Challenge of the night-time observation on diurnal primates: Investigation on the first observed rumination behaviour and anti-predator strategy in proboscis monkeys

尽管在偏好的物种中选择了更丰富的植物物种，但包括长鼻猴在内的Colobine猴倾向于选择含有较高蛋白质水平的叶子，这表明具有反刍行为的灵长类动物（即长鼻猴）和非反刍行为的灵长类动物（其他灵长类动物）之间没有特定的食物偏好。基于非人灵长类动物之间的离散平均粪便颗粒大小的比较，我们代表了间接证据，在长鼻猴可能在夜间经常使用反刍。事实上，他们的反刍行为更频繁地记录在夜间比白天。

Colobine monkeys including proboscis monkeys tended to prefer leaves containing higher protein levels, although more abundant plant species were chosen within the preferred species, suggesting that there is no specific food preferences between the primates with rumination (i.e. proboscis monkey) and non-rumination (other primates) behaviours. Based on the comparisons of the discrete mean faecal particle size among non-human primates, we represented circumstantial evidence for regular use of rumination in proboscis monkeys probably during the night-time. Indeed, their rumination behaviours were more frequently recorded during the night-time than during the day-time.