Change of nipple preference between successive offspring in Japanese macaques

Selective use of nipples among free-ranging infant Japanese macaques (Macaca fuscata) was studied. Each infant held only one of its mother's two nipples in the mouth during an average of 90.9% ± 1.5% (SEM) of total nipple contact time. The next offspring born to the same mother tended to use the nipple that its previous sibling had not used. Maternal behavior did not cause use of one nipple or the other.     

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 — Offspring Conflict in the Saharan Arrui,Ammotragus lervia sahariensis: Relation to Weaning and Mother's Sexual Activity

Behavioural conflict between mother and offspring was investigated in a captive population of the Saharan arrui (Ammotragus lervia sahariensis, Artiodactyla: Bovidae). The frequency of agonistic behaviours (mother's aggressiveness and calf's retreats) and unsuccessful suckling attempts, Hinde's proximity index and the distances between mother and calf have been analysed in relation to weaning and sexual activity of the mother. Mothers that conceive in the following mating season accelerate the weaning process of their current offspring; furthermore, high-ranking females wean their male calves earlier. Behavioural conflict occurs during the resumption of the mother's sexual activity; however, no conflict appears to happen during weaning.     

Nipple contact in captive black-faced chimpanzees (Pan t troglodytes [Blumenbach, 1779])

Three chimpanzee (Pan t troglodytes) mother-infant dyads were studied from months 3 to 11 of the infants' lives in order to obtain data on nipple contact. Three conclusions were obtained: (1) There were fluctuations in the time spent in nipple contact. (2) Both female offspring were in nipple position for less time than the male offspring. (3) Grooming of the infants by their mothers during nipple contact was observed more frequently in the mother-female offspring pairs.     

Development of ecological competence in Sumatran orangutans

Data on orangutans (Pongo pygmaeus abelii) living in a Sumatran swamp forest yield an estimated median interbirth interval of at least 8 years, concurring with findings from other sites. This longest known mammalian interbirth interval appears due to maternal amenorrhea during the long exclusive dependence of the offspring. We describe the development of various components of offspring independence. In this arboreal ape, 3‐year‐olds had largely reached locomotor independence. Nest‐building skills were also well‐developed in 3‐year‐olds, but immatures shared their mother's nest until weaned at around age 7. At time of birth of the new sibling, association with the mother had begun to decline for both male and female offspring, suggesting that the immatures had mastered all the necessary skills, including basic tool use, to feed themselves. By about 11 years of age, they also ranged independently from the mother. These results show that orangutans do not develop independence more slowly than chimpanzees. Why, then, is weaning 2 years later in orangutans? In chimpanzees, mothers are often accompanied by two or even three consecutive offspring, unlike in orangutans. This contrast suggests that an orangutan mother cannot give birth until the previous offspring is ecologically competent enough to begin to range independently of her, probably due to the high energy costs of association. Thus, the exceptionally long interbirth intervals of orangutans may be a consequence of their solitary lifestyle. Am J Phys Anthropol, 2004. © 2004 Wiley‐Liss, Inc.     

Maternal effects are long‐lasting and influence female offspring's reproductive strategy in the swordtail fish Xiphophorus multilineatus

The adaptive benefits of maternal investment into individual offspring (inherited environmental effects) will be shaped by selection on mothers as well as their offspring, often across variable environments. We examined how a mother's nutritional environment interacted with her offspring's nutritional and social environment in Xiphophorus multilineatus, a live‐bearing fish. Fry from mothers reared on two different nutritional diets (HQ = high quality and LQ = low quality) were all reared on a LQ diet in addition to being split between two social treatments: exposed to a large adult male during development and not exposed. Mothers raised on a HQ diet produce offspring that were not only initially larger (at 14 days of age), but grew faster, and were larger at sexual maturity. Male offspring from mothers raised on both diets responded to the exposure to courter males by growing faster; however, the response of their sisters varied with mother's diet; females from HQ diet mothers reduced growth if exposed to a courter male, whereas females from LQ diet mothers increased growth. Therefore, we detected variation in maternal investment depending on female size and diet, and the effects of this variation on offspring were long‐lasting and sex specific. Our results support the maternal stress hypothesis, with selection on mothers to reduce investment in low‐quality environments. In addition, the interaction we detected between the mother's nutritional environment and the female offspring's social environment suggests that female offspring adopted different reproductive strategies depending on maternal investment.     

