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FEATURED STUDENT RESEARCH PAPER
Behavioral Ecology and Sociobiology (2025) 79:42
https://doi.org/10.1007/s00265-025-03582-8
Peter M. Kappeler and Marie J. E. Charpentier contributed equally to
this work.
Communicated by M. A van Noordwijk.
Extended author information available on the last page of the article
Abstract
Mammalian species with slow life histories invest heavily in ospring care to meet ospring nutritional and developmental
requirements, typically at signicant costs to mothers. While maternal care has been extensively studied, understanding
the mechanisms driving variation in mother‒ospring relationships during key ospring developmental periods require
more comparative data from natural populations. Using eight years of behavioral data, we analyzed mother-ospring
interactions in 68 infants born to 46 mothers in wild mandrills (Mandrillus sphinx), spanning multiple birth cohorts and
the entire rst year of infant life, a critical period for individual social and physical development. We found that mothers
dynamically adjusted caregiving behavior as infants aged, reducing physical contact while promoting spatial independence
and social integration. Maternal traits, such as age, social rank, and reproductive history, shaped maternal phenotypes:
high-ranking mothers promoted infant socialization while reducing carrying, and older, multiparous mothers invested more
in grooming and physical contact than younger, inexperienced females. Previous infant loss predicted reduced maternal
aggression, potentially due to fewer immatures to care for or behavioral adjustments aimed at improving ospring sur-
vival. Finally, mothers fostered closer bonds with their daughters while encouraging their sons’ independence, possibly
resulting in more frequent tantrums observed in males. This sex-biased pattern likely reects preparation for contrasting
life histories between the sexes in this species. By combining extensive longitudinal observations with ne-scale, indi-
vidual analyses, our study emphasizes the dynamic and multifaceted nature of early mother-ospring interactions and their
evolutionary implications in long-lived mammals.
Signicance statement
Caring for ospring is energetically costly, requiring mothers to balance their own condition with their infants’ needs
through exible behaviors that can also have long-term consequences for ospring development and survival. Using eight
years of data on wild mandrills, our study revealed how maternal traits such as age, rank, and reproductive history inu-
ence caregiving behavior during the rst year of the infant’s life. Notably, high-ranking and experienced mothers facili-
tated their infants’ social engagement while fostering independence. The closer bonds observed with daughters and the
greater independence encouraged in sons may reect preparation for their contrasting adult roles (i.e., female philopatry
and male natal dispersal). These ndings deepen our understanding of the exibility and evolutionary drivers of mater-
nal care in long-lived mammals, highlighting the complex interplay between maternal behavior, infant needs, and future
reproductive success.
Keywords Mother-infant relationships · Maternal investment · Infant development and independence · Mandrill
(Mandrillus sphinx)
Received: 11 December 2024 / Revised: 26 February 2025 / Accepted: 5 March 2025 / Published online: 22 March 2025
© The Author(s) 2025
Toward independence: maternal social status and experience shape
mother–infant relationships in mandrills
BertaRoura-Torres1,2,3 · AliceBaniel3· AnnaCryer4· LoïcSauvadet4· MélyssaDe Pastors4· GeorgeHavill4·
MélodieKreyer4· JadeMeric de Bellefon4· StevenAbaga4· MélanieHarté4· Peter M.Kappeler1,2 ·
Marie J. E.Charpentier3,5
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Behavioral Ecology and Sociobiology (2025) 79:42
Introduction
Maternal investment during early development has far-
reaching consequences for ospring, with pervasive eects
that can be observed until adulthood, inuencing their
behavior, social relationships, health, reproductive suc-
cess, and mortality risk (Clutton-Brock 1991; Royle et al.
2012). Studies on mother-ospring relationships during
early life may inform about the adaptive responses of long-
lived animals to challenges from their physical and social
environments (Alberts 2019) as well as underlying genetic
and maternal eects (Moore et al. 2019). Long-lived animal
species generally exhibit slow life histories (Promislow and
Harvey 1990), characterized by an extended postnatal period
of development and parental investment, which appear to
reinforce each other over evolutionary times (Zipple et al.
2024). Mammalian ospring, in particular, rely heavily on
their mothers for nourishment, transportation, protection,
learning opportunities, and social support (Clutton-Brock
1991). While research on maternal care in mammals is sub-
stantial (Lee et al. 1991; van Noordwijk 2012; Liebal et al.
2024), opportunities remain to explore the behavioral out-
comes of maternal investment and its dynamics over time,
particularly in little studied species.
Mammalian motherhood is inherently costly, as it
requires signicant physiological and behavioral invest-
ments in gestation, lactation, and postnatal care (Clut-
ton-Brock 1991; Weiss et al. 2023). The optimal level of
maternal investment sought by ospring typically exceeds
what mothers should provide to maximize their lifetime
reproductive success, leading to mother-ospring conict
with consequences for both maternal and ospring tness
(Trivers 1974). For example, in many species, the transi-
tion from maternal nutritional dependence to independence,
known as weaning, represents a typical stage of this conict
(Martin 1984; Lee et al. 1991; Lee 1996). Ospring may
require prolonged nursing, whereas mothers may reduce
this period of nutritional dependence (Trivers 1974) or alter
nursing patterns to minimize interference with other mater-
nal activities (Barrett et al. 1995). These conicts may gen-
erate behavioral manifestations, such as increased maternal
rejection or aggression (e.g., in rhesus macaques, Macaca
mulatta, Simpson et al. 1986), changes in mother-ospring
proximity dynamics (e.g., African elephants, Loxodonta
africana, Lee and Moss 1986), and increased infant solic-
iting behaviors, such as tantrums (e.g., displays of intense
emotional outbursts, typically characterized by behaviors
such as loud vocalizations, physical agitation, or aggressive
gestures; e.g., humans, Homo sapiens, LeVine and LeVine
1988), which aect mother-ospring relationships overall.
Maternal investment can vary exibly in response to both
maternal energetic condition and ospring needs (Smith
2005). Mothers in prime condition generally provide opti-
mal resources to their ospring during development (Martin
1984; Stearns 1992; Lee 1996). For example, in gregarious
mammals with female dominance hierarchies, high-ranking
mothers often have priority of access to high-quality food
sources improving their physiological and body conditions,
such as milk production and quality, ultimately enhancing
ospring growth (Ellis 1995; Stockley and Bro-Jørgensen
2011; Clutton-Brock and Huchard 2013). Additionally,
in matrilineal species, immature ospring often inherit
their mothers’ social rank, granting dierential access to
resources during critical stages of development (Hole-
kamp et al. 1996). Consequently, immature mammals born
to high-ranking females generally reach weaning sooner
without compromising their survival (e.g., red deer, Cer-
vus elaphus: Clutton-Brock et al. 1986; spotted hyenas,
Crocuta crocuta: Holekamp et al. 1996; African wild dogs,
Lycaon pictus: Creel et al. 1997; chimpanzees, Pan troglo-
dytes: Pusey et al. 1997; meta-analysis: Shivani et al. 2022).
