Stable isotopic variation in tropical forest plants for applications in primatology

Tooth enamel nitrogen isotope composition records trophic position: a tool for reconstructing food webs

Nitrogen isotopes are widely used to study the trophic position of animals in modern food webs; however, their application in the fossil record is severely limited by degradation of organic material during fossilization. In this study, we show that the nitrogen isotope composition of organic matter preserved in mammalian tooth enamel (δ¹⁵N_enamel) records diet and trophic position. The δ¹⁵N_enamel of modern African mammals shows a 3.7‰ increase between herbivores and carnivores as expected from trophic enrichment, and there is a strong positive correlation between δ¹⁵N_enamel and δ¹⁵N_{bone-collagen} values from the same individuals. Additionally, δ¹⁵N_enamel values of Late Pleistocene fossil teeth preserve diet and trophic level information, despite complete diagenetic loss of collagen in the same specimens. We demonstrate that δ¹⁵N_enamel represents a powerful geochemical proxy for diet that is applicable to fossils and can help delineate major dietary transitions in ancient vertebrate lineages.

Paleodietary reconstruction of endemic rodents from the precolumbian Dominican Republic: Discriminating wild feeding behavior from diets linked to human niche construction activities

In the Greater Antilles, certain animal taxa that have long been theorized to have been managed by indigenous peoples prior to AD1492, the main candidates being a group of endemic caviomorph rodents known as hutias (Capromyinae). This isotopic study investigates the paleodiets of several species of endemic rodents from three late precolonial sites in the northern Dominican Republic: El Flaco (cal. ad 990-1452), El Carril (cal. ad 1030-1262), and La Entrada (cal. ad 840-900) to assess whether human influence over animal diets can be determined. We examined bone collagen carbon (δ13Cco) and nitrogen (δ15N) and tooth enamel carbon (δ13Cen) isotope values of three species of hutias, Isolobodon portoricensis, Isolobodon montanus, and Plagiodontia aedium, alongside edible rat (Brotomys sp.), and domestic guinea pig (Cavia porcellus). To estimate dietary source contributions, we employed a Bayesian dietary mixing model (FRUITS v.3.0) and ran three different permutations to assess the relative contributions of C3 or C4/CAM plants. The addition of an extra 79 wild C3 and 40 wild C4/CAM plant species' isotope values from published sources to an established isotopic foodweb for the Caribbean region enabled us to discriminate between wild and domestic C3 and C4/CAM plant food sources in two of these models. Our results provide evidence of the significant consumption of domestic C4/CAM plants by some animals. This likely represents maize (Zea mays) consumption, which is known to have been ubiquitously cultivated by indigenous peoples in the region. This is particularly the case for I. portoricensis, as FRUITS modeling suggests that a few individuals consumed C4/CAM plants well beyond their expected natural diets as determined from feeding studies of extant hutia species. This may indicate human influence over endemic rodent diets due to niche construction activities such as horticultural practices and may reflect either opportunistic feeding on human produce or the purposeful supplementation of hutia diets by humans.

A chimpanzee enamel-diet δ13C enrichment factor and a refined enamel sampling strategy: Implications for dietary reconstructions

Reconstructing diets from stable carbon isotopic signals in enamel bioapatite requires the application of a δ¹³C enamel-diet enrichment factor, or the isotopic offset between diet and enamel, which has not been empirically determined for any primate. In this study, an enamel-diet enrichment factor (ε∗_enamel-diet) of 11.8 ± 0.3‰ is calculated for chimpanzees (Pan troglodytes) at Ngogo in Kibale National Park, Uganda, based on a comprehensive isotopic assessment of previously analyzed dietary plant data and new isotopic analyses of enamel apatite. Different enamel sampling methods are evaluated to determine the potential influence of weaning on isotopic enamel values and dietary interpretations. The new chimpanzee enrichment factor and a sampling strategy that excludes teeth that formed before weaning completion are applied to all known chimpanzee δ¹³C_enamel data, either previously published or newly derived in this study, resulting in a dietary range of almost 6‰ across all chimpanzees sampled. This new chimpanzee enamel-diet enrichment factor is then used to reassess dietary reconstructions of 12 fossil hominin species whose isotopic enamel signatures have been determined. Results reveal hominin diets that are isotopically more positive than previously reconstructed, highlighting the widespread contribution of ¹³C-enriched C₄/crassulacean acid metabolism (CAM) resources in fossil hominin diets and emphasizing the broad use of these resources during human evolution. These findings stress the importance of ascertaining and employing an appropriate enrichment factor for dietary reconstructions of specific taxa as well as standardizing the sampling protocol for tooth enamel in isotopic paleodietary reconstructions.

