Non-invasive acoustic detection of wolves

Monitoring wolves (<i>Canis lupus</i>) is a difficult and often expensive task due to high mobility, pack dynamic, shyness and nocturnal activity of this species. Wolves communicate acoustically through howling, within pack and with packs of the neighbourhood. A wolf howl is a low-frequency vocalization that can be transmitted over long distances and thus it can be used for monitoring. Elicited howling survey is a current method to monitor wolves in different areas all over the world. Elicited howling, however, may be invasive to residential wolf packs and could create possible negative reactions from the human population. Here we show that it is possible to detect wolves by recording spontaneous howling events. We measured the sound pressure level of wolf howls by captive individuals and we further found that elicited howling may be recorded and clearly identified up to a distance of 3 km. We finally conducted a non-invasive acoustic detection of wolves in a free-ranging population. The use of passive sound recorders may provide a powerful non-invasive tool for future wolf monitoring and could help to establish sustainable management plans for this species.

灰狼（Canis lupus）的监测工作往往难度颇高且成本不菲，这是由于该物种具备极强的移动性、社群结构动态变化、生性羞怯且昼伏夜出的特性。灰狼通过嚎鸣进行声学交流，既可在本狼群内部传递信息，亦可与邻近狼群开展互动。狼嚎属于低频发声，可实现远距离传播，因此可被应用于灰狼监测工作。诱发式狼嚎调查法是目前全球各地用于灰狼监测的主流手段之一，但该方法可能会对定居狼群造成干扰，且有可能引发当地民众的负面反馈。本研究证实，通过记录自发性狼嚎事件即可实现灰狼的侦测。我们对圈养灰狼的狼嚎声压级进行了测量，进一步发现诱发式狼嚎在3公里范围内均可被清晰录制并识别。最后，我们针对一处野生灰狼种群开展了非侵入式声学侦测。被动声学记录仪的应用可为未来的灰狼监测工作提供高效的非侵入式工具，亦有助于为该物种制定可持续的管理方案。