Maternal Behavior and Infant Congenital Limb Malformation in a Free-Ranging Group of <Emphasis Type="Italic">Macaca fuscata</Emphasis> on Awaji Island,Japan

We studied the relationship between maternal behavior and infant disability in 12 mother-infant dyads for the first 5 weeks of infant life in the free-ranging Japanese macaque (Macaca fuscata) group on Awaji Island, Japan, from May to September 2001. Congenital limb malformations are prevalent in this population, and as such carry implications for behavior and conservation. We did not detect any differences in maternal activity budgets, mother-infant physical contact, infant holding, and overall nursing and infant transport time between mothers of non-disabled infants, disabled infants that were able to cling to their mothers, and disabled infants whose limb structure prevented clinging. Mothers of infants with limb malformations severe enough to prevent normal clinging behavior manually supported their infants during nursing and locomotion significantly more than other mothers did theirs. Increased support-carrying and support-nursing, and higher frequencies of holding the infant to one's ventrum, suggest that mothers of extensively malformed infants may be investing more to facilitate the survival of their offspring and that infant disability appears to be influencing maternal behaviors in this population.     

Variability in the development of mother-infant relationships among free-ranging Japanese macaques

Mother-infant relationships were studied during the infant's first year in free-ranging Japanese macaques (Macaca fuscata). Three possible factors controlling the mother-infant relationships were examined using multivariate analysis. Parity was determined to exert the strongest influence on mother-infant relationships. Specifically, during month 1, multiparous mothers showed greater maternal suckling rejection than primiparous mothers, and primparae and multiparae differed in their responses to suckling behavior. During month 6, multiparous mothers prompted independence of their offspring more than primiparous mothers. By month 8, however, parity differences in maternal behavior were substantially reduced. Maternal rank was a less important factor, although during month 1, high-ranking mothers showed greater maternal restriction than low-ranking ones. In the present study, infant gender appeared to have no effect on mother-infant relationships. That most differences were due to parity indicates that mother-infant relations were largely determined by the mothers. This observation conflicts with the “learning-to-mother” hypothesis. Allo-mothering of neonates by nulliparae is rare among Japanese macaques. Primiparous mothers learned appropriate suckling care from handling their own infants.     

The process of weaning in hanuman langursPresbytis entellus entellus

Twelve langur infants (seven males and five females) of three focal bisexual unimale troops of Hanuman langurs,Presbytis entellus entellus living near Kailana, Jodhpur, Rajasthan (India) were observed for their weaning behaviour. Weaning starts between 7.0 to 10.0 months of age, average 8.6 months. The process of weaning lasts between 3.2 to 5.6 months, average 4.2 months. A 13-month-old infant is fully weaned. Infants are independent at this age. Male infants are weaned earlier compared to females. Males react to their mothers' rejections more fearlessly and are more vocal compared to females. By and large, infants were found in stress during this period as their mothers are often very harsh, hostile, punitive, and indifferent to their infants. By severing ties with their infants, mothers serve dual purpose of allowing their infants to become independent and may be to become ready to bear offspring.     

The development of behavioural sex differences in infant rhesus macaques (Macaca mulatta)

Studies of infant rhesus macaques have generally reported sex differences in the frequency of expression of some behaviour patterns, such as rough-and-tumble play and socio-sexual mounting. In contrast, sex differences in other behaviour patterns, such as proximity to the mother, have been less consistantly reported. Using data on the behavioural development of infant rhesus macaques living in captive social groups, we have attempted to provide further evidence for, or against, sex differences in behaviour and to investigate the possible influence of maternal rank and parity on sex differences in infant behaviour and mother-infant interactions. The behaviour of 14 male and 20 female infants and their mothers was studied during the first six months of life, including measures of play behaviour socio-sexual mounting, and mother-infant interactions. Our data reveal that, on average, male infants exhibited more rough-and-tumble play and mounting than female infants, and also exhibited stationary play, chasing play, and initiated play more frequently than females. Such sex differences appear to be robust in macaques and have been reported in a variety of housing conditions. male and female infants did not differ in the amount of time spent at particular distances from their mothers, and mothers were not found to behave differently towards sons and daughters, using measures of restraint, rejection, and grooming. These results are in contrast to previous studies on singly-housed mother-infant pairs but similar to those on free-ranging populations. Mothers did behave differently towards their infants depending upon the mother's rank and previous number of offspring. These maternal characteristics may have significant consequences for the behavioural development of both male and female infant primates.     

