Serotine Bat – Eptesicus serotinus
Habitat: Pastures, Parklands
Description: A large bat with light brown fur and darker facial features and wings.
Size: One of the larger UK bat species.
Origin & Distribution: Native. Found across southern England and occasionally in Wales. They are absent from Scotland and Northern Ireland. Records of roosts, trapping and grounded animals suggest roost occupation is declining in the south-east England, whilst increasing in the south-west. Genetic evidence suggests there must be some travel across the English Channel.
Diet: An early emerging species, they feed on moths, beetles, and flies. They feed mostly on the wing (hawker), and will on occasion, capture prey off the ground (gleaning).
General Ecology: Summer roosts are usually in roofs and walls of large houses. The serotine is quiet, resulting in building roosts being under-recorded. Few winter roosts are known, however, they are occasionally captured swarming whilst roosting at underground sites. Their flight is slow, yet highly manoeuvrable allowing it to fly very close to the ground as well as amongst the canopies of trees. They have a relatively large foraging range, with an average commute of 6.5km in pastoral regions and 8km in more arable regions of southern England. They follow treelines or hedgerows when commuting.
Breeding: Maternity colonies tend to be small and almost exclusively formed by adult females, with males roosting separately or in small groups. These roosts are almost exclusively located in buildings, particularly residential houses constructed in the late 19th and early 20th century which have high gables and a substantial roof space. Roosts are chosen that are close to woodland, water, and pastures.
Conservation Status: Although registered as Least Concern globally, serotine bats are registered as Vulnerable in Great Britain and regionally in England and Wales. Legally protection of serotine bat roosts is likely to help increase populations in the future. They are negatively affected by a reduction in prey availability due to pesticides used in agriculture. They also suffer from high juvenile fatality rates making the species vulnerable to increased weather fluctuations during the summer months induced by climate change. Changes to building conditions with an increase in cases of entanglement. In the future their range is predicted to increase, whilst their habitat is in decline, resulting in unpredictable population dynamics.
One of the larger British bats, the serotine bat has a rounded tragus and a dark muzzle, ears, and wing membrane. They have a post-calcarial lobe and a free tail tip. Compared to the noctule bat, the serotine bar has longer, darker fur. Droppings are larger and may be confused with those of the greater horseshoe bat but are oval in profile.
- Muzzle: Projecting part of face, including nose and mouth.
- Wing Membrane: An extension of the skin of the bats body which covers the wings.
- Tragus: Piece of skin near the ear canal.
- Post-calcarial lobe: An extension (lobe) of skin found on the wing behind the back foot and ancle spur (calcar).
- Free tail tip: end of the tail is not connected to the wing membrane.
Range: 22-55 kHz
Most energy: 31 kHz
Average duration: 8.8 ms
Nyctalus leisleri (Leisler’s bat) and Nyctalus noctule (noctule bat)