Winter is the period between autumn and spring. The calendar winter begins on 21 December, when the night is longest and the day is shortest. It lasts until 21 March, when spring arrives and the night is the same length as the day, known as the equinox.

TREES

Trees start preparing for winter at the end of summer. They gradually reduce the amount of water they take in so that they don't freeze in winter. They produce as many sugars as possible by photosynthesis, which they store in the roots and under the bark. They also extract chlorophyll (green dye) from the leaves, so that even in autumn the leaves turn colour, leaving only shades of red and brown. Then it is time for the leaves to fall.

In autumn we also usually have strong storms with winds that loosen the soil and make the trees unstable. On wet ground, the trees' roots find it difficult to cling to the ground and resist the wind. If they had leaves that act like big sails, many of them would break. Being leafless also helps in winter, as snow does not get trapped over large areas and break branches as it would otherwise.

Conifers keep their leaves - the needles. The needles contain essential oils that prevent frost. Conifers grow vertically upwards, with horizontal and weakly branched branches. When snow falls, the branches drop down as if they were leaning on each other to support themselves, reducing their surface area and making it easier for them to withstand the weight of the snow.

ANIMALS

Animals are adapted differently to the harsh winter conditions. Migratory birds easily escape winter and move away. But not all animals can travel more than 1000 km to warm places, so they have to adapt a little differently.

Amphibians and reptiles hide under stumps, natural burrows, and even a toad can dig a burrow of its own and hibernate there. We say they hibernate. During this time, their metabolism slows down and they use very little energy.

Warm-blooded animals, such as birds and mammals, have a constant body temperature that they need to maintain with energy. The best way to get energy is to eat, which is how many animals get plumper in autumn, as they spend all summer building up their subcutaneous fat reserves. They also adapt to the cold temperatures by growing thicker fur and fluff. A hermelin can grow as many as 37 underfur hairs for every one fringe of hair. The birds like to bask in the sun in winter and trap air between their feathers, which is a good insulator. This makes the birds look rounder in winter, often hiding their heads and feet in their feathers and fluffing themselves up to keep warm. Interestingly, winter birds' feathers are brightly coloured in preparation for their spring nuptials, whereas mammals have pale grey top hairs to make them easier to hide.

Some animals cope with low temperatures and food deprivation by hibernating. Bears are often said to hibernate all winter. But bears and squirrels only sleep for the winter. They lower their body temperature by a few degrees, reduce the number of breaths they take and slow down their metabolism, similar to animals that hibernate. Animals that only weigh up to about 5 kg also go into hibernation. The largest of these is the marmot. It sleeps like a slug and is as fat as a slug, which is true. That's how slugs, hedgehogs and bats sleep through the winter. In a bat, the number of breaths is reduced from the normal 60/90 breaths down to 4/6 breaths per minute. The heart rate also drops from 250 beats to 18 to 80 times a minute.

As all animals conserve energy in winter, the disturbance of humans can be fatal for them. Gams use much more energy to escape in high snow than they do on land, and it is difficult to replace this energy in winter. Wildlife needs peace and quiet in winter. That is why it is extremely important to keep our four-legged friends on a leash, because after the chase our furry companion returns with us in our warm house, where for a deer, running in the snow can be fatal.

Some animals wouldn't survive the winter, so in the fall, they lay their eggs in a safe place and then die. For example, butterflies like moths and many spiders overwinter in the form of eggs, protected in silky cocoons. Beetles mostly survive the winter as larvae, while butterflies typically overwinter as pupae. However, brimstone and peacock butterflies overwinter as adult butterflies, hiding in safe shelters. That's why, on particularly warm winter days, you might see them flying around. Under bark, you can find excellent hiding places for ladybugs, earwigs, and firebugs. In addition to the amphibians, grasshoppers and stinkbugs like to burrow into the soil, while the crickets go numb in their holes in the ground. 

Winter doesn't affect earthworms much either, as they, like ants, retreat deep into the soil through their tunnels. Among insects, bees remain somewhat active, but only enough to warm the hive by vibrating their wings.

What about snails? Snails with shells protect themselves from winter conditions with a solid limestone cap, with which they close the entrance to the shell.