Wild Neroche a multi-taxa, baseline passive acoustic monitoring survey 2025

Wild Neroche a multi-taxa, baseline passive acoustic monitoring survey 2025

BTO Research Report, 2026

Citation

Thorley, J., Newson, S., Dutta, A., Colaço, T., Gillings, S. & Ashton-Butt, A. 2026. Wild Neroche a multi-taxa, baseline passive acoustic monitoring survey 2025. BTO Research Report 804: British Trust for Ornithology, Thetford

Overview

This report summarises results from the first year of Passive Acoustic Monitoring undertaken at Wild Neroche during spring and summer 2025. The intention is to establish a baseline dataset that will inform future assessments of how active management influences biodiversity across the Neroche area.

In more detail

This report summarises results from the first year of Passive Acoustic Monitoring undertaken at Wild Neroche during spring and summer 2025. Wild Neroche is one of four of Forestry England’s Wilder Forests, and is located in south-west England.The intention is to establish a baseline dataset that will inform future assessments of how active management influences biodiversity across the Neroche area. 

Bird communities were surveyed at 10 sites using autonomous recording devices operating in the audible range. During the initial deployment period, audible recordings were collected continuously during both day and night. The same devices were also operated in ultrasonic mode at nine of these sites to monitor bats, small mammals, and bush-crickets; ultrasonic recordings were restricted to night-time only. Audible recordings were collected on 140 days between April and September, while ultrasonic recordings were obtained on 67 nights between June and August. Devices were placed to survey a range of habitats including mixed deciduous woodland, coniferous woodland, heathland, and mesotrophic grassland. 

Analysis of ultrasonic data identified 13 species of bat, including the regionally important Barbastelle (Barbastella barbastellus) and Bechstein’s Bat (Myotis bechsteinii), both of which are included on the red list of British Mammals. In addition, three terrestrial small mammal species, four bush-cricket species, and two audible moth species were confirmed. One standout result of the ultrasonic survey was the exceptional number of detections of Hazel Dormouse (Muscardinus avellanarius), with 4,418 triggered recordings across six sites. Dormouse acoustic activity peaked in late July. In total, 73 species of birds were confirmed, including 35 species listed as Amber or Red on the UK Birds of Conservation Concern list. The repeated detection of Goshawk (Astur gentilis) across the survey area is also of particular interest.