Reconstructing infant weaning histories at Roman period Kellis, Egypt using stable isotope analysis of dentition

Studies of infant feeding and weaning patterns in past populations that rely on a cross-sectional approach must make the assumption that no infant mortality bias exists. Previous investigations of infant weaning patterns at the Dakhleh Oasis, Egypt, relied on cross-sectional isotope data. In this study, we re-examine this weaning pattern, using a simulated longitudinal approach, which does not require any assumptions regarding potential infant mortality biases. This involves examining the dental isotopic signatures of individuals who survived the weaning process. Stable isotope signatures from juveniles and adults (102 individuals, 297 teeth) were examined to reconstruct the weaning history of those that survived the weaning process. Both deciduous and permanent teeth were sampled. Homogenized enamel and dentin samples were isolated from each tooth and analyzed for delta(13)C(ap) and delta(18)O(ap) from the enamel and delta(15)N(coll) and delta(13)C(coll) from dentin collagen. We investigate differences between in utero versus postbirth, preweaning versus postweaning, and juvenile versus adult stable isotope values as reflected in the dentition. A random permutation procedure was used to test for statistically significant differences in stable isotope values between tooth types. Statistically significant differences were observed in all stable isotopes between permanent and deciduous teeth, and between early and later forming permanent teeth in delta(13)C(ap) and delta(15)N(coll) isotopes. These results indicate dietary change between in utero and postbirth, and changes occurring during the weaning period. These results provide a more comprehensive picture of infant weaning practices at Kellis and provide further support that complete weaning occurred by 3 years of age.     

Detection of breastfeeding and weaning in modern human infants with carbon and nitrogen stable isotope ratios

Carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope ratios were longitudinally measured in fingernail and hair samples from mother-infant pairs where infants were exclusively breastfed (n = 5), breast- and formula-fed (n = 2), or exclusively formula-fed (n = 1) from birth. All exclusively breastfed infants had a dual enrichment in carbon ( approximately 1 per thousand) and nitrogen ( approximately 2-3 per thousand) when compared to maternal values. In contrast, breast- and formula-fed subjects had reduced enrichments compared to exclusively breastfed subjects, and the exclusively formula-fed infant showed no increase in delta(13)C or delta(15)N values. This finding of a carbon trophic level effect in breastfeeding infants suggests that (13)C-enrichments of approximately 1 per thousand in archaeological populations are not necessarily the result of the consumption of C(4)-based weaning foods such as maize or millet. During the weaning process, the delta(13)C results for breastfed infants declined to maternal levels more rapidly than the delta(15)N results. This suggests that delta(13)C values have the potential to track the introduction of solid foods into the diet, whereas delta(15)N values monitor the length of time of breast milk consumption. These findings can be used to refine the isotopic analysis of breastfeeding and weaning patterns in past and modern populations.     

Stable carbon and nitrogen isotope values of bone and teeth reflect weaning age at the Medieval Wharram Percy site,Yorkshire, UK

We report on the measurements of carbon and nitrogen stable isotopes of both bone and teeth from a single site and population (Medieval Wharram Percy), undertaken to explore variations due to weaning in a past population. There have been a number of recent studies of weaning using delta(15)N values of ribs, and we indicate a number of assumptions that must be met before the results of such studies can be correctly interpreted. We found that rib collagen delta(15)N values decrease to adult levels after age 2 years, indicating that weaning occurred at or before this age. Rib collagen delta(13)C values are also more enriched than adult delta(13)C values before age 2 years, and we argue that this is due to the so-called "carnivore" effect in delta(13)C. We measured teeth and rib delta(15)N values from the same individuals and found that for individuals up to age 11 years, tooth dentine delta(15)N is higher than adult rib delta(15)N values, indicating that the dentine was formed during breast-feeding and that there was almost no turnover of dentine since. We observed some decrease in delta(13)C and delta(15)N rib values, compared to adult rib and teeth values, for the few years after weaning that may relate to a theoretically predicted physiological nitrogen imbalance during this period of rapid growth, but this is more likely due to a childhood diet (up to age 9) which was isotopically different from later diet, possibly consisting of a greater proportion of plant foods.     

