Data from: Vocal characteristics of prairie dog alarm calls across an urban noise gradient

Prairie dog alarm calls were recorded across an urban gradient at three distinct colonies from 28 August to 6 December 2014. Alarm calls were elicited by the observer approaching a randomly selected prairie dog. Once the prairie dog began alarm calling the observer remained stationary and recorded 30 seconds of vocalization while the animal was in situ. A band-limited automated detector was used in Raven Pro v1.5 to select each of the individual barks in the 30-second calling bouts and to optimize extraction of call parameters. Before measurements were extracted on the individual barks, all detections were examined manually for accuracy and adjusted to maximize the detection of all barks within a recording period and to ensure the entire bandwidth and duration of calls were selected. Random selections of half of the barks in a calling bout (n = 4516) were then measured. Four acoustic metrics were calculated for each bark: (1) minimum frequency (Hz) – the lower frequency limit of the call, a commonly used metric in previous studies; (2) frequency 5% (Hz) – the frequency where the summed energy equals 5% of the total, a measure of lower frequency properties; (3) peak frequency (Hz) – the frequency with the highest concentration of energy; and (4) bark duration (milliseconds). Ambient sound levels were measured using a calibrated Larson-Davis 831 sound level meter (frequency weighting = A) over a 2-minute period as soon as the vocalization recording was completed. Sound pressure levels were measured as 1-second frequency weighted (12.5Hz - 20kHz) equivalent continuous levels (LAeq, 1s).

2014年8月28日至12月6日，研究人员沿城市梯度（urban gradient）于三个独立的草原犬鼠（Prairie dog）群居群落中记录其警戒叫声。警戒叫声的诱发方式为：观察者随机选取一只草原犬鼠并靠近，待该动物开始发出警戒叫声后，保持静止并在其原位录制30秒的鸣叫声。研究人员使用Raven Pro v1.5软件中的带限自动检测器，从30秒的鸣叫片段中提取每一次单次吠叫，并优化叫声参数的提取流程。在提取单个吠叫的测量参数前，需人工核查所有自动检测结果的准确性，并进行调整，以最大化单段录音中所有吠叫的检出率，同时确保完整选取叫声的带宽与时长。随后，随机选取各鸣叫片段中半数的吠叫，共计4516个样本开展测量分析。为每一次吠叫计算四项声学指标：(1) 最低频率（Hz）：叫声的低频下限，为既往研究中的常用指标；(2) 5%能量频率（Hz）：累计能量占总能量5%时对应的频率，用于表征低频特性；(3) 峰值频率（Hz）：能量集中度最高的频率；(4) 吠叫时长（毫秒）。鸣叫声录制结束后，立即使用经过校准的Larson-Davis 831声级计（频率计权为A计权）开展为期2分钟的环境声级测量。声压级以1秒频率计权（12.5Hz-20kHz）等效连续声级（LAeq, 1s）的形式进行记录。