The serotine bat (Eptesicus serotinus) is a common nocturnal mammal found across Europe. This widespread species often uses human-made structures for roosting, making it familiar in many European landscapes.
Identifying the Serotine Bat and Its Home
The serotine bat is one of the larger bat species found in Britain, with a head and body length ranging from 58 to 80 millimeters and a wingspan between 320 and 380 millimeters. Its fur is dark brown on the upper side, contrasting with a paler, yellowish-brown underside, while its face, wings, and ears are black or dark brown. The ears are large and pointed, and its broad wings contribute to a highly maneuverable flight style that often includes short glides or steep descents.
This species is widely distributed across the Palearctic region, extending from southern Sweden and Denmark westward to Great Britain, and stretching as far south as Greece and Turkey, with populations further east into Tajikistan and Nepal. Serotine bats prefer habitats such as open woodlands, hedgerows, parklands, and pastures, and they are observed in towns and villages. They primarily roost in buildings, favoring structures with high gables and cavity walls, including older buildings and churches, and are rarely found in trees. These roosts are often hidden in crevices around chimneys, within cavity walls, or beneath floorboards.
Life and Habits of the Serotine Bat
Serotine bats are insectivores, with their diet primarily consisting of large flying insects like beetles, particularly chafers and dung beetles, though they also consume flies and moths. They employ echolocation to locate and capture prey, emitting calls ranging from 15 to 65 kHz. Foraging occurs within 2 kilometers of their roost, but they can travel up to 6 kilometers, often feeding around street lamps or even catching prey from the ground. They use three main foraging strategies: short flights, ground feeding, and aerial hawking, often flying at treetop height, around 10 meters above the ground.
The breeding season for serotine bats occurs in autumn, with females forming maternity colonies in buildings in May. These colonies can range from 60 to 300 individuals and remain at a single roost site throughout the breeding season. A single pup is born in early July, though births can occur as late as mid-August, and the pup is carried by the mother for its first few days. The young bats become independent at six weeks of age. Serotine bats hibernate during the winter months, from October to March, seeking shelter in old buildings, often within cavity walls or disused chimneys.
Protecting the Serotine Bat
The global conservation status of the serotine bat is categorized as “Least Concern” by the IUCN Red List of Threatened Species. Despite this global status, local populations in some regions, such as Great Britain, are listed as “Vulnerable.” The species faces threats including habitat loss, the destruction or disturbance of their roosting and hibernation sites in buildings. Changes in agricultural practices, such as the depletion of insect-rich soil due to pesticide use, also impact their insect prey base. Collisions with vehicles near roads and railways pose a risk.
Protective measures are in place to safeguard serotine bats and their habitats. In the UK, they are protected under the Wildlife and Countryside Act 1981, and they are also designated as a European Protected Species under Annex IV of the European Habitats Directive. These legislative frameworks aim to prevent the killing, injury, or disturbance of bats and to protect their roosts, which are legally protected even when bats are not present. Conservation efforts focus on preserving existing roost sites, mitigating the impact of development, and promoting practices that maintain a healthy insect population.