Every autumn during our dormouse box survey we normally expect to come across nests of wood mice (Apodemus sylvaticus) or yellow-necked mice (Apodemus flavicollis). This year has been notable for their total absence. We were, however, pleasantly surprised to discover two separate multiple roosts of brown long-eared bats (Plecotus auratus) during the September 2018 survey.
We recorded solitary brown long-eared bats roosting in dormouse boxes in 2015 and 2016, so we were aware that they were likely to be present in Sherradspark Wood. What was unusual was the large number of individuals clustered in the individual dormouse boxes.
Brown long-eared bats are medium-sized weighing between six to twelve grams with distinctively long ears. When not in flight the ears are folded back resembling rams’ horns. The adults have brown fur whilst the juveniles tend to be more greyish. They do use echolocation to pinpoint prey but equally they are able to detect prey by sight and sound using their large eyes and ears. Brown long-ear bats usually catch insects in flight but as they are slow flyers hovering close to the ground, they are more vulnerable to predators than other species of bats.
In summer colonies of about twenty long-eared bats usually roost in older residential and non-residential buildings as well as trees. In winter they migrate to underground sites such as caves or tunnels. The autumn is the period when mating takes place. It is very likely that the two roosts found during the September box survey were mating roosts. Upon close inspection of one box conducted by Roger Havard, the local bat ecologist, it turned out that out of the eight examined bats, five were post-lactating females and three juvenile males.
Roger says that Sherrardspark Wood offers an ideal habitat for brown long-eared bats with its open woodland. This is a result of the on-going programme of coppicing sections of the woodland on the rotation basis, which the Wood Wardens carry out in accordance with the long-term management plan. Opening up the tree canopy stimulates the growth of the understory and thus improves the habitat for insects and small vertebrates. Consequently, the increased population of prey attracts other species, such as bats and birds.
Brown long-eared bat is the second most common species of bat in the United Kingdom after the Pipistrelle. Their population has declined over the years largely due to the changing land use and conversion of old buildings resulting in the loss of suitable feeding and roosting habitats. It is heartening to witness the growing presence of brown long-eared bats in Sherrardspark Wood.