Energetic consequences of seasonal breeding in female Japanese macaques (Macaca fuscata).код для вставкиСкачать
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 146:161–170 (2011) Energetic Consequences of Seasonal Breeding in Female Japanese Macaques (Macaca fuscata) Cécile Garcia,1* Michael A. Huffman,2 Keiko Shimizu,3 and John R. Speakman4 1 Laboratoire de Dynamique de l’Evolution Humaine, CNRS UPR 2147, 44 rue de l’Amiral Mouchez, 75014 Paris, France 2 Department of Ecology and Social Behavior, Primate Research Institute, Kyoto University, Inuyama, Japan 3 Department of Zoology, Faculty of Science, Okayama University of Science, Japan 4 Aberdeen Centre for Energy Regulation and Obesity (ACERO), Institute of Biological and Environmental Science, University of Aberdeen, UK KEY WORDS deuterium method; nutritional status; body composition; reproductive costs ABSTRACT Japanese macaques inhabit a relatively cold environment and females of this species could have developed strategies of energy economy to face the sometimes-harsh seasonal conditions of temperate climates, as well as reproductive costs, and thus regulate their energy balance. Here, we explore the relationship between nutritional status, body composition, seasonality, and reproductive status using isotope-labeled water, anthropometric measurements, and leptin assays from 14 captive female Japanese macaques. Our results indicated that body mass provided the best predictor of fatfree mass and fat mass. These females varied in estimated percent body fat between 8 and 25% (18% on average at the beginning of the mating season and 13% during the birth season). Higher body mass and body fat content were observed at the beginning of the mating How energetics inﬂuence female reproductive function in primates remains the subject of considerable debate as to mechanisms and controls. Several studies in humans and non-human primates have shown that inadequate caloric intake, strenuous physical activity, and short-term negative energy balance may induce reproductive dysfunction and decreased fertility (Dewey, 1998; Loucks and Thuma, 2003; Schneider, 2004; De Souza et al., 2007; Williams et al., 2007). Although there is large consensus that nutritional status is a key factor inﬂuencing female ﬁtness, accurate monitoring of energetic condition and body composition in wild or semi-free ranging primates remains a signiﬁcant methodological challenge, so that relatively little attention has focused on the energetic stresses of mating activity and lactation, speciﬁcally in seasonally reproducing species. These two reproductive activities are considered to entail more energy costs than pregnancy (Lee, 1996; Key and Ross, 1999), and include the energy expanded on intra-sexual competition for mates and parental care in addition to the daily energy expenditure. Whereas lactation length may be used as a proxy for energy costs of parental care, it is nevertheless difﬁcult to assess the energy costs of intrasexual competition directly; and other costs associated with intra- or inter-sexual conﬂicts, such as risk of injury, are not easily translated into energetic terms. Primates and many other mammalian species living in seasonal environments exhibit a variety of physiological and behavioral characteristics that enable them to cope with temporal ﬂuctuations in climate and energy availC 2011 V WILEY-LISS, INC. season, which supports the hypothesis that individual females need to attain a sufﬁcient physical condition to cover energy costs associated with mating activity, and to survive under severe ecological conditions in winter with high thermoregulatory costs. We found a relationship between conception rates and energetic condition or body fat, with females that conceived during one mating season being fatter after the end of their previous mating season. Together, these results suggest that, even in captive settings with constant food availability, seasonal breeding entails relatively high energy costs, and that females with higher energy status could invest more in reproductive activities and could afford to reproduce more rapidly. Am J Phys Anthropol 146:161–170, 2011. C 2011 V Wiley-Liss, Inc. ability. Therefore, energy balance and adiposity are not maintained at a constant set point but rather vary with season and also with reproductive status. This is exacerbated in seasonally breeding animals, especially for females, which are characterized by annual changes in body mass and adiposity (Rousseau et al., 2003). In the seasonal environment, primates accumulate and subsequently loose energy stores in a yearly body mass gain– loss cycle (Mori, 1979; Richard et al., 2000; Kurita et al., 2002; Hamada et al., 2003; Pusey et al., 2005) and most of the increase/decrease in mass seems due to an increase/decrease in fat reserves. During periods of food scarcity, endogenous lipids are the main source of energy utilized and proteins are spared. Studies on protein or Grant sponsors: Ministry of Foreign Affairs, France; Japan Society for the Promotion of Science; Institutional Research Funds. *Correspondence to: Dr. Cécile Garcia, Laboratoire de dynamique de l’évolution humaine, CNRS UPR 2147, 44 rue de l’Amiral Mouchez, 75014 Paris, France. E-mail: email@example.com Received 1 July 2010; accepted 18 April 2011 DOI 10.1002/ajpa.21553 Published online 8 August 2011 in Wiley Online Library (wileyonlinelibrary.com). 162 C. GARCIA ET AL. fat sparing were mainly conducted on rodent species or heterothermic primates (Giroud et al., 2010), but few data are available in homeotherms and primates inhabiting highly seasonal environments. Seasonal breeding is one potential factor in the timing of energy saving mechanisms among cercopithecoids. If breeding seasonality evolved in response to predictable seasonal energy shortfalls, females may be selected to develop efﬁcient fat deposition mechanisms to help them get through harsh seasonal conditions and offset the increased metabolic requirements of reproductive effort. Japanese macaques (Macaca fuscata) show marked seasonal changes in body mass in response to the predictable cycle of food allocation (Kurita et al., 2002; Hamada et al., 2003). They inhabit an environment characterized by an extreme seasonality in terms of both temperature and precipitation variation, and they are found at the most northerly extent of any primate’s range. They are widely distributed in Japan and are seasonal breeders, mating from late autumn to early winter, and give birth from spring to early summer (Kawai, 1969). This species form multi-male/multi-female social groups in which females mate promiscuously throughout the mating season and mate when they are not ovulating, but with some selectivity (Huffman, 1991; Inoue and Takenaka, 2008). Competition between males, female mate choice (Huffman, 1992; Soltis et al., 1997a, 1997b), male sexual coercion of females and alternative male mating strategies (sneak copulations) are all suggested to be important determinants of mating and reproductive success in this species (Soltis et al., 2001). Male aggression against females both constrains female mate choice and imposes costs on females so that coercive aggression could increase male copulation rates through at least two mechanisms: by overcoming female resistance (direct coercion), and/or by limiting female promiscuity (mate guarding). Several types of sexual coercion have been identiﬁed (Smuts and Smuts, 1993; CluttonBrock and Parker, 1995; van Schaik et al., 2004): forced copulation (violent restraint resulting in immediate mating), harassment (repeated attempts to copulate inducing eventual female submission), intimidation (physical punishment of female refusals to mate increasing the likelihood of submission and matings in the future) and mate guarding (aggression at females to prevent them from mating with other males), all of them imposing energy costs on females. Forced copulation is not known to occur in Japanese macaques, but harassment, intimidation, and mate guarding may occur, especially in captivity where there is less availability for sneak copulations and fewer areas to avoid male aggression (Soltis et al., 1997a, 2001). These constraining behaviors impose energy costs on females, in terms of energy spent to escape from males and in terms of increased physiological stress (Muller et al., 2007). Moreover, in this species living in relatively cold habitats, the problem of energy sparing could be crucial. Under such ecological pressures, it should be very advantageous to accumulate fat reserves, which can be used during temporary energy imbalance and weight loss within a restricted breeding season. Compared to primate species living in more tropical climates, this species could be characterized by speciﬁc behavioral and physiological adaptations and unique fat-depositing mechanisms which have evolved to cope with cold weather. Japanese macaques are therefore a good model for understanding seasonal variation in fat deposition, and the link between energetic condition and reproduction. American Journal of Physical Anthropology Knowing the changes in body composition that accompany seasonal ﬂuctuations in body mass is essential to further understand the nature and the limits of the strategy of energy economy used by female Japanese macaques to face predicted/unpredicted food shortage and reproductive costs, and thus regulate their energy balance. The present study extends previous observations (Garcia et al., 2009b, 2010) of the relationship among female nutritional status, reproductive outcome, and social parameters in the Japanese macaque by investigating body composition changes during two successive seasons with labeled-water technique, which is the most precise method to establish body composition. We speciﬁcally hypothesized that this species would use fat-sparing strategies to adjust energy expenditure to the behavioral and reproductive requirements of a given season. We therefore predict that body composition and body fat accumulation will depend on seasonality with females accumulating fat reserves in autumn to sustain the costs of mating activity, prepare for pregnancy, and/ or to survive under severe ecological conditions in winter. Moreover, based on previous studies showing that dominance status may affect energetic condition (Whitten, 1983; Smuts and Nicolson, 1989; Altmann, 1998; Gerald, 2002; Koenig, 2002; Altmann and Alberts, 2005), with low-ranking females having higher rates of interruption during feeding bouts and higher energy expenditure, we predict that these disadvantages will result in worse body condition for low-ranking females compared to high-ranking ones. METHODS Animals, housing, and diet The subjects of this study were 14 captive female Japanese macaques (14.8 6 6.3 years of age, range 5 5–24 years) living in an outdoor corral enclosure (960 m2 with climbing structures) at the Primate Research Institute of Kyoto University, Inuyama, Japan. All subjects were part of a longitudinal study of nutritional and stress effects on reproductive outcome. In this troop, females mate mainly between October and February, and give birth between April and August. This cross-sectional research was conducted at the beginning of the 2006– 2007 mating season (October 2006) and during the following birth season (May 2007). We selected all the adult multiparous females in this group for that year (excluding one very old female), and excluded subadult or nulliparous females in order to avoid confounding factors due to maternal experience and maturational age. In October 2006, the group was composed of 52 individuals consisting of 7 adult and 9 subadult males, 17 adult, and 9 subadult females and their immature offspring (10 infants younger than 1-year-old: 7 females and 3 males). All animals had free access to water except during the experimental period. During the study, food was provided once daily and the individuals were fed vegetables (sweet potatoes) and standard primate pellets. Experimental protocol As per the guidelines of the Primate Research Institute, all monkeys underwent yearly health assessment, with all individuals being trapped for tattooing of infants, tetanus inoculations, morphometrics, and collection of biological samples from all individuals. We conducted the deuterium experiment and morphometric ENERGETICS AND SEASONALITY IN FEMALE MACAQUES measurements during this health assessment in October 2006. Upon recapture, in May 2007, the same experiment was done using the same methodology. The same investigator (CG) was responsible for all anthropometric measurements to minimize inter-observer error. Deuterium experiment. The females were anesthetized with ketamine (10 mg kg21 by intramuscular injection), a widely accepted dissociative anesthetic used in studies requiring transient animal tranquillization. An initial 3 ml blood sample was taken at the cubital vein (for background enrichment, i.e., the natural enrichment of 2H). Immediately after, about 0.1 g kg21 2H2O 99.9% (Wako Pure Chemical Industries, Japan) was injected subcutaneously in the scapular region. The average quantity injected was 0.102 g kg21 body weight (60.008, N 5 14). After injection, the females were kept in separate cages until the next blood sampling. Previous investigations in macaque species indicated that the injected stable isotope should be nearly equilibrated within 1 h of administration and fully equilibrated within 2 h (Macaca nemestrina, Kodama, 1970; Macaca mulatta: Walker et al., 1984). Blood samples (1 ml) were therefore obtained after an interval of 2 h. During the experimental period, the females had no access to food or water. Upon completion of the measurements, they were released back into their social group as soon as any effects of the anesthesia had worn off. Blood samples were ﬂame-sealed into capillary tubes immediately after collection and stored at 48C until analysis at the Aberdeen Centre for Energy Regulation and Obesity (Aberdeen University, Scotland). Capillaries were vacuum-distilled (Nagy, 1983), and water from the resulting distillate was used to produce H2 (methods in Speakman and Król, 2005). The isotope ratios 2H/1H were analyzed using gas source isotope ratio mass spectrometry (Optima, Micromass IRMS, Manchester, UK) with isotopically characterized cylinder gases of H2 (CP grade gases; BOC Ltd) in the reference channel. These cylinder gases were characterized relative to the isotopic standards mean ocean water (SMOW) and standard light arctic precipitate (SLAP) (de Wit et al., 1980) supplied by the International Atomic Energy Agency (IAEA, Vienna, Austria). In each batch of samples for analysis, we ran our own laboratory standards to ensure day-to-day variation in performance of the analyzer was not a signiﬁcant factor. All isotope enrichments were measured in d/ml