MOTHER-INFANT SPATIAL RELATIONS IN CAPTIVE BOTTLENOSE DOLPHINS,TURSIOPS TRUNCATUS

The prolonged nursing period and strong, extended mother-infant bond observed among bottlenose dolphins may reflect social and physical ontogeny critical for infant survival. This study was conducted to quantify ontogentic changes in mother-infant contact time and the amount of time infants spent in specific spatial states with their mothers from birth to age 12 mo. These behaviors were studied through a systematic, longitudinal study of six mother-infant pairs of captive bottlenose dolphins from three different social groups. There was a significant decrease in the time infants spent with their mothers (logistic regression, P < 0.001), following the general mammalian pattern of increasing independence with age. When with their mothers, the probability that infants would be found in “echelon” position, flanking the mother, decreased as the calf aged (logistic regression, P <0.001), possibly due to anatomical and hydrodynamic factors. The probability that infants would be found in “infant” position, underneath the mother, increased with calf age (logistic regression, P < 0.001). Results obtained in this study are consistent with similar studies of wild bottlenose dolphin mother-infant pairs, indicating a suite of ontogenetically comparable behaviors between wild and captive bottlenose dolphins.     

Mother-infant interactions in slow lorises (Nycticebus bengalensis) and pygmy lorises (Nycticebus pygmaeus)

The study had three purposes: (1) to obtain information about mother-infant interactions in a rarely studied nocturnal prosimian, the pygmy loris (Nycticebus pygmaeus); (2) to compare pygmy lorises with a closely related and better-studied nocturnal prosimian, the Bengal slow loris (Nycticebus bengalensis); and (3) to determine how the presence of a second offspring affected mother-infant interactions in pygmy lorises. Three Bengal slow loris mothers and 3 pygmy loris mothers served as subjects, along with their 10 offspring (4 Bengal slow loris singletons, 2 pygmy loris singletons and 2 sets of pygmy loris twins). Observations were carried out in a zoo research facility for the first 24 weeks of the infants' lives. Although the two species differ in size and reproductive patterns, mother-infant interactions were similar. The primary modes of infant and adult contact were ventral and passive contact, respectively. Mothers parked their infants from the first week, and infants followed from the second week. Mothers displayed little protection or rejection, and there was little aggression. Infants solicited play and social grooming from their mothers. Pygmy loris mothers engaged in social grooming and play with their infants more frequently and for longer periods if the infant was a singleton rather than a twin.     

No evidence for sex biases in milk macronutrients,energy, or breastfeeding frequency in a sample of filipino mothers

Maternal reproductive investment includes both the energetic costs of gestation and lactation. For most humans, the metabolic costs of lactation will exceed those of gestation. Mothers must balance reproductive investment in any single offspring against future reproductive potential. Among mammals broadly, mothers may differentially invest in offspring based on sex and maternal condition provided such differences investment influence future offspring reproductive success. For humans, there has been considerable debate if there are physiological differences in maternal investment by offspring sex. Two recent studies have suggested that milk composition differs by infant sex, with male infants receiving milk containing higher fat and energy; prior human studies have not reported sex‐based differences in milk composition. This study investigates offspring sex‐based differences in milk macronutrients, milk energy, and nursing frequency (per 24 h) in a sample of 103 Filipino mothers nursing infants less than 18 months of age. We found no differences in milk composition by infant sex. There were no significant differences in milk composition of mothers nursing first‐born versus later‐born sons or daughters or between high‐ and low‐income mothers nursing daughters or sons. Nursing frequency also showed no significant differences by offspring sex, sex by birth order, or sex by maternal economic status. In the Cebu sample, there is no support for sex‐based differences in reproductive investment during lactation as indexed by milk composition or nursing frequency. Further investigation in other populations is necessary to evaluate the potential for sex‐based differences in milk composition among humans. Am J Phys Anthropol 152:209–216, 2013. © 2013 Wiley Periodicals, Inc.     