Beyond these nutritional aspects, dominance status is also a
major determinant of females’ social life and status. Low-
ranking mothers and their ospring generally face greater
social risks, with frequent aggression and harassment from
social companions (Abbott 1987; Maestripieri 1994; Fair-
banks 1996; Clutton‐Brock and Huchard 2013). These
rank-related dierences may profoundly shape mother‒
ospring relationships. For example, low-ranking mothers
often appear both more protective and restrictive with their
infants than high-ranking mothers (e.g., White and Hinde
1975; Altmann 1980; Berman 1984). In contrast, in species
with more tolerant societies, where social risk is perceived
to be lower, maternal protectiveness does not vary with
social rank (Maestripieri 1994).
Beyond rank-related dierences in energy availability
and mobilization, maternal age and experience similarly
inuence the allocation of resources for ospring care.
For example, young and primiparous mothers often repro-
duce before reaching full adult size, generating trade-os
between the allocation of resources to reproduction versus
somatic growth (Stearns 1992). Consequently, primiparous
mothers may adjust their maternal behaviors to compensate
for their limited energy reserves. In chimpanzees, primip-
arous females nurse and groom their ospring more than
multiparous mothers resulting in similar ospring survival
outcomes (Stanton et al. 2014). Across several mamma-
lian species, however, older and more experienced moth-
ers generally enjoy greater success in raising ospring (e.g.,
bighorn sheep, Ovis canadensis: Festa-Bianchet 1988; Ant-
arctic fur seals, Arctocephalus gazella: Lunn et al. 1994;
feral horses, Equus caballus: Cameron et al. 2000). One rea-
son is that mothers are expected to progressively increase
their investment in their successive ospring because
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Behavioral Ecology and Sociobiology (2025) 79:42
female reproductive value tends to decline with age (i.e.,
females have fewer opportunities to reproduce in the future;
Clutton-Brock 1984). In addition, maternal experience
gained throughout motherhood may allow mothers to target
care to the most critical periods of ospring development
(Green 1993; Fairbanks 1996; Cameron et al. 2000). In feral
horses, for example, age-dierentiated maternal behavior is
apparent only during the rst 20 days of the foal’s life, with
older mares maintaining closer contact with their foals dur-
ing this critical period but showing reduced eort thereafter
(Cameron et al. 2000). In contrast, adverse maternal experi-
ence, such as the death of previous ospring, may disrupt
this generalized age-related behavioral pattern (Fairbanks
1988). Vervet monkey (Cercopithecus aethiops) mothers
who experienced reproductive failure (i.e., pregnancy loss
or perinatal infant death) are more protective and attentive
to their next ospring (Fairbanks 1988). Similarly, feral
horse mares who have lost a foal subsequently increase
maternal eort by maintaining closer proximity to their next
ospring (Cameron et al. 2000).
Finally, maternal investment is shaped not only by the
mother’s condition and experience but also by ospring
traits, with sex being a key factor inuencing the allocation
of maternal care because of the dierential tness outcomes
of rearing sons versus daughters (Clutton-Brock et al. 1981;
Fairbanks 1996). In sexually dimorphic mammals, male o-
spring typically require more maternal resources than female
ospring because of greater somatic growth and increased
energetic demands associated with male development (Clut-
ton-Brock et al. 1985; Lindström 1999). For example, male
African elephant calves suckle more frequently than female
calves do (Lee and Moss 1986), and bighorn ewes experi-
ence delayed reproduction following the birth and rearing of
males (Hogg et al. 1992). In contrast, in group-living matri-
lineal mammals, where female ospring inherit their moth-
ers’ dominance rank and social support from their maternal
kin (Holekamp and Smale 1991), investing in females rather
than in males may yield greater tness benets, particularly
for high-ranking females (Silk 1983).
Here, we contributed to this body of research on mother-
ospring relationships by studying how the dynamic
interplay between multiple maternal and ospring charac-
teristics shape maternal investment, in a natural population
of mandrills (Mandrillus sphinx), using a large sample of
infants spanning several cohorts. Mandrills are particu-
larly interesting to study in this context because of several
salient aspects of their biology. First, they live in very large,
cohesive social groups composed mainly of adult females,
the philopatric sex, and their ospring, whereas males dis-
perse from their natal group around puberty, and immi-
grant males are nonpermanent residents of these groups
(Abernethy et al. 2002; Brockmeyer et al. 2015). Mandrills
form typical matrilineal societies where maternally related
females show lifelong preferential associations and sociality
(Charpentier et al. 2007, 2020). In these societies, females
inherit their mother’s dominance rank, with adult daugh-
ters commonly positioned below her, following a reverse
age hierarchy where younger sisters generally outrank older
sisters (Setchell et al. 2002). Dominant matrilines typically
enjoy priority of access to nutritional and social resources
(Dezeure et al. 2022). As a result, high-ranking females
generally have shorter interbirth intervals than low-ranking
females (median interbirth interval: 15.0 months versus.
22.0 months, respectively; Dezeure et al. 2022). How-
ever, because mandrills are seasonal breeders, with most
births occurring between November and March (Dezeure
et al. 2022), birth spacing varies across females, leading to
diverse motherhood proles. Depending on their reproduc-
tive history, females may simultaneously care for one or
multiple dependent ospring of dierent ages. Reproduc-
tive patterns observed in this study population lead to an
alternation between very large birth cohorts (up to 94) and
small ones (5; MJEC unpubl. data). Consequently, the social
environment in which infants are born may vary dramati-
cally (see also Charpentier et al. 2020). Finally, sexual size
dimorphism is extreme in this primate, starting as soon as 12
months of age, with adult male mandrills being more than
three times heavier than adult females (Setchell et al. 2001).
Here, we analyzed nine social behavioral variables char-
acterizing mother-infant relationships in wild mandrills,
using eight years of continuous observations of 68 infants
throughout their critical rst year of development. Man-
drill infants reach locomotor independence within the rst
months of life, but they maintain close proximity to their
mothers even after weaning, which occurs at approximately
eight months of age in captive settings (Setchell et al. 2002).