relative to the working standards and then converted to ppm using the established ratios for these reference materials. Total body water (TBW) was calculated from the deuterium dilution space as follows: TBW (kg) = 1,000 (Alpha D 3mass injected) =Dr D with Alpha D = 0.899 and Dr D ¼ðð2 H=1 HÞt2 ð2 H=1 HÞt0 Þ=eðkd 3tÞ where t 5 times and kd 5 disappearance rate of the isotope. The 2H2O dilution space typically overestimates by about 4% the total body water as determined by carcass analysis (Sheng and Huggins, 1979) while H218O dilution space is equivalent to total body water (Lifson et al., 1955) and provides values similar to those obtained by direct evaluation for various species (Nagy and Costa, 1980). In the present experiment, total body water was calculated from 2H dilution space after correction by the factor 1.04 (Speakman et al., 1993; Speakman, 1997, 163 1998). Fat-free mass (FFM) was derived from TBW assuming a hydratation coefﬁcient of 73.2% (Pace and Rathburn, 1945; Walker et al., 1984; Power et al., 2001; Garcia et al., 2004). Total body fat (TBF in kg) was then calculated from the difference between body mass and fat-free mass. Body measurements. A complete description of the anthropometric measurements can be found in Garcia et al. (2010). In brief, we monitored body mass, body length, arm and calf circumferences, and skinfold thickness at three different sites (abdominal, supra-iliac, subscapular). By summing the skinfold thickness at those three sites, we therefore calculated the total skinfold thickness (TS) for each individual (Hamada et al., 2003). Female physical condition was assessed as the relationship between: 1) body mass (BM) and length using the Quetelet Index (QI) (Bowman and Lee, 1995; Garcia et al., 2004) deﬁned as follows: QI 5 (BM in kg)/(crownrump length in m)2. Quetelet index approximates condition in the same way as does body mass index or BMI (Norgan, 1987; Garcia et al., 2009a). 2) Body mass and anterior trunk length (ATL) using the physical index (PI) deﬁned by Hamada et al. (1996): PI 5 1.05 3 (BM in kg)/(ATL in mm)2.3 3 107. Hormonal assays. We performed blood sampling and hormonal assays in October 2006 and May 2007, as described previously (Garcia et al., 2010). Samples were analyzed for concentrations of leptin, having been shown to be an indicator of nutritional status and body condition. Brieﬂy, the leptin radioimmunoassay (Linco Research, St. Charles, MO) had a sensitivity of 0.5 ng ml21 with intra-assay and inter-assay coefﬁcients of variation \10%. Hormonal analysis revealed that 2 of the 14 females were pregnant in May 2007. Leptin values from these two pregnant females were subsequently excluded from the analysis because of higher values compared to those from non-pregnant females. Behavioral observations. The study subjects were part of a longitudinal study on the determinants of reproductive success. Behavioral observations on mating activity were conducted daily by a single observer (CG) over a period of 15 months from the start of the 2006 mating season (October) through December 2007. We determined if conception occurred during the ﬁrst mating season (2006–2007), and the day of conception was assessed using fecal hormone analysis (for more details, see Garcia et al., 2009b). We conﬁrmed pregnancy by palpation during the physical exam and by ultrasound scan during the second experiment in May 2007. We also classiﬁed the females as lactating or non-lactating by the presence or absence of milk and the duration of lactation in individual females was estimated by infant ages (range 5 66–158 days in October 2006). Of 14 females available in the group in October 2006 (9 lactating and 5 non-lactating), 2 females conceived during the 2006–2007 mating season and gave birth to a surviving offspring. Before the beginning of the next mating season (2007–2008), three females were excluded from the initial sample because of death or illness. Among the 11 females remaining in the social group (2 lactating and 9 non-lactating), 7 females conceived during the 2007–2008 mating season and the date of conception was calculated by subtracting 176 days of mean gestation length (Fujita et al., 2004) from the birth date reported in the long-term database of the Primate Research Institute. American Journal of Physical Anthropology 164 C. GARCIA ET AL. TABLE 1. Body composition estimated by deuterium dilution space at the beginning of the mating season (period 1) and during birth season (period 2) in female Japanese macaques Period 1 (N 5 14) Variables Total body water (kg) Water content (%) Total body fat (kg) Body fat (%) Fat-free mass (kg) Fat-free mass (%) 5.18 60.29 1.56 17.64 7.08 82.36 6 6 6 6 6 6 Period 2 (N 5 10) 0.44 3.03 0.55 4.14 0.60 4.14 5.34 63.92 1.09 12.67 7.29 87.33 6 6 6 6 6 6 0.57 2.92 0.42 3.99 0.78 3.99 We also monitored female dominance rank using ad libitum observations of the outcome of agonistic and approach–avoidance interactions, following methods used by Garcia et al. (2006). There was no rank reversal between subject individuals through the study period. Female rank was expressed as the proportion of females dominated providing a relative rank ranging between 0 (low-ranking) and 1 (high-ranking). Statistical analysis Data are presented as means and standard deviations. However, due to the small sample size (N 5 14), normal distribution of variables with equal variances cannot be always assumed. Where data were not normal, we used non-parametric Mann-Whitney U tests and Wilcoxon matched-pairs signed-ranks tests in comparisons between groups of females and Spearman’s rank correlation coefﬁcients for correlations. Throughout the analysis, the sample size of analyzed data varied to a small extent due to experimental limitations. When data were missing for any individual female, she would be excluded from relevant analyses, although she might contribute to other analyses where data were available. Thus sample sizes vary in the different statistical tests. Of 14 females available in the group at the beginning of the study, four females had to be excluded during the second deuterium experiment in May due to illness or experimental problems with deuterium injection. All statistical tests were conducted with SPSS 15.0 for Windows and used twotailed probabilities with a signiﬁcance level of 0.05. Ethical considerations All manipulations and treatments of the subjects followed Primate Research Institute animal handling guidelines to minimize pain and distress. The small sample used here was intentional as the use of the absolute minimum numbers of primates in any experimental procedure is the international norm. Furthermore, in the context of the broader study, we aimed to maintain normal social and sexual behavior, and to minimize any physiological stress associated with capture and re-capture. RESULTS Relations among measures of body composition Mean values for body composition are presented in Table 1. The Pearson’s correlations of the individual morphometric measures and leptin with FFM and TBF measured by isotopic method are presented in Table 2. We found a strong positive relationship between TBF at the beginning of the mating season and BM, and none of the other anthropometric measurements correlated more American Journal of Physical Anthropology TABLE 2. Univariate correlation matrix of body composition to morphometric measurements, nutritional indexes, and leptin levels at