How do earthworms adapt to life underground?

The behavior of the earthworm in cold and hot conditions

In the winter and summer months, earthworms are very rarely seen. At best, during a downpour, you can watch the animals crawl out of the ground and stay on the damp ground. As soon as the weather conditions become less favorable for them, they disappear back into the ground. In spring and autumn, on the other hand, earthworms are much more frequent on the ground. Apparently they like the climatic conditions much more in these months. Why is that?

The earthworm - an animal that is cold-blooded

Earthworms do not have a constant body temperature and are therefore cold-blooded animals. This means that your organism is unable to maintain its own temperature in external heat or cold. You can influence them through their behavior alone.

If the climatic conditions become uncomfortable or even life-threatening for them, they look for more favorable temperature zones. In contrast to cold-blooded animals, organisms of the same temperature, like most birds and mammals in general, can regulate their body temperature to a certain extent.

In which temperature range do earthworms feel comfortable?

Our native earthworms prefer temperatures between 10 and 14 degrees. Temperatures below this are more likely to be tolerated than significant deviations upwards. The dungworms are an exception. They spend their lives in the compost heap or in the dung heap and feel most comfortable in warm temperatures between 20 and 25 degrees.

Temporary withdrawal in hot or cold conditions

As soon as the temperatures deviate from the earthworm's tolerance range, it retreats to climatic zones that are comfortable for it. If their acceptance values ​​are moderately exceeded or not reached, the animals first move to deeper areas of the ground that are not yet affected by the changed outside temperature. There they wait to see whether the weather takes a turn that is acceptable to them. If this is not the case, they use another survival mechanism: They fall into rigidity, cold or dry.

The stasis

Both in summer and in winter, earthworms repeatedly or continuously fall into the stasis that is vital for them - whenever the weather deviates too much from their needs. In this state, the animals cease their vital functions for the most part. Similar to other cold-blooded animals that only survive extreme climatic conditions through this measure, they curl up like a ball. This often happens in small groups or entire colonies.

The place for this retreat is usually far below their usual living tubes at a depth of up to one meter below the surface of the earth. In winter, heat-storing places under tree stumps or large stones are often chosen. A high snow cover has an isolating effect anyway. The resting place is lined with excrement and stabilized. It is sealed off from the outside world by a dung plug at the entrance.

How long an earthworm can withstand this mode of survival depends mainly on its age. In general, young animals have a better chance of surviving a longer period of rest. But they also lose a large part of their original body weight in the meantime, which under certain circumstances can lead to death.

What happens to the offspring during the winter?

The earthworm cocoons deposited by earthworms usually survive the cold season unscathed, as they are deposited in a protected and frost-free place at the appropriate depth. During the cold months they continue to develop until the young hatch in spring.