sources of variance in the duration of IBIs and of their
 component phases: postpartum amenorrhea (PPA), sexual cycling, and
 pregnancy. We also examined how body fat and fecal hormone concentrations
 varied during female IBI. Results: We found that IBIs tended to be shorter
 (reproduction was accelerated) when female traits and environmental
 variables promoted energy acquisition, but with different specific effects
 for different component phases of the IBI. We also found that females lost
 a substantial amount of body fat during PPA, indicating that PPA imposes
 accumulating energetic costs as it progresses. Prior to cycle resumption
 females began to regain body fat; body fat was stable across the cycling
 phase and increased throughout most of pregnancy. However, body fat scores
 per se were not associated with the duration of any of the component
 phases. Finally, we found that fecal glucocorticoid concentrations
 decreased as PPA progressed, suggesting a decline in energetic stress over
 this phase. Fecal progestogen and estrogen concentrations changed over
 time during sexual cycling; the direction of these changes depended on the
 phase of the sexual cycle (luteal versus early or late follicular phases).
 Discussion: Our study lends insight into the energetic constraints on
 female primate reproduction, revealing how female environments, changes in
 body fat, and steroid hormone concentrations relate to IBI duration and to
 reproductive readiness.
description: IBI
 durationThis dataset was used to
 conduct our first analysis, which examined the duration of IBIs and their
 component phases. For this analysis we used 36 years of data (collected
 between 1977 and 2012) on reproductive states, demographic events,
 dominance rank, and rainfall for 160 wild-feeding females. Specifically,
 we had a total of 490 IBIs for 160 females that fit our analysis criteria
 (see Methods - Data Analysis), with each female contributing an average of
 3 IBIs to the dataset (range: 1-10). Note that female identity and
 pregnancy identity have been anonymized and the ID given were identical
 across tables.Fat
 ScoreThis dataset included
 the body fat scores, which were used to conduct our second analysis. For
 this analysis, we had 345 body fat scores for 105 females during 260 IBIs
 (collected between 2008 and 2014). Scores were collected during July,
 August, or November of each year, and the timing of the score within the
 IBI varied across females. 183 fat scores were assessed during PPA, 70
 during cycling, and 92 during pregnancy. For any given phase of a given
 IBI, females were usually assessed once, but in a few cases females were
 assessed twice during a given PPA (n=11). For these 11 cases an average
 body fat score was calculated so that each female contributed only one
 score for each PPA.Fecal
 hormonesThis dataset includes
 the data for our third analysis, which examined fecal glucocorticoids
 (fGC), fecal estrogens (fE), and fecal progestogens (fP) during PPA as a
 function of the number of months to sexual cycle resumption, or during the
 various phases of the sexual cycles (early or late follicular and luteal)
 as a function of the number of cycles to conception. For fGC and fE we had
 a total of 5,470 hormone samples collected between 2000 and 2014 for 138
 females during 549 IBIs. Of these samples, 4,150 fecal samples were
 collected during PPA, and 1,320 were collected during cycling. Each female
 contributed fecal samples from an average of 4 IBIs (range: 1-11) with an
 average of 10 hormone samples per IBI (range: 1-55) and an average total
 number of 40 samples per female (range: 1-145). For fP, we had a smaller
 sample size of 4,095 hormone samples collected between 2003 and 2014 for
 130 females during 456 IBIs; 2,922 were collected during PPA and 1,173
 during cycling. Each female contributed samples from an average of 3.5
 IBIs (range 1-8), with an average of 9 (range 1-47) samples per IBI, for
 an average total number of 32 (range 1-141) samples per
 female.