Costs and benefits of maternal aggression in lactating female rhesus macaques

Data from over 400 hr of observation of mother-infant rhesus macaques indicate that during the first 12 weeks of lactation infants are at risk from other group members and that mothers use aggression as well as restraining to protect them. Maternal aggression was negatively correlated with infant restraining. High-ranking mothers reacted aggressively to individuals handling their infants more than did middle- and low-ranking mothers. Conversely, middle- and low-ranking mothers restrained their infants more than did high-ranking mothers. Maternal aggression did not vary with infant age. Maternal aggression was directed toward a higher proportion of higher-ranking adult females and their immature offspring and was more likely to be followed by counter-aggression than nonmaternal aggression, i.e. aggression not related to interactions involving the infant. Middle-and low-ranking mothers suffered higher costs in terms of retaliation than high-ranking mothers. It is argued that the occurrence and distribution of maternal aggression among species and individuals should depend on the risk posed to infants by conspecifics as well as on the characteristics of the social structure (e.g. degree of asymmetry of agonistic contests) and of the mother (e.g. her dominance rank) which may affect the probability of retaliation.     

Brief Communication: Orphaned male Chimpanzees die young even after weaning

If a social‐living animal has a long life span, permitting different generations to co‐exist within a social group, as is the case in many primate species, it can be beneficial for a parent to continue to support its weaned offspring to increase the latter's survival and/or reproductive success. Chimpanzees have an even longer period of dependence on their mothers' milk than do humans, and consequently, offspring younger than 4.5–5 years old cannot survive if the mother dies. Most direct maternal investments, such as maternal transportation of infants and sharing of night shelters (beds or nests), end with nutritional weaning. Thus, it had been assumed that a mother's death was no longer critical to the survival of weaned offspring, in contrast to human children, who continue to depend on parental care long after weaning. However, in theory at least, maternal investment in a chimpanzee son after weaning could be beneficial because in chimpanzees' male‐philopatric society, mother and son co‐exist for a long time after the offspring's weaning. Using long‐term demographic data for a wild chimpanzee population in the Mahale Mountains, Tanzania, we show the first empirical evidence that orphaned chimpanzee sons die younger than expected even if they lose their mothers after weaning. This suggests that long‐lasting, but indirect, maternal investment in sons continues several years after weaning and is vital to the survival of the sons. The maternal influence on males in the male‐philopatric societies of hominids may be greater than previously believed. Am J Phys Anthropol, 153:139–143, 2014. © 2013 Wiley Periodicals, Inc.     

Mother-infant interactions of wild-born,individually-caged cynomolgus monkeys (Macaca fascicularis) during the first 14 weeks of infant life

This study documents age-related changes in the interactions of wild-born cynomolgus macaque mothers and their infants living in individual cages during the first 14 weeks of infant life. Body contact between mother and infant, maternal holding, and infant sucking were found to decrease, and the mothers showed an increased frequency of aggression toward their infants with age. These results were broadly similar to those reported for mother-infant interactions in other macaques living in social groups. Nevertheless, a clear difference between the present cynomolgus macaques and other macaques in social groups was apparent. The cynomolgus macaque mothers tended to permit their infants to move about freely without displaying maternal protectiveness such as restraint or retrieval, unlike other macaque mothers in social groups. Such maternal behaviors might derive from the experience of living in individual cages for many years and the relative safety of living in individual cages. The lack of maternal restraint and retrieval could be responsible for the observed sex differences in behavior: male infants moved more actively, and broke, and made contact with their mothers more frequently than did female infants. Moreover, mothers of female infants held and groomed them more frequently and were less aggressive toward them.     

Artificial weaning of Old World monkeys: benefits and costs

Permanent mother-infant separation prior to natural weaning is a common hus-bandry practice in monkey breeding colonies. In the United States, all eight Re-gional Primate Research Centers have such colonies. Under undisturbed conditions, Old World monkey mothers wean their infants at the age of about 1 year (Hall & DeVore, 1965; Poirier, 1970; Roonwal & Mohnot, 1977; Southwick, Beg, & Siddiqi, 1965). Natural weaning is a gradual process. It implies that the mother, over a period of several weeks or months, more and more consistently discourages her infant to suck on her breasts. Once the mother stops nursing the infant for good, the affectionate bond between the two is not broken (Altmann, Altmann, Hausfater, & McCuskey, 1977; Lindburg, 1971; Poirier, 1970; Roonwal & Mohnot, 1977). The young usually remains in the ma-ternal group at least until prepuberty. Under confinement conditions, artificial weaning is an abrupt occurrence that takes place several months prior to the biologically normal age of weaning. It im-plies that the still-nursed infant is taken away from the mother and subsequently reared alone or with other artificially weaned infants.     

