Bat hibernacula in the Mønsted and Daugbjerg limestone mines
Daubenton's, pond, Natterer's, Brandt's/whiskered, brown long-eared bats — 10,000+ hibernating in Northern Europe's largest limestone mines. Mønsted Kalkgruber and Daugbjerg Kalkgruber, near Viborg (Central Jutland), Denmark.
Best time: 25 Aug – 30 Sep (August to September). Where: Mønsted Kalkgruber, Daugbjerg Kalkgruber (Denmark). Time of day: Swarming at the mine mouths from about an hour after sunset, peaking between 22:00 and 01:00 in late summer.
- Partly on your own
- Entry fee
- 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: 25 Aug – 30 Sep. Late August to end of September (swarming at the mine mouths at night); winter hibernation Nov–March with the mines closed
Active from 15 Aug to 15 Oct (August to October) in a typical year.
Time of day
Swarming at the mine mouths from about an hour after sunset, peaking between 22:00 and 01:00 in late summer.
- Swarming: 1 h after sunset → 01:00
What will you hear?
Audible 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.
Binoculars?
No binoculars needed. Bats swarm at the mine mouths in the dark; a bat detector matters, binoculars do not.
Where to go
- Mønsted Kalkgruber — 60 km of galleries; visitor mine open spring–autumn with bat evenings in late summer; the mine closes for the bats in winter. Map
- Daugbjerg Kalkgruber — Smaller neighbouring mine, also open to visitors in season; bat colony. Map
How to go on your own, and what it costs
Mønsted: the visitor mine is ticketed (150 DKK adult, 2026) and open 20 March–31 Oct, 10:00–16:00, with bat evenings in late summer; the swarming is recorded outside the entrances at night — tell the mine office and stay by the car park/road. Daugbjerg: same pattern. Never enter the galleries after hours or in winter.
Cost: Mønsted Kalkgruber 150 DKK adult (2026); bat evenings (check current prices); outside free.
Free or no-guide alternative: Stand outside the Mønsted mine mouths from the car park after dark in September with the office's agreement: the swarming is audible and detectable from the entrance road, free.
Who runs access
- Mønsted Kalkgruber – bat evenings (private site (owner)) — Public 'flagermus' evenings in late summer; tickets online.
Field-recording notes
Both mines are protected bat roosts; the swarming is recorded outside, at the mine mouths, with the mine offices' agreement (they run public bat evenings, which are the easy way in). Full-spectrum at 384 kHz+ and a normal pair for the audible rustle. The sites are rural — the Viborg–Holstebro road is 2 km away — and quiet at night. Do not enter the galleries outside opening hours or in winter; hibernating bats woken by disturbance die.
Sources
Similar spectacles
Bat emergence & autumn swarmingMostly ultrasonic: echolocation and feeding buzzes, social calls. Noctule social calls and some horseshoe calls are partly audible.
Autumn bat swarming at the Segeberg Kalkberg caveAudible 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.
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.
More: all spectacles in Denmark · bats · Denmark in August · Denmark in September