Data from: Digital recorders increase detection of Eleutherodactylus frogs

Improved methods for large-scale and long-term amphibian monitoring projects would aid species status assessments and identification of potentially declining species (e.g., Stuart et al. 2004). Acoustical surveys allow researchers to quickly determine species presence and calling activity level (Lips et al. 2001; Zimmerman 1994). The North American Amphibian Monitoring Program, a large-scale monitoring effort, uses acoustical surveys to monitor species in ponds and wetlands (United States Geological Survey 2004). A challenge of this approach is accurate species identification, which is particularly problematic in a tropical area with high anuran species diversity (e.g., anuran species richness in the Neotropics was greater than in the Neartic, Duellman 1999). Furthermore, abundant or loud species may lower the detection probability of other species. An assumption that needs to be tested in acoustical surveys is that detection is highly correlated with the species presence or activity. Without an appropriate correction for detection probability, data will not accurately reflect the status of the species (MacKenzie et al. 2002). This may result in inappropriate management decisions that could waste time and money. Digital recorders can be used as a standard method for species detection and determination of calling activity level in amphibian choruses in long-term monitoring projects. Digital recordings can be stored and transferred easily and can allow experts to analyze the recordings at their convenience. In addition, loud or abundant species can be filtered using computer software to increase the detection of other species. I tested the hypothesis that detection of species presence and calling activity level in anuran choruses will be higher when recordings are analyzed with the help of computer software compared to only hearing the recordings. The resulting increase in detection should result in improved population status data and reduced false negatives during species inventories (i.e., when a species is not detected due to interference).

适用于大规模、长期两栖动物（Amphibian）监测项目的改良方法，可有效助力物种现状评估与潜在衰退物种的识别（例如Stuart等，2004）。声学调查（acoustical surveys）能够帮助研究人员快速确定物种存在情况与鸣叫活动强度（Lips等，2001；Zimmerman，1994）。北美两栖动物监测计划（North American Amphibian Monitoring Program）作为一项大型监测项目，采用声学调查手段对池塘与湿地内的两栖动物物种开展监测（美国地质调查局，2004）。该方法面临的核心挑战之一是物种的精准识别，在无尾目（Anuran）物种多样性较高的热带区域，这一问题尤为突出（例如新热带区的无尾目物种丰富度高于新北区，Duellman，1999）。此外，种群数量庞大或鸣叫声洪亮的物种，可能会降低其他物种的检测概率。声学调查中需要验证的一项核心假设为：检测概率与物种存在情况或活动水平高度相关。若未对检测概率进行恰当校正，监测数据将无法准确反映物种的实际种群状态（MacKenzie等，2002），进而可能导致不当的管理决策，造成时间与资金的无谓浪费。数字录音设备（digital recorders）可作为标准化手段，应用于长期监测项目中两栖动物合唱群的物种检测与鸣叫活动强度测定。数字录音文件易于存储与传输，且支持专家在便捷时机开展录音分析。此外，还可通过计算机软件过滤掉鸣叫声洪亮或种群数量庞大的物种，以提升对其他物种的检测效果。本研究验证了如下假设：相较于仅通过人工聆听录音，借助计算机软件分析录音时，对无尾目合唱群的物种存在情况与鸣叫活动强度的检测准确率更高。检测准确率的提升应能优化种群现状数据，并减少物种调查过程中的假阴性（false negatives）结果（即因干扰因素而未检测到物种存在的情况）。