Maternal care and infant development in <Emphasis Type="Italic">Callimico goeldii</Emphasis> and <Emphasis Type="Italic">Callithrix jacchus</Emphasis>

Callimico goeldii gives birth to single offspring, whereas other callitrichids, including Callithrix jacchus, twin. This study compares maternal effort and infant development in C. goeldii and C. jacchus; it is the first study to look at nursing frequency. Infants were observed from birth for 7 weeks in two captive groups each of C. goeldii and C. jacchus. C. goeldii mothers physiologically invested the same or less than C. jacchus mothers. C. goeldii mothers gained the same amount of weight during pregnancy in absolute terms as did the smaller C. jacchus. This results in a smaller gain in proportion to maternal weight but an equivalent proportional gain on a per fetus basis. C. goeldii mothers nursed their infants less based on duration of nursing bouts compared with C. jacchus mothers. C. goeldii mothers transported their infants exclusively through the first 2 weeks of life, which is longer than C. jacchus mothers, who exclusively transported infants only during the first week of life. As maternal infant carriage declined, other group members transported offspring in both species. C. goeldii infants engaged in independent locomotive sequences later in development and tasted solid foods less frequently than C. jacchus infants when compared at equivalent ages. A single, opportunistic milk sample obtained from a C. goeldii mother when her infant was 48 days old indicates that C. goeldii milk contains gross energy from crude protein within the range of variation observed in Callithrix milk. Despite the similarities in milk quality and prenatal effort in individual fetuses, C. goeldii infants gain weight faster from 0 to 18 months than do C. jacchus infants. A reduction in litter size allows C. goeldii mothers to spend more time carrying their infant and to delay weaning, thereby allowing accelerated infant and juvenile growth rates compared with C. jacchus.     

The breeding system of wild red ruffed lemurs (<Emphasis Type="Italic">Varecia rubra</Emphasis>): a preliminary report

Captive studies have shown that ruffed lemurs (Varecia) have an unusual suite of reproductive traits combined with extremely high maternal reproductive costs. These traits include the bearing of litters, nesting of altricial young, and absentee parenting. To characterize the breeding system of this enigmatic lemur, reproductive traits must be contextualized in the wild. Here, I provide a preliminary report of mating and infant care in one community of wild red ruffed lemurs (Varecia rubra). Observations span a 15-month period covering two birth seasons and one mating season on the Masoala Peninsula, Madagascar. Factors that are not possible to replicate in captivity are reported, such as mating pattern, natality and mortality rates, the location of nests within the home range, and the structuring of infant care within a natural community. V. rubra at Andranobe have a fission-fusion, multifemale-multimale grouping pattern and a polygamous mating system. They do not mate monogamously or live strictly in family-based groups as suggested by previous workers. During the first 2 months of life, nests and infant stashing localities are situated within each mother's respective core area, and inhabitants of each core area within the communal home range provide care for young. As part of their absentee parenting system, infants are left in concealed, protected, and supportive spots high in the canopy, while mothers travel distantly. This practice is termed 'infant stashing'. Alloparenting appears to be an integral part of V. rubra's overall reproductive strategy in the wild, as it was performed by all age-sex classes. Among the alloparental behaviors observed were infant guarding, co-stashing, infant transport, and allonursing. Alloparenting and absentee parenting may mitigate high maternal reproductive costs. Furthermore, V. rubra may have a breeding system in which genetic partners (i.e., mating partners) do not always correspond to infant care-providers. Combined with recently available information on the behavioral ecology of wild ruffed lemurs, this preliminary report suggests directions for in-depth studies on Varecia's breeding system.     

神农架川金丝猴投食群的母婴关系

灵长类动物母亲的育婴行为不仅对后代的存活起着关键作用,而且对婴猴的发育和成年后的社会交往有着重大影响,因此母-婴关系一直是灵长类学研究的热点之一。为了解川金丝猴的母-婴关系,探讨川金丝猴母-婴关系个体差异的影响因素,我们于2013年3月至2014年10月,以母-婴间相对距离表示照料强度,对神农架川金丝猴的母-婴照料关系以及母亲照料强度个体差异的影响因素进行了定量研究。结果表明：母亲照料行为强度、母亲对阿姨行为的容忍与婴猴年龄相关,限制行为与婴猴年龄不相关。身体接触与婴猴年龄不相关;腹部接触以及母-婴相对距离小于1 m与婴猴年龄呈负相关;相对距离1 m至5 m、相对距离5 m至10 m和相对距离大于10 m与婴猴年龄呈正相关;母亲对阿姨行为的拒绝与婴猴年龄呈负相关;母亲对婴猴的限制行为与年龄不相关。总的来说,即随着婴猴成长,母婴间距离越来越远,母亲也逐渐减少对婴猴的保护。母亲的生育经验、婴猴性别、婴猴出生先后和社会单元大小对神农架川金丝猴母婴关系没有显著影响,补食群丰富的食物资源和群内雌性友好的关系可能是导致本结果的原因。     

