群体大小和觅食环境变化对东黑冠长臂猿日移动距离的影响

日移动距离是反映动物觅食努力的重要指标之一，相关研究有助于了解动物对生境的适应策略，对濒危物种的保护至关重要。东黑冠长臂猿（Nomascus nasutus）是一种极度濒危的树栖小型类人猿，主要生活在一夫二妻制的群体中，平均群体大小6.3只，目前对于该物种的日移动距离仍然缺乏足够的科学研究。我们以广西邦亮长臂猿国家级自然保护区内两群东黑冠长臂猿群作为研究对象，在2008年4月至2009年12月、2016年10月至2017年8月两个时期对其进行了157个全天跟踪，使用5 min间隔的瞬时扫描法记录长臂猿的取食行为和食物类型，每30 min记录长臂猿的位点，并使用轨迹法测算出日移动距离。结果发现东黑冠长臂猿在两个观察时期的不同食物类型取食比例有显著差异，全年的平均日移动距离为1 373 m （354~2 837 m），相比于低纬度地区营一夫一妻制（平均群体大小3.8只）生活的长臂猿类群没有明显增加。这一结果说明，虽然群体更大，但是东黑冠长臂猿并没有增加每天的觅食努力，不符合生态限制模型的预测。更大的食物斑块、更小的种间竞争和低群体密度可能是支持东黑冠长臂猿无需付出更多的觅食努力来维持更大群体的原因。另外，我们还发现东黑冠长臂猿在人类干扰强度低的研究时期果实类取食比例提高，日移动距离更长，且在果实丰富的雨季日移动距离显著高于果实匮乏的旱季，表明它们可能采取能量保守的策略来应对高质量食物匮乏的环境。总的来说，本研究在更大数据量的基础上更加准确和详细地描述了东黑冠长臂猿的日移动距离，并以此探究长臂猿对高质量食物匮乏环境的响应，为该极度濒危物种的保护提供更多的科学信息。

The influence of group size and foraging environment on the daily path length of a critically endangered primate Nomascus nasutus

Daily path length can reflect animals'foraging efforts and offer insights into their foraging strategy, which is essential for implementing effective conservation plans for endangered species.The Cao Vit gibbon(Nomascus nasutus) is a small, critically endangered arboreal ape living in polygynous social groups(average group size 6.3).Research on its daily path length related to foraging habits is still limited.During two distinct periods, one from April 2008 to December 2009 and the other from October 2016 to August 2017, we followed two gibbon groups(G1 and G4) in Bangliang National Nature Reserve, Guangxi Province, China.We collected feeding behavioral and dietary data using instantaneous scan sampling at 5 min intervals on gibbon groups and mapped the gibbon groups' positions every 30 minutes.A total of 157 full-day observations were used to analyze the dietary changes and calculate the gibbons' daily path lengths.The gibbons changed their diet significantly in the two observation periods, and we found that they traveled on average 1 373 m per day(range:354-2 837 m), similarly to monogamous gibbon species living in low-latitude areas with smaller group sizes(3.8 in average).These findings indicate that, despite Cao Vit gibbons' relatively bigger group sizes, their daily foraging effort is not higher than other species, conflicting with the ecological constraints model.The availability of larger food patches, lower inter-species competition, and low group density might be the main reason for allowing Cao Vit gibbons to survive in bigger groups without increasing foraging efforts.Furthermore, the gibbons fed more fruits and traveled longer distances when anthropogenic disturbances were lower, while they significantly decreased their movements during the fruit-scarce dry season.This points to a potential energy conservation strategy employed by Cao Vit gibbons as an adaptation to cope with limited high-quality food.The large amount of data provided by the present work significantly amplified our understanding of Cao Vit gibbons travel patterns related to their foraging behavior when facing food scarcity, and improved the scientific knowledge that fosters the conservation of critically endangered wildlife.