Latin name: Eptesicus serotinus
Weight: 15 to 35 grams
Wingspan: 32 to 38 cm
The serotine bat is one of the largest bat species in the Netherlands and has relatively long and broad wings. Its coat is two-coloured: coffee brown on its back and café au lait on its underside. Its face, ears, and skin are blackish-brown. Its ears are relatively small and longer than they are wide. The serotine bat got its name because it flies out later in the evening than another large bat, the common noctule (serotine is derived from the Latin serotinus, meaning ‘evening’).
The sounds that the serotine bat makes during its hunting flight are FM-qcf pulses of 60-25 kHz with a pulse duration of 13 milliseconds. In open spaces, it produces FM-qcf pulses of 27-25 kHz. The highest volume is 25 kHz.
As far as we know, serotine bat nursery colonies are only found in buildings. They live in cavity walls, behind panelling, under cornices and roof tiles or under the lead around chimneys. Sometimes, they are also found in attics. Serotine bat are rarely found in bat boxes. During mating season (September-October) similar habitats are used. The (nursery) groups usually consist of a few dozen and rarely more than 150 animals. Their hunting grounds are within a radius of 1 to 5 km (rarely more) around the colony.
In winter, serotine bats search for narrow and relatively dry places such as cavity walls, cracks and tears in attics, old cellars, and sometimes cracks close to the entrance of caves. Little is known about their hibernation strategy. From November to March/April, they practically disappear from our radar.
The serotine bat hunts above open to semi-open landscape, especially in the shelter of ascending elements, such as forest edges, hedges, and lanes. It often flies at a height of 5 to 10 m, but sometimes it flies higher between the treetops. In villages and on the outskirts of cities, serotine bats can be seen at dusk hunting around lampposts, in gardens, and in parks. Occasionally, they hunt in groups. Characteristic of serotine bats are their relatively slow wing stroke and slow flight in long paths, with wide curves and sudden drops.
Serotine bats mainly catch insects from the air, but sometimes they also snatch prey from leaves or from the ground. They primarily catch larger species of moths, beetles, and mosquitoes.