Maternal lactational investment is higher for sons in chimpanzees (original) (raw)
Related papers
The energetics of lactation and the return to fecundity in wild chimpanzees
Behavioral Ecology, 2012
xpected to compromise future offspring production. This trade-off is particularly salient for mammals in which mothers bear the exclusive burden of lactation and draw from their own energy reserves to provision offspring. The degree to which lactation impacts future reproductive ability should vary not only by the absolute cost of milk production but also by the ability of individual mothers to afford it. Few studies have been able to quantify the costs of lactation or how they affect reproductive rates. Here, we examine the metabolic load of lactation in chimpanzees, a species with intensive parental investment and extremely slow reproductive rates. We used urinary C-peptide of insulin to trace changes in energetic condition in 17 wild, unprovisioned chimpanzee mothers in Kibale National Park, Uganda. C-peptide levels of nursing mothers were depressed for six months postpartum, thereafter showing a net increase through the second year. These changes are consistent with milestones of infant physical and behavioral development. Mothers inhabiting lower quality foraging areas experienced a higher metabolic load of lactation, as indicated by lower C-peptide profiles than mothers in food-rich areas. Ovarian activity was closely correlated with energetic condition. Cycling resumed only after a sustained period of energy gain, suggesting that the slow reproductive pattern in wild chimpanzees results not only from the direct expense of milk production but also from the long period that mothers require to recover their physical condition in a food-limited environment.
Alloparenting, when individuals other than the mother assist with infant care, can vary between and within populations and has potential fitness costs and benefits for individuals involved. We investigated the effects of alloparenting on the speed with which infants were weaned, a potential component of maternal fitness because of how it can affect inter-birth intervals, in wild chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Uganda. We also provide, to our knowledge, the first description of alloparenting in this population and present a novel measure of the contribution of milk to infant diets through faecal stable nitrogen isotopes (δ 15 N). Using 42 mother–infant pairs, we tested associations of two alloparenting dimensions, natal attraction (interest in infants) and infant handling (holding, carrying), to the proportion of time mothers spent feeding and to maternal lactation effort (mean nursing rates and mother–infant δ 15 N differences). Neither natal attraction nor infant handling was significantly associated with feeding time. Infant handling was inversely associated with both measures of lactation effort, although natal attraction showed no association. Alloparenting may benefit mothers by enabling females to invest in their next offspring sooner through accelerated weaning. Our findings emphasize the significance of alloparenting as a flexible component of female reproductive strategies in some species.
Royal Society open science, 2016
Alloparenting, when individuals other than the mother assist with infant care, can vary between and within populations and has potential fitness costs and benefits for individuals involved. We investigated the effects of alloparenting on the speed with which infants were weaned, a potential component of maternal fitness because of how it can affect inter-birth intervals, in wild chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Uganda. We also provide, to our knowledge, the first description of alloparenting in this population and present a novel measure of the contribution of milk to infant diets through faecal stable nitrogen isotopes (δ(15)N). Using 42 mother-infant pairs, we tested associations of two alloparenting dimensions, natal attraction (interest in infants) and infant handling (holding, carrying), to the proportion of time mothers spent feeding and to maternal lactation effort (mean nursing rates and mother-infant δ(15)N differences). Neither natal attraction nor in...
American Journal of Human Biology, 2009
Lactation represents the greatest postnatal energetic expenditure for human and non-human primate females, and the ability to sustain the costs of lactation is influenced by a mother's physical condition. This is especially true for young mothers that initiate reproduction shortly after adolescence. These mothers have fewer bodily reserves available for lactation and face tradeoffs between reproduction and their own growth. Milk synthesis among captive rhesus macaques (Macaca mulatta) was investigated at the California National Primate Research Center from 2005 to 2007 (N 5 114). Rhesus macaques produced low energy density milk typical of the primate order, but there was substantial individual variation among mothers in both milk energy density and yield. As a consequence, the available milk energy (AME), the product of milk energy density and milk yield, to support infant growth, development, and activity, varied tenfold among mothers. Primiparous mothers (N 5 40) had fewer bodily resources, as measured by mass and body mass index, available for lactation than did multiparous mothers (N 5 74) and showed poorer lactational performance. Mothers of sons produced milk of higher energy density, especially primiparous mothers, but lower milk yield, such that AME was the same for sons and daughters. Although AME from the mother was the same for sons and daughters, there was significant sexual dimorphism in infant mass. These data indicate that selection has likely favored sex-specific regulation of growth and development that is not necessarily contingent on greater maternal investment. Am.