We thus studied typical maternal investment behaviors (nurs-
ing, carrying), maternal interactions (grooming, restraining,
and aggression), infant soliciting behaviors (tantrums), and
mother-infant spatial associations (body contact, indices of
proximity initiation and maintenance). We hypothesized
that changes in mother-infant relationships as infants age
would depend on maternal characteristics, infant traits, and
the social environment where infants are born. First, as a
consequence of priority access to resources by high-rank-
ing mothers, we predicted that they should cease maternal
investment earlier than low-ranking mothers, involving an
earlier decline in nursing and carrying, coupled with inde-
pendence-promoting behaviors, such as less contact seeking
and more rejections. In turn, infants born to high-ranking
mothers should perform more tantrums than those born to
low-ranking mothers as a behavioral manifestation of this
earlier decline in maternal investment. Second, we predicted
that young, primiparous females and mothers who lost their
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Behavioral Ecology and Sociobiology (2025) 79:42
cohort, with the transition date between two cohorts being
September 1st following the seasonal birth pattern in this
population. We determined the sex of newborns through
observations of their genitalia.
Behavioral data
All mandrills from the study group are individually recog-
nizable from the face (e.g., shape, presence of distinctive
scars or marks, coloration patterns). Trained eld assistants,
unaware of the aim of this study, have been collecting daily
data on group composition, movements and demography,
individual life histories, and social behavior. To minimize
observer bias, blinded methods were used when all behav-
ioral data for this study were collected on 68 infants (i.e.,
individuals aged less than one year) from January 2015 to
November 2023 on a daily basis via 5-minute continuous
focal sampling (Altmann 1974). During each focal obser-
vation, observers recorded all infant activities, including
mother-infant interactions. Additionally, we collected up to
two scan samples during each focal observation (one at the
beginning and one at the end) to estimate the spatial associa-
tion between the focal infant and its groupmates (i.e., either
in body contact, or separated by less than 1 m, or by less
than 5 m). We divided the rst year of infants’ age into four
quarters (90-day periods), and we considered only those
infants for whom we collected at least 30 min of focal obser-
vations and nine scans per quarter, for at least three out of
four quarters, in the following analyses. With these restric-
tions, we used a total of 346 h of focal observations (mean ±
SD minutes of observation per infant: quarter 1 = 103 ± 59;
quarter 2 = 87 ± 46; quarter 3 = 74 ± 41; quarter 4 = 71 ± 36)
and 7764 scans (mean ± SD scan samples per infant: quarter
1 = 36.2 ± 21.1; quarter 2 = 32.9 ± 18.6; quarter 3 = 28.6 ±
17.9; quarter 4 = 27.7 ± 15.9) collected from 34 females and
34 males belonging to six dierent cohorts and born to 46
dierent mothers (see Supplementary Table S1).
We focused on nine mother-infant interactions previ-
ously described in other primates (i.e., Hinde and Simpson
1975; Altmann 1980; Tanaka 1989; Schino et al. 1995; Mae-
stripieri 1998; Bardi et al. 2001; De Lathouwers and van
Elsacker 2004; Verderane and Izar 2019; Arbaiza-Bayona
et al. 2022; Table 1). These include typical maternal behav-
iors, such as nursing (i.e., infant making sustained contact
with its mouth to the mother’s nipple) and carrying (i.e.,
ventral – occasionally dorsal – transport of the infant),
both recorded as binary occurrences (presence or absence)
during each focal observation to avoid pseudoreplication.
We further considered maternal grooming as a total dura-
tion (in seconds per focal observation), and recorded the
total number of events per focal observation of restraining
behaviors (i.e., behaviors limiting infant’s movements, such
previous infant would invest more in their ospring and
display more protective behaviors (e.g., increased restrain-
ing and contact seeking) than experienced and successful
mothers. Moreover, we predicted that female mandrills
should foster stronger social bonds (e.g., more grooming)
with their philopatric daughters than with their sons. How-
ever, we also predicted that mandrill mothers should nurse
their sons more than their daughters because of the extreme
sexual size dimorphism observed in this species. Finally, in
the study population, infants born in large cohorts tend to
spend more time playing with their peers compared to those
born in small cohorts (BR-T pers. obs.). Thus, we predicted
that infants born with numerous peers available to socialize
with, would be more independent from their mothers (e.g.,
less grooming, more disruption of associations initiated by
infants) than those born with few age-mates. By document-
ing longitudinal changes throughout the rst year of life in a
large sample of infants, we aimed to provide a comprehen-
sive understanding of how maternal investment unfolds dur-
ing infant development in response to maternal and infant
traits.
Materials and methods
Study site and population
The study population consists of a natural social group of
mandrills (Mandrillus sphinx) fully habituated to human
presence, freely roaming Lékédi Park and its surroundings
(Bakoumba, Gabon; 2.2642° S, 11.5651° E). This group
originated from two release events of 65 captive-bred man-
drills from CIRMF (Centre Interdisciplinaire de Recherches
Médicales de Franceville) in 2002 and 2006 (Peignot et
al. 2008). Soon after their release, founder females repro-
duced with wild migrant males. By November 2023, the
group comprised approximately 300 wild-born individu-
als, with only four founder females remaining, the oldest
being 23 years old at the time of the study. This group has
been monitored since 2012, when a long-term eld project
was initiated to study the socioecology of this species (the
“Mandrillus Project”: Poirotte et al. 2017; Charpentier et
al. 2020). The birth dates were accurately known for most
of the studied individuals born after 2012 and for the indi-
viduals born at the CIRMF (N = 68 infants and 36 mothers;
mean ± SD estimated days from birth date: infants = 2.29 ±
5.40; mothers = 47.00 ± 168.96). The age of the remaining
individuals (N = 10 mothers) was estimated on the basis of
patterns of tooth eruption and wear (i.e., with age, molars
become atter; Galbany et al. 2014) and an assessment
of general body condition (i.e., coloration patterns of the
face, hands and feet). Each birth was assigned to a birth
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Behavioral Ecology and Sociobiology (2025) 79:42
Fixed eects Level CI Estimate
x2
P
2.5% 97.5%
Nursing
Infant age -8.030 -6.283 -7.156 318.618 < 0.001
Infant age20.465 2.093 1.279 360.520 < 0.001
Infant sex Male (ref: female) -0.086 0.116 0.015 0.081 0.776
Dominance rank -0.011 0.098 0.043 2.426 0.119