Dismembering bodies for display: a bioarchaeological study of trophy heads from the Wari site of Conchopata, Peru

This study integrates isotopic, palaeopathological, and historical evidence to investigate infant and young child feeding practices in a Roman period (1st to 3rd centuries AD) skeletal sample from the Isola Sacra necropolis (Rome, Italy). Stable isotope analysis of bone collagen from 37 rib samples indicates that transitional feeding began by the end of the first year and weaning occurred by 2-2.5 years of age. Both delta(15)N and delta(13)C data clearly show the trophic level effect associated with breastfeeding. Childhood diet is investigated using dental pathology data in the deciduous dentitions of 78 individuals aged between 1 and 12 years. The presence of calculus, caries, and tooth wear in young children suggests that individuals were provided complementary foods and other items that impacted their dental health at an early age. The isotopic and dental data are generally consistent with the historical evidence from the Roman period with respect to the general timetable of weaning and the character of complementary foods. This is the first study to integrate isotopic and deciduous dental pathology data to explore infant and young child feeding practices in the Roman world.     

中国古代儿童断奶模式与喂养方式初探——以安徽薄阳城遗址人骨的C、N稳定同位素分析为例

了解古代儿童的断奶模式和喂养方式,可望为揭示古代儿童的营养状况、生长发育以及其死亡原因提供有价值的重要信息。近些年来,通过对古代儿童骨骼的C、N稳定同位素分析,重建古代儿童的断奶模式和喂养方式,成为国际生物考古界的研究前沿,但在我国尚无任何相关报道。为此,本文以安徽滁州薄阳城遗址人骨(包含不同年龄阶段的儿童和成年人)样品为研究材料,通过对同一个体肋骨和肢骨的C、N稳定同位素分析和比较,重点探讨了我国西周时期儿童的断奶模式及喂养方式。研究结果显示:儿童在2岁已有辅食的摄入,大多数儿童在3-4岁已经完成断奶;断奶后的儿童,其食物中包含更多的植物作为辅食。本研究,印证了我国历史文献中有关儿童喂养模式的最早记载(唐代孙思邈的医书《千金方》),也为系统探索我国古代儿童的断奶模式和喂养方式提供了很好的范例。     

Isotopic evidence for breastfeeding and possible adult dietary differences from Late/Sub-Roman Britain

Historical documents indicate that breastfeeding and weaning practices have fluctuated in England through history. In order to obtain evidence for general breastfeeding patterns in Late/Sub-Roman Britain, stable carbon and nitrogen isotope values were measured in juvenile and adult skeletons (n = 87) from the cemetery of Queenford Farm, Dorchester-on-Thames, Oxfordshire. As the site contained few individuals between 0-1.5 years of age, it was not possible to determine the initial timing for the introduction of weaning foods. Between ages 2-4 years, the mean +/- SD delta(13)C results (-20.2 +/- 0.3 per thousand) are significantly more negative (t = -4.03, P < 0.001) compared to adult females (-19.7 +/- 0.3 per thousand). This is interpreted as evidence of a different diet being fed to children during weaning. After age 2, the delta(15)N values gradually decline, indicating complete cessation of breastfeeding by 3-4 years. Among adults, stature (males = 1.68 +/- 0.06 m; females = 1.58 +/- 0.07 m) and sexual dimorphism (106) were low, suggesting that the population was possibly under environmental stress. The delta(13)C results for adults are similar, but females show a small but statistically significantly (t = -2.86, P < 0.01) lower mean delta(15)N value (9.9 +/- 0.9 per thousand) compared to males (10.6 +/- 0.5 per thousand). These lower female delta(15)N values possibly reflect the different physiology of the sexes (pregnancy and/or lactation) or the reduced consumption of animal/fish protein by women, and this may have been influenced by individual preference, family needs, or societal values of the era.     

A biocultural investigation of the weanling's dilemma in Kathmandu, Nepal: do universal recommendations for weaning practices make sense?

The primary objective of this report is to use data from a study of infant growth and weaning practices in Kathmandu, Nepal, to investigate universal recommendations about exclusive breast-feeding up to 6 months postpartum. A secondary objective is to demonstrate the complexity of the biocultural nature of infant feeding practices. A sample of 283 children under 5 years of age and their 228 mothers living in a peri-urban district of Kathmandu participated in this study. The children's height/length and weight were measured three times over 9 months. At each session, a demographic, child health and infant feeding survey was administered; between sessions, in-depth interviews were conducted with mothers regarding infant feeding practices. While a few of the infants under 2 months were receiving non-breast milk foods, at 3 months of age half of the sample had been introduced to non-breast milk foods and by 7 months all infants were eating non-breast milk foods. A comparison of growth indices and velocities between exclusively and partially breast-fed infants from birth to 7 months of age shows no evidence for a difference in nutritional status between the two groups. Although there are cultural rules about breast-feeding that vary by ethnic group, all mothers followed a feeding method that depended on their assessment of whether the child was getting enough breast milk. The conclusion is that exclusive breast-feeding up to 6 months may not be appropriate for all infants. In this sample, breast-feeding duration is not shortened by the early introduction of non-breast milk foods, as the median age of breast-feeding cessation is 36 months. One of the main reasons for severance was the onset of another pregnancy. Investigation of infant feeding practices must be contextualized in the local ecology of the population. While cultural beliefs about breast-feeding are relevant, mothers' individual assessments of their children's nutritional needs and demographic events in parents' lives must also be considered.     