the beginning of the mating season (period 1) and during the birth season (period 2) in female Japanese macaques Fat-free mass (kg) Total body fat (kg) Variables Period 1 Period 2 Period 1 Period 2 Body mass Crown-rump length Arm circumference Calf circumference Abdominal skinfold Suprailiac skinfold Subscapular skinfold Total skinfold Quetelet Index Physical Index Leptin 0.962*** 0.573* 0.736** 0.644** 0.687** 0.531* 0.389 0.743** 0.724** 0.620* 0.206 0.946*** 0.542 0.832** 0.819** 0.403 0.336 0.166 0.375 0.764** 0.801** 0.510 0.954*** 0.438 0.822*** 0.700** 0.607* 0.419 0.363 0.645** 0.816*** 0.643** 0.400 0.802** 0.359 0.684* 0.684* 0.830** 0.663* 0.487 0.816** 0.719* 0.584 0.077 * P \ 0.05, **P \ 0.01, ***P \ 0.001 (italics 0.05\ P \ 0.1). highly with TBF than did BM. Concerning FFM at either the beginning of the mating season or the birth season, BM was also the single best predictor. Stepwise multiple regressions analyses were used to determine whether combinations of the morphometric measurements could provide greater accuracy in the prediction of TBF and FFM. Table 3 presents the amount of variance explained and the best regression formulae for predicting lean and fat mass in this sample. We found in particular that the ability to predict TBF during the birth season was increased by combining morphometric variables, with TBF being best predicted by BM and total skinfolds. The predicted vs. observed fat mass or fat-free mass values showed overall mean differences of less than 3%, which suggests that morphometric variables were appropriate for predicting fat mass and fat-free mass. Energetic condition dynamics Despite a lack of difference in the leptin levels between the beginning of the mating season and the birth season (Wilcoxon test: Z 5 20.51, NS), there were, nevertheless, body mass differences with female Japanese macaques losing on average 0.65 kg between the two seasons (beginning of the mating season: 9.03 6 1.03 kg, range 5 7.80–10.90 kg, N 5 10; birth season: 8.38 6 1.07 kg, range 5 7.30–10.10 kg, N 5 10; Z 5 22.81, P 5 0.005), i.e., about 7% of their body mass (range 5 0.98–19.78%). On the one hand, fat-free mass remained unchanged between the two seasons (7.31 6 0.54 kg vs. 7.29 6 0.78 kg; Z 5 20.18, NS, N 5 10). On the other hand, total body fat and percent body fat were different between the two seasons (beginning: TBF: 1.72 6 0.55 kg, range 5 1.11–2.72 kg, percent body fat: 18.70% 6 4.08%, range 5 13.55–24.94%, N 5 10; birth season: TBF: 1.09 6 0.42 kg, range 5 0.63–1.59 kg, percent body fat: 12.67% 6 3.99%, range 5 8.49–19.23%, N 5 10; Z 5 22.80, P 5 0.005), with females being signiﬁcantly leaner during the birth season. Because of the small sample size, the observed percent body fat differences between the two seasons were absent when considering non-lactating females only, but were still signiﬁcant for lactating females (Z 5 22.53, P 5 0.012), with the mean differences reported in non-lactating females being comparable to those in lactating ones (6.87% 6 3.10%, N 5 2 vs. 5.81% 6 2.80%, N 5 8). On 165 ENERGETICS AND SEASONALITY IN FEMALE MACAQUES TABLE 3. Regression formulae for total body fat (TBF) and fat-free mass (FFM) in female Japanese macaques a TBF TBFb FFMa FFMb 0.476 3 (BM) 2 2.554 0.193 3 (BM) 1 0.135 3 (TS) 2 1.717 0.524 3 (BM) 1 2.554 0.685 3 (BM) 1 1.551 R R2 F P SEE 0.954 0.907 0.962 0.946 0.911 0.823 0.925 0.896 122.64 16.28 148.38 68.6 \0.001 0.002 \0.001 \0.001 0.172 0.201 0.172 0.267 BM, body mass; TS, total skinfold; SEE, standard error of estimate. a Beginning of the mating season. b Birth season. TABLE 4. Linear, quadratic, and cubic curve ﬁt statistics for fat mass and fat-free mass at the beginning of the mating season with age Model Fat mass Fat-free mass r2 SEE Sig. Coefﬁcients Linear 0.362 0.460 0.023 b 5 20.053 Quadratic 0.372 0.477 0.077 b 5 20.107 c 5 0.002 Cubic 0.466 0.461 0.087 b 5 0.477 c 5 20.043 d 5 0.001 Linear 0.427 0.476 0.011 b 5 20.063 Quadratic 0.452 0.486 0.036 b 5 0.028 c 5 20.003 Cubic 0.649 0.408 0.012 b 5 0.949 c 5 20.074 d 5 0.002 Sig. 0.023 NS NS NS NS NS 0.011 NS NS 0.041 0.035 0.040 SEE 5 standard error of estimate. Fig. 1. Linear regression of total body fat at the beginning of the mating season against age in 14 female Japanese macaques. average, females lost 32.53% (612.93) of their body fat between the two seasons (range 5 10.35–53.97%), and there was no difference between lactating and nonlactating females (Mann-Whitney test: U 5 5.00, NS, N 5 10). Among lactating females, there was a trend for an effect of lactation stage on body fat loss between the two seasons, with females in mid-lactation (i.e., with infants aged between 3 and 5 months) at the beginning of the mating season losing a larger proportion of fat than females in late lactation (with infants above the age of 5 months) at the beginning of the mating season (35.70% 6 12.67% vs. 14.13% 6 5.34%, U 5 0.00, P 5 0.064). To examine inter-individual variation in body condition with age, we ﬁtted curves for BM, FFM, and TBF against age in years for all females using a curve-ﬁt process. We used polynomials least-squares ﬁtting and compared linear, quadratic, and cubic regressions. There was a negative linear relationship between BM at the beginning of the mating season and age (r 5 20.656, P 5 0.011, N 5 14). A linear negative association was also observed between age and TBF at the beginning of the mating season (r 5 20.602, P 5 0.023, Fig. 1 and Table 4) and we found a third-order polynomial relationship between FFM measured at the beginning of the mating season and age (r2 5 0.649, P 5 0.012, Fig. 2 and Table 4). We reported a trend for a relationship between age and leptin levels at the beginning of the mating season (see Garcia et al., 2010). There was no signiﬁcant association between age and any of the body composition measurements (BM, FFM, and TBF) or lep- Fig. 2. Third-order polynomial regression of fat-free mass at the beginning of the mating season against age in 14 female Japanese macaques. tin levels during the birth season, i.e., when females were lighter and leaner. Nevertheless, we found a cubic relationship between age and %BF loss between the two seasons (r2 5 0.755, P 5 0.029). We found an inverse correlation between rank and %BF at the beginning of the mating season (rs 5 20.534, P 5 0.049, N 5 14), with a tendency for a relationship between rank and BM (rs 5 20.504, P 5 0.066, N 5 14). There was no relationship between rank and leptin levels and there was no correlation between delta mass (i.e., the difference between BM at the beginning of the mating season and BM during the birth season) or delta fat mass and rank (rs 5 20.455 and rs 5 20.248 American Journal of Physical Anthropology 166 C. GARCIA ET AL. DISCUSSION Body composition in female Japanese macaques and comparison with other primates Fig. 3. Quetelet index during the birth season 2007 for females who conceived (N 5 7) during the following mating season (2007–2008), compared to those that did not conceive (N 5 4). Plot shows median (bar), interquartile range (box), and highest and lowest values (whiskers). respectively, NS). There was a slight trend for an effect of rank on relative mass loss (100 3 (BM1 - BM2)/BM1) between the two seasons with low-ranking females tending to lose proportionally more mass than high-ranking ones (rs 5 20.503, P 5 0.09, N 5 12). Nutritional status and reproduction Despite a difference