Maternal parity Multiparous
(ref: primiparous)
-0.219 0.014 -0.102 2.949 0.086
Cohort size -0.154 0.084 -0.035 0.336 0.562
Full-null model comparison:
x2
2
=205.170, P < 0.001 (AIC full = 1217.700, AIC null = 1412.900)
Carrying
Infant age -17.576 -14.417 -0.160 391.093 < 0.001
Infant age2-4.051 -1.819 -2.935 512.190 < 0.001
Infant sex Male (ref: female) -0.184 0.017 -0.084 2.675 0.102
Dominance rank -0.138 -0.037 -0.087 11.362 0.001
Maternal parity Multiparous
(ref: primiparous)
-0.171 0.059 -0.056 0.908 0.341
Cohort size -0.104 0.004 -0.050 3.300 0.069
Full-null model comparison:
x2
2
=328.520, P < 0.001 (AIC full = 1199.100, AIC null = 1473.500)
Restraining
Infant age -1.837 -1.366 -1.601 177.633 < 0.001
Infant sex Male (ref: female) -0.176 0.435 0.130 0.690 0.406
Dominance rank -0.297 0.062 -0.117 1.649 0.199
Maternal parity Multiparous
(ref: primiparous)
-0.039 0.693 0.327 3.065 0.080
Cohort size -0.127 0.677 0.275 1.797 0.180
Full-null model comparison:
x2
2
=167.540, P < 0.001 (AIC full = 649.150, AIC null = 806.690)
Aggression
Infant age 1.776 8.120 4.948 7.416 0.006
Infant age2-8.299 -2.382 -5.340 19.030 < 0.001
Infant sex Male (ref: female) -0.503 0.265 -0.119 0.370 0.543
Dominance rank -0.024 0.396 0.186 3.001 0.083
Maternal parity Multiparous
(ref: primiparous)
-0.493 0.399 -0.047 0.042 0.837
Cohort size -0.141 0.738 0.299 1.774 0.183
Full-null model comparison:
x2
2
=25.363, P < 0.001 (AIC full = 609.060, AIC null = 622.420)
Tantrums
Infant age -6.714 -1.375 -4.045 4.712 0.030
Infant age2-7.841 -2.844 -5.343 22.662 < 0.001
Infant sex Male (ref: female) 0.185 0.921 0.553 8.674 0.003
Dominance rank -0.013 0.397 0.192 3.375 0.066
Maternal parity Multiparous
(ref: primiparous)
-0.719 0.134 -0.293 1.809 0.179
Cohort size -0.224 1.036 0.406 1.598 0.206
Full-null model comparison:
x2
2
=35.889, P < 0.001 (AIC full = 949.84, AIC null = 973.720)
Grooming
Infant age 0.120 0.341 0.231 16.801 < 0.001
Infant sex Male (ref: female) -0.374 0.173 -0.100 0.517 0.472
Dominance rank 0.061 0.336 0.198 8.025 0.005
Maternal parity Multiparous
(ref: primiparous)
0.103 0.725 0.414 6.809 0.009
Cohort size -0.229 0.450 0.110 0.406 0.524
Table 1 Statistical results of the full models, including both primiparous and multiparous females
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Behavioral Ecology and Sociobiology (2025) 79:42
Maternal dominance rank was assessed via approach‒
avoidance interactions among adult females collected ad
libitum or during focal observations to compute a hierar-
chy via normalized David scores (David 1987). We then
assigned each female a single relative rank by averaging
annual ranks over the study period (since annual ranks were
highly correlated across years and observation eort varies
yearly; Dezeure et al. 2022), which represented the propor-
tion of females dominated by the focal female. The values
ranged from 0 (lowest-ranking females) to 1 (highest-rank-
ing females).
Individual data
We used long-term life history records to calculate the moth-
er’s age (in years) at the beginning of each quarter and the
infant weighted age for each quarter. The infant’s weighted
age was computed by averaging the infant’s age recorded
during each focal observation, weighted by the duration of
as pulling, grabbing, or blocking them from moving away),
and maternal aggression (i.e., biting, pushing, hitting, slap-
ping, and grasping). Note that maternal aggression, in our
study population, serves primarily as a form of rejection of
infants’ demands to be carried or to access the nipple (BR-T
pers. obs.). We also recorded infant tantrums as a total num-
ber of events observed per focal. In mandrills, tantrums are
dened by every instance of infant crying (i.e., vocaliza-
tions such as screaming, moaning, and gecking; Delaunay
et al. 2024). Finally, we studied patterns of mother-infant
spatial associations by recording rst mother-infant body
contacts recorded during scans and by then considering two
behaviors recorded during focal observations: approaches
(i.e., when an individual moves toward a conspecic, enter-
ing a 1-meter-radius circle around the latter) and leaves (i.e.,
when an individual moves away from a conspecic, exit-
ing a 1-meter-radius circle around the latter). Approaches
and leaves were considered both as total number of events
observed per focal observation.
Fixed eects Level CI Estimate
x2
P
2.5% 97.5%
Full-null model comparison:
x2
2
=29.331, P < 0.001 (AIC full =-1004.850, AIC null =-985.520)
Body contact
Infant age -9.305 -7.741 -8.523 545.346 < 0.001
Infant age20.045 1.480 0.762 559.713 < 0.001
Infant sex Male (ref: female) -0.155 0.081 -0.037 0.378 0.539
Dominance rank -0.040 0.088 0.024 0.539 0.463
Maternal parity Multiparous
(ref: primiparous)
-0.149 0.130 -0.009 0.017 0.895
Cohort size -0.135 0.126 -0.004 0.004 0.948
Full-null model comparison:
x2
2
=616.66, P < 0.001 (AIC full = 1327.100, AIC null = 1931.700)
Brown’s index
Infant age 1.784 3.637 2.711 27.203 < 0.001
Infant age2-3.124 -1.472 -2.298 54.791 < 0.001
Infant sex Male (ref: female) 0.022 0.290 0.156 5.193 0.023
Dominance rank -0.130 0.012 -0.059 2.675 0.102
Maternal parity Multiparous
(ref: primiparous)
-0.187 0.094 -0.047 0.420 0.517
Cohort size -0.188 0.121 -0.033 0.177 0.674
Full-null model comparison:
x2
2
=66.340, P < 0.001 (AIC full = 1083.300, AIC null = 1137.700)
Hinde’s index
Infant age -1.568 -0.468 -1.008 13.266 < 0.001
Infant age20.223 1.296 0.759 21.361 < 0.001
Infant sex Male (ref: female) -0.171 0.001 -0.082 3.432 0.064
Dominance rank -0.048 0.043 -0.001 0.003 0.959
Maternal parity Multiparous
(ref: primiparous)
-0.068 0.135 0.037 0.508 0.476
Cohort size -0.067 0.108 0.023 0.246 0.620
Full-null model comparison:
x2
2
=25.319, P < 0.001 (AIC full = 89.562, AIC null = 102.881)
Note. The Table shows estimates, 95% condence inter vals (CI), chi-square and P values for the predictors of the GLMMs and LMMs (Hinde’s
index), including infant, mother and cohort identities as three random eects. Signicant eects are highlighted in bold. Mean ± SD for infant
age: 172.791 ± 101.413; dominance rank: 0.447 ± 0.326; cohort size: 38.402 ± 14.421
Table 1 (continued)
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Behavioral Ecology and Sociobiology (2025) 79:42
signicant predictors of the previous models along with
maternal age (in years) and its quadratic term and the out-
come of the previous reproductive event (death of previous
infant: yes versus no). Mothers experiencing the death of
an infant generally showed larger age gaps between their
two last living ospring than other females did. To explore
whether changes in mother-infant behaviors were directly
related to previous infant death or related to the energy
required to take care of close-in-age ospring, we reran the
models where the outcome of previous reproduction was
signicant excluding mothers whose previous infant had
died and instead including the length of the interbirth inter-
val (IBI) to the previous living ospring as a xed eect
(see Supplementary Table S7).