Trophic level and macronutrient shift effects associated with the weaning process in the Postclassic Maya

The weaning process was investigated at two Maya sites dominated by Postclassic remains: Marco Gonzalez (100 BC-AD 1350) and San Pedro (1400-AD 1650), Belize. Bone collagen and bioapatite were analyzed from 67 individuals (n < or = 6 years = 15, n > 6 years = 52). Five isotopic measures were used to reconstruct diet and weaning: stable nitrogen- and carbon-isotope ratios in collagen, stable carbon- and oxygen-isotope ratios in bioapatite, and the difference in stable carbon-isotope values of coexisting collagen and bioapatite. Nitrogen-isotope ratios in infant collagen from both sites are distinct from adult females, indicating a trophic level effect. Collagen-to-bioapatite differences in infant bone from both sites are distinct from adult females, indicating a shift in macronutrients. Oxygen-isotope ratios in infant bioapatite from both sites are also distinct from adult females, indicating the consumption of breast milk. Among infants, carbon- and nitrogen-isotope ratios vary, indicating death during different stages in the weaning process. The ethnohistoric and paleopathological literature on the Maya indicate cessation of breast-feeding between ages 3-4 years. Isotopic data from Marco Gonzalez and San Pedro also indicate an average weaning age of 3-4 years. Based on various isotopic indicators, weaning likely began around age 12 months. This data set is not only important for understanding the weaning process during the Postclassic, but also demonstrates the use of collagen-to-bioapatite spacing as an indicator of macronutrient shifts associated with weaning.     

Infant feeding practices among mildly wasted children: a retrospective study on Nias Island, Indonesia

Background

This study investigated the infant feeding practices of participating mothers who were recruited into a research project aimed at improving the nutritional status of mildly wasted children (< -1.0 to ?? -1.5 Weight-for-Height Z-scores) aged ?? 6 to < 60 months on Nias Island, Indonesia.

Methods

Cross-sectional, questionnaire-based interview of mothers of the index children (n = 215) who were admitted to the community program for mildly wasted children in the study area. Four focus groups and twenty in-depth interviews were conducted to explore further information on infant feeding practices in the study area.

Results

Retrospective results indicated that 6% of the mothers never breastfed. Fifty two percent of mothers initiated breastfeeding within six hours of birth, but 17% discarded colostrum. Exclusive breastfeeding until 6 months of age was practiced by 12%. Seventy-four percent of the mothers offered supplementary liquids besides breast milk within the first 7 days of life, and 14% of infants received these supplementary liquids from 7 days onwards until 6 months of age. Moreover, 79% of the infants were given complementary foods (solid, semi-solid, or soft foods) before 6 months of age. About 9% of the children were breastfed at least two years. Less than one in five of the mildly wasted children (19%) were breastfed on admission to the community program. Qualitative assessments found that inappropriate infant feeding practices were strongly influenced by traditional beliefs of the mothers and paternal grandmothers in the study areas.

Conclusion

Generally, suboptimal infant feeding was widely practiced among mothers of mildly wasted children in the study area on Nias Island, Indonesia. To promote breastfeeding practices among mothers on Nias Island, appropriate nutrition training for community workers and health-nutrition officers is needed to improve relevant counseling skills. In addition, encouraging public nutrition education that promotes breastfeeding, taking into account social-cultural factors such as the influence of paternal grandmothers on infant feeding practice, is needed.     

