Migration is what happens when an animal can't easily cope with the cold, winter temperatures of the areas they spend the summer. To help make the long, winter months easier to cope with, the animals will prepare by making a journey, usually a rather long one, to a warmer climate. It would be like humans moving to another house - a holiday home - every six months or so.
Bats are just one of the animals that migrate for the winter. They find the cold temperatures very difficult to live with, particularly the lack of bugs and other insects that they use to make up a huge proportion of their diet. Fruits and flowers also do not grow, which do not provide the bats with food in the form of fruits and seeds, and they also won't be attracting those insects. Food is scarce, and if it weren't for that migratory journey, many of the colony would die.
The little brown bat, one of the most common bats found across America, is just one species that travels across the world to migrate. However, they do not just migrate, they also hibernate. Some of them stick the winter out and choose to sleep through it, and some colonies fly and migrate. It very much depends on where in the world their roosts are, and how close to the warmer temperatures they currently are. Not much is known about the migratory and hibernation habits and patterns of so many species of bats, and studies are constantly ongoing. They sure are strange little creatures, and we are learning more about them every day.
Places in Africa see bats turning up in November and December of most years, yet it is not know where those bats originally came from - where they are migrating from. They also can't seem to work out where they are going also. The flying creatures are outsmarting us. It is believed, however, that expectant mothers will be more likely to migrate than hibernate, hunting out better climates and plentiful food supplies to give their young the strongest and best start in life.
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