ELECTRONIC SUPPLEMENTARY MATERIAL
(a) Additional sampling methods
Using known parturition dates and a 135-day gestation period to estimate conception dates
(Drea, 2011), we selected for chemical analysis samples of labial secretions obtained within
approximately one month of conception and at roughly mid-pregnancy. Serum endocrine data
were obtained from a previously published study (Drea, 2011), but were re-analyzed to include
only endocrine data from comparable reproductive conditions (i.e., within one month of
conception, and at roughly mid-pregnancy, on average).
(b) Investigating potential effects of age on female genital odorants
Because the age range of our study subjects was broad (spanning roughly 20 years), we first
tested for potential effects of a female’s age at the time of sample collection on her chemical
richness. Age (in months) was not normally distributed, so we used a logarithmic transformation
to achieve normality for these data (Shapiro-Wilk W test, P = 0.12, n.s.). We then tested for a
significant linear relationship between age (in months) and chemical richness. The regression
was not significant, regardless of whether we considered all of the samples (F1, 26 = 0.2, P = 0.66,
n.s., R2 = 0.008), only the samples collected prior to conception (F1, 12 = 0.07, P = 0.8, n.s., R2 =
0.006), or only the samples collected during pregnancy (F1, 12 = 0.53, P = 0.48, n.s., R2 = 0.04).
Because any potential relationship between age and chemical richness need not be linear,
we conducted a second set of age analyses in which we divided the samples into two categories:
based on the mean age of our subjects at the time of sampling (average ± SEM: 108 ± 15
months), we created a below-average age group and an above-average age group. Individual t-
tests revealed no differences in chemical richness owing to this categorical age difference,
regardless of whether we considered all of the samples (t15.18 = 0.94, P = 0.36, n.s.), only the
samples collected prior to conception (t8.75 = 0.07, P = 0.94, n.s.), or only the samples collected
during pregnancy (t7.62 = 1.34, P = 0.22, n.s.). Because a female’s chemical richness showed no
relation to her age, consistent with previous findings discounting an age effect on patterns in the
chemical richness of lemur genital secretions (Boulet et al., 2009; Charpentier et al., 2008), we
did not consider age in subsequent analyses.
(c) Investigating potential effects of season and litter size on genital odorants during
pregnancy
Ring-tailed lemurs can cycle up to three times in one breeding season (Drea, 2011), which in the
Northern Hemisphere and, hence, at the Duke Lemur Center, is shifted by six months from the
breeding season in Madagascar (see Drea (2007)). All of our sampling of lemur genital
secretions at preconception (i.e., from October-February) occurred during the breeding season,
but because females conceived in different oestrus cycles, roughly half (43%) of our sampling
during pregnancy (i.e., from January-February) also occurred during the breeding season and
roughly half (57%; i.e., from March-May) occurred during the subsequent nonbreeding season.
Because of broad seasonal patterns previously detected in female scent (Boulet et al., 2009;
Scordato et al., 2007), we wanted to ascertain that any scent patterns detected during pregnancy
did not owe to seasonal effects. Moreover, ten of the pregnancies we sampled resulted in
singletons, with twins accounting for the remaining four pregnancies. We thus also wanted to
address any potential effect of litter size on a dam’s scent. We tested for potential effects of
season and litter size on the chemical richness of pregnant females using individual t-tests (JMP
PRO 11.0, SAS). Because we found no significant difference in richness as a function of either
of these variables (season: t12 = 1.11, P = 0.29, n.s.; litter size: t11.77 = -1.56, P = 0.14, n.s.), we
collapsed these variables in subsequent analyses.
(d) Chemical and endocrine analyses
In cases in which we had sampled a subject multiply, either during the same pregnancy or across
repeated pregnancies involving the same foetal sex (i.e., females bearing daughters or FBD vs.
females bearing sons or FBS, as defined in the main text), we averaged her chemical complexity,
as well as her serum steroid concentrations, across samples for use in the following analyses. The
raw chemical richness data, as well as the serum concentrations of 17-hydroxyprogesterone
(OHP), were normally distributed (Shapiro-Wilk W test, P = 0.58, n.s. and P = 0.24,
respectively; JMP PRO 11.0, SAS); however, the serum concentrations of the other three
hormones significantly deviated from the normal distribution (testosterone or T: P < 0.01;
androst-4-ene-3,17,dione or A4: P < 0.01; 17-oestradiol or E2, P < 0.01). We used a logarithmic
transformation to achieve normality for these data (P > 0.05, n.s., in each case) and all of our
reported analyses involving these three hormones were conducted on log-transformed data. The
residuals obtained from the reported two-factor ANOVAs for the chemical and endocrine data
were all normally distributed (chemical richness: P = 0.80, n.s.; T: P = 0.59, n.s.; A4: P = 0.064,
n.s.; OHP, P = 0.34, n.s.; E2, P = 0.52, n.s.). Furthermore, the variances between preconception
and pregnancy, analysed separately for each foetal-sex category, were equal for all chemical and
endocrine measures (Brown-Forsythe test, P > 0.05, n.s., in each case; JMP PRO 11.0, SAS).
(e) Analysis of chemical data from previous studies to contextualize present effects
To contextualize the main effect of reproductive stage on chemical complexity, we used
previously published chemical data to calculate absolute differences in average chemical
richness between several previously studied groups comprising both sexes. To calculate average
individual differences, we first obtained an average chemical richness from each individual
(from Scordato et al. (2007)) and then calculated absolute pairwise differences for each malemale or female-female pair; we then averaged these pairwise differences for each sex. To
calculate average differences between relatively homozygous and relatively heterozygous males,
we classified males with a mean neutral heterozygosity below that of our study population
average (0.59 ± 0.03) as relatively homozygous (n = 10) and all other males as relatively
heterozygous (n = 9; the genetic and chemical data were obtained from Charpentier et al.
(2008)). Average richness values for females and males during the breeding and nonbreeding
seasons were obtained from Boulet et al., (2009) and represent within-subjects comparisons for
each sex. Average differences in richness between hormonally intact and hormonally
contracepted females were obtained from Crawford et al. (2011) and likewise represent a withinsubjects comparison. These data are presented in Table 1 of the main text.
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