Weaning Age,Infant Care,and Behavioral Development in <Emphasis Type="Italic">Trachypithecus leucocephalus</Emphasis>

Primate infants are born in an altricial state and rely on the care of their parents for a relatively long period of time. Parental investment is critical to offspring survival and thus to the reproductive success of the parent as well. However, mothers and infants may experience a conflict of interest, in that infants may benefit by receiving prolonged maternal care but mothers may curtail such care in a tradeoff between investment in current versus future offspring. Documenting life history characteristics, such as age at weaning, is important not only for understanding the conflicts of interest and tradeoffs; such information can also provide insights about female reproductive rates and be valuable for conservation efforts. Little is known about the life history of white-headed langurs (Trachypithecus leucocephalus), despite their endangered status. We were the first to investigate mother-infant relationships and infant behavioral development in the species. We studied 3 wild mother-infant pairs throughout infancy. We used data from >460 h of focal subject sampling to calculate the proportion of time individuals spent in different behavioral states and the frequency of instantaneous events, such as maternal rejection. White-headed langur infants depended on their mothers for 19–21 mo, at which time they were weaned. Maternal rejection facilitated infant independence in the early stages of infant development, and mothers stopped investing in their infants when they resumed estrus. The weaning age of the wild white-headed langurs we studied was dramatically longer than that of captives, possibly as a result of the nutritional differences between wild and captive populations. Weaning age was also longer than for most other Asian colobines, and may be attributable to the degradation and fragmentation of their natural habitat.     

When and why are babies weaned?

A prospective study was designed to investigate the weaning practices of 50 primiparous mothers whose babies were born between September 1976 and March 1978. The question whether the age of weaning influenced growth from birth to 6 months was also considered. The mothers and babies were seen in hospital and then at a follow-up clinic at 1, 2, 3, and 6 months. Details were taken of feeding practices, and measurements made of the babies'' weight, length, and subscapular and triceps skinfold thicknesses. Seventeen infants who were breastfed received their first solid food at a mean age of 13.8 weeks, compared with 8.3 weeks for the 33 bottle-fed infants. Most (38) mothers weaned because they though their babies were hungry (crying after a feed or demanding more frequent feeds, or both). The age of weaning did not influence weight gain, growth in length, or change in skinfold thicknesses. The results suggest that the "4-month rule" for weaning is unrealistic. The decision to wean should be based more on the mother''s interpretation of her baby''s needs than on age alone.     

The time of determination of gynoparae and males in the bird cherry–oat aphid, Rhopalosiphum padi

Apterous exules of Rhopalosiphum padi which experienced short photoperiods only during the first half of their nymphal life all produced gynoparae which made up 57% of the offspring produced in the first 7 days of the mother's reproductive life. Short photoperiods during the second half of a mother's nymphal life did not induce the production of gynoparae. However, when short photoperiods were experienced throughout a mother's nymphal life significantly more gynoparae (82%) were produced. Ten per cent of the offspring of mothers that experienced short photoperiods only during their adult life developed into gynoparae. Of the offspring reared in short photoperiods, but born to mothers reared and kept in long photoperiods, 30% developed into gynoparae. When mothers were exposed to short photoperiods in their adult life and their offspring so treated, then 90% of the offspring developed into gynoparae. Males only occurred amongst the last offspring of mothers that experienced short photoperiods in either the first or the second half of their nymphal life.     

