More than 18.000 bats in the mine
More than 18.000 bats overwinter in the limestone mine. Most of these are water bats, but there are also many of the otherwise rare pond bats. In the spring and summer months, there are not many bats in the mines, as they go out to most of Jutland, where they eat insects, so they are ready to winter again.
In the summer, the females live together in colonies where they feed their cubs, but already in August the bats meet again in Mønsted Limestone mine, where they mate before they overwinter. During the first winter months, most bats hide in loose lime or cracks. As spring draws near, and most bats have been a trip outside the mine, to see if it’s still winter, all the bats eventually hang on walls and ceilings in the mine, awaiting the arrival of spring.
When the bats settle into crevices and cracks in the underground passages to hibernate, they adjust their body temperature to the surroundings. Here with us, this means that the bats turn their body temperature down from the usual 38 degrees to only 8 degrees, which is the year-round temperature in the old mining corridors. In this way, the bats can run at ‘low flare’ all winter, using as little energy as possible. Breathing is reduced, the heart rate slows down and the combustion are reduced, so bats can live all winter long from the insects’ fat reserves built up throughout the summer.
If the bats are disturbed during their overwinter, the body temperature can be raised in a matter of minutes. However, this requires a great deal of energy consumption and should preferably not be done during the winter, as the bats then run out of fuel and can risk dying.
In Mønsted we have five different species of bats that overwinter in the mines; pond bats, water bats, long-eared bats, brandts bats and fringe bats.
Out of this stock, about 80% consists of pond and water bats.