Food scarcity is a major challenge for primates living in temperate forests, where food availability varies markedly among seasons. In Japanese macaques, which are exclusively distributed in temperate zones, the fat accumulation ability has been highlighted as an adaptation for survival during the lean season and for reproductive success. However, the knowledge of energetic strategies of Japanese macaques has been mainly derived from data on cool-temperate forests, where fallback foods comprise winter buds and bark. Data on Japanese macaques in warm-temperate forests where fallback foods comprise mature leaves are still lacking. We aimed to identify seasonal variations in energy balance and the relative importance of ingestion rates (dry matter intake per feeding time), energy content of the food, and feeding time in energy intake of Japanese macaques in the coastal forest of Yakushima. We estimated energy balance of 6–12 adult females from October 2012 to October 2013. We estimated energy intake based on the data on feeding behavior and energy content of the diet and calculated energy expenditure based on the previously established relationship between body mass and total energy expenditure. We also quantified urinary C-peptide, which is a non-invasive biomarker of energetic conditions. We demonstrated that energy balance was more positive in the fruit/seed-feeding period than in the mature-leaf-feeding and fruit/fungi-feeding periods and that ingestion rates were the most important component of energy intake. The present study suggests that the fat accumulation ability is an essential adaptation in Japanese macaques even in warm-temperate forests.

中文翻译：

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暖温带森林中野生日本猕猴（Macaca fucata yakui）能量平衡的季节性变化：对屋久岛沿海森林的初步评估

食物短缺是生活在温带森林中的灵长类动物面临的主要挑战，那里的食物供应因季节而异。在仅分布于温带地区的日本猕猴中，脂肪积累能力已被强调为在淡季生存和繁殖成功的适应性。然而，日本猕猴能量策略的知识主要来自冷温带森林的数据，在那里后备食物包括冬芽和树皮。仍然缺乏关于暖温带森林中的日本猕猴的数据，这些森林的后备食物包括成熟的叶子。我们旨在确定能量平衡的季节性变化以及摄入率（每次喂食时间的干物质摄入量）、食物的能量含量、屋久岛沿岸森林日本猕猴能量摄取时间及摄食时间. 我们估计了 2012 年 10 月至 2013 年 10 月 6-12 名成年女性的能量平衡。我们根据饮食行为和能量含量的数据估计了能量摄入，并根据先前建立的体重和总能量之间的关系计算了能量消耗支出。我们还量化了尿 C 肽，它是能量状况的非侵入性生物标志物。我们证明，果实/种子喂养期的能量平衡比成熟叶喂养期和果实/真菌喂养期更为积极，并且摄食率是能量摄入的最重要组成部分。