Coverage: Over four survey seasons, from 2021 to 2024, 2,364 different locations across the Bailiwick of Guernsey were surveyed. Recording was undertaken on 879 different nights mainly between April and the end of October in each year, amounting to a total of 9,426 nights of recording effort across sites.

Results: Overall, 16,192,045 five second triggered recordings were collected which, following analyses and validation, were found to include 4,019,529 bat identifications and 35,354 small terrestrial mammal identifications. There were also over eight million identifications of bush-crickets as ‘by-catch’, for which we report species presence on a site and night basis.

Following a process of manual species validation, the study confirmed the presence of at least 14 bat species, five small mammal species, and seven species of bush-crickets. This included six bat species that had not previously been recorded on any island in the Bailiwick of Guernsey, including Serotine Eptesicus serotinus, Leisler’s Bat Nyctalus leisleri, Common Noctule Nyctalus noctula, Lesser Horseshoe Bat Rhinolophus hipposideros, Whiskered or Brandt’s Bat Myotis mystacinus or M. brandtii and Parti-coloured Bat Vespertilio murinus.

In addition to bats, the project highlights the value of identifying other species groups as ‘by-catch’ during bat surveys. This includes the discovery of a new species of bush-cricket for the Channel Islands, Large Conehead Ruspolia nitidula, which was recorded on several islands. Whilst not initially discovered through this project, Brown-Spotted Bush-cricket Tessellana tessellata was also recorded on Guernsey, as a new species for the Channel Islands. As a consequence of the Bailiwick Bat Survey, we have a much better understanding now of the status of bats, small mammals and bush-crickets across the Bailiwick of Guernsey.

The report includes a full species-by-species breakdown of spatial, seasonal, and through-the-night patterns of activity.