Bat surveys throughout the country are measuring the range and number of Daubenton's bats. You can help, writes Anthony King
Fancy a spot of bat watching? You will have an opportunity this summer with an all-Ireland survey of water bats under way.
Little is known about the number or distribution of Irish bats, so Bat Conservation Ireland has been filling in the gaps with the help of public volunteers interested in some nocturnal action.
Last August, more than 100 volunteer teams in 26 counties ventured out after dark to count Daubenton's bats for a pilot survey. Many of the volunteers had no experience of bat study, but with the aid of a bat detector and torch, they recorded bat activity on rivers and canals.
Organiser Dr Tina Aughney says volunteer participation in the survey was phenomenal. "We felt if we could get 50 volunteers in the country we would be doing really well. But we ended up with over 200 people trained throughout the 32 counties."
Daubenton's bat skims low and fast over water surfaces, foraging for mayfly, midges and caddis flies. Survey volunteers recorded the number of times bats flew through their torch beams; they could monitor the echolocation calls of approaching bats on their bat detectors. These calls allow bats to locate prey using sonar.
Of the 134 waterways surveyed during last year's study, bat activity was recorded on 92 per cent of them. "To get the distribution of this [ species of] bat was significant. We now have a pretty good idea that it is present across almost every waterway," says Aughney.
Another survey is planned for this summer and for 2008. "The aim is to determine the status of Daubenton's bats in Ireland and to be able to detect whether the population is decreasing or stable," she says.
The only well-documented bat species in Ireland is the brown long-eared bat. National Parks and Wildlife Service rangers count these bats as they hang in their roosts. The other nine bat species in Ireland roost in crevices and very little is know about their populations.
Aughney says surveys are now essential because the Government must report to the EU by 2012 on the status of the 10 bat species here. All are protected under EU and Irish law.
DAUBENTON'S BATS PREFER unpolluted waterways with a good variety of mature, riverside trees, according to Prof John Altringham at the University of Leeds, an expert on the Daubenton species. Trees offer food and shelter for insects and bats.
Altringham warns that waters polluted by sewage or fertiliser often have a low diversity of vegetation and insects. This can lead to a patchy supply of insects, which can particularly affect female bats with young, as they need a regular supply of food while weaning their offspring.
Augheny says bats are a natural indicator of the health of our environment. "If there is a good bat population in an area it tends to reflect that there's nice woodland, good tree line and hedgerow in the landscape," she says.
Unfortunately, bat species are in decline across Europe. For Irish bats, the main threats are loss of hedgerow and use of pesticides, says Aughney. "The renovation of old buildings in the countryside and strengthening of stone bridges can also have a detrimental effect." She says repairs can be carried out without damaging roosts or entombing bats within.
Bat Conservation Ireland is offering three-hour training sessions for those interested in participating in this year's survey. Volunteers are assigned a 100-meter stretch of waterway within 10km of their home. They record bat activity at 10m intervals for two nights in August. Training courses start in the last week of June and run during July.
"For a lot of volunteers it's their first time ever to survey a bat, but the statistical analysis takes into account experience levels." Bat Conservation Ireland aims to raise awareness of bats and dispel myths. The charity notes that bats don't damage people's property, are an integral part of the food chain, and keep insect numbers down. A single common pipistrelle bat can munch its way through 3,000 midges each night.
The Daubenton's bat survey is sponsored by National Parks and Wildife Service, Waterways Ireland and the Environment and Heritage Service in Northern Ireland.
See details of training courses at www.batconservationireland.org