While rarely seen, Britain's mice, voles, shrews, rats and dormice do occasionally give away their presence through their vocalisations. A team of researchers has spent the last 18 months recording and studying these vocalisations in order to develop 'acoustic classifiers', which can be used to reveal the presence of different small mammal species in recordings made by automatic recording devices left in the field. This approach could be particularly valuable for determining the presence of different small mammal species on nature reserves or at sites where development is being planned.
To the human ear, the vocalisations made by small mammals may sound like a simple high-pitched squeak, but the calls are in fact extremely complex, extending beyond the range of our hearing into the ultrasonic and showing a great deal of variation in their structure. The vocalisations of small mammals serve a variety of purposes, including communication between parent and offspring and use in aggressive encounters. By studying the detailed nature of these different calls, the researchers have been able to develop a sound library of calls, something that has now been shared through an article in British Wildlife magazine and an online resource hosted by the British Trust for Ornithology.
Dr Stuart Newson, lead researcher on the project, commented "Our approach complements existing monitoring approaches for small mammals, adding data from many more locations for a suite of species whose status information is difficult to obtain and, in many cases, is lacking or not up to date. The collection of acoustic data for small mammals could be extremely cost-effective; small mammals often vocalise at night and their calls are often collected as 'by-catch' by those surveying bats. By running these recordings through the BTO's acoustic pipeline, small mammal calls can be detected, and the species identified."
Dr Newson continued "This approach could help conservation efforts by providing an economical and robust method for detecting the presence and abundance of small mammals, such as Hazel Dormice in woodland or introduced Brown Rats on seabird islands."
Huma Pearce, co-author, commented "Small mammals provide vital ecosystem services including seed dispersal, insect control and management of soil structure and chemical composition as well as providing a vital food resource to a large number of predators such as owls. Nevertheless, their value is largely overlooked with relatively few species receiving legal protection. It is hoped that this novel approach to monitoring small mammals will improve our understanding of their distribution and abundance and ultimately raise awareness of their significance in ensuring healthy ecosystem function."