Introducing fecal stable isotope analysis in primate weaning studies

This research investigates the potential of a new, noninvasive method for determining age of weaning among primates using stable carbon and nitrogen isotope ratios in feces. Analysis of stable isotope ratios in body tissues is a well‐established method in archeology and ecology for reconstructing diet. This is the first study to investigate weaning in primates using fecal stable isotope ratios. Diets of a single François’ langur (Trachypithecus francoisi) mother–infant pair at the Toledo Zoo are reconstructed using this technique to track changes in infant suckling behavior over the weaning period. Stable isotope ratios in feces are sampled instead of more traditional samples such as bone or hair to enable daily, noninvasive snapshots of weaning status. Isotopic assessments of weaning status are compared to visual assessments to identify any discordance between the two. Three measurements documented the transition from breast milk to solid foods: stable carbon isotope ratios (δ¹³C), stable nitrogen isotope ratios (δ¹⁵N), and nitrogen content of feces (%N). It appears that solid foods were introduced at approximately 2 months of infant age, but that nursing continued into the 12th month, when sample collection ceased. Stable isotope data exposed a much longer weaning period than what was expected based on previously published data for captive langurs, and clarified visual estimates of weaning status. This reflects the method's sensitivity to suckling at night and ability to distinguish actual nursing from comfort nursing. After testing this method with zoo animals, it can readily be applied among wild populations. An isotopic approach to weaning provides a new, accurate, and biologically meaningful assessment of interbirth intervals, and facilitates a better understanding of mother–infant interactions. Both of these outcomes are critical for developing successful conservation strategies for captive and wild primates. Am. J. Primatol. 74:926‐939, 2012. © 2012 Wiley Periodicals, Inc.     

A simplified method using commercial milk powder for hand-rearing of the Caesarean-derived infant rabbits (author's transl)

An efficient and simplified method for hand-rearing of Caesarean-derived infant rabbits under gnotobiotic condition was devised. The Caesarean-derived infant Dutch or Japanese-White rabbits and their hybrids (F1; Japanese-White female x Dutch male) were reared in sterilized vinyl-isolators by hand-feeding with two kinds of milk diets, A and B, consisted mainly ofa commercial milk powder for dogs and cats (Esbilac) supplemented with several minor components (Table 2) and administered intragastrically once a day through a Nelaton's catheter. Bacteriological examinations revealed that feces and urine were sterile for the first three days. On the third day, Escherichia coli, Staphylococcus epidermidis, Streptococcus faecalis, Bacillus subtilis, Enterococcus, and Bacteroides sp. were given with milk diet and the infant rabbits were reared until 10 to 12 weeks of age. The weaning rate at 5 weeks of age and the raising rate at 3 months of age were approximately 78% and 77%, respectively (Table 3), indicating that feeding once-a-day with a milk diet mainly composed of Esbilac is suitable for the hand-rearing of infant rabbits. There was, however, no significant difference milk diet A and B on the weaning rate.     

Infant feeding practices and chronic child malnutrition in the Indian states of Karnataka and Uttar Pradesh

As measured by degree of stunting, close to half of India's children suffer from chronic malnutrition and about a quarter from severe chronic malnutrition. Data from the 1998-1999 National Family Health Survey (NFHS) are analysed to assess whether recommended infant feeding practices help to alleviate the prevalence of stunting. The evidence supports some recommended practices, including the advice that mother not squeeze the colostrum from her breasts, not use a feeding bottle with a nipple, exclusive breastfeeding for the first 4-6 months and feeding supplementary foods (solids and mushy foods) at about 7 months, and suggests that, for some children, better feeding practices could reduce the prevalence of severe stunting by up to 30%. The paper also examines a range of other issues related to stunting--whether medical supplementations and inoculations have an effect, whether mothers more actively involved in health decisions have less stunted children, and the links between stunting, diarrhoea and anaemia. An explanation is offered for the positive relationship between using oral rehydration salts and stunting.     

Stable isotopes as indicators of altitudinal distributions and movements in an Ecuadorean hummingbird community

Altitudinal migration and dispersal is an important component of the life history of several temperate and tropical birds but remains poorly understood due to the limited success of mark and recapture techniques. Stable isotopes of hydrogen (deltaD) in rainfall, and to a lesser extent, carbon (delta13C) in plants are known to change with altitude and hence may provide the basis of a technique for tracking the altitudinal movements in birds and other wildlife. We investigated the potential for this technique by measuring delta13C, deltaD, and delta15N values in tail feathers of eight species of hummingbirds ( Phaethornis malaris, P. syrmatophorus, P. guy, Adelomyia melanogenys, Coeligena torquata, C. lutetiae, Metallura baroni, M. williami) along an altitudinal gradient (300-3,290 m asl) in the Andes Mountains of Ecuador. Feather delta13C and deltaD values were correlated and each changed significantly with elevation above 400 m. In general, we found good agreement between feather deltaD values and those predicted from a generalized relationship of precipitation and surface water deltaD with altitude. Similarly, feather delta13C values showed an enrichment of approximately 1.5 per thousand per 1,000 m over the linear portion of the elevational response. Stable-nitrogen isotope values were variable, and so did not provide useful information on elevation in birds, apart from trophic effects. Overall there appears to be good potential for using the (deltaD, delta13C) stable isotope approach to track altitudinal movements and to elucidate previously unrecognized patterns of life history variation in both temperate and tropical species that migrate across elevational isotopic gradients.     

Investigating the weaning process in past populations

The 19th century St. Thomas' Anglican churchyard in Belleville, Ontario, Canada is associated with a large and well-preserved infant skeletal collection (n = 149) and good-quality parish records that document interments in the graveyard (1821–1874). By using a combination of historical demographic and stable nitrogen isotope analyses on the parish records and skeletal remains, respectively, a general pattern of extended nursing for about 14 months, introduction of foods other than breast milk by around 5 months of age, and variation in breast-feeding and weaning behaviours were detected for St. Thomas' infants. The results demonstrate that it is possible to go beyond the concept of weaning age to explore the weaning process in past populations when appropriate and large samples of documentary and skeletal data are available. Am J Phys Anthropol 105:425–439, 1998. © 1998 Wiley-Liss, Inc.     

Annual variability in dentin δ15N and δ13C reveal sex differences in weaning age and feeding habits in Risso's dolphins (Grampus griseus)

Teeth of odontocetes accumulate annual dentinal growth layer groups (GLGs) that record isotope ratios, which reflect the time of their synthesis. Collectively, they provide lifetime records of individual feeding patterns from which life history traits can be inferred. We subsampled the prenatal dentin and postnatal GLGs in Risso's dolphins (Grampus griseus) (n = 65) that stranded or were collected as bycatch in Taiwan (1994–2014) and analyzed them for δ¹⁵N and δ¹³C. Age‐specific δ¹⁵N and δ¹³C values were corrected for effects of calendar year, stranding site, C/N, and sex. δ¹⁵N values were higher in prenatal layers (14.94‰ ± 0.74‰) than in adult female GLGs (12.58‰ ± 0.20‰), suggesting fetal enrichment during gestation. Decreasing δ¹⁵N values in early GLGs suggested changes in dietary protein sources during transition to complete weaning. Weaning age was earlier in males (1.09 yr) than in females (1.81 yr). Significant differences in δ¹⁵N values between weaned males and females suggest potential sexual segregation in feeding habits. δ¹³C values increased from the prenatal to the 4th GLG by ~1.0‰, indicative of a diet shift from ¹³C‐depleted milk to prey items. Our results provide novel insights into the sex‐specific ontogenetic changes in feeding patterns and some life history traits of Risso's dolphins.     

Iron Age breastfeeding practices in Britain: isotopic evidence from Wetwang Slack, East Yorkshire

We present here the results of carbon and nitrogen isotopic analysis of bone collagen undertaken on all skeletal remains of infants and young children below the age of 6 years (n = 34) from the internationally important British cemetery site at Wetwang Slack in East Yorkshire (middle Iron Age, ca. 4th to 2nd centuries BC). The aim of the study is to investigate infant diet, with particular reference to breastfeeding and weaning practices, and to compare the data with previously published studies of archaeological populations, particularly in the context of the variation in data patterns to be seen between sites. The skeletal remains from Wetwang Slack form the only prehistoric collection in the UK, prior to the Romano-British period, with sufficient individuals in this age group to make such an isotopic study viable alongside associated adults and older children. The data are compared in detail with published data from two other sites, one from 19th century Canada and the other from Medieval Britain. The results suggest an unusual situation at Wetwang Slack, with neither the nitrogen nor the carbon isotope ratios conforming to expectations when compared with the putative mothers. We discuss how these data compare with the expectation for breastfed infants and we interpret the divergence in this case to be due to restricted breastfeeding and the early introduction of supplementary foods.     

Weaning age among foragers at Matjes river rock shelter, South Africa, from stable nitrogen and carbon isotope analyses

Matjes River Rock Shelter is a large shell midden on the southern coast of South Africa. Stable nitrogen (delta(15)N) and carbon (delta(13)C) isotope ratios were measured in bone collagen and dentine from human skeletons excavated from this site in order to establish a weaning curve in mid-Holocene hunter-gatherers. delta(15)N results show a progressive increase in individuals from birth to 1.5 years old. delta(13)C results are more tightly clustered and mirror the steady progressive change seen for delta(15)N. We deduce that children at Matjes River Rock Shelter were breastfed for at least the first 1.5 years after birth, and were weaned sometime between 2-4 years of age. A similar pattern was documented for historic-era Kalahari foraging people, where the interbirth spacing was approximately 3 years. This study provides the first direct evidence for an extended period of breastfeeding, and thus long interbirth intervals, among prehistoric foragers, even when those foragers lived in an environment with abundant food resources.     