Carbon and nitrogen stable isotopic offsets between diet and hair/feces in captive orangutans

Estimating stable isotopic offset values is crucial for dietary reconstructions. Although research into stable isotope ecology of wild nonhuman primates is increasing overall, only a minority of studies involve laboratory experiments. This study is the first to report the carbon and nitrogen stable isotopic offset values in hair and feces of orangutans. During an experiment lasting 1 week, the weight of each consumed food item was recorded for each of six captive Bornean orangutan (Pongo pygmaeus) individuals. The food, hair, and fecal samples were collected for a few days, and their stable carbon and nitrogen isotope ratios were measured using an elemental analyzer/isotope ratio mass spectrometer. Subsamples of feces were treated with ethanol during the preservation process. Monte Carlo analyses showed that the 95% confidence intervals (CIs) of the carbon and nitrogen offset values between hair and diet were +0.9‰ to +3.9‰ and +2.3‰ to +4.5‰, respectively. The 95% CIs of the carbon and nitrogen offset values between feces and diet were -3.7‰ to -0.9‰ and +0.3‰ to +2.7‰, respectively. The effect of ethanol treatment on the stable isotope ratios of feces was unclear and inconclusive. The computed offset values of hair in captive orangutans are similar to those reported in other nonhuman primates, although those of feces showed greater interspecies variations. The offset values estimated in this study contribute to isotopic studies into the feeding ecology of free-ranging orangutans who are critically endangered in most wild settings.

Stratigraphy of stable isotope ratios and leaf structure within an African rainforest canopy with implications for primate isotope ecology

The canopy effect describes vertical variation in the isotope ratios of carbon (δ¹³C), oxygen (δ¹⁸O) and partially nitrogen (δ¹⁵N) within plants throughout a closed canopy forest, and may facilitate the study of canopy feeding niches in arboreal primates. However, the nuanced relationship between leaf height, sunlight exposure and the resulting variation in isotope ratios and leaf mass per area (LMA) has not been documented for an African rainforest. Here, we present δ¹³C, δ¹⁸O and δ¹⁵N values of leaves (n = 321) systematically collected from 58 primate food plants throughout the canopy (0.3 to 42 m) in Côte d'Ivoire, West Africa. Besides leaf sample height and light availability, we measured leaf nitrogen and carbon content (%N, %C), as well as LMA (n = 214) to address the plants' vertical resource allocations. We found significant variation in δ¹³C, δ¹⁸O and δ¹⁵N, as well as LMA in response to height in combination with light availability and tree species, with low canopy leaves depleted in ¹³C, ¹⁸O and ¹⁵N and slightly higher in %N compared to higher canopy strata. While this vertical isotopic variation was not well reflected in the δ¹³C and δ¹⁵N of arboreal primates from this forest, it did correspond well to primate δ¹⁸O values.

CH4/CO2 Ratios and Carbon Isotope Enrichment Between Diet and Breath in Herbivorous Mammals

Breath and diet samples were collected from 29 taxa of animals at the Zurich and Basel Zoos to characterize the carbon isotope enrichment between breath and diet. Diet samples were measured for δ13C and breath samples for CH4/CO2 ratios and for the respired component of δ13C using the Keeling plot approach. Different digestive physiologies included coprophagous and non-coprophagous hindgut fermenters, and non-ruminant and ruminant foregut fermenters. Isotope enrichments from diet to breath were 0.8 ± 0.9‰, 3.5 ± 0.8‰, 2.3 ± 0.4‰, and 4.1 ± 1.0‰, respectively. CH4/CO2 ratios were strongly correlated with isotope enrichments for both hindgut and foregut digestive strategies, although CH4 production was not the sole reason for isotope enrichment. Average CH4/CO2 ratios per taxon ranged over several orders of magnitude from 10–5 to 10–1. The isotope enrichment values for diet-breath can be used to further estimate the isotope enrichment from diet-enamel because Passey et al. (2005b) found a nearly constant isotope enrichment for breath-enamel for diverse mammalian taxa. The understanding of isotope enrichment factors from diet to breath and diet to enamel will have important applications in the field of animal physiology, and possibly also for wildlife ecology and paleontology.

