Hurtling through the night with unique abilities

Author: Michael Frede
Author: Michael Frede

Hunting in the dark without night-vision glasses         

Bats can fly in total darkness because they use ultrasound for orientation. Similar to a radar device, they emit ultrasonic waves that are reflected from structures in their vicinity and are received again by the bats. In this way, they can manoeuvre even in dense treetops or cave systems. And in addition to their own navigation signals, they still precisely discern the sounds made by flying, crawling or calling prey.

During the extremely fast-paced hunt, a bat's heart beats at a very high frequency: the extremely oxygen-rich blood can be pumped through the arteries at more than 850 beats per minute.

When the density of their prey (mainly insects) decreases due to cold temperatures in the last quarter of the year, bats withdraw into caves, tunnels, buildings, etc., in which the temperature does not fall below 0 degrees Celsius for any lengthy period of time. Here they creep into the narrowest crevices or hang motionless upside down from the ceiling and only move from this winter roosting place if absolutely necessary. The heart rate is then reduced to as little as 20 beats per minute.

In the spring the animals awake. In the females, most of whom mated in the autumn, fertilization now takes place with the sperm, which stayed dormant throughout the winter in their womb. While the embryo is growíng, the females form larger groups for the birth of their young (usually one per female). The living quarters of these females are called nurseries. They must be located very close to insect-rich feeding habitats.

In their habitats bats need structures such as trees, hedges or buildings for orientation by means of ultrasound. For some species, a multi-lane road or featureless agricultural landscape can become a barrier. If there is sufficient food availability in the vicinity of a nursery (in some species foraging flights may be longer than 20 kilometres), the young bats become independent of their mothers in the late summer.

For the adult bats, the mating period then commences.

So far, 21 species of bats have been recorded in NRW, but two of them are currently thought to have become extinct in our region.