At a glance
| Size: | Length 55–80 mm; wingspan 320–380 mm; weight 15–350 g. |
|---|---|
| IUCN (GB): | Least Concern. |
| Call peak: | ~25-30 kHz. |
| Active: | Emerges around 20–30 minutes after sunset. |
Flying in a slow but powerful manner, often close to treetops, over meadows, parkland, and around street lamps.
Identification
A large bat with broad wings, giving a slower, heavy flight (sometimes compared to a “flying rodent” in silhouette).
Life history
- Breeding: Maternity colonies of 20–150 females form in tree cavities during spring/summer. Single pup born late June–July; Flying at ~3–4 weeks
- Mating: Autumn “swarming” at roost entrances and during flight.
- Lifespan: Average 7–10 years, maximum recorded over 20 years in Europe.
Roosting
Summer maternity colonies usually in older buildings, behind soffits, tiles, or in roof voids; tree cavities used less frequently. Colonies can number from 20–60 females.
Hibernation
From late October to March, often in buildings (churches, barns, houses) and sometimes caves or cellars; usually singly or in small numbers.
Feeding & foraging
Prefers larger beetles, moths, and cockchafers; often audibly crunches prey in flight (sometimes audible to people on quiet nights!).
Echolocation
Calls are relatively low frequency: peak 25–30 kHz, dropping into the 20–25 kHz range during approach/feeding buzz. Social calls can be variable and often lower.
Population & conservation
- Largely restricted to southern England and south Wales, with a stronghold in lowland counties; rare further north.
- Widespread but patchy, often tied to older building stock and pastoral landscapes
- Threats include loss of roos sites, pesticide usage (reducing insect populations) and increased light pollution.
- Conservation would be helped by retaining, or better, increasing pasture, hedgerows, and dark corridors that help support foraging.
In Sussex
- Serotines are regularly recorded but remain less common than Noctules.
- They are often associated with villages, farmsteads, and the Weald, where older barns and houses provide roosts.
How to help
- Keep access points (gaps under tiles, soffits, ridge beams) open where bats use them.
- Install bat boxes (ideally large, crevice-type or Kent-style boxes) on barns, farm buildings, or mature trees.
- Keep ponds, ditches, and streams natural and unpolluted for aquatic insects.