Limited evidence of C4 plant consumption in mound building Macrotermes termites from savanna woodland chimpanzee sites

Stable isotope analysis is an increasingly used molecular tool to reconstruct the diet and ecology of elusive primates such as unhabituated chimpanzees. The consumption of C4 plant feeding termites by chimpanzees may partly explain the relatively high carbon isotope values reported for some chimpanzee communities. However, the modest availability of termite isotope data as well as the diversity and cryptic ecology of termites potentially consumed by chimpanzees obscures our ability to assess the plausibility of these termites as a C4 resource. Here we report the carbon and nitrogen isotope values from 79 Macrotermes termite samples from six savanna woodland chimpanzee research sites across equatorial Africa. Using mixing models, we estimated the proportion of Macrotermes C4 plant consumption across savanna woodland sites. Additionally, we tested for isotopic differences between termite colonies in different vegetation types and between the social castes within the same colony in a subset of 47 samples from 12 mounds. We found that Macrotermes carbon isotope values were indistinguishable from those of C3 plants. Only 5 to 15% of Macrotermes diets were comprised of C4 plants across sites, suggesting that they cannot be considered a C4 food resource substantially influencing the isotope signatures of consumers. In the Macrotermes subsample, vegetation type and caste were significantly correlated with termite carbon values, but not with nitrogen isotope values. Large Macrotermes soldiers, preferentially consumed by chimpanzees, had comparably low carbon isotope values relative to other termite castes. We conclude that Macrotermes consumption is unlikely to result in high carbon isotope values in either extant chimpanzees or fossil hominins.

Seasonality and interindividual variation in mandrill feeding ecology revealed by stable isotope analyses of hair and blood

Mandrills are large-bodied terrestrial forest primates living in particularly large social groups of several hundred individuals. Following these groups in the wild to assess differences in diet over time as well as among individuals is demanding. We here use isotope analyses in blood and hair obtained during repeated captures of 43 identified free-ranging mandrills (Mandrillus sphinx) from Southern Gabon, to test how dietary variation relates to the season as well as an individual's age and sex. We measured the stable carbon (δ¹³ C‰) and nitrogen (δ¹⁵ N‰) isotope ratios in 46 blood and 214 hair section samples as well as from a small selection of mandrill foods (n = 24). We found some seasonal isotopic effects, with lower δ¹³ C values but higher δ¹⁵ N values observed during the highly competitive long dry season compared to the fruit-rich long rainy season. Variation in δ¹³ C was further predicted by individual age, with higher δ¹³ C values generally found in younger individuals suggesting that they may consume more high canopy fruit than older individuals, or that older individuals consume more low canopy foliage. The best predictor for δ¹⁵ N values was the interaction between age and sex, with mature and reproductively active males revealing the highest δ¹⁵ N values, despite the observation that males consume substantially less animal food items than females. We interpret high δ¹⁵ N values in these mature male mandrill blood and hair sections to be the result of nutritional stress associated with intense male-male competition, particularly during mating season. This is the first study showing isotopic evidence for nutritional stress in a free-ranging primate species and may spark further investigations into male mandrill diet and energy balance.

Isotopic and elemental corroborates for wild bearded capuchin (Sapajus libidinosus) omnivorous dietary adaptation at Fazenda Boa Vista, Brazil

RATIONALE

This study analyzes variability in the diets of wild bearded capuchin monkeys, Sapajus libidinosus, by analyzing stable carbon (δ¹³ C) and nitrogen (δ¹⁵ N) isotope ratios and elemental concentrations (%C and %N) of fecal samples and food items. Developing isotopic and elemental correlates for diets of habituated subjects is a necessary step towards applying similar methods to interpret diets of unhabituated or cryptic subjects.

METHODS

Fecal samples from wild capuchins and their foods were collected at Fazenda Boa Vista, Brazil. Fecal samples from laboratory-housed Sapajus spp. and their foods were analyzed to establish diet-feces offsets for δ¹³ C, δ¹⁵ N, %C, and %N. Samples were dried, powdered, and measured for isotopic and elemental values. A Bayesian mixing model commutes isotopic and elemental data from wild capuchins into likely proportions of different food categories.

RESULTS

The captive study shows small diet-feces spaces for Sapajus spp. of -0.8 ± 0.7‰ for δ¹³ C, -0.2 ± 0.4‰ for δ¹⁵ N, -6.1 ± 1.7% for %C, and -1.0 ± 0.6% for %N. The wild study shows omnivorous diets based on C₃ , C₄ , and CAM plants, and fauna. Subject diets are highly varied within and between days. Fecal data show age-related differences in diet and crop-raiding. There is no consistent isotopic or elemental difference between mothers and infants.