in subscapular skinfolds between lactating (4.83 6 0.61 mm) and non-lactating females (4.00 6 0.61 mm) at the beginning of the mating season (U 5 7.00, P 5 0.035, N 5 14), there was, nevertheless, no effect of lactation status on %BF at either the beginning of the mating season or during the birth season (U 5 13.00, N 5 14, NS and U 5 8.00, N 5 10, NS). Neither baby age nor baby sex was associated with TBF or FFM. Of 14 females available in the group in 2006, 3 females were excluded as dead or ill during the 2007– 2008 mating season. Among the 11 females remaining in the social group at the beginning of the 2007–2008 mating season, we found that females who conceived during this mating season (N 5 7) had a larger Quetelet Index (Fig. 3; U 5 1.00, P 5 0.014) and higher TBF during the previous birth season than did females who did not conceive (U 5 0.00, P 5 0.040). We also found that females with higher TBF at the beginning of the previous mating season (2006–2007) were more likely to conceive during the next mating season (P 5 0.072, N 5 11). Predictors of conception status for the 2007–2008 mating season were also analyzed by entering morphometric measures into a logistic regression along with fertility in the previous year as statistical control. When birth in 2007 and Quetelet Index (during birth season 2007) were entered in the model together (v2 5 8.36, P 5 0.004), Quetelet Index was still signiﬁcant (P 5 0.022) but birth status in the previous year was not a signiﬁcant predictor. Moreover, percent body fat in May 2007 was not a good predictor of birth date within the following birth season (rs 5 0.071, NS). American Journal of Physical Anthropology The purpose of our study was not only to examine the relations among reproduction and energetic status in a sample of captive female Japanese macaques but also to provide a comparative study of the relations among various body composition techniques. The estimation of nutritional status in primates has generally been inferred from morphometrics (Bercovitch, 1987; Campbell and Gerald, 2004) and speciﬁcally from measurements of body mass. However, body mass may not necessarily be the best estimator of body fat, since age, sex, reproductive state, muscle mass, and bone density can all affect the relationship between mass and fat levels and thereby reduce the accuracy of body fat estimates. Various other methods are also used to assess the nutritional status of captive and wild animals such as carcass analysis (Lewis et al., 1986; Rutenberg et al., 1987; Zihlman and McFarland, 2000), dual energy X-ray absorptiometry (DEXA) (Hamada et al., 2003; Takahashi et al., 2006), total body electroconductivity (TOBEC) (Power et al., 2001), blood sampling to assess insulin, leptin, or cholesterol levels (Chen et al., 2002; Kemnitz et al., 2002; Muehlenbein et al., 2005; Takahashi et al., 2006; Whitten and Turner, 2008; Garcia et al., 2010), and urine sampling to measure ketones or C-peptide (Knott, 1998; Sherry and Ellison, 2007; Deschner et al., 2008). Determination of nutritional status and energy balance can also be monitored by using the labeled-water technique (Altmann et al., 1993; Garcia et al., 2004; Blanc et al., 2005; Schmid and Speakman, 2009; Simmen et al., 2010). The main advantage of this isotope-based method over alternative techniques is that it permits the study of subjects living unrestricted in their natural environment. However, a reliance on blood samples as the source of body water in which to measure the concentrations of the isotopes used in the technique, 2H and 18 O, has restricted application of this method to captive animals or animals easy to catch. Our comparative study of nutritional status in Japanese macaques involved use of three techniques: anthropometry, blood sampling to assess leptin levels, and labeled-water dilution. This is the ﬁrst study presenting body composition data using the stable isotope method in the Japanese macaque. Leptin correlated very poorly with total body fat measured with isotopic method but anthropometric measurements, such as body mass and skinfold thickness, could provide valid estimates of total body fat, as suggested in previous studies using DEXA (Colman et al., 1999; Hamada et al., 2003; Takahashi et al., 2006). Given the results obtained with the deuterium technique, the anthropometric measurements, even though less precise, remain a valid method for estimating body condition because it provides an easy, inexpensive, and non-invasive way of doing serial evaluations of body composition changes. These female Japanese macaques varied in estimated percent body fat from 8.5 to 24.9% (18% on average at the beginning of the mating season and about 13% during the birth season). If we consider our ﬁndings in light of the available literature for cercopithecoid primates and with respect to similarities and differences with humans, percent body fat of our captive females was well within the range found in several groups of primates previously studied (18.3% for multiparous female ENERGETICS AND SEASONALITY IN FEMALE MACAQUES rhesus macaques (Walker et al., 1984); 1.9% for wild-feeding baboons and 23.2% for garbage-feeding baboons (Altmann et al., 1993); 16.9% for captive baboons (Rutenberg et al., 1987); 20% in captive baboons (Comuzzie et al., 2003)), and none of our animals were obese (obesity deﬁned as [27% body fat: Hamada et al., 2003). Our results were also in the range, though lower than those observed in humans (Heymsﬁeld et al., 2005: mean percent body fat of 27.6% in a Reference Caucasian Woman). It seems that non-human primates can become as fat as humans under environmental circumstances of low physical activity and abundant food supply, which are associated with provisioning and captivity and are similar to those of afﬂuent societies (Altmann et al., 1993; Dufour and Sauther, 2002). While sparse, data from non-human primates seem to suggest that fat deposition in humans is only slightly greater than in non-human primates (Dufour and Sauther, 2002) and this supports the view that an abundance of body fat is an evolutionarily derived condition for modern humans and that lower levels of body fat may have been the norm during most of human evolution. However, it remains to be demonstrated whether the characteristic fat deposition in humans is a unique trait, shared with other primate species but manifested to a greater extent, i.e., a difference of evolutionary relevance between human and non-human primates, or whether it is a more recent result of certain cultural changes such as food storage and agriculture. Moreover, even if data on percent body fat in captive female primates overlap considerably those reported in human females, the anatomical distribution of body fat in different regions or compartments of the body (i.e., subcutaneous adipose tissue vs. abdominal visceral adipose tissue) may differ between human and non-human primates and further studies on that topic may help determine if the relatively large fat reserves accumulated by humans can be considered a distinctive feature of the species. Rank and age effects on body composition Given that dominance rank is often presumed to confer priority of access to resources (Whitten, 1983; Altmann, 1998; Gerald, 2002; Koenig, 2002), we hypothesized that dominant females would exhibit greater fat reserves that subordinate ones. Contrary to this prediction, we found that there