1. With one million animal species at risk of extinction, there is an urgent need to regularly monitor threatened species. However, in practice this is challenging, especially with wide‐ranging, elusive and cryptic species or those that occur at low density.
2. Here we compare two non‐invasive methods, passive acoustic monitoring (n = 12) and camera trapping (n = 53), to detect chimpanzees Pan troglodytes in a savanna‐woodland mosaic habitat at the Issa Valley, Tanzania. With occupancy modelling we evaluate the efficacy of each method, using the estimated number of sampling days needed to establish chimpanzee absence with 95% probability, as our measure of efficacy.
3. Passive acoustic monitoring was more efficient than camera trapping in detecting wild chimpanzees. Detectability varied over seasons, likely due to social and ecological factors that influence party size and vocalization rate. The acoustic method can infer chimpanzee absence with less than 10 days of recordings in the field during the late dry season, the period of highest detectability, which was five times faster than the visual method.
4. Synthesis and applications. Despite some technical limitations, we demonstrate that passive acoustic monitoring is a powerful tool for species monitoring. Its applicability in evaluating presence/absence, especially but not exclusively for loud call species, such as cetaceans, elephants, gibbons or chimpanzees provides a more efficient way of monitoring populations and inform conservation plans to mediate species‐loss.

中文翻译：

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收听和观看：摄像机陷阱或声音传感器是否能更有效地检测出开放栖息地中的野生黑猩猩？

1. 由于有一百万种动物处于灭绝的危险中，迫切需要定期监测受威胁的物种。但是，在实践中，这尤其具有挑战性，特别是对于范围广，难以捉摸和神秘的物种，或以低密度出现的物种。
2. 在这里，我们比较了两种非侵入性方法，即被动声学监测（n  = 12）和摄像机诱捕（n  = 53），以检测坦桑尼亚伊萨谷地热带稀树草原马赛克生境中的黑猩猩Pan穴居人。通过占用模型，我们以建立黑猩猩缺勤率（95％概率）所需的估计采样天数作为评估疗效的方法，评估每种方法的有效性。
3. 在检测野生黑猩猩方面，被动声学监测比照相机诱捕更为有效。可检测性随季节变化，可能是由于影响聚会规模和发声率的社会和生态因素所致。声学方法可以推断出黑猩猩的缺席，在干燥季节后期，田间记录不到10天，这是可检测性最高的时期，比视觉方法快了五倍。
4. 综合与应用。尽管存在一些技术限制，但我们证明了无源声学监测是进行物种监测的有力工具。它在评估是否存在时的适用性，尤其是但不仅限于鲸类，大象，长臂猿或黑猩猩等响尾蛇物种，提供了一种更有效的方法来监控种群并提供保护计划以调解物种损失。