Irish Bat Monitoring Programme 2018-2021

Abstract

The Irish Bat Monitoring Programme is comprised of four schemes currently under the management of Bat Conservation Ireland. This report provides the results from these schemes from 2018-2021 along with long term trends in bat populations, where available. The surveys have been funded by the National Parks and Wildlife Service (NPWS) in the Republic of Ireland and the Northern Ireland Environment Agency (NIEA) in Northern Ireland. Data for these schemes are collected in a standardized fashion by numerous volunteer citizen scientists, as well as professionals, across the island. The Car-based Bat Monitoring Scheme (2003-2021) collects data on common and soprano pipistrelles as well as Leisler's bat, while the All Ireland Daubenton's Bat Waterways Monitoring Scheme (2006-2021), the Brown Long-eared Bat Roost Monitoring Scheme (2007-2021) and the Lesser Horseshoe Bat Roost Monitoring Scheme are single species surveys. Different methods are used for sampling bat activity or occurrence: - the Car-based Bat Monitoring Scheme uses driven transects and full spectrum bat detectors (formerly time expansion detectors); the waterways survey for Daubenton's bat uses stationary points along walked waterway transects and heterodyne/ tuneable detectors; the brown long-eared bat is counted at summer roosts either externally using detectors during emergence or internally during daylight hours; and the lesser horseshoe bat survey is a dual season programme whereby the bats are counted in summer either externally using detectors or video cameras, or internally in the roost, and in winter in hibernacula. The co-ordination and implementation of all schemes were impacted by the global SARS-Cov-2 pandemic in 2020 and 2021. The sudden move to online recruitment and training in spring 2020, as well as constraints associated with field surveys, meant that some targets were not fully met in that year. Despite similar constraints in 2021, however, all targets were met, with the single exception of winter hibernation counts at lesser horseshoe sites which were carried out prior to COVID-19 vaccination roll-out. All four schemes collect sufficient data to allow detection of red or amber alert declines in their target species. Additional information for other species such as Nathusius' pipistrelle (Pipistrellus nathusii) and Myotis spp. (combined) is also gathered by the Car-based Bat Monitoring Scheme. Due to the recent changeover in detector used in this scheme the number of records for these species has increased and we have seen a corresponding decrease in the width of error bars associated with their trends. The news for bats in Ireland over the past 12+ years has been largely positive with significant increases seen in several species such as common pipistrelle, soprano pipistrelle, Leisler's bat and the Annex II listed lesser horseshoe bat. The population trend of the brown long-eared bat appears to be currently stable. Daubenton's bat trend is also reasonably stable, with error bars that encompass the baseline for the species, but it has declined somewhat in the past four years. In addition, we now note with concern a significant decreasing trend shown in the composite Myotis species index derived from car-based bat monitoring surveys. While there is insufficient information to determine whether this index reflects either or both whiskered and/or Natterer’s bat, and it may even include some Daubenton's bat passes, the extent of the decline observed well exceeds Red Alert levels. As part of the monitoring schemes Bat Conservation Ireland continues to target participation by members of the public. Well-attended Daubenton's bat training courses are run by Bat Conservation Ireland every year, thus improving awareness and encouraging citizen science across the island - over 3,000 people have participated in this scheme to-date. Equipment upgrades are ongoing, Batlogger detectors were fully phased in for the Car-based Bat Monitoring Scheme in 2020. Camcorders coupled with infra-red lamps are used to improve accuracy of brown long-eared bat counts and to provide training for new volunteer teams. Ancillary data such as records collected for other vertebrates during the Car-based Bat Monitoring Scheme are also discussed with trends in a number of roadside mammals also provided.