Bats are both fascinating and frightening creatures. In the past they were seen as bringers of bad luck and bad omens of accidents or deaths. These days we know more about them, but they can still be perceived as mystical animals.

Bats are divided into two species: megabats, the majority of which eat mainly fruit and use their sense of smell and sight to find food. The other species is the microbat, which mainly eats insects and uses their echolocator to find food. The bat species found in Sweden are all microbats and belong to the family of Vesper bats.

20 of the world's 1100 bat species can be found in Sweden and 8 of these have been sighted in Tykarpsgrottan during the yearly winter inventories.

All the bat species found in Sweden hibernate during the cold winter months when there are very few insects for them to eat. During early autumn the bats build up the reserves of body fat that will keep them alive all through winter. For this reason you should never wake a hibernating bat because it needs to preserve its energy until spring when it wakes up and starts hunting for insects again.

Hibernation lasts between three and eight months and during this time the bats' heart rate decreases from about 400 beats per minute to 25 beats per minute.

Down in Tykarpsgrottan the bats sleep hanging from the cave ceiling and on pillars from October until March/April. The cave is closed during this period, except for during the annual Christmas fair, so as not to disturb the hibernating bats.

The bats fly out of the cave to hunt when the weather gets milder above ground and insects start appearing again.