Reproductive strategy as a major factor determining female body size and fertility of a gregarious parasitoid

The generally known “adult size‐fitness hypothesis” (ASFH) is applied to the gregarious parasitic wasp Anaphes flavipes (Foerster, 1841) (Hymenoptera: Mymaridae). ASFH is dependent on the reproductive strategy of the mother, which means the larger females have more offspring compared to smaller females. Two main factors, the mother's body size and food quantity received during larval development, can affect the body size of the offspring. For the first time, we present a study on the relative effect of both factors on fitness of the same species, wasp A. flavipes. Our data confirmed that females of A. flavipes with larger body sizes had more offspring compared to smaller ones. At the same time, mother's body size does not seem to affect the body size of the offspring. The other studied factor, quantity of food received during larval development, can be influenced by reproductive strategy (number of parasitoids developing in one host egg), host quality or the duration of development. We found only the reproductive strategy to have a statistically significant effect on body size. We demonstrated that the variable reproductive strategy (VRS) of wasp A. flavipes causes a plasticity in body size and future number of offspring. The generally known “trade‐off” scheme (more small offspring or fewer bigger offspring) does not apply to A. flavipes, because their large females have more offspring and it is their reproductive strategy that determines body size.     

Social Effects of Maternal Age and Experience in Bison: Pre- and Post-weaning Contact Maintenance with Daughters

Effects of maternal age and experience on long-term contact maintenance interactions with female offspring were examined in bison (Bison bison), as part of a study of factors influencing dyadic behavioural interaction. During the first five months, patterns of change in interactions varied with maternal age and parity. Young (largely primiparous) mothers and their calves steadily increased the frequency with which they maintained contact, while older mothers and their calves became increasingly independent (e.g. calves walked away from mothers more and followed them less often). Filial independence was most extreme in the (last) calves of the two oldest mothers. These age-specific patterns appeared to result largely from contrasting shifts in maternal behaviour from Month 1 to 2; differences between groups before and after this shift were opposite in direction. In the first month, older mothers maintained more frequent contact and were behaviourally more synchronized with their calves. After the first month, however, the efforts of older mothers to maintain dyadic proximity abruptly decreased, while those of young mothers and their calves gradually increased. Subsequent differences between groups were more consistent. Young mothers and their daughters maintained closer contact and continued to do so well past weaning, at least as late as the third year, when daughters reached sexual maturity. Filial behaviour played an important role in determining patterns of dyadic spatial relations; the close proximity maintained by young mothers and their offspring appeared due largely to the frequency with which these calves followed their mothers' movements. The relatively independent calves of older mothers took greater initiative in contact interactions with mothers (e.g. nosing, licking). Young mothers appeared to strengthen long-term bonds with daughters by initiating contact frequently; the closeness of post-weaning dyadic association increased with the frequency of pre-weaning maternal contact.     

Tenacious nipple attachment in rodents: the sibling competition hypothesis

Tenacious attachment to the mother's nipples by suckling pups has been observed in many rodent species, but apeears to be absent in others. The natural history of this behaviour is reviewed, along with the possible adaptive value. Four hypotheses are extracted from the literature: the antipredator, anti-falling, anti-drowning, and infant-nipple contact hypotheses. These hypotheses are found to be ad hoc and supported by only anecdotal evidence. An alternative hypothesis is presented, that tenacious nipple attachment is an adaptation to sibling competition for maternal resources (nipples and milk). Morphological specialization, developmental time course, and patterns of pup mortality support the new model. The behaviour has been noted only in the Muridae. Quantitative interspecific comparisons within the Muridae demonstrate that tenacious nipple attachment is associated with reproductive tactics that promote sibling competition: breeding by means of litter overlap, low mammary number, and more offspring per mammary.     

