From hibernation to antifreeze - the animals' tricks for overwintering

"The seasons" - this is the theme of the spring season of the Siegen Children's University. The second event focused on animals: "From hibernation to antifreeze - what tricks do animals use to survive the cold season?". Biologist Dr. Theodora Fuß familiarized the children with the individual hibernation strategies in a very illustrative way. A research project at the University of Siegen is studying the life of a colony of swifts near Olpe. Theodora Fuß: "The swifts migrate to warmer regions in late summer." Mona and Max - two "Olpe" swifts - are fitted with transmitters. As a result, the scientists have been able to track their flight paths to and from Africa for years. They cover up to 10,000 kilometers and reach speeds of up to 100 km/h. The animals sleep and eat in flight. The birds only stay in the Sauerland region between May and August to breed and raise their young. Theodora Fuß: "Between August and May, the swifts are only in the air".

Animals such as squirrels and jays are industrious food gatherers for the winter. The jay can memorize almost 10,000 food hiding places. This is despite the fact that the landscape often looks completely different in winter than in fall, when the food is hidden. This is made possible by the targeted and temporary growth of certain areas of the brain - more precisely, the hippocampus, which is responsible for spatial memory. Because the growth of nerve cells consumes a lot of energy, these brain cells shrink again in spring.

Roe deer and stags grow a thick coat for the winter. The hairs are shaped like drinking straws. The fur is thicker than in summer and therefore functions similarly to a down jacket. The animals can also reduce their body temperature to 15 degrees C. Furthermore, the animals avoid unnecessary fast movements so as not to consume too much energy.

Many animals switch to energy-saving mode in winter. Some hibernate, others go into hibernation and still others go into torpor. This always means that the metabolism is shut down. The metabolism is comparable to the engine of a car. It is based on food and digestion. The energy metabolism is responsible for vital functions such as body temperature, heartbeat, respiration and digestion. There is also the building metabolism for building, repairing and cleaning up. The energy metabolism ensures that living beings can produce their own body heat. The body gradually uses this up. Without food, the stores are depleted. The consequences are, for example, tiredness and freezing.

Theodora Fuß with regard to hibernation and hibernation: "The rhythm is crucial. When the animals have eaten a lot, their energy stores are full and their willingness to sleep increases." Marmots, hedgehogs and bats, for example, hibernate. They reduce their body temperature considerably, breathe less frequently and their heartbeat slows down. Marmots lose 30 to 50 percent of their weight during their hibernation, which lasts around six months. Theodora Fuß: "Animals in hibernation must not be woken up!" Otherwise they have little chance of survival.

Squirrels, badgers, raccoons and brown bears, for example, hibernate. They have long sleep phases and short, slightly slower waking phases. Their body temperature remains almost constant.

Amphibians and reptiles go into hibernation. They are alternately warm and cold because their energy metabolism cannot produce its own heat. From around October to March, the animals retreat into caves, tree openings, piles of stones or leaves and no longer move. Their heartbeat and breathing become extremely slow. The wood frog is a survival artist. It stores a lot of sugar in the fall so that its blood does not freeze completely and the ice crystals that form are less sharp. The tiny glacier flea can survive down to -15°C because it can produce antifreeze proteins to protect body fluids from freezing. Things become dangerous for the glacier flea in spring. It dies from a temperature of 12 °C.

According to Theodora Fuß, the animals generally need to conserve energy in winter. People should be quiet when walking in the forest. You can help animals to hibernate, for example, by leaving piles of leaves in the garden and providing water points all year round.