was an inverse relationship between social rank and body fatness, but that low-ranking females tended to lose proportionally more mass between the two seasons. Energy cost of lactation and infant growth rates may underlie at least some of the variation in body condition with rank. The conversion of maternal nutrients or body reserves to milk may differ between dominant and subordinate females. There could be differential postnatal maternal expenditure in terms of milk input or gross energy transfer, or even different extraction and conversion of maternal resources by infants of high and lowranking females. Then, there could be complex deterministic processes involved in the relationship between rank and body condition. Further investigation of the role of dominance rank and social stress is therefore warranted and a close hormonal monitoring of social stress is currently underway to assess exposure to chronic stress and its relationship to body condition. According to previous studies (Glassman and Coelho, 1987; Rutenberg et al., 1987; Campbell and Gerald, 2004), body mass and body fat declined as a function of 167 age. However, our investigation was cross-sectional, and our sample did not contain enough older individuals for complete analysis of this relation. Therefore, these results should be viewed with these methodological limitations in mind and further studies are needed to determine if our current ﬁndings can be generalized to other populations of Japanese macaques, especially in the wild. Whether such relationships between age and body condition translate into differences in reproductive performance between young and old females, and whether older females do not have enough fat reserves to cover the energetic costs of reproduction, still warrant further investigation. Seasonality in nutritional status We have reported a large seasonal ﬂuctuation in body mass and fat levels. These results are in agreement with previous studies in Verreaux’s sifaka (Richard et al., 2000), brown mouse lemurs and ring-tailed lemurs (Randrianambinina et al., 2003; Simmen et al., 2010), showing that body mass ﬂuctuated with the seasons and that individuals needed to attain a sufﬁcient physical condition prior to the long dry season. According to our hypothesis, there was an impact of seasonal breeding on body condition with females gaining weight and accumulating energy reserves in fall to prepare for mating activity and the next conception, and/or to survive under severe conditions in winter with high thermoregulatory costs (Nakagawa, 1997; Muroyama et al., 2006). As suggested by Hamada et al. (2003), it seems that body fat accumulation and loss depend on a physiological mechanism based on a ﬁxed circannual cyclicity. Japanese macaques may have been selected to respond to body composition changes over the course of the mating and breeding season. These results conﬁrmed that even in captive individuals with constant food, nutritional status was markedly inﬂuenced by season. Seasonal changes in nutritional status thus may not necessarily be related to seasonal ﬂuctuations in energy and protein intake from natural foods but may also be inﬂuenced by differences in energy expenditure and energy balance caused by seasonal changes in resource allocation strategies, activity budgets, and thermoregulation (Nagy and Milton, 1979; Agetsuma, 2000). There is an increase in energy expenditure for thermoregulation in winter, with energy expenditure of Japanese macaques at 58C being 2.5 times more important than that at 298C (Nakayama et al., 1971). If this increase is not counterbalanced by an increase in energy intakes, it may lead to a temporary negative energy balance associated with a depleted condition and potential consequences for reproductive success and survival. Moreover, Bercovitch (1997) has shown that activity budgets differed between the seasons in captive male rhesus macaques, with feeding time plunging from 17 to 8% of the day between the non-mating and mating season. These changes occurred despite the availability of a constant quantity of monkey chow throughout the year. Therefore, feeding strategies may have direct repercussions on nutritional status, with time and energy devoted to mating probably corresponding to reduced time spent feeding. Most of the decrease in mass between the two seasons was due to a decrease in fat reserves, suggesting that females spared fat-free mass, i.e., protein mass, and relied on fatty acids for energy over the course of the American Journal of Physical Anthropology 168 C. GARCIA ET AL. mating season. Endogenous lipid reserve constituted the primary source of energy used and the relatively high fat mass level in fall seemed to be sufﬁcient to cover energy costs. Therefore fat-free mass was not used to meet energy needs and maintain a stable energy balance, indicating that there was no protein oxidation in lean females. for their technical assistance in handling and nursing the animals during the experimental period. They further thank S. Hayakawa, S. Higaki, T. Kunieda, C.A.D. Nahallage, and K. Takumi for assistance in anthropometric measurements and blood sampling. They thank Y. Hamada for allowing using his anthropometric equipment. The comments of two anonymous reviewers and editors also greatly improved an earlier draft of this article. Energetics and reproductive effort Reproductive status of a female is another factor potentially inﬂuencing body condition, as the energy costs of carrying and suckling an infant add to the costs of maintenance. In this study, lactating females had larger subscapular skinfolds than did non-lactating ones suggesting that fatter, better condition females are those who could afford the demands of lactation and reproduce more rapidly (Johnson and Kapsalis, 1995; Campbell and Gerald, 2004). However, we were unable to document any differences in body fat between lactating and non-lactating females. We cannot completely rule out the possibility that the small sample size and the corollary lack of power may have obscured the relationship between body fatness and lactation status. However, females in mid-lactation tended to lose a larger proportion of fat between the two seasons than females in late lactation suggesting that this period of peak lactation and maximum infant growth rate represents the highest energetic costs to the mother (Oftedal, 1984; Lee, 1987). The energy invested in lactation determines infant growth rates and may determine in part the delay between reproductive events (Garcia et al., 2009a), with a trade-off between investment in current and future reproduction. Our results suggested that not only did the reproductive status of the female inﬂuence her body condition but also that condition played a role in reproductive success and fecundity. Physiological modulation of reproductive outcome in females starts with mechanisms that adjust the probability of conception in response to maternal energy availability. We found that differences in conception rates were associated with differences in body fat and body condition, suggesting that females with a higher energy status were those who could afford to reproduce more rapidly. These results are in agreement with previous studies showing that in sifakas, female body mass at the outset of the mating season strongly inﬂuenced the probability to give birth to an infant that survived the dry season and weaning (Richard