CONCLUSIONS

Fecal stable isotope and elemental evidence employed in a Bayesian mixing model reflects the highly varied diets of capuchin monkeys in an isotopically heterogeneous environment. The isotopic and elemental variability reported here will aid similar diet reconstructions among unhabituated subjects in the future, but precludes tracking weaning isotopically among capuchins in this environment.

Isotopic niche partitioning in two sympatric howler monkey species

OBJECTIVES

Ecological similarity between species can lead to interspecific trophic competition. However, when ecologically similar species coexist, they may differ in foraging strategies and habitat use, which can lead to niche partitioning. As the body tissues of consumers contain a stable isotope signature that reflects the isotopic composition of their diet, stable isotope analysis is a useful tool to study feeding behavior. We measured the isotopic niche width, which is a proxy for trophic niche width, of mantled (Alouatta palliata) and black (A. pigra) howler monkeys. Specifically, studied populations in allopatry and sympatry to assess whether these species showed niche partitioning.

MATERIALS AND METHODS

Between 2008 and 2012, we collected hair samples from 200 subjects (113 black and 87 mantled howler monkeys) and used continuous flow isotope ratio mass spectrometry to estimate δ¹³ C and δ¹⁵ N. We described the isotopic niche width of each species in allopatry and sympatry with the Bayesian estimation of the standard ellipse areas.

RESULTS

In allopatry, isotopic niche width and isotopic variation were similar in both species. In sympatry, black howler monkeys had a significantly broader isotopic niche, which was mainly determined by high δ¹⁵ N values, and included the majority of mantled howler monkeys' isotopic niche. The isotopic niche of mantled howler monkeys did not differ between sympatry and allopatry.

CONCLUSIONS

The coexistence of these ecologically similar species may be linked to trophic niche adjustments by one species, although the particular features of such adjustments (e.g., dietary, spatial, or sensory partitioning) remain to be addressed.

Revisiting the Foraging Ecology and Extinction History of Two Endemic Vertebrates from Tenerife, Canary Islands

We used carbon (δ13C) and nitrogen (δ15N) isotopes to examine the foraging ecology of Tenerife giant rats (Canariomys bravoi) and lizards (Gallotia goliath) in northwestern Tenerife, which until recently, were the island’s largest terrestrial vertebrates. We combined new isotope data for 28 C. bravoi and 14 G. goliath with published regional data for both species and then compared these with data for co-occurring extant taxa and modern C3 plants. Isotope data suggest both extinct species relied primarily on C3 resources and were trophic omnivores. However, the two species appear to have partitioned their resources when living in sympatry. Isotopic overlap between C. bravoi and Rattus spp., and between G. goliath, extant Gallotia galloti, and introduced rabbits (Oryctolagus cuniculus) suggests reliance on similar foods. We radiocarbon dated four C. bravoi and two G. goliath with the most extreme isotope values. These new dates do not settle the question of what triggered the demise of either species. Nevertheless, the data are most consistent with anthropogenically-induced extinction. Temporal isotopic trends contradict expectations if regional climate were responsible, and confidence intervals for radiocarbon dates suggest it is highly likely that both species were present when humans first settled the island.

Stable isotope variation in savanna chimpanzees (Pan troglodytes verus) indicate avoidance of energetic challenges through dietary compensation at the limits of the range

OBJECTIVES

Food scarcity is proposed to be a limitation to chimpanzees at the limits of their range; however, such a constraint has never been investigated in this context. We investigated patterns of δ¹³ C and δ¹⁵ N variation along a latitudinal gradient at the northwestern West African chimpanzee (Pan troglodytes verus) range limit with the expectation that isotope ratios of chimpanzees at the range limit will indicate different dietary strategies or higher physiological constraints than chimpanzees further from the edge.

MATERIALS AND METHODS

We measured δ¹³ C and δ¹⁵ N values in hair (n = 81) and plant food (n = 342) samples from five chimpanzee communities located along a latitudinal gradient in Southeastern Senegal.

RESULTS

We found clear grouping patterns in hair δ¹³ C and δ¹⁵ N in the four southern sites compared to the northernmost site. Environmental baseline samples collected from these sites revealed overall higher plant δ¹⁵ N values at the northernmost site, but similar δ¹³ C values across sites. By accounting for environmental baseline, Δ¹³ C and Δ¹⁵ N values were clustered for all five sites relative to total Pan variation, but indicated a ¹³ C-enriched diet at the range limit.

