Brown long-eared bat maternity roost
Ecologists from Johns Associates have been surveying the buildings at Chalcroft Farm, One Horton Heath since 2018. One of the buildings, Pond Cottages, was originally identified to provide space for a maternity roost of brown long-eared bats (Plecotus auritus) in 2014.
A maternity roost is a gathering of a sizeable colony of female bats, which come together each year from May onwards to give birth to their young. If female bats are healthy and there is enough of their insect food source available, each bat will give birth to one baby per year once sexually mature. The gestational period is between 8 - 9 weeks, and the young will be weaned after they are around 6 weeks old. The colony are faithful to their maternity roost and will return to the same location every year for the duration of their lifetime, which can be up to 30 years.
As the colony emerge from their roost at dusk it provides a spectacular sight, with groups of bats swooping and twisting around the building before flying off to their foraging grounds. Social calls have been recorded as bats leave and re-enter the roost, which is a modified type of call to the normal echolocation used by bats. These social calls are used between mothers and pups to communicate with each other, along with other members of the colony.
As part of the One Horton Heath development, a future bespoke bat house will be designed and constructed, which will provide a replacement space for the brown long-eared maternity colony.
The design will incorporate numerous features favoured by brown long-eared bats, including an open flight space with perching locations, gable end mortar gaps, a tiled roof, and a rainwater soak-away to increase humidity. As the main food source of brown long-eared bats is moths, a planting area will be created surrounding the bat house, with choice plant species incorporated to encourage moths (such as night scented flowers).
Once constructed, the new habitat will be monitored by our ecologists for a period of no less than 10 years to make sure that the brown long-eared colony are well looked after. This work will be undertaken under a European Protected Species licence from Natural England.
Authored by Ellie Hack, Senior Ecologist, Johns Associates, October 2022
Brown long-eared bats in Pond Cottages, May 2022: