That is what 17 volunteers set out to establish at the weekend when the National Trust hosted a Big Bat Count in the courtyard and buildings it occupies in the grounds of the Crom Castle. If there were over 1,500 bats in residence then it would qualify as the biggest known roost in these islands.

    Forget the horror stories, the legends and the myths, these little creatures do not fly into people’s hair nor drink human blood. They’re insect eaters. In fact they gulp down thousands of blood sucking mosquitoes and biting midges every night!

    They are also sensitive creatures. If something is wrong with the environment they will be among the first to suffer. They are therefore a good indicator of a healthy, natural environment.

    Sadly the eight species of bats that we have in Northern Ireland have been struggling for survival in recent times. All eat only insects so anything that affects insect numbers will affect bat populations. Modern agricultural methods, the cultivation of a single crop on a farm rather than a variety of crops and the use of insecticides, can all have an impact.

    Many bats roost in our buildings, and as we insulate and renovate our older properties the nooks and crannies where they live are gradually lost.

    Fortunately these creatures of the night have friends and they are helping with various conservation initiatives to improve the bats’ habitats and roosting places. They are also protected by law. It is illegal to disturb bats or block up the entrances to their roosts.

    As Anja Rösler, nature conservation warden at Crom, explains: “Monitoring numbers of bats is also important so that we can see if these conservation measures are having the desired effect.”

    So Anja rustled up 17 volunteers for a Big Bat Count.

    The tell-tail droppings on the ground beneath the eaves of the buildings was a sure sign of bats in residence. The amount of droppings suggested a huge roost.

    Phil Richarson, the National Trust’s bat conservation officer, was so intrigued at the prospect that he travelled from England to brief the volunteers and supervise the count.

    On Saturday, as night fell, the volunteers moved into positions around the old stable block and other buildings close to Crom Castle.

    According to Anja they were interested in one species of bat in particular.

    “Crom has a large colony of soprano pipistrelles. One aim of this monitoring was to see if the population was still healthy, but another aim was to try to beat the UK record for the most bats of this species seen emerging from a roost, which stands at over 1500 bats,” she states.

    All of the bats in these roosts are mothers with babies. No-one knows where the males go. It remains one of intriguing mysteries surrounding these fascinating little animals.

    The volunteers were provided with ultra-sonic detectors, which pick up the inaudible high frequency calls of the bats and convert them into a series of clicks and slaps.

    “In this way the bats are not only seen emerging, but heard, too - very necessary in the deepening gloom of a summer’s evening,” says Anja. The first bats began emerging around 9.50pm.

    “These pipistrelles are all females that have gathered to produce their babies - only one each - so once the emergence began a distinctive audible chattering could be heard from the roost as some of the babies called after their mothers. Counting at this time is never easy as some mums return after a few minutes to check that their babies are safe, and this can cause headaches for the counting bat workers. They persevered and by 11pm all bats had emerged and the volunteers reassembled to compare notes and work out the final tally for the evening,” adds Anja.

    The volunteers counted 1,320 soprano pipistrelles; not quite the record of 1,500 but a healthy population nontheless. The also counted 85 leisler’s bats.

    And they are not giving up on the record.

    According to Anja the main roost in the stable block had fragmented and formed smaller roosts in cottages around the estate.