DISCUSSION

Clustering in Δ¹³ C and Δ¹⁵ N values supports that strategic shifting between preferred and fallback foods is a likely ubiquitous but necessary strategy employed by these chimpanzees to cope with their environment, potentially allowing chimpanzees at their limits to avoid periods of starvation. These results also underline the necessity of accounting for local isotopic baseline differences during inter-site comparison.

Of lemurs and louse flies: The biogeochemical and biotic effects of forest disturbance on Propithecus edwardsi and its obligate ectoparasite Allobosca crassipes in Ranomafana National Park, southeastern Madagascar

From alleles to ecosystems and landscapes, anthropogenic activity continues to affect the environment, with particularly adverse effects on biodiversity hotspots such as Madagascar. Selective logging has been proposed as a "win-win" conservation strategy, yet its effects on different components of biodiversity are still not fully understood. Here we examine biotic factors (i.e., dietary differences) that may be driving differences in biogeochemical stocks between disturbed and undisturbed forests. We present the stable nitrogen (δ¹⁵ N) and carbon (δ¹³ C) isotope composition of hair from the lemur Propithecus edwardsi and of whole bodies of its obligate ectoparasite, the louse-fly Allobosca crassipes, from sites in Ranomafana National Park (RNP) that are comparable except for the history of logging and subsequent forest regeneration. P. edwardsi and A. crassipes from the disturbed (i.e., heavily selectively logged) site are lower in ¹⁵ N and ¹³ C relative to P. edwardsi and A. crassipes from sites that were minimally selectively logged or not commercially logged at all. There is a ∼3‰ decrease in ¹⁵ N between disturbed and undisturbed sites that corresponds to a difference of nearly a full trophic level. Flowers from Bakerella clavata, a staple food source for P. edwardsi in disturbed habitats and a fallback food for P. edwardsi in primary forests, were also analyzed isotopically. B. clavata is δ¹⁵ N-depleted in both disturbed and undisturbed sites. Data from longitudinal behavioral surveys of P. edwardsi in RNP and other forests in eastern Madagascar point to significant differences in consumption patterns of B. clavata, with P. edwardsi in disturbed forests consuming almost twice as much of this plant. Depletion of ¹⁵ N in animal tissues is a complex issue, but likely the result of the interaction of physiological and ecological factors. Anthropogenic disturbance in RNP from selective logging has had both biotic and biogeochemical effects that are observable trophically.

Carbon and nitrogen stable isotopic offsets between diet and hair/feces in captive chimpanzees

RATIONALE

Estimation of the stable isotopic offsets between tissue and diet is important for dietary reconstructions. Although stable isotopic studies of chimpanzees (Pan troglodytes) are increasing, the isotopic offsets in chimpanzees have never been studied. In this study, the carbon and nitrogen stable isotopic offset values in hair and feces were measured for 13 captive chimpanzees for the first time.

METHODS

All consumed food items and quantities were recorded for each individual for 1 week. Food samples were typically collected three times, hair was collected 3 weeks after the experimental week, and feces were collected ad libitum during the experimental week. The stable carbon and nitrogen isotope ratios were measured using elemental analyzer-isotope ratio mass spectrometry (EA-IRMS).

RESULTS

As the results of Monte Carlo analysis, the estimated carbon and nitrogen offsets between the hair and diet were +3.0 to +3.9‰ and +2.8 to +3.7‰, respectively, for the 95% confidence intervals (CIs). The 95% CIs of the carbon and nitrogen offset values between the feces and diet were -1.6 to 0.0‰ and +1.2 to +2.7‰, respectively.

CONCLUSIONS

These offset values are generally consistent with those of the other primate species reported in previous studies. However, potential variations in the offset values due to dietary and physiological factors should be studied in detail in the future. Copyright © 2016 John Wiley & Sons, Ltd.

A novel fecal stable isotope approach to determine the timing of age-related feeding transitions in wild infant chimpanzees

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 (δ¹³ C, δ¹⁵ 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.

RESULTS

Infants ≤1 year old showed average δ¹⁵ N, δ¹³ C and %N ratios that were 2.0‰, 0.8‰ and 1.3% greater than their mothers, respectively, interpreted as trophic level effects. Although data collected on newborns were few, results suggest that solid foods were consumed within 2-5 months after birth. Trophic level differences decreased steadily after 1 year, which indicates a decreasing relative contribution of milk to the diet. Isotopic results indicated infants were weaned by 4.5 years old-more than a year earlier than observations of nipple contacts ceased, which revealed the occurrence of "comfort nursing." Juvenile isotopic signatures indicate no nursing overlap between siblings.