Maternal Oxytocin Is Linked to Close Mother-Infant Proximity in Grey Seals (Halichoerus grypus)

Maternal behaviour is a crucial component of reproduction in all mammals; however the quality of care that mothers give to infants can vary greatly. It is vital to document variation in maternal behaviour caused by the physiological processes controlling its expression. This underlying physiology should be conserved throughout reproductive events and should be replicated across all individuals of a species; therefore, any correlates to maternal care quality may be present across many individuals or contexts. Oxytocin modulates the initiation and expression of maternal behaviour in mammals; therefore we tested whether maternal plasma oxytocin concentrations correlated to key maternal behaviours in wild grey seals (Halichoerus grypus). Plasma oxytocin concentrations in non-breeding individuals (4.3 ±0.5 pg/ml) were significantly lower than those in mothers with dependent pups in both early (8.2 ±0.8 pg/ml) and late (6.9 ±0.7 pg/ml) lactation. Maternal plasma oxytocin concentrations were not correlated to the amount of nursing prior to sampling, or a mother’s nursing intensity throughout the dependant period. Mothers with high plasma oxytocin concentrations stayed closer to their pups, reducing the likelihood of mother-pup separation during lactation which is credited with causing starvation, the largest cause of pup mortality in grey seals. This is the first study to link endogenous oxytocin concentrations in wild mammalian mothers with any type of maternal behaviour. Oxytocin’s structure and function is widely conserved across mammalian mothers, including humans. Defining the impact the oxytocin system has on maternal behaviour highlights relationships that may occur across many individuals or species, and such behaviours heavily influence infant development and an individual’s lifetime reproductive success.     

Reproductive parameters of wild Trachypithecus leucocephalus: seasonality,infant mortality and interbirth interval

Understanding the reproductive parameters of endangered primate species is vital for evaluating the status of populations and developing adequate conservation measures. This study provides the first detailed analysis of the reproductive parameters of wild white‐headed langurs (Trachypithecus leucocephalus), based on demographic data collected over an 8‐year period in the Nongguan Karst Hills in Chongzuo County, Guangxi, China. From 1998 to 2002, a total of 133 live births were recorded in the population based on systematic censuses. Births occurred throughout the year, but the temporal pattern was highly correlated with seasonal variation in temperature and rainfall, with the birth peak coinciding with the dry and cold months of November–March. The average birthrate was 0.47±0.13 births per female per year and mortality for infants younger than 20 months was 15.8%. From 1998 to 2006, 14 females gave birth to 41 infants in four focal groups. The average age at first birth for female langurs was 5–6 years (n=5) and the interbirth interval (IBI) was 23.2±5.2 months (median=24.5 months, n=27). Infants are weaned at 19–21 months of age. The IBI for females with infant loss before weaning was significantly shorter than those for females whose infants survived. It appears that birth seasonality in the white‐headed langurs is influenced by seasonal changes in food availability. The timing of conceptions was found to coincide with peak food availability. The reproductive parameters for white‐headed langurs reported here are quite similar to those reported for other colobine species. One major difference is our observation of lower infant mortality in Trachypithecus. Am. J. Primatol. 71:558–566, 2009. © 2009 Wiley‐Liss, Inc.     

The evolution of non-maternal care in anthropoid primates: a test of the hypotheses

