Autumn bat swarming at the Segeberg Kalkberg cave
Daubenton's, Natterer's, pond bat, Brandt's/whiskered, brown long-eared, Bechstein's — 30,000+ hibernating, 7–8 species. Bad Segeberg, Schleswig-Holstein, Germany.
Best time: 20 Aug – 25 Sep (August to September). Where: Noctalis – Welt der Fledermäuse and the Kalkberghöhle, Kalkberg open-air theatre (Karl-May-Spiele) (Germany). Time of day: Swarming builds from about 22:00 and peaks between midnight and 02:00 in September.
- Partly on your own
- Low cost
- No binoculars needed
- Sound 3/5
Open it in the interactive calendarSunrise and sunset listening times for the day you pick, and the map.
When is the best time?
Peak: 20 Aug – 25 Sep. 20 August to 25 September (swarming at the entrances from 1–2 h after sunset); hibernation Nov–March
Active from 1 Aug to 15 Oct (August to October) in a typical year.
Time of day
Swarming builds from about 22:00 and peaks between midnight and 02:00 in September; record from outside the fence with Noctalis's agreement.
- Swarming: 22:00 → 02:00
What will you hear?
Audible chatter and wing-flutter of hundreds of Myotis circling the cave mouth; on a full-spectrum detector, dense FM sweeps and social calls — one of the busiest bat soundscapes in northern Europe.
Binoculars?
No binoculars needed. Bats swirl at the cave mouth in the dark; a bat detector matters, binoculars do not.
Where to go
- Noctalis – Welt der Fledermäuse and the Kalkberghöhle — Bat centre directly at Northern Europe's largest natural hibernaculum; cave tours April–Sept; swarming observed from the entrances (Noctalis runs evening events). Map
- Kalkberg open-air theatre (Karl-May-Spiele) — The stage sits on the same hill; after the season ends (early Sept) the site is quiet. Map
How to go on your own, and what it costs
The cave entrances are gated and protected: record from outside the fence with Noctalis's agreement (they are used to researchers), from the public path on the Kalkberg. Noctalis exhibition Tue–Sun, cave tours daily April–Sept (ticketed); they run detector night walks.
Cost: Outside the fence free; Noctalis exhibition and cave tour tickets (check current prices).
Free or no-guide alternative: Stand on the public Kalkberg path outside the cave fence after 22:00 in September (tell Noctalis first): the swarming is audible and detectable from there, free.
Field-recording notes
The cave and its entrances are a protected roost (BNatSchG §44) and are gated — record from outside the fence with Noctalis's agreement; they are used to researchers. Town noise is real (Bad Segeberg centre is 300 m away, B206 nearby), so expect a floor; the bats themselves are close and loud enough. Full-spectrum at 384 kHz or higher plus a normal pair for the audible wing-noise. September nights are cool and calm; avoid the Karl-May season (late June to early Sept, evening shows with pyrotechnics).
Sources
Similar spectacles
Bat hibernacula in the Mønsted and Daugbjerg limestone minesAudible squeaks and wing-flutter of hundreds of Myotis swarming at the entrances; on a detector, dense FM sweeps and social calls; tawny owls in the beech above; otherwise rural silence.
Bat emergence & autumn swarmingMostly ultrasonic: echolocation and feeding buzzes, social calls. Noctule social calls and some horseshoe calls are partly audible.
Bat emergence from karst cavesAudible squeaks and wing rustle at cave mouths from Miniopterus colonies of thousands; with a bat detector, horseshoe-bat constant-frequency calls at 80–110 kHz and bent-winged FM sweeps.
The Plateau fruit bats of Abidjan — a city-centre roost flying out to the Banco forestA shrieking, squabbling wall of sound from the big trees of the Plateau administrative district, wing-slaps and jostling, then the rush of the evening emergence over the avenues and the lagoon bridges. The return at first light is quieter and more musical — thousands of bats settling and arguing over branches above the empty Sunday streets.
Straw-coloured fruit bat roost at 37 Military Hospital, AccraA continuous shrieking, chattering wall of sound from the roost trees over the hospital and the 37 lorry station, wing-slaps and squabbling as bats jostle, then the rushing of the evening emergence over Liberation Road. Pied crows and a few raptors work the edges.
Straw-coloured fruit bats over FreetownThe squabbling, squeaking chorus of a straw-coloured fruit bat roost and the wing-rush of the dusk emergence over a city — one of the great urban wildlife sounds of West Africa, if the colony can be found.
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