In all models, we accounted for observational eort by
including the log-transformed observation time as an oset
(except for models based on the proportions of grooming
and body contact). We further considered infant, mother and
birth cohort identities as three random eects to control for
pseudoreplication.
For the counts of nursing, carrying, restraining, aggres-
sion, and tantrums, we used generalized linear mixed mod-
els (GLMMs) with a negative binomial distribution (for
overdispersed data typically characterizing social behav-
iors) and a log-link function. Maternal grooming was mod-
eled with a GLMM with a beta family distribution and a
logit link function. For body contacts and Brown’s index,
we ran two GLMMs with a binomial error structure with a
logit link function to study a proportion N/T, where N was
the total number of scans in which a given dyad was in body
contact (or the total number of approaches and leaves initi-
ated by the mother), and T was the total number of scans (or
the total number approaches and leaves observed within the
dyad). Finally, we modelled Hinde’s index as a linear mixed
model (LMM) with a Gaussian error structure, as residuals
were normally distributed, with an identity link function.
All statistical analyses were conducted via R Studio soft-
ware (version 4.2.1; R Core Team 2022). We ran GLMMs
with the “glmmTMB” function from the glmmTMB pack-
age (Brooks et al. 2017) and LMMs with the “lmer” function
from the lme4 package (Bates et al. 2015). We assessed t
singularity via the “check_singularity” function and over-
dispersion via the “check_overdispersion” function from
the performance package (Lüdecke et al. 2021). When mod-
eling negative binomial distributions, we compared their t
with negative binomial type I and II models, selecting the
one with the lowest Akaike’s information criterion (Zuur
et al. 2009). All quantitative predictors were z-transformed
(i.e., scaled with a mean of 0 and a standard deviation of
1) to compare eect sizes among estimates and to facili-
tate model convergence (Harrison et al. 2018). We ensured
that the estimation of the coecients in our models was
that focal observation, across all focal observations. Moth-
ers were further categorized on the basis of their reproduc-
tive history. First, they were considered either primiparous,
when the focal infant was their rst surviving infant, or
multiparous otherwise. Second, among multiparous moth-
ers only, we classied them as those whose previous infant
either died or survived infancy, i.e. at least 12 months of
age. Finally, we determined cohort size as the number of
infants born in the same birth cohort as the focal infants
but who were alive by the end of each quarter of the study
period.
Statistical analyses
We studied nine behaviors per quarter as follows. Events
(counts) included the total number of nursing and carry-
ing behaviors recorded across all infant focal observations
(with multiple occurrences within a single focal observa-
tion counted as one to prevent pseudoreplication), as well
as maternal restraining, aggression, and infant tantrum. We
calculated the proportion of time mothers spent grooming
their infants by dividing the total grooming time by the
total observation time, and the proportion of scans in body
contact by dividing the total number of times mothers and
infants were observed in body contact by the total num-
ber of scans performed on the infant (see Supplementary
Table S1). To assess which individual of the dyad actively
changed proximity, we calculated Brown’s index (see Sup-
plementary Table S2) as the total number of approaches and
leaves initiated by the mother divided by the total number
of approaches and leaves observed within the dyad (Brown
2001). This index ranged from 0 to 1, with values below
0.5 indicating infant responsibility for most of the proximity
changes between the dyad and above 0.5 indicating mater-
nal responsibility. We further calculated Hinde’s index (see
Supplementary Table S3) as the proportion of approaches
initiated by the mother minus the proportion of her leaves
(Hinde and Atkinson 1970). This index ranged from − 1,
indicating that the mother initiated more leaves than
approaches, to + 1, indicating that the mother initiated more
approaches than leaves. Together, these indices complement
each other: while Hinde’s index highlights mothers’ role in
approaching versus leaving the infant, Brown’s index indi-
cates the proportion of total proximity changes initiated by
the mother (Arbaiza-Bayona et al. 2022).
For each model performed, we considered the following
covariates: infant weighted average age (ranging from 25.6
to 336.6 days) and its quadratic term, infant sex (female
versus male), maternal dominance rank (ranging from 0
to 1), maternal parity (primiparous versus multiparous)
and cohort size (ranging from 5 to 56). In a second step,
we focused on multiparous females and included only the
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Behavioral Ecology and Sociobiology (2025) 79:42
Results
Infant age, or its quadratic term, was a major predictor of all
studied behaviors (Table 1; Fig. 1). As infants grew older,
rates of nursing, carrying, restraining, and body contact
decreased signicantly, although not always linearly. In
contrast, the amount of time mothers spent grooming over-
all increased with infant age. Both infant tantrums and the
number of maternal aggressions peaked between the second
and third quarters. Additionally, we observed a progres-
sive transition in spatial association patterns, with moth-
ers becoming more likely to change proximity (increased
not inuenced by multicollinearities (all Variance Ination
Factors, VIF, were inferior to 2; Lüdecke et al. 2021). After
running full-null (equivalent model without xed eects)
model comparisons, we tested the signicance of our xed
factors by running Wald chi-square tests and obtained the
associated p values for each model via the “Anova” func-
tion from the car package (Fox and Weisberg 2019). We
obtained 95% condence intervals and eect estimates via
the function “connt”. Finally, to validate the signicance
of our models, we checked the distribution of the residuals
with the “simulateResiduals” function from the DHARMa
package (Hartig and Lohse 2022).
