The annual population trend of the brown long-eared bat is assessed every year by counts at a sample of roost sites across the Republic of Ireland. Over 40 sites are counted twice between May and August. In order to derive reliable trends the same sites are counted year after year.
A combination of bat group volunteers, roost owners and BCIreland staff carry out these counts.
Since 2007 brown long-eared bat trends appear to be reasonably stable.