Seasonal variation and sex differences in the nutritional status in two local populations of wild Japanese macaques

Abstract

Seasonal variations and sex differences in the nutritional status in two local populations of wild Japanese macaques (Macaca fuscata fuscata) were examined. It was hypothesized that the ecological condition and/or reproductive strategies of each sex determine the nutritional condition and its seasonal fluctuation in each sex. Morphometric measures such as body mass, thoracic and femoris circumferences, skinfold thickness in four places (triceps, biceps femoris, subscapular, and abdomen), and wet mass of mesenteric and omental fat were used for comparisons between sexes, seasons, and populations. Animals of the Shimane population were larger than those of the Boso population in most morphometric measures, abdominal skinfold, and mesenteric and omental fat mass, suggesting environmental and/or genetic differences in the two populations. Females of both populations had larger skinfolds and mesenteric and omental fat mass than males, indicating that females had more fat than males. Females showed seasonality in most measures, having two peaks of body mass, thoracic and femoris circumferences, abdominal skinfold, and mesenteric and omental fat masses in early spring and late fall. In contrast, males exhibited no clear seasonal variations for most measurements, except for biceps femoris and subscapular skinfolds, which showed peaks in summer. Most morphometric measurements significantly correlated to each other, particularly in females, but most skinfolds had no correlation with other measurements. These findings suggest that sexual dimorphism in body composition and its fluctuation may be affected by the different reproductive strategies of males and females.

Linking feeding ecology and population abundance: a review of food resource limitation on primates

“…Gibbon density was not correlated with the overall food tree density, suggesting abundance of fallback food is more important than the total annual food availability (Marshall and Leighton 2006). Concerning the second condition, fat accumulation has been reported in temperate macaques, orangutans, many lemurs, and humans (Wada 1975;Zhao 1994;Knott 1998;Atsalis 1999;Muroyama et al 2006), but it has not been examined carefully for most species. As for the third condition, leaves are often considered a superabundant fallback food; however, the quality of leaves is quite variable and primates are very selective with respect to leaf quality (Milton 1979;Ganzhorn 1992;Hanya and Bernard 2012).…”

Dietary adaptations of temperate primates: comparisons of Japanese and Barbary macaques

“…Since the fruiting phenology and climate are highly annually periodic in temperate forests, it is possible for animals to predict when to start fat deposition and how long a food shortage will last. In fact, patterns of seasonal change in deposited fat are quite similar among different populations of Japanese macaques, having peaks in early spring and late autumn, corresponding to the seasonal change in food availability (Muroyama et al 2006). Therefore, dependence on deposited fat is a safe strategy in temperate regions, and fat deposition is in fact prevalent in temperate and arctic endotherms (Pond 1978).…”

Energetic consequences of seasonal breeding in female Japanese macaques (Macaca fuscata)

“…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.…”