Passive acoustic monitoring (PAM) is an effective remote sensing approach for sampling acoustically active animal species and is particularly useful for elusive, visually cryptic species inhabiting remote or inaccessible habitats. Key advantages of PAM are large spatial coverage and continuous, long-term monitoring. In most cases, a signal detection algorithm is utilized to locate sounds of interest within long sequences of audio data. It is important to understand the demographic/contextual usage of call types when choosing a particular signal to use for detection. Sampling biases may result if sampling is restricted to subsets of the population, for example, when detectable vocalizations are produced only by a certain demographic class. Using the African forest elephant repertoire as a case study, we test for differences in call type usage among different age-sex classes. We identified disproportionate usage by age-sex class of four call types—roars, trumpets, rumbles, and combination calls. This differential usage of signals by demographic class has implications for the use of particular call types in PAM for this species. Our results highlight that forest elephant PAM studies that have used rumbles as target signals may have under-sampled adult males. The addition of other call types to PAM frameworks may be useful to leverage additional population demographic information from these surveys. Our research exemplifies how an examination of a species' acoustic behavior can be used to better contextualize the data and results from PAM and to strengthen the resulting inference.

中文翻译：

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被动声学监测中目标信号选择的影响：非洲森林象（Loxodonta cyclotis）年龄和性别依赖的声音库使用的例子

被动声学监测（PAM）是一种有效的遥感方法，用于对声学活跃的动物物种进行采样，对于居住在偏远或难以到达的栖息地的难以捉摸、视觉上神秘的物种特别有用。PAM 的主要优点是空间覆盖范围大和连续、长期监测。在大多数情况下，信号检测算法用于在长音频数据序列中定位感兴趣的声音。在选择用于检测的特定信号时，了解呼叫类型的人口统计/上下文使用非常重要。如果采样仅限于人口的子集，例如，当仅由特定人口类别产生可检测的发声时，可能会导致采样偏差。使用非洲森林象曲目作为案例研究，我们测试了不同年龄性别类别之间呼叫类型使用的差异。我们发现四种呼叫类型（咆哮声、喇叭声、隆隆声和组合呼叫）按年龄性别分类的使用率不成比例。这种按人口统计类别对信号的不同使用对于该物种在 PAM 中使用特定呼叫类型具有影响。我们的结果强调，使用隆隆声作为目标信号的森林象 PAM 研究可能对成年雄性进行了采样不足。在 PAM 框架中添加其他呼叫类型可能有助于利用这些调查中的其他人口统计信息。我们的研究举例说明了如何利用对物种声学行为的检查来更好地了解 PAM 的数据和结果，并加强由此产生的推论。