MATERNAL INHERITANCE OF CONDITION AND CLUTCH SIZE IN THE COLLARED FLYCATCHER

Maternal effects may strongly influence evolutionary response to natural selection but they have been little studied in the wild. We use a novel combination of experimental and statistical methods to estimate maternal effects on condition and clutch size in the collared flycatcher, where we define “condition” to be the nongenetic component of clutch size. We found evidence of two maternal effects. The first (m) was the negative effect of mother's clutch size on daughter's condition, when mother's condition was held constant. The second (M) was the positive effect of mother's condition on daughter's condition, when mother clutch size was held constant. These two effects oppose one another because mothers in good condition also lay many eggs. The maternal effects were large: Experimentally adding an egg to a mother's nest reduced clutch sizes of her daughters by 1/4 egg (i.e., m = -0.25). Measured degree of resemblance between mother and daughter clutch sizes yielded M = 0.43. The results weakly support the presence of heritable genetic variation in clutch size: additive genetic variance/total phenotypic variance = 0.33. This estimate was highly variable probably because, as we show, mother-daughter resemblance may depend hardly at all on the amount of genetic variance when maternal effects are present. Daughter-mother regression (a standard method for estimating heritability) is consequently a poor guide to the amount of genetic variance in clutch size. Our results emphasize the value of combining field experiments with observations for studying inheritance.     

Initial breastfeeding attitudes and practices of women born in Turkey, Vietnam and Australia after giving birth in Australia

Background

Many studies of the impact of breastfeeding on child or maternal health have relied on data reported retrospectively. The goal of this study was to assess recall accuracy among breastfeeding mothers of retrospectively collected data on age of weaning, reasons for cessation, breast pain, lactation mastitis, and pumping.

Methods

Women in Michigan and Nebraska, U.S.A. were interviewed by telephone every 3 weeks during the first 3 months after the birth of their child, and mailed a questionnaire at 6 months. A subset was interviewed again by telephone approximately 1–3.5 years after the birth. The results for the three recall periods, collected 1994–1998, were compared using correlation, linear and Cox regression analysis, and sensitivity and specificity estimates.

Results

The 184 participants were aged 18–42, mostly white (95%) and 63% had an older child. The age of weaning tended to be overestimated in interviews 1–3.5 years after birth compared to those within 3 weeks of the event, by approximately one month for 1–3.5 year recall and two weeks for 6-month recall (p < 0.001 in both cases). Recall accuracy of reasons for weaning varied greatly by reason, with mastitis and return to work having the most recall validity. The sensitivity of 1–3.5 year recall of mastitis was 80%, but was only 54% for nipple cracks or sores.

Conclusion

Breastfeeding duration among short-term breastfeeders tended to be somewhat overestimated when measured at 1–3.5 years post-partum. Reporting of other breastfeeding characteristics had variable reliability. Studies employing retrospective breastfeeding data should consider the possibility of such errors.     

Mothers and offspring: The rabbit as a model system in the study of mammalian maternal behavior and sibling interactions

This article is part of a Special Issue “Parental Care”.Jay Rosenblatt effectively promoted research on rabbit maternal behavior through his interaction with colleagues in Mexico. Here we review the activities of pregnant and lactating rabbits (Oryctolagus cuniculus), their neuro-hormonal regulation, and the synchronization of behavior between mother and kits. Changing concentrations of estradiol, progesterone, and prolactin throughout gestation regulate nest-building (digging, straw-carrying, fur-pulling) and prime the mother's brain to respond to the newborn. Nursing is the only mother–young contact throughout lactation. It happens once/day, inside the nest, with ca. 24 h periodicity, and lasts around 3 min. Periodicity and duration of nursing depend on a threshold of suckling as procedures reducing the amount of nipple stimulation interfere with the temporal aspects of nursing, though not with the doe's maternal motivation. Synchronization between mother and kits, critical for nursing, relies on: a) the production of pheromonal cues which guide the young to the mother's nipples for suckling; b) an endogenous circadian rhythm of anticipatory activity in the young, present since birth. Milk intake entrains the kits' locomotor behavior, corticosterone secretion, and the activity of several brain structures. Sibling interactions within the huddle, largely determined by body mass at birth, are important for: a) maintaining body temperature; b) ensuring normal neuromotor and social development. Suckling maintains nursing behavior past the period of abundant milk production but abrupt and efficient weaning occurs in concurrently pregnant-lactating does by unknown factors. Conclusion: female rabbits have evolved a reproductive strategy largely dissociating maternal care from maternal presence, whose multifactorial regulation warrants future investigations.     