et al., 2000; Lewis and Kappeler, 2005). This suggests that female condition inﬂuences competence and quality of ovarian cycles, with individual variation in condition and energy balance appearing to play a signiﬁcant role in reproductive potential (Garcia et al., 2006). Although energy is not the only limiting resource to be considered in optimizing reproductive effort, it is certainly the principal one for primates as for other organisms (Ellison, 2003). However, due to the small sample size, we were unable to document any effect of body fat on infant birth dates the following year, and thus infant survival and further studies are therefore required to clarify this issue. ACKNOWLEDGMENTS The authors thank the staff of the Center for Human Evolution Modeling Research, especially the veterinarians, American Journal of Physical Anthropology LITERATURE CITED Agetsuma N. 2000. Inﬂuence of temperature on energy intake and food selection by macaques. Int J Primatol 21:103–111. Altmann J, Alberts SC. 2005. Growth rates in a wild primate population: ecological inﬂuences and maternal effects. Behav Ecol Sociobiol 57:490–501. Altmann J, Schoeller D, Altmann SA, Muruthi P, Sapolsky RM. 1993. Body size and fatness of free-living baboons reﬂect food availability and activity levels. Am J Primatol 30:149–161. Altmann SA. 1998. Foraging for survival: yearling baboons in Africa. Chicago: University of Chicago Press. Banks WA, Phillips-Conroy JE, Jolly CJ, Morley JE. 2001. Serum leptin levels in wild and captive populations of baboons (Papio): implications for the ancestral role of leptin. J Clin Endocrinol Metab 86:4315–4320. Bercovitch FB. 1987. Female weight and reproductive condition in a population of olive baboons (Papio anubis). Am J Primatol 12:189–195. Bercovitch FB. 1997. Reproductive strategies of rhesus macaques. Primates 38:247–263. Blanc S, Colman R, Kemnitz J, Weindruch R, Baum S, Ramsey J, Schoeller D. 2005. Assessment of nutritional status in rhesus monkeys: comparison of dual-energy X-ray absorptiometry and stable isotope dilution. J Med Primatol 34:130–138. Bowman JE, Lee PC. 1995. Growth and threshold weaning weights among captive rhesus macaques. Am J Phys Anthropol 96:159–175. Campbell BC, Gerald MS. 2004. Body composition, age and fertility among free-ranging female rhesus macaques (Macaca mulatta). J Med Primatol 33:70–77. Chen Y, Ono F, Yoshida T, Yoshikawa Y. 2002. Relationship between body weight and hematological and serum biochemical parameters in female cynomolgus monkeys (Macaca fascicularis). Exp Anim 51:125–131. Clutton-Brock TH, Parker GA. 1995. Sexual coercion in animal societies. Anim Behav 49:1345–1365. Colman RJ, Hudson JC, Barden HS, Kemnitz JW. 1999. A comparison of dual-energy X-ray absorptiometry and somatometrics for determining body fat in rhesus macaques. Obes Res 7:90–96. Comuzzie AG, Cole SA, Martin L, Carey KD, Mahaney MC, Blangero J, VandeBerg JL. 2003. The baboon as a nonhuman primate model for the study of the genetics of obesity. Obes Res 11:75–80. De Souza MJ, Lee DK, VanHeest JL, Scheid JL, West SL, Williams NI. 2007. Severity of energy-related menstrual disturbances increases in proportion to indices of energy conservation in exercising women. Fertil Steril 88:971–975. De Wit JC, van der Straaten CM, Mook WG. 1980. Determination of the absolute isotopic ratio of V-SMOW and SLAP. Geostand Newslett 4:33–36. Deschner T, Kratzsch J, Hohmann G. 2008. Urinary C-peptide as a method for monitoring body mass changes in captive bonobos (Pan paniscus). Horm Behav 54:620–626. Dewey KG. 1998. Effects of maternal caloric restriction and exercise during lactation. J Nutr 128:386S–389S. Dufour DL, Sauther ML. 2002. Comparative and evolutionary dimensions of the energetics of human pregnancy and lactation. Am J Hum Biol 14:584–602. Ellison PT. 2003. Energetics and reproductive effort. Am J Hum Biol 15:342–351. ENERGETICS AND SEASONALITY IN FEMALE MACAQUES Fujita S, Sugiura H, Mitsunaga F, Shimizu K. 2004. Hormone proﬁles and reproductive characteristics in wild female Japanese macaques (Macaca fuscata). Am J Primatol 64:367– 375. Garcia C, Huffman M, Shimizu K. 2010. Seasonal and reproductive variation in body condition in captive female Japanese macaques (Macaca fuscata). Am J Primatol 72:277–286. Garcia C, Lee PC, Rosetta L. 2006. Dominance and reproductive rates in captive female olive baboons, Papio anubis. Am J Phys Anthropol 131:64–72. Garcia C, Lee PC, Rosetta L. 2009a. Growth in colony living anubis baboon infants and its relationship with maternal activity budgets and reproductive status. Am J Phys Anthropol 138:123–135. Garcia C, Rosetta L, Ancel A, Lee PC, Caloin M. 2004. Kinetics of stable isotope and body composition in olive baboons (Papio anubis) estimated by deuterium dilution space: a pilot study. J Med Primatol 33:146–151. Garcia C, Shimizu K, Huffman M. 2009b. Relationship between sexual interactions and the timing of the fertile phase in captive female Japanese macaques (Macaca fuscata). Am J Primatol 71:868–879. Gerald MS. 2002. Social status correlates inversely with feedingpriority amongst pairs of unfamiliar adult male vervet monkeys (Cercopithecus aethiops sabaeus). Primates 43:127–132. Giroud S, Perret M, Stein P, Goudable J, Aujard F, Gilbert C, Robin JP, Le Maho Y, Zahariev A, Blanc S, Momken I. 2010. The grey mouse lemur uses season-dependent fat or protein sparing strategies to face chronic food restriction. PloS ONE 5:e8823. Glassman DM, Coelho AM. 1987. Principal components analysis of physical growth in savannah baboons. Am J Phys Anthropol 72:59–66. Hamada Y, Hayakawa S, Suzuki J, Watanabe K, Ohkura S. 2003. Seasonal variation in the body fat of Japanese macaques Macaca fuscata. Mamm Stud 28:79–88. Hamada Y, Watanabe T, Iwamoto M. 1996. Morphological variation among local populations of the Japanese macaque (Macaca fuscata). In: Shotake T, Wada K, editors. Variations in the Asian macaques. Tokyo: Tokai University Press. p 97– 115. Heymsﬁeld SB, Lohman TG, Wang Z, Going SB. 2005. Human body composition. Champaign, IL: Human Kinetics. Huffman MA. 1991. Mate selection and partner preferences in female Japanese macaques. In: Fedigan LM, Asquith PJ, editors. The monkeys of Arashiyama: thirty-ﬁve years of research in Japan and the West. Albany, NY: State University of New York Press. p 101–122. Huffman MA. 1992. Inﬂuences of female partner preference on potential reproductive outcome in Japanese macaques. Folia Primatol 59:77–88. Inoue E, Takenaka O. 2008. The effect of male tenure and female mate choice on paternity in free-ranging Japanese macaques. Am J Primatol 70:62–68. Johnson RL, Kapsalis E. 1995. Determinants of postnatal weight in infant rhesus monkeys: implications for the study of inter-individual differences in neonatal growth. Am J Phys Anthropol 98:343–353. Kawai M. 1969. Ecology of Japanese Monkeys. Tokyo: KawadeShobo-Shinsha. Kemnitz JW, Sapolsky RM, Altmann J, Muruthi P, Mott GE, Stefanick ML. 2002. Effects of food availability on serum insulin and lipid concentrations in free-ranging baboons. Am J Primatol 57:13–19. Key C, Ross C. 1999. Sex differences in energy expenditure in non-human primates. Proc R Soc Lond B 266:2479–2485. Kodama AM. 1970. Total body water of the pigtailed macaque, Macaca nemestrina. J Appl Physiol 29:260–262. Knott CD. 1998. Changes in orangutan caloric intake, energy balance, and ketones in response to ﬂuctuating fruit availability. Int J Primatol 19:1061–1079. Koenig A. 2002. Competition for resources and its behavioral consequences among female primates. Int J Primatol 23:759– 783. 