The amount of non-maternal care (allocare) found in primates varies greatly from species to species. Our paper examines this variation and focuses on possible reasons why mothers in some anthropoid primate species are prepared to relinquish their infants to other carers whereas others are not. We use data collected from the literature to test a number of hypotheses that attempt to explain the observed variation in non-maternal care. Analyses were carried out using comparative methods that control for the influence of both body size and phylogeny on life-history and ecological variation. The results support previous studies of both primates and other mammals in finding a clear link between the amount of allocare provided and female reproductive rates. Species with high allocare levels grow rapidly post-natally and wean their infants at a younger age (but at the same relative size) than species of the same body size with lower allocare levels. This early weaning allows high allocare species to support higher birth rates than low allocare species but does not result in earlier maturation. Our results, therefore, suggest that mothers allow non-maternal care of their infants in order to increase their own reproductive output. It is not clear whether such a strategy also benefits the infant, as we could find no link between the presence of allocare and early maturation (which would increase the infant's reproductive output) or between allocare levels and infant survival (as measured by vulnerability to infanticide). This suggests that mothers and infants might come into conflict over transfer to other carers, as the benefits to the mother may not be accompanied by benefits to the infant. However, although mothers may benefit from allocare in some circumstances, they will not be expected to allow allocare if the costs are high (e.g. if there is a high risk to the infant).     

Peer-rearing influences subsequent maternal behavior and infant survival in a newly formed herpes B-virus negative rhesus macaque group

The maternal behavior of primiparous rhesus macaques (Macaca mulatta), peer-reared since 1/2 years(s) of age as part of aHerpesvirus simiae (herpes B-virus) screening protocol, was examined and compared to a control group of conspecifics reared in their natal group. Infant survival was significantly higher in control groups as compared to the test group, a result attributed to the high incidence of infant kidnapping/abandonment in the test group. Among the test subjects, infant survival rate increased as the birth season progressed, thus it is possible that exposure to mothers/infants helped in the maternal success of those females who gave birth later in the season. Test group infants were touched by group members significantly more than the infants of control subjects, whereas these infants were groomed by their mothers and in a ventral position for a greater time relative to the infants of the test subjects. This study suggests that females, partially reared in peer groups, may be at early risk for maternal incompetence and consequent greater infant mortality, and that exposure to mother-infant dyads may augment the proficiency of maternal skills.     

A case of infant swapping by wild northern muriquis (<Emphasis Type="Italic">Brachyteles hypoxanthus</Emphasis>)

Allo-parenting has been observed in a variety of female primates, and typically infants are reunited with their biological mothers assuming that their mothers are alive. We observed an exception to this pattern when two wild northern muriquis (Brachyteles hypoxanthus) exchanged infants of different sexes and then reared their adopted infants through weaning. The process of this exchange began when the infants were 4 and 8 days old, respectively. The mother of a 4-day old female carried and nursed her own daughter and the 8-day old son of a second female. The exchange ended when the second mother was first observed carrying the wrong infant 1.5 days later. This observation raises questions about the age and mechanisms of mother–infant recognition in this species, and about assumptions of mother–infant relatedness based on behavioral observations alone.     

Birth Timing and Behavioral Responsiveness Predict Individual Differences in the Mother–Infant Relationship and Infant Behavior During Weaning and Maternal Breeding

There is a great deal of variability in mother–infant interactions and infant behavior across the first year of life in rhesus monkeys. The current article has two specific aims: (1) to determine if birth timing predicts variability in the mother–infant relationship and infant behavior during weaning and maternal breeding, and (2) to identify predictors of infant behavior during a period of acute challenge, maternal breeding. Forty‐one mother–infant pairs were observed during weaning when infants were 4.5 months old, and 33 were followed through maternal breeding. Subjective ratings of 16 adjectives reflecting qualities of maternal attitude, mother–infant interactions, and infant attitude were factor analyzed to construct factors relating to the mother–infant relationship (Relaxed and Aggressive) and infant behavior (Positive Engagement and Distress). During weaning, late born infants were more Positively Engaged than peak born infants (ANOVA, P < 0.05); however, birth timing did not affect the mother–infant relationship factors Relaxed and Aggressive or the infant attitude factor Distress. During maternal breeding, early born infants had less Relaxed relationships with their mothers than peak or late born infants, higher Positive Engagement scores than peak or late born infants, and tended to have higher Distress scores than peak born infants (repeated‐measures ANOVA, P < 0.05). In addition, Distress scores were higher during maternal breeding than during the pre‐ and postbreeding phases. Finally, multiple regression (P < 0.05) indicated that while infant behavioral responsiveness predicted infant Positive Engagement during the acute challenge of maternal breeding, qualities of the mother–infant relationship predicted infant Distress. These data suggest that birth timing influences the patterns of mother–infant interactions during weaning and maternal breeding. Additionally, infant behavioral responsiveness and mother–infant relationship quality impact infant social engagement and affect expression, respectively. Am. J. Primatol. 74:734‐746, 2012. © 2012 Wiley Periodicals, Inc.