DISCUSSION

Our results resemble the stable isotope differences of human babies. This study contributes to a model of chimpanzee nutritional development required to understand early life history patterns in hominins.

Comparative isotope ecology of African great apes

The isotope ecology of great apes is a useful reference for palaeodietary reconstructions in fossil hominins. As extant apes live in C₃-dominated habitats, variation in isotope signatures is assumed to be low compared to hominoids exploiting C₄-plant resources. However, isotopic differences between sites and between and within individuals are poorly understood due to the lack of vegetation baseline data. In this comparative study, we included all species of free-ranging African great apes (Pan troglodytes, Pan paniscus, Gorilla sp.). First, we explore differences in isotope baselines across different habitats and whether isotopic signatures in apes can be related to feeding niches (faunivory and folivory). Secondly, we illustrate how stable isotopic variations within African ape populations compare to other extant and extinct primates and discuss possible implications for dietary flexibility. Using 701 carbon and nitrogen isotope data points resulting from 148 sectioned hair samples and an additional collection of 189 fruit samples, we compare six different great ape sites. We investigate the relationship between vegetation baselines and climatic variables, and subsequently correct great ape isotope data to a standardized plant baseline from the respective sites. We obtained temporal isotopic profiles of individual animals by sectioning hair along its growth trajectory. Isotopic signatures of great apes differed between sites, mainly as vegetation isotope baselines were correlated with site-specific climatic conditions. We show that controlling for plant isotopic characteristics at a given site is essential for faunal data interpretation. While accounting for plant baseline effects, we found distinct isotopic profiles for each great ape population. Based on evidence from habituated groups and sympatric great ape species, these differences could possibly be related to faunivory and folivory. Dietary flexibility in apes varied, but temporal variation was overall lower than in fossil hominins and extant baboons, shifting from C₃ to C₄-resources, providing new perspectives on comparisons between extinct and extant primates.

Mapping the Elephants of the 19th Century East African Ivory Trade with a Multi-Isotope Approach

East African elephants have been hunted for their ivory for millennia but the nineteenth century witnessed strongly escalating demand from Europe and North America. It has been suggested that one consequence was that by the 1880s elephant herds along the coast had become scarce, and to meet demand, trade caravans trekked farther into interior regions of East Africa, extending the extraction frontier. The steady decimation of elephant populations coupled with the extension of trade networks have also been claimed to have triggered significant ecological and socio-economic changes that left lasting legacies across the region. To explore the feasibility of using an isotopic approach to uncover a ‘moving frontier’ of elephant extraction, we constructed a baseline isotope data set (δ¹³C, δ¹⁵N, δ¹⁸O and ⁸⁷Sr/⁸⁶Sr) for historic East African elephants known to have come from three distinct regions (coastal, Rift Valley, and inland Lakes). Using the isotope results with other climate data and geographical mapping tools, it was possible to characterise elephants from different habitats across the region. This baseline data set was then used to provenance elephant ivory of unknown geographical provenance that was exported from East Africa during the late nineteenth and early twentieth centuries to determine its likely origin. This produced a better understanding of historic elephant geography in the region, and the data have the potential to be used to provenance older archaeological ivories, and to inform contemporary elephant conservation strategies.

Advances in primate stable isotope ecology-Achievements and future prospects

Stable isotope biogeochemistry has been used to investigate foraging ecology in non-human primates for nearly 30 years. Whereas early studies focused on diet, more recently, isotopic analysis has been used to address a diversity of ecological questions ranging from niche partitioning to nutritional status to variability in life history traits. With this increasing array of applications, stable isotope analysis stands to make major contributions to our understanding of primate behavior and biology. Most notably, isotopic data provide novel insights into primate feeding behaviors that may not otherwise be detectable. This special issue brings together some of the recent advances in this relatively new field. In this introduction to the special issue, we review the state of isotopic applications in primatology and its origins and describe some developing methodological issues, including techniques for analyzing different tissue types, statistical approaches, and isotopic baselines. We then discuss the future directions we envision for the field of primate isotope ecology. Am. J. Primatol. 78:995-1003, 2016. © 2015 Wiley Periodicals, Inc.