169 Kurita H, Shimomura T, Fujita T. 2002. Temporal variation in Japanese macaque bodily mass. Int J Primatol 23:411–428. Lee PC. 1987. Nutrition, fertility and maternal investment in primates. J Zool Lond 213:409–422. Lee PC. 1996. The meanings of weaning: growth, lactation, and life history. Evol Anthropol 5:87–98. Lewis DS, Bertrand HA, Masoro EJ. 1986. Total body water-tolean body mass ratio in baboons (Papio sp.) of varying adiposity. J Appl Physiol 61:1234–1236. Lewis RJ, Kappeler PM. 2005. Seasonality, body condition, and timing of reproduction in Propithecus verreauxi verreauxi in the Kirindy forest. Am J Primatol 67:347–364. Lifson N, Gordon GB, McClintock R. 1955. Measurement of total carbon dioxide production by means of D2O18. J Appl Physiol 7:704–710. Loucks AB, Thuma JR. 2003. Luteinizing hormone pulsatility is disrupted at a threshold of energy availability in regularly menstruating women. J Clin Endocrinol Metab 88:297–311. Mori A. 1979. Analysis of population changes by measurement of body weight in the Koshima Troop of Japanese monkeys. Primates 20:371–391. Muehlenbein MP, Campbell BC, Richards RJ, Watss DP, Svec F, Falkenstein KP, Murchison MA, Myers L. 2005. Leptin, adiposity, and testosterone in captive male macaques. Am J Phys Anthropol 127:335–341. Muller MN, Kahlenberg SM, Emery Thompson M, Wrangham R. 2007. Male coercion and the costs of promiscuous mating for female chimpanzees. Proc R Soc B 274:1009–1014. Muroyama Y, Kanamori H, Kitahara E. 2006. Seasonal variation and sex differences in the nutritional status in two local populations of wild Japanese macaques. Primates 47:355–364. Nagy KA. 1983. Doubly-labelled water: a guide to its use. Los Angeles: UCLA Publications. Nagy KA, Costa DP. 1980. Water ﬂux in animals: analysis of potential errors in the tritiated water method. Am J Physiol 238:R454–R465. Nagy KA, Milton K. 1979. Energy metabolism and food consumption by wild howler monkeys (Alouatta palliata). Ecology 60:475–480. Nakagawa N. 1997. Determinants of the dramatic seasonal changes in the intake of energy and protein by Japanese monkeys in a cool temperate forest. Am J Primatol 41:268– 288. Nakayama T, Hori T, Nagasaka T, Tokura H, Tadaki E. 1971. Thermal and metabolic responses in the Japanese monkey at temperatures of 5–388C. J Appl Physiol 31:332–337. Norgan NE. 1987. Human body composition and fat distribution. Euro/Nut report 8. The Hague: CIP-gegevens Koninklijke Bibliotheek. Oftedal OT. 1984. Milk composition, milk yield and energy output at peak lactation: a comparative review. Symp Zool Soc Lond 51:33–85. Pace N, Rathburn EN. 1945. Studies on body composition III: The body water and chemically combined nitrogen content in relation to fat content. J Biol Chem 158:685–691. Power RA, Power ML, Layne DG, Jaquish CE, Oftedal OT, Tardif SD. 2001. Relations among measures of body composition, age, and sex in the common marmoset monkey (Callithrix jacchus). Comp Med 51:218–223. Pusey AE, Oehlert GW, Williams JM, Goodall J. 2005. Inﬂuence of ecological and social factors on body mass of wild chimpanzees. Int J Primatol 26:3–31. Randrianambinina B, Rakotondravony D, Radespiel U, Zimmermann E. 2003. Seasonal changes in general activity, body mass and reproduction of two small nocturnal primates: a comparison of the golden brown mouse lemur (Microcebus ravelobensis) in northwestern Madagascar and the brown mouse lemur (Microcebus rufus) in eastern Madagascar. Primates 44:321–331. Richard AF, Dewar RE, Schwartz M, Ratsirarson J. 2000. Mass change, environmental variability and female fertility in wild Propithecus verreauxi. J Hum Evol 39:381–391. Rousseau K, Atcha Z, Loudon SI. 2003. Leptin and seasonal mammals. J Neuroendocrinol 15:409–414. American Journal of Physical Anthropology 170 C. GARCIA ET AL. Rutenberg GW, Coelho AM, Lewis DS, Dee Carey K, McGill HC. 1987. Body composition in baboons: evaluating a morphometric method. Am J Primatol 12:275–285. Schmid J, Speakman JR. 2009. Torpor and energetic consequences in free-ranging grey mouse lemurs (Microcebus murinus): a comparison of dry and wet forests. Naturwissenschaften 96:609–620. Schneider JE. 2004. Energy balance and reproduction. Physiol Behav 81:289–317. Sheng HP, Huggins RA. 1979. A review of body composition studies with emphasis on total body water and fat. Am J Clin Nutr 32:630–647. Sherry DS, Ellison PT. 2007. Potential applications of urinary C-peptide of insulin for comparative energetics research. Am J Phys Anthropol 133:771–778. Simmen B, Bayart F, Rasamimanana H, Zahariev A, Blanc S, Pasquet P. 2010. Total energy expenditure and body composition in two free-living sympatric lemurs. PLoS One 5:e9860. Smuts B, Nicolson N. 1989. Reproduction in wild female olive baboons. Am J Primatol 19:229–246. Smuts B, Smuts RW. 1993. Male aggression and sexual coercion of females in nonhuman primates and other mammals: evidence and theoretical implications. Adv Stud Behav 22:1–63. Soltis J, Mitsunaga F, Shimizu K, Yanagihara Y, Nozaki M. 1997a. Sexual selection in Japanese macaques I: female mate choice or male sexual coercion? Anim Behav 54:725–736. Soltis J, Mitsunaga F, Shimizu K, Nozaki M, Yanagihara Y, Domingo-Roura X, Takenaka O. 1997b. Sexual selection in Japanese macaques II: female mate choice and male-male competition. Anim Behav 54:737–746. Soltis J, Thomsen R, Osamu T. 2001. The interaction of male and female reproductive strategies and paternity in wild Japanese macaques, Macaca fuscata. Anim Behav 62:485– 494. American Journal of Physical Anthropology Speakman JR. 1997. Doubly labelled water: theory and practice. London: Chapman and Hall. Speakman JR. 1998. The history and theory of the doubly labelled water technique. Am J Clin Nutr 68:932S–938S. Speakman JR, Król E. 2005. Comparison of different approaches for the calculation of energy expenditure using doubly labeled water in a small animal. Physiol Biochem Zool 78:650–667. Speakman JR, Nair KS, Goran MI. 1993. Revised equations for calculating CO2 production from doubly labelled water in humans. Am J Physiol 264:E912–E917. Takahashi T, Higashino A, Takagi K, Kamanaka Y, Abe M, Morimoto M, Kang KH, Goto S, Suzuki J, Hamada Y, Kageyama T. 2006. Characterization of obesity in Japanese monkeys (Macaca fuscata) in a pedigreed colony. J Med Primatol 35:30–37. van Schaik CP, Pradhan GR, van Noordwijk MA. 2004. Mating conﬂict in primates: infanticide, sexual harassment and female sexuality. In: Kappeler P, van Schaik CP, editors. Sexual selection in primates: new and comparative perspectives. Cambridge, UK: Cambridge University Press. p 131– 150. Walker ML, Schwartz SM, Wilson ME, Musey PI. 1984. Estimation of body fat in female rhesus monkeys. Am J Phys Anthropol 63:323–329. Whitten PL. 1983. Diet and dominance among female vervet monkeys (Cercopithecus aethiops). Am J Primatol 5:139–159. Whitten PL, Turner TR. 2008. Ecological and reproductive variance in serum leptin in wild vervet monkeys. Am J Phys Anthropol 137:441–448. Williams NI, Berga SL, Cameron JL. 2007. Synergism between psychosocial and metabolic stressors: impact on reproductive function in cynomolgus monkeys. Am J Physiol Endocrinol Metab 293:E270–E276. Zihlman AL, McFarland RK. 2000. Body mass in lowland gorillas: a quantitative analysis. Am J Phys Anthropol 113:61–78.