Offspring provisioning is one of the most energetically demanding aspects of reproduction for female mammals. Variation in lactation length and weaning strategies between chimpanzees (Pan troglodytes), our closest living relative, and modern human societies have been reported. When and why these changes occurred is frequently debated. Our study used stable nitrogen isotope data of tooth root dentine from wild Western chimpanzees (Pan troglodytes verus) in Ta€ ı National Park, Côte d'Ivoire, to quantify weaning in these chimpanzees and explore if infant sex plays a role in maternal investment. We analyzed serial sections of deciduous lateral incisor root dentine from four Ta€ ı chimpanzees to establish the d 15 N signal of nursing infants; we then analyzed serial sections of first permanent mandibular molar root dentine from 12 Ta€ ı chimpanzees to provide quantitative d 15 N data on weaning in this population. Up to 2 years of age both sexes exhibited dentine d 15 N values 2-3& higher than adult female Ta€ ı chimpanzees, consistent with a nursing signal. Thereafter a steady decrease in d 15 N values consistent with the onset, and progression, of weaning, was visible. Sex differences were also evident, where male d 15 N values decreased at a significantly slower rate compared to females. Confirmation of sex differences in maternal investment among Ta€ ı chimpanzees, demonstrates the viability of using isotope analysis to investigate weaning in non-human primates. Additionally, assuming that behaviors observed in the Ta€ ı chimpanzees are illustrative of the ancestral pattern, our results provide a platform to enable the trajectory of weaning in human evolution to be further explored. Am J Phys Anthropol 153:635-642,
American Journal of Primatology
Weaning is a transition in early development with major implications for infant survival and well-being, and for maternal lifetime reproductive success. The particular strategy a primate mother adopts in rearing her offspring represents a negotiation between her ability to invest and her need to invest, and can be considered adaptive and influenced by biological and social factors. Any investigation into how and why maternal weaning strategies differ among non-human primates is limited by the precision of the measurement tool used to assess infants’ weaning ages. Stable carbon and nitrogen isotope analysis of soft tissues (e.g., hair, nails, feces, urine, blood) offers an objective means of monitoring the weaning status of infants. In this study, we assess stable isotope ratios in blood serum from 14 captive rhesus macaque dyads (Macaca mulatta) at infant ages 2, 5, 6, 7, 8, and 10 months to estimate the timing of weaning events. Male infants wean earlier than female infants. Infants with the lowest birth weights wean latest. Most infants wean upon reaching 2.5 times their birth weights, sooner than when weaning elsewhere has been predicted for captive cercopithecine primates. The longest weaning periods (ca. 10 months) are observed among infants of small mothers. The shortest weaning period, between 2 and 5 months, was among the lowest ranking dyad. Parity andmothers’ ages had no discernible effect on the timing of weaning events. The stable carbon and nitrogen isotope values of dams during lactation are significantly different than those of a nonlactating adult female outgroup, raising questions about the suitability and selection of adult comparative baselines in studies where lactating mothers cannot be sampled longitudinally (e.g., bioarchaeology; paleontology). Am. J. Primatol.
Objectives: Determining nutritional development in wild primates is difficult through observations because confirming dietary intake is challenging. Physiological measures are needed to determine the relative contributions of maternal milk and other foods at different ages, and time of weaning. We used fecal stable carbon and nitrogen isotopes (d 13 C, d 15 N) and fecal nitrogen concentrations (%N) from wild chimpanzees at Ngogo, Uganda, to derive physiological dietary indicators during the transition from total reliance on maternal milk to adult foods after weaning. Materials and Methods: We analyzed 560 fecal samples collected non-invasively from 48 infants, their mothers, and 6 juvenile siblings. Most infant and juvenile samples (90%) were matched to samples collected from mothers on the same day. Isotopic assessments were compared with observations of nursing and feeding.
Maternal condition and maternal investment during lactation in mantled howler monkeys
American journal of physical anthropology, 2018
Lactation is a costly reproductive state for females, as it may entail decreased body condition, increased morbidity, and increased mortality risk. To offset these costs, mothers should allocate investment in infant care as a function of their physical condition. Here, we assessed the relationship between maternal condition and maternal investment in wild mantled howler monkeys (Alouatta palliata) to determine: (1) whether maternal physical condition varied as a function of food availability, activity levels and feeding effort throughout lactation; (2) whether maternal investment was affected by maternal condition and offspring age. We studied six adult females while rearing their immature offspring. We determined weekly food availability, C-peptide levels (as a measure of energy balance) in urine samples (306 samples), mothers' time budgets, feeding rates, time spent vigilant, and time spent carrying their offspring (for two years; 600 observation hours). C-peptide levels were ...
American Journal of Physical Anthropology, 2014
Offspring provisioning is one of the most energetically demanding aspects of reproduction for female mammals. Variation in lactation length and weaning strategies between chimpanzees (Pan troglodytes), our closest living relative, and modern human societies have been reported. When and why these changes occurred is frequently debated. Our study used stable nitrogen isotope data of tooth root dentine from wild Western chimpanzees (Pan troglodytes verus) in Taï National Park, Côte d'Ivoire, to quantify weaning in these chimpanzees and explore if infant sex plays a role in maternal investment. We analyzed serial sections of deciduous lateral incisor root dentine from four Taï chimpanzees to establish the δ15N signal of nursing infants; we then analyzed serial sections of first permanent mandibular molar root dentine from 12 Taï chimpanzees to provide quantitative δ15N data on weaning in this population. Up to 2 years of age both sexes exhibited dentine δ15N values ≈2–3‰ higher than adult female Taï chimpanzees, consistent with a nursing signal. Thereafter a steady decrease in δ15N values consistent with the onset, and progression, of weaning, was visible. Sex differences were also evident, where male δ15N values decreased at a significantly slower rate compared to females. Confirmation of sex differences in maternal investment among Taï chimpanzees, demonstrates the viability of using isotope analysis to investigate weaning in non-human primates. Additionally, assuming that behaviors observed in the Taï chimpanzees are illustrative of the ancestral pattern, our results provide a platform to enable the trajectory of weaning in human evolution to be further explored.