Fig. 1 Behavioral variables studied to characterize mother-infant
relationships in mandrills as a function of infant age (for graphical
purposes, data were divided into quarters of 90 days). The variables
were as follows. Nursing and carrying: proportion of focals with any;
restraining, aggression and tantrums: number of events per hour,
recorded during all focals; grooming: proportion of focal time mother
groomed her infant; body contact: proportion of scans where mother
and infant were in contact (see Table S1, S2, and S3 for full descrip-
tion). Dashed lines represent the transition of responsibility, solid lines
indicate tted regressions, and shaded areas correspond to 95% con-
dence intervals
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Behavioral Ecology and Sociobiology (2025) 79:42
These age-related behavioral shifts align with typical
patterns of infant development in other mammals (Northern
elephant seals, Mirounga angustirostris: Reiter et al. 1978;
African elephants: Lee and Moss 1986; Sumatran orang-
utans, Pongo abelii: Revathe et al. 2024), which reects the
gradual progression toward autonomy, essential for infants
to achieve adequate size and acquire essential skills to sur-
vive, but also for mothers to sustain successful future repro-
duction. Some maternal behaviors, however, did not follow
a linear pattern across the rst year of life, which suggests
that some periods of infancy may be particularly critical for
development. In mandrills, indeed, most signicant changes
in mother-infant relationships occurred between the third
and ninth months, with a marked decline in maternal invest-
ment (nursing, carrying) alongside peaks in maternal rejec-
tion and infant solicitation. Interestingly, this period also
roughly corresponds to the critical weaning phase (approxi-
mately eight months in captivity; Setchell et al. 2002),
when mother-ospring conicts — often characterized by
maternal aggression and infant tantrums— are expected to
peak. As mandrill infants transition toward nutritional inde-
pendence, their decreasing reliance on maternal milk may
intensify these behavioral conicts. In the study population,
however, nursing may continue for several months in the
absence of a younger sibling (Delaunay et al. 2024), imply-
ing that these interactions probably fulll roles beyond
nutrition. Similarly, in wild chimpanzees, nutritional wean-
ing can be completed more than a year before infants stop
nipple contact (Bădescu et al. 2017), possibly as a form of
comfort nursing without milk transfer (Martin 1984; Reit-
sema 2012). Such extended nursing behavior in both species
may indicate an emotional comfort function, which high-
lights that the end of weaning does not necessarily mark a
denitive end of infant dependency to maternal attention.
Although mother-infant relationships generally stabi-
lized after nine months, with only minor uctuations, the
transition to independence varied with maternal domi-
nance rank. In polygynous species such as mandrills,
high-ranking females typically enjoy preferential access to
resources, leading to better physical conditions for them-
selves and their ospring, as well as greater reproductive
success. In our study population, for example, high-ranking
females produce more ospring on average than low-rank-
ing females (Dezeure et al. 2022). These advantages often
result in high-ranking mothers caring for closely spaced
immature siblings, which likely explains the reduced fre-
quency of infant carrying compared with low-ranking moth-
ers. This trend mirrors patterns observed in yellow baboons
(Papio cynocephalus; Altmann and Samuels 1992) and
spotted hyenas, where dominant females terminate mater-
nal investment earlier than subordinates (Holekamp et al.
1996; Holekamp and Dionak 2009; East and Hofer 2010).
Brown’s index) and being less responsible for seeking
proximity (decreased Hinde’s index) to their infants as they
aged, although these changes with age were also not linear.
In addition to these age-related eects, maternal domi-
nance rank and reproductive experience both profoundly
shaped mother-infant relationships (Tables 1 and 2). First,
high-ranking mothers carried their infants less but spent
more time grooming them than low-ranking mothers
(Fig. 2). Second, primiparous and younger mothers spent
less time grooming their infants than did multiparous (Fig.
S1) and older (Fig. 3) mothers, the latter also being more fre-
quently in body contact with their infants (Fig. 3). Although
maternal aggression was relatively infrequent (0.58 events
per hour on average), mothers who lost a previous infant
were less aggressive toward their current infant than were
those whose previous infant survived (Fig. 4). When we
excluded mothers whose previous infant died and included
the IBI to the previous living ospring instead, we found
that mothers who had spaced births (long IBIs) were less
aggressive to their infants than mothers with close-in-age
ospring (Fig. S2; Supplementary Table S8). Moreover,
mothers changed association patterns more frequently with
their sons than with their daughters (Brown’s index), mean-
ing that mothers were found less often in close proximity
to males than to females, although the proportion of scan
spent in body contact was not sex-dependent. Male infants
performed more tantrums than females did possibly either
as a result of frequent association disruptions initiated by
their mother or as a cause of it (Table 1; Fig. 5). Finally,
the social environment where infants were born (i.e., cohort
size) did not inuence mother-infant relationships (p > 0.05
in all instances, Table 1).
Discussion
In this study, based on a large sample of infants across eight
birth cohorts, we showed that mother-infant relationships in
a long-lived primate were shaped by a complex interplay
of maternal dominance rank, age, previous reproductive
experience, and infant sex. Interestingly, the social environ-
ment — specically, the number of peers born at the same
time — did not appear as a critical factor in shaping these
relationships, which is not surprising at such a young age.
At this stage, mothers are the primary social partners of their
ospring, a role that changes rapidly as infants transition
to juvenile stages, where interactions with peers become
increasingly important (Charpentier et al. 2020). Yet, as
infants progress through developmental stages, mother‒
infant relationship dynamics evolve predictably, with
maternal care behaviors decreasing as behaviors promoting
independence increased.