Determinants of fecundity and reproductive success in captive vervet monkeys

Between 1975 and 1983, adult female vervet monkeys (Cercopithecus aethiops sabaeus) over 3.5 years of age, living in two undisturbed social groups in a captive colony in Sepulveda, California, have averaged 1.0 births per female year with a mean interbirth interval of 10.7 months. Increased fecundity did not result in decreased survival rates of offspring in this population. Fecundity was influenced by the mother's age and dominance rank. The primary factor in the age-fecundity relationship was the age at first birth, which varied from three to five years. High-ranking females contributed the most to the high rate of fecundity, with significantly shorter interbirth intervals, more births per female year, and more surviving infants compared to low-ranking females.     

Advanced paternal age is associated with lower facial attractiveness

In view of disease risk, Kong et al. (2012) demonstrated that most of the new mutations are explained by the age of the father at conception. Accordingly, paternal age effects have been found for a variety of offspring traits, from physical and mental health to intelligence. Here, we investigated whether facial attractiveness is significantly associated with paternal age. We used the Wisconsin Longitudinal Study (n = 4018 male and 4416 female high school graduates) to analyze the association between an individual's father's age at birth and that individual's facial attractiveness (estimated by rating the high school yearbook photographs from 1957), controlling for sex, age as well as mother's age. We find that subject's facial attractiveness decreased with advancing paternal but not maternal age, suggesting that facial attractiveness might be a cue of an individual's new mutation load.     

Development of Independence from the Mother in Gorilla gorilla gorilla

In gorillas, the mother takes full responsibility for carrying and feeding offspring, and lactational amenorrhea prevents her from investing in another offspring while suckling. Therefore, mothers should encourage immature gorillas to become gradually more independent until they are physically able to acquire sufficient resources, travel independently, and manage social relationships unaided. We investigated the development of independence in a population of wild western gorillas (Gorilla gorilla gorilla) at Mbeli Bai, Nouabalé-Ndoki National Park, Republic of Congo. We observed the spatial proximity, the development of travel, patterns of suckling and weaning, and the nature of mother-offspring interactions for 42 immature gorillas to investigate the nature of the relationship between mother and offspring. Though mother-offspring distance and independent travel increased during immaturity, with few active interactions between the dyads, offspring still continued to suckle until a median age of 4.6 yr, longer than in mountain gorillas. The tolerance of the mother toward suckling by older offspring may reflect the importance of continued nutritional investment: the temporal nature of the diet of western gorillas means that succulent fruits—likely to be preferred weaning foods—are not always available. We propose that to buffer against potential fruit shortage, mothers continue to nurse their offspring to decrease the likelihood of death from care-dependent factors and to improve an offspring’s chances of survival.     

Changes in incidence of infanticidal and parental responses during the reproductive cycle in male and female wild mice Mus musculus

Most studies of infanticide in rodents have been carried out on laboratory animals. In the present study, pairs of infanticidal male and female wild mice were observed for changes in their responsiveness to alien pups during the reproductive cycle. Females killed pups during pregnancy, adopted alien pups during the lactation period, and killed pups again a month after the weaning of their offspring. In males, the transition from infanticidal to parental responses occurred as early as the first half of their mates' pregnancy, and only half of them resumed infanticide a month after the weaning of their litters. Subsequent experiments showed that two independent factors, the experience of copulation and cues from the pregnant female, accounted for the cessation of infanticide and onset of parental care in the male. The adaptive value of the co-existence of multiple mechanisms underlying the cessation of infanticide in male and female house mice is discussed with respect to the social life of this species.