Non-invasive acoustic detection of wolves

Monitoring wolves (Canis lupus) 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.

监测灰狼（Canis lupus）是一项兼具难度与高成本的工作，该物种凭借极强的移动能力、复杂的狼群动态、生性羞怯的习性以及夜行性活动特征，使得监测工作难以开展且成本高昂。灰狼通过嚎叫声实现声学交流，既可用于同狼群内部的信息传递，也可与邻近狼群进行沟通。狼嚎属于低频发声信号，可实现远距离传播，因此可被应用于该物种的监测工作。人工诱导嚎叫调查是当前全球各地用于灰狼监测的主流方法，但该方式可能会对定居狼群造成侵扰，同时可能引发人类群体的负面反馈。本研究证实，通过记录自发狼嚎事件即可实现灰狼的检测。我们对圈养个体的狼嚎声压级进行了测量，进一步发现人工诱导产生的狼嚎可在3公里范围内被清晰录制并识别。最后，我们针对一个野生灰狼种群开展了非侵入式声学检测。被动声学记录仪的应用可为未来的灰狼监测提供高效的非侵入式工具，助力该物种的可持续管理方案的制定。