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Behavioral Ecology and Sociobiology (2025) 79:42
Fixed eects Level CI Estimate
x2
P
2.5% 97.5%
Nursing
Infant age -7.221 -5.182 -6.201 185.077 < 0.001
Infant age20.129 1.958 1.044 208.52 < 0.001
Maternal age -0.102 0.024 0.070 1.24 0.265
Death sibling Yes (ref: no) -0.096 0.236 0.070 0.68 0.409
Full-null model comparison:
x2
2
= 143.400, P < 0.001 (AIC full = 908.580, AIC null = 1043.980)
Carrying
Infant age -17.777 -13.540 -0.157 367.142 < 0.001
Infant age2-4.607 -1.835 -3.221 319.431 < 0.001
Dominance rank -0.171 -0.040 -0.106 10.041 0.002
Maternal age -0.050 0.089 0.0198 0.312 0.577
Death sibling Yes (ref: no) -0.133 0.246 0.056 0.342 0.559
Full-null model comparison:
x2
2
=263.890, P < 0.001 (AIC full = 824.130, AIC null = 1078.020)
Restraining
Infant age -1.891 -1.291 -1.591 108.286 < 0.001
Maternal age -0.214 0.225 0.005 0.002 0.961
Death sibling Yes (ref: no) -0.653 0.426 -0.114 0.170 0.680
Full-null model comparison:
x2
2
= 102.85, P < 0.001 (AIC full = 491.63, AIC null = 588.48)
Aggression
Infant age -0.164 6.790 3.313 4.697 0.030
Infant age2-9.250 -3.064 -6.157 18.122 < 0.001
Maternal age -0.374 0.126 -0.124 0.943 0.332
Death sibling Yes (ref: no) -1.413 -0.053 -0.733 4.467 0.035
Full-null model comparison:
x2
2
=26.180, P < 0.001 (AIC full = 440.590, AIC null = 458.770)
Tantrums
Infant age -6.417 -0.484 -3.451 3.135 0.077
Infant age2-6.547 -1.054 -3.800 10.819 0.004
Infant sex Male (ref: female) 0.171 1.104 0.638 7.176 0.007
Maternal age -0.119 0.347 0.114 0.923 0.337
Death sibling Yes (ref: no) -0.455 0.650 0.097 0.120 0.729
Full-null model comparison:
x2
2
= 17.542, P = 0.004 (AIC full = 689.560, AIC null = 697.100)
Grooming
Infant age 0.206 0.454 0.330 27.352 < 0.001
Dominance rank 0.123 0.434 0.279 12.388 < 0.001
Maternal age 0.032 0.312 0.172 5.790 0.016
Death sibling Yes (ref: no) -0.281 0.474 0.097 0.253 0.615
Full-null model comparison:
x2
2
=35.104, P < 0.001 (AIC full = -707.490, AIC null = -680.380)
Body contact
Infant age -0.595 -0.485 -0.540 371.135 < 0.001
Maternal age 0.010 0.141 0.076 5.154 0.023
Death sibling Yes (ref: no) -0.097 0.243 0.073 0.713 0.398
Full-null model comparison:
x2
2
= 406.230, P < 0.001 (AIC full = 994.230, AIC null = 1394.460)
Brown’s index
Infant age 1.133 2.992 2.063 18.237 < 0.001
Infant age2-2.704 -1.041 -1.873 36.424 < 0.001
Infant sex Male (ref: female) 0.001 0.372 0.191 4.280 0.039
Maternal age -0.138 0.001 -0.064 2.833 0.092
Death sibling Yes (ref: no) -0.244 0.131 -0.056 0.347 0.556
Full-null model comparison:
x2
2
= 44.110, P < 0.001 (AIC full = 803.190, AIC null = 837.300)
Hinde’s index
Infant age -0.101 -0.178 -0.059 7.825 0.005
Maternal age -0.037 0.073 0.019 0.468 0.494
Table 2 Statistical results of the reduced models, focusing on multiparous females
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Behavioral Ecology and Sociobiology (2025) 79:42
than low-ranking mothers. Maternal grooming is thought
to promote ospring independence while facilitating social
development and integration (Meaney 2001). Our nd-
ings suggest that high-ranking mothers may use groom-
ing behavior to enhance their ospring’s social experience
Additionally, faster growth in infants born to high-ranking
mothers (Setchell et al. 2001) could further accelerate the
cessation of maternal carrying. Interestingly, despite hav-
ing ospring that are often closer in age, high-ranking
mandrill mothers spent more time grooming their infants
Fig. 2 Partial residuals of a. the proportion of time spent grooming per
hour and b. carrying rates (number of focal observations with at least
one event per hour) as a function of maternal dominance rank. Solid
lines indicate tted regressions, and shaded areas correspond to 95%
condence intervals
Fixed eects Level CI Estimate
x2
P
2.5% 97.5%
Death sibling Yes (ref: no) -0.047 0.239 0.097 2.156 0.142
Full-null model comparison:
x2
2
=9.486, P = 0.023 (AIC full = 74.875, AIC null = 78.361)
Note. The Table shows estimates, 95% condence inter vals (CI), chi-square and P values for the predictors of the GLMMs and LMMs (Hinde’s
index), including infant, mother and cohort identities as three random eects. Signicant eects are highlighted in bold. Mean ± SD for infant
age: 175.040 ± 102.020); dominance rank: 0.477 ± 0.338); cohort size: 36.862 ± 14.734
Table 2 (continued)
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Behavioral Ecology and Sociobiology (2025) 79:42
Similarly, in species such as bison (Bison bison) and horses,
experienced mothers maintain closer contact with ospring
during critical preweaning periods, followed by abrupt
changes in proximity, suggesting strategic investment dur-
ing periods of vulnerability (Green 1993; Cameron et al.
2000;). However, maternal behavior is not shaped solely by
experience per se. Young mothers, still growing themselves,
are likely to face additional nutritional demands that can
limit their ability to synchronize activities with their infants
(Green 1993). For example, female mandrills typically
reproduce before reaching full adult body size (Setchell et
al. 2002), and younger individuals spend more time forag-
ing than adults (Nsi Akoue et al. 2017). These factors may
during early life, potentially conferring advantages in navi-
gating their complex social environment. This behavioral
pattern may reect the broader reproductive benets associ-
ated with high social rank in mandrills.
Maternal parity and age also emerged as key factors of
mother-infant relationships in our study population. Mul-
tiparous and older mothers showed higher rates of body
contact and spent more time grooming their infants, which
are behaviors known to foster infant development and
social integration (Maestripieri et al. 2009). In contrast to
ndings in other mammals, where primiparous females are
often more protective and less rejecting (Clutton-Brock et
al. 1982; Fairbanks 1988), we observed that maternal expe-
rience in mandrills appears to enhance caregiving skills.
Fig. 3 Partial residuals of a. the proportion of time spent grooming
per hour and b. the probability of body contact (proportion of scans in
which the mother and infant were in body contact) as a function of the
mother’s age. Solid lines indicate tted regressions and shaded areas
correspond to 95% condence intervals
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Behavioral Ecology and Sociobiology (2025) 79:42
mothers of surviving infants often care for another juve-
nile born in close succession, requiring resource allocation
across multiple dependent ospring, which could exacerbate
mother‒ospring conicts (Fairbanks 1988). Consistent
with this, we found that shorter interbirth intervals between
surviving ospring were also associated with increased
maternal aggression. Furthermore, the energetic relief pro-
vided by the loss of a growing infant might allow moth-
ers to regain a better physical condition, which may result
in less frequent displays of rejection or aggression during
subsequent caregiving eorts. Distinguishing between these
competing hypotheses — adaptive behavioral adjustment
versus resource reallocation dynamics — lies beyond the
explain the reduced grooming and body contact observed in
younger mandrill mothers.
Infant loss and pregnancy failure may, however, alter
these rank- and age-related patterns of mother-ospring
relationships, as observed in other mammals such as ver-
vet monkeys and horses, where females increase maternal
investment following infant loss, probably to secure o-
spring survival (Fairbanks 1988; Cameron et al. 2000). In
mandrills, mothers whose previous infant died were signi-
cantly less aggressive toward their next infant. This pattern
may reect not only an adaptive adjustment to increase sur-
vival chances but also a reduced need to manage compet-
ing demands from multiple close-in-age ospring. Indeed,
Fig. 4 Partial residuals of maternal aggression rates (number of aggres-
sion events per hour) as a function of survival of the previous infant.
