When it's cold outside, people just turn up the heat and spend more time indoors. But what do animals do? Seals protect themselves from the cold with a thick layer of fat. And when the water begins to freeze, they make sure that there are breathing holes in the ice.
Many animals grow an extra, thick and warm winter coat when conditions get colder. These Bactrian camels have long and shaggy fur in the winter because temperatures can drop to minus 30 degrees Celsius in their habitat, the arid regions of Central Asia.
Stoats, which are related to weasels, don't only get a thick coat. In the winter, their brown fur turns white, so that they are better camouflaged against the snow and ice.
Brown bears hibernate in the winter, withdrawing into caves to sleep. To save energy, their heart rate and metabolism become slower during this time as well. But they wake up every now and then to look for food. Female bears also give birth in winter.
Unlike brown bears, hedgehogs hibernate uninterrupted in winter. During this time, their body temperature drops sharply. They eat nothing and rely on fat reserves to keep their body warm. Disturbing an animal that is hibernating can often result in its death.
Groundhogs hibernate even longer, often for six months or longer. They roll into groups together in holes in the ground. Breathing only two times per minute, their body temperature drops to five degrees Celcius. And their stomachs and intestines reduce to half their normal size.
Bats spend the winter hanging from the ceiling of caves. These little guys have made their home in the cellar of an old brewery in Frankfurt (Oder), near Germany's border to Poland. Often, they huddle together to stay warm.
Huddling to keep warm isn't only popular with hibernating animals. The German winter is especially hard for these poor mongooses in Frankfurt zoo. They are better acclimatized to the warmth of the African grasslands.
When it gets too cold, Europe's migratory birds fly south. These white storks are spending their winter in the Serengeti in Tanzania. Other storks even fly as far south as South Africa, which is around 16,000 kilometers (10,000 miles) away from their normal habitat.
Cold is relative. Other migratory birds from the Arctic head to Germany in the winter. Every year, thousands of wild geese spend their winter in the lower Rhine region, where the temperatures are more pleasant than back at home. The flocks of bird are even a tourist attraction.
In the fall, squirrels put aside eating supplies. The bury the food in the ground or stow it in crotches. They remember some of their hiding places, but they find most again through their keen sense of smell. If they forget, the seeds germinate in the spring.
Animals that do not hibernate have to eat a great deal to maintain their body temperature. Getting enough food can be a challenge for small birds like the blue tit. They are always happy to feed on fat-rich bird food.
In zoos, the carers leave heat lamps for exotic animals, so that they do not freeze. These meerkats, which are native to Southern Africa, are very grateful for the warmth.
Domesticated pets have it easy in comparison to animals in the wild. They can stay in the warmth of their owners' homes. And, for some, there's even specially-made little jackets to keep them comfortable.
Winter is back - with a vengeance. People are shoveling the snow, wearing their heaviest winter coats and spending more time indoors. But what are the animals doing?