Potential for coupling the monitoring of bush-crickets with established large-scale acoustic monitoring of bats

Speckled Bush-cricket, photograph by Tom Houslay

Author(s): Newson, S. E., Bas, Y., Murray, A. & Gillings, S.

Published: 2 January 2017

Journal: Methods in Ecology and Evolution

Digital Identifier No. (DOI): 10.1111/2041-210X.12720

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Bush-crickets are a little-known group of insects that inhabit our marshes, grasslands, woods, parks and gardens. Some may be seen in the summer when they are attracted to artificial lights, but as most produce noises that are on the edge of human hearing, we know little about their status. There are suggestions that some bush-crickets may be benefiting from climate change, while others may be affected by habitat changes. But how to survey something that is difficult to see and almost impossible to hear?

Advances in autonomous recording devices are transforming our understanding of bats, but the large-scale deployment of such devices has the potential to improve our understanding of other species groups that produce loud and characteristic sounds too. The original objective of BTO's Norfolk Bat Survey, led by Stuart Newson, was to trial the recording of bat activity using passive real-time detectors, to gauge the willingness of members of the public to engage in bat monitoring at a large scale, and to determine the suitability of automated identification routines for processing large volumes of citizen-science collected bat recordings. However, it soon became clear that bush-crickets were also being recorded in large numbers.

Working with the Museum of Natural History in Paris and Natural England, BTO staff developed a computer algorithm to identify the sounds made by different species of bush-crickets. After carefully validating these state-of-the-art methods using field recordings in Norfolk, the daily activity patterns of different species of bush-cricket was examined to determine where different species live. The Speckled Bush-cricket, for example, would normally be easy to overlook because it occurs in vegetation and stridulates at a frequency too high for humans to hear. With over 260,000 recordings of this species collected through the Norfolk Bat Survey, this study found this species to be common and widespread, with a distribution that extends into the city of Norwich. At the other extreme, Great Green Bush-cricket, previously known from only a few locations in Norfolk, was recorded at two locations, of which one was a new site for this species.

This research demonstrates the huge potential to take advantage of established large-scale bat monitoring to also collect high-quality monitoring data for bush-crickets. It is likely that large volumes of information on bush-crickets are already being collected incidentally by bat workers using static detectors, but this information is at best noticed and ignored. This work also marks an important step towards the development of automated sensor networks, which are likely to play growing role in the future biodiversity surveying, and the whole approach enables members of the public to become actively engaged in wildlife monitoring, with important conservation implications.
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