Boxes represent the interquartile range (IQR), with the lower and
upper edges corresponding to the rst (Q1) and third (Q3) quartiles,
respectively. The horizontal line within the box indicates the median.
Whiskers extend to the smallest and largest values within 1.5 times the
IQR from Q1 and Q3
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Behavioral Ecology and Sociobiology (2025) 79:42
daughters who inherit their social status (Charpentier et al.
2007, 2020). In this population, juvenile daughters also ini-
tiate more grooming with their mothers than juvenile sons
(Delaunay et al. 2024). Thus, from an early age, mandrill
mothers may foster stronger bonds with their daughters,
while encouraging their sons’ independence by frequently
altering their proximity to them, thereby beginning to pre-
pare them for future natal dispersal. In addition, in highly
sexually dimorphic species such as mandrills, where male
reproductive skew is high, the advantages provided by
sons may be more variable. Overall, daughters may confer
greater average tness advantages than sons due to life-
long social support. The more frequent tantrums observed
scope of this study but provides an intriguing avenue for
future research, potentially expanding our understanding of
maternal strategies in resource allocation and ospring care.
Finally, mandrill mothers were more likely to maintain
proximity with their daughters than with their sons, which
is consistent with the expected increased maternal invest-
ment in the philopatric sex, where reproductive advantages
are socially transmitted (Altmann 1980; Hiraiwa-Hasegawa
1993). For example, in chimpanzees, where males are philo-
patric and mothers can inuence their son’s reproductive
success, male infants are weaned later than females in some
populations (Bădescu et al. 2022). Female mandrills are
philopatric with lifelong close bonds between mothers and
Fig. 5 Partial residuals of a. Brown’s index and b. infant tantrum rates
(number of observed events per hour) as a function of infant sex.
Dashed lines represent the transition of responsibility. Boxes represent
the interquartile range (IQR), with the lower and upper edges corre-
sponding to the rst (Q1) and third (Q3) quartiles, respectively. The
horizontal line within the box indicates the median. Whiskers extend
to the smallest and largest values within 1.5 times the IQR from Q1
and Q3
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Behavioral Ecology and Sociobiology (2025) 79:42
CENAREST/CG/CST/ CSAR) and followed all applicable interna-
tional, national, and/or institutional guidelines for the care and use of
animals.
Conict of interest The authors declare that they have no competing
interests.
Open Access This article is licensed under a Creative Commons
Attribution 4.0 International License, which permits use, sharing,
adaptation, distribution and reproduction in any medium or format,
as long as you give appropriate credit to the original author(s) and the
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ditional and non-traditional factors. In: Small MF (ed) Female
in male infants may reect these sex-biased dierences in
proximity maintenance. However, similar to other species
with pronounced sexual dimorphism (Lee and Moss 1986;
Piedrahita et al. 2014; Eckardt et al. 2016), male mandrills
grow at a faster rate than females, as early as the rst year
of life (males: 2.25 kg/year versus females: 1.85 kg/year;
Wickings and Dixson 1992). Therefore, males may demand
more investment because of their higher growth require-
ments, which may explain the increased frequency of tan-
trums observed in these individuals.
In conclusion, this study reveals the complex dynam-
ics of mother–infant relationships in mandrills. While the
gradual shift toward infant independence is a common pat-
tern in mammals, mandrills stand out among highly sexu-
ally dimorphic species because of the inuence of maternal
dominance rank and sex-specic investment strategies. Our
ndings emphasize the critical role of social factors, such as
rank inheritance and lifelong social bonds, in shaping mater-
nal behavior and ospring development. Overall, our results
underscore the adaptive exibility of maternal behaviors,
demonstrating how maternal care can be ne-tuned to opti-
mize both individual survival and long-term reproductive
success in a species with complex social dynamics.
Supplementary Information The online version contains
supplementary material available at h t t p s : / / d o i . o r g / 1 0 . 1 0 0 7 / s 0 0 2 6 5 - 0
2 5 - 0 3 5 8 2 - 8.
Acknowledgements We are grateful to the past and present eld
assistants of the Mandrillus Project for their daily data collection. We
also thank the SODEPAL-COMILOG society (ERAMET group) for
their long-term logistical support. We thank Iulia Bădescu, Maria van
Noordwijk, and one anonymous reviewer who provided constructive
feedback that improved this manuscript greatly. This is a Project Man-
drillus publication number 36 and ISEM 2025-025 SUD.
Author contributions BR-T, MJEC, and PMK conceived the study
and design. BR-T, AC, LS, MDP, GH, MK, JMdB, SA and MH col-
lected the behavioral data. BR-T analyzed the data. BR-T, MJEC, and
PMK wrote the manuscript with feedback from AB. MJEC and AB
manage the long-term project that has generated the data. MJEC and
MH manage the associated databases. MJEC and PMK acquired the
funding. All authors read and approved the nal manuscript.
Funding Open Access funding enabled and organized by Projekt
DEAL.
This study was funded by several grants that allowed long-term data
collection: SEEG Lekedi (INEE-CNRS), the Leakey Foundation
(S202210309), the Max Planck Society to MJEC, and Deutsche Forsc-
hungsgemeinschaft (DFG; KA 1082/45 − 1) to PMK and MJEC.
Data availability The dataset supporting this article is available as
supplementary material.
Declarations
Ethical approval This study was approved by an authorization from
the CENAREST Institute (permit number, AR017/22/MESRSTTCA//
1 3
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Authors and Aliations
BertaRoura-Torres1,2,3 · AliceBaniel3· AnnaCryer4· LoïcSauvadet4· MélyssaDe Pastors4· GeorgeHavill4·
MélodieKreyer4· JadeMeric de Bellefon4· StevenAbaga4· MélanieHarté4· Peter M.Kappeler1,2 ·
Marie J. E.Charpentier3,5
Berta Roura-Torres
rouratorresberta@gmail.com
1 Department of Sociobiology/Anthropology, Institute of
Zoology and Anthropology, Johann-Friedrich-Blumenbach,
Georg-August University Göttingen, Kellnerweg 6,
37077 Göttingen, Germany
2 Behavioral Ecology and Sociobiology Unit, German Primate
Center, Leibniz Institute for Primate Research, Kellnerweg 4,
37077 Göttingen, Germany
3 ISEM, UMR5554 – University of Montpellier/CNRS/IRD/
EPHE, Place Eugène Bataillon (cc065), Montpellier
34095, France
4 Projet Mandrillus, Parc de la Lékédi, BP 52, Bakoumba,
Gabon
5 Department for the Ecology of Animal Societies, Max Planck
Institute of Animal Behavior, Bücklestraβe 5,
78467 Konstanz, Germany
1 3
42 Page 18 of 18
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