Why Do Earthworms Come Out At Night?

If you have a compost pile in your garden or know about working your soil, you must be familiar with the shiny and sluggish earthworms.

Despite their (not-so-attractive) looks, these invertebrates are essential to the health of your garden. With their activity, they