Reconstructing temporal variation in great ape and other primate diets: A methodological framework for isotope analyses in hair

Abstract

Stable isotope analysis of carbon and nitrogen in hair provides a versatile tool for reconstructing feeding behavior in elusive primate species. Particularly in great apes, researchers can sample long hair completely non-invasively from nests, allowing the investigation of inter- and intra-individual dietary variation. Given its incremental growth pattern, hair records temporal shifts in diet over long periods and allows one to reconstruct seasonal dietary patterns in species that cannot be directly observed. However, as for other sample materials, there are potential drawbacks related to the properties of hair keratin. Here I review some important facts on the nature of primate hair and also introduce new isotopic data from infant bonobo hair to provide methodological recommendations for future sample collection in the field and sample preparation in the laboratory. While these methodological guidelines focus on great apes which can be sampled strictly non-invasively, I also consider applications to other free-ranging primates. The biochemical composition, growth cycle, isotope turnover rate and isotopic fractionation in hair keratin are particularly relevant for data analysis and interpretation. Also, one can microscopically identify infant hairs and analyze them separately to study nursing and weaning behavior in primates. The goal of this article is to encourage primatologists to analyze the stable isotope ratios of hair to assess primate feeding ecology. Am. J. Primatol. 78:1004-1016, 2016. © 2015 Wiley Periodicals, Inc.

Food mechanical properties and isotopic signatures in forest versus savannah dwelling eastern chimpanzees

“…By focussing on nest groups we tried to ensure the sampling of different members of a chimpanzee party with the aim to minimise potential errors easily introduced by pseudoreplication 67 . Hair samples were prepared following the procedure outlined in detail by Oelze 68 , with an emphasis on removing potential infant hairs and lipid contaminants from the material used for isotope analysis. All hair used contained root bulbs in the telogen stage and was cut sequentially in 5 or 10 mm long sections as weight for analysis allowed (<3.5 mg).…”

“…Each hair yielded multiple isotope measurements with hair section isotope values reflecting the previous 2 weeks (5 mm) or one month (10 mm) of diet if human hair growth rates are used as a proxy. As a result, each complete hair sample reaches several months back into time and covers on average six previous months of chimpanzee dietary behaviour 68 .…”

Stable and fluctuating social preferences and implications for cooperation among female bonobos at LuiKotale, Salonga National Park, DRC

“…We used LMMs with Gaussian error structure to determine whether variation in social preference indices (response variables) was influenced by the following dyadic attributes (test predictors): (1) Putative maternal relatedness, based on results of the genetic analyses; (2) Scaled rank distance, calculated as: (Dyadic rank distance AB − Dyadic rank distance min )/(Dyadic rank distance max − Dyadic rank distance min ); (3) Duration of observation time during which both females had offspring less than four years of age, based on evidence that most young are weaned by that age (De Lathouwers & Van Elsacker, ; Oelze, ); and (4) Dyadic co‐residency time at the beginning of the study, categorized as short (1 year), intermediate (4 years) or long (8+ years). To account for potential influences of adult sons on female social behavior (e.g., Surbeck, Mundry, & Hohmann, ), we included whether each female had an adult son (categorical) as a control predictor.…”

Inter‐individual variation in weaning among rhesus macaques (Macaca mulatta): Serum stable isotope indicators of suckling duration and lactation

“…We explore variation in the timing of weaning events among captive rhesus macaques ( Macaca mulatta ) to demonstrate the potential of stable carbon and nitrogen isotope analysis of blood serum for estimating the timing of weaning events with greater precision than what is possible using observational data. This study contributes to a growing body of literature in ecology and primatology advancing isotopic methodology in the study of weaning [Austin et al, ; Fahy et al, ; Habran et al, ; Macho & Lee‐Thorp, ; Newsome et al, ; Oelze, in press; Polischuk et al, ; Reitsema, ; Smith et al, ]. Importantly, with increased precision in estimating weaning age, a greater range of hypothesis‐testing concerning maternal investment is possible.…”