Our Bat Colony

The IAM Manager, Matt and Harm Deenen (a trained field ecologist) have been conducting regular bat counts and surveys at Johnstown since 2015. In 2016 they carried out weekly counts of the maternal colony of soprano pipistrelle bats which use the first floor roof of the museum (west side). This work has continued this year so they can build up comparative data and monitor the health of the colony.

The bats gather in this roost from March until October although they reckon some individuals may hibernate there in the winter too. The roost reaches its peak in May with the biggest count being 714 individuals recorded on 5 May 2016. They have been told by experts that this is the third largest recorded roost in the country. In June the pups are born and can sometimes be seen on infra-red camera that they have in the roof.

The team have a theory that other species of bat may also use the same roost from time-to-time but in much smaller numbers – they think they have detected a daubenton bat emerging from the roost this year. Counting bats means standing outside the roost at sunset and counting for an hour in ten minute intervals – 20 to 30 mins after sunset is the peak emergence time. They use various specialist bat equipment to aid them. Records of bat counts are submitted to Bat Conservation Ireland, National Biodiversity Centre and are also available on the Irish agricultural museum website.

They also carry out regular patrol surveys around the grounds and have detected brown long-eared bats, common pipistrelle, leisler bats and daubenton bats (water specialists). They have been told that bats have used the castle in the past but they have no evidence to support this being the case at the moment.

Johnstown has the perfect habitat for Irish bats. The team intend to keep recording to build up their knowledge of bats on the site and to continue to monitor the maternal roost so it becomes the best recorded roost in the country and a flagship for bat conservation.