Subsistence strategies of two "savanna" chimpanzee populations: the stable isotope evidence.

Twenty-two chimpanzee hair samples collected from night nests at two different "savanna" sites were analyzed for carbon and nitrogen stable isotope ratios represented as delta13C and delta15N values. The first at Ugalla, Tanzania is a miombo woodland with grass groundcover and small patches of forest. The second at Ishasha, Democratic Republic of the Congo is a habitat composed of riverine gallery forest, semideciduous thicket forest, wooded grassland, and grassland. Based on comparative data from other primates, Ugalla hair delta13C values suggest that the chimpanzees are feeding primarily in the woodland rather than in forest patches or on grassland foods (grasses or grammivorous fauna). Similar comparisons indicate that the Ishasha chimpanzees are feeding within the forests and not in more open areas. In addition, the Ugalla chimpanzees had delta15N values that indicate extensive ingestion of leguminous flowers, seeds, and/or leaves. The Ishasha samples show a range encompassing three trophic levels. Two samples with the most positive values may indicate a nursing signal or vertebrate-feeding. Three individuals with intermediate values are similar to those in omnivorous nonhuman primate species. The four individuals with the lowest values are very similar to those in herbivorous monkeys. Stable isotope ratios permit time-averaged and habitat-specific dietary comparisons among sites, even without habituation or detailed foraging observations.     

Stable isotope ratio analysis of breastfeeding and weaning practices of children from medieval Fishergate House York,UK

Rib collagen of 51 juveniles and 11 adult females from the late medieval Fishergate House cemetery site (York, UK) were analyzed using nitrogen and carbon stable isotope ratio analysis to determine the weaning age for this population and to reconstruct diet. The juveniles' ages ranged from fetal to 5–6 years, while the females were of reproductive age. Previous researchers suggested that the children from Fishergate House might have been weaned later than the medieval British norm of 2 years, based on a mortality peak at 4–6 years of age. The results show weaning was complete by 2 years of age, agreeing with previous British weaning studies. The adult female δ¹⁵N values have a mean of 11.4‰ ± 1.1‰ and the δ¹³C values have a mean of ?19.4‰ ± 0.4‰. These findings are consistent with previous isotopic studies of female diet in York during this period, though slightly lower. The weaned juvenile nitrogen values were found to be higher than the adult females (12.4‰ ± 1.0‰ for δ¹⁵N and ?19.7‰ ± 0.5‰ for δ¹³C), which might indicate a dependence on higher trophic level proteins such as marine fish or pork. Marine fish is considered a high status food and children are considered low‐status individuals at this time, making this a particularly interesting finding. Weaning does not appear to coincide with peak mortality, suggesting environment factors may be playing a larger role in child mortality at Fishergate House. Am J Phys Anthropol 152:407–416, 2013. © 2013 Wiley Periodicals, Inc.     

Isotopic ecology and dietary profiles of Liberian chimpanzees

An extensive suite of isotopic data (δ¹³C, δ¹⁵N, and δ¹⁸O) from enamel apatite and bone collagen of adult male and female wild chimpanzees establishes baseline values for Pan troglodytes verus in a primary rainforest setting. The Ganta chimpanzee sample derives from a restricted region in northern Liberia. Diet is examined using stable light isotopes at three life stages—infant, young juvenile, and adult—and developmental differences are investigated within and between individual males and females. The isotopic data are very homogeneous with few exceptions. Juvenile females show consistent enrichment in ¹³C relative to infants, while juvenile males do not. These data suggest that age at weaning may be more variable for male offspring who survive to adulthood than for female offspring. Alternatively, or additionally, the weaning diet of males and females may differ, with greater consumption of technologically extracted insects and/or nuts by young females. Metabolic differences, including growth and hormone-mediated responses, may also contribute to the observed variation.The Ganta chimpanzee data offer an independent and objective line of evidence to primatologists interested in the dietary strategies of the great apes and to paleoanthropologists seeking comparative models for reconstructing early hominin subsistence patterns. Despite the high diversity of dietary items consumed by chimpanzees, isotopic signatures of chimpanzees from a primary rainforest setting exhibit narrow ranges of variation similar to chimpanzees in more open habitats.