The recently established Hainan Tropical Rainforest National Park has designated the Hainan gibbon (Nomascus hainanus) as its flagship species, providing new hope for recovery of the last surviving population of the world's rarest primate. However, current monitoring methods are labour-intensive and only conducted for discrete periods, meaning that detailed information is still lacking on key Hainan gibbon population parameters (such as movement patterns, sleeping site selection and home range size). Alternative monitoring techniques are therefore necessary to supplement traditional methods and provide more accurate estimates of population parameters. Here, we tested whether flying two drones (DJI MAVIC2 Enterprise Advanced), one in the understory and the other above the canopy, could provide new information on Hainan gibbon biology and ecology. During a total of 60 flights, we successfully collected clear RGB and thermal infrared footage of Hainan gibbons. These data provide new baseline information on gibbon movement within the understory and the canopy, their surface body temperatures (23.0–34.7°C), and their movement area during the survey period. The low cost of this equipment could reduce the running costs for Hainan gibbon monitoring. Although drone-based monitoring has some limitations (e.g. monitoring efficiency could be affected by variation in forest structure and gibbon group size), this new method could complement existing monitoring approaches. Drone-based monitoring, using multiple drones and a real-time transmission network, could therefore contribute further towards Hainan Tropical Rainforest National Park's conservation planning for this Critically Endangered primate.

中文翻译：

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商用无人机可以对世界上最稀有的灵长类动物进行准确有效的监测

最近成立的海南热带雨林国家公园将海南长臂猿（Nomascus hainanus）指定为其旗舰物种，为世界上最稀有灵长类动物最后幸存种群的恢复带来了新的希望。然而，目前的监测方法是劳动密集型的，并且仅在离散时期进行，这意味着仍然缺乏关于海南长臂猿种群关键参数（例如运动模式、睡眠地点选择和活动范围大小）的详细信息。因此，需要替代监测技术来补充传统方法并提供更准确的人口参数估计。在这里，我们测试了飞行两架无人机（DJI MAVIC2 Enterprise Advanced）（一架在林下，另一架在树冠上方）是否可以提供有关海南长臂猿生物学和生态学的新信息。在总共60次飞行中，我们成功采集到了海南长臂猿的清晰RGB和热红外影像。这些数据提供了关于长臂猿在林下和树冠内的运动、其表面体温（23.0–34.7°C）以及调查期间的运动区域的新基线信息。该设备成本低廉，可降低海南长臂猿监测的运行成本。尽管基于无人机的监测存在一些局限性（例如监测效率可能会受到森林结构和长臂猿群体规模变化的影响），但这种新方法可以补充现有的监测方法。因此，使用多架无人机和实时传输网络进行无人机监测可以进一步促进海南热带雨林国家公园对这种极度濒危灵长类动物的保护规划。