Received: 12 October 2010 Revised: 17 December 2010 Accepted: 18 December 2010 Published online in Wiley Online Library: 2011 Multi-tissue analysis of oxygen isotopes in wild rhesus macaques (Macaca mulatta) Carolyn A. Chenery 1 * , Angela L. Lamb 1 , Hannah J. O’Regan 2 and Sarah Elton 3 1 NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK 2 Research Centre in Evolutionary Anthropology and Palaeoecology, School of Natural Sciences and Psychology, Liverpool John Moores University, Liverpool L3 3AF, UK 3 Centre for Anatomical and Human Sciences, Hull York Medical School, University of Hull, Cottingham Road, Hull HU6 7RX, UK Oxygen isotopes in animal tissues are directly related to body water composition and thus the environment. Accurate measurement of animal tissue d 18 O provides information about local climate, an animal’s geographical origin and subsequent movements, with wide applications in palaeobiology and forensic science. The genesis and evolution of tissue-based oxygen isotopes within species and within individuals are complex. We present the first data, for non-human primates, rhesus macaques (Macaca mulatta), on the relationship between oxygen isotope sources in bio-apatite (PO 4 and PCO 3 ) and hair taken from six sample sites in Asia, ranging from western India to northern Vietnam. The range of values is similar within each tissue type, with good correlation between tissues (r ¼ 0.791 to 0.908), allowing cross-tissue extrapolations. This is important when the availability of suitable tissues is limited. Biological interpretation of the small data set is difficult: macaque diets are eclectic, and the samples are from various locations. However, factors such as overall climate, precipitation quantity and source, and altitude are clearly influencing the results for each discrete geographical grouping. Future work could be aimed at assessing d 18 O tissue associations for other species as the relationships appear to be species-specific. Copyright ß 2011 John Wiley & Sons, Ltd. d 18 O in mammalian tissues Globally, the oxygen isotope composition of meteoric water varies in relation to climatic controls such as precipitation and evaporation rates and altitude, amongst others. [1–4] In broad terms, the animal body water d 18 O is correlated with the d 18 O of local precipitation (d 18 O precip ). [5–7] If the body water d 18 O can be accurately measured in animal tissues there is the potential to study associated changes in d 18 O precip and thus climate, animal origin and migration. This relationship has been utilised for a wide range of forensic, archaeological and paleontological investigations. [8–16] In mammals, the most commonly measured oxygen- bearing tissue is bio-apatite [generalised as Ca 10 (PO 4 ,- CO 3 ) 6 (OH.CO 3 ) 2 ] found in teeth and bone. In bio-apatite measurable oxygen isotopes are present in two ionic forms: phosphate oxygen (PO 4 ) and structural carbonate (PCO 3 ), which also substitutes for Ca and OH. The PO 4 ion accounts for 92% and PCO 3 accounts for only between 1.6 and 8% of the total oxygen in bio-apatite. [6,17–19] However, there is still little information on how the oxygen isotope composition varies between different body tissues and exactly how meteoric water is assimilated into them. The oxygen atoms in CO 2 3 and PO 3 4 are cogenetic and are in isotopic equilibrium with oxygen body water. [6,17,20] The relationship for d 18 O between the PO 4 and PCO 3 ions has been established for a number of species. [6,21–28] The data from these studies have been reviewed by Martin et al. [28] (and by ourselves) and confirm our observations that the relationship between the d 18 O PO4 and d 18 O PCO3 (slope, intercept and D PCO 3 -PO 4 ) differs between species, suggesting that a different equation may be needed for each species. The relationship for phosphate oxygen isotopes (d 18 O PO4 ) in bio-apatite and precipitation/drinking water is well under- stood and has been defined for several species, although not for non-human primates. [29–35] Our review of these existing equations for d 18 O PO4 – meteoric/drinking water conversion (not shown) indicates that, while they follow the same positive trend, they differ between species (see Martin et al. [28] ). The choice of which tissue to analyse may simply be a case of which is available; the analysis of bio-apatite requires access to tooth or bone material from the animals in question, with related ethical and legal implications. As the measure- ment of PCO 3 is the most cost- and time-efficient means of determining d 18 O in bio-apatite, it is the most common form of analysis. However, the PCO 3 ion is thought to be more susceptible to diagenetic alteration, [23,36] and at present there are no direct correlations between PCO 3 and precipitation/ drinking-water. Hair is a much more readily available resource, which is shed by an animal in the course of its day-to-day life. Surprisingly, however, there have been relatively few studies analysing the relationships between the oxygen isotopes of hair and bio-apatite from the same individuals. Here we present the first data on oxygen isotope relationships between three oxygen sources (PO 4 , PCO 3 and hair) in a non-human primate, the rhesus macaque Macaca mulatta. Rapid Commun. Mass Spectrom. 2011, 25, 779–788 (wileyonlinelibrary.com) DOI: 10.1002/rcm.4916 Research Article * Correspondence to: C. A. Chenery, NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK. E-mail: cac@bgs.ac.uk Rapid Commun. Mass Spectrom. 2011, 25, 779–788 Copyright ß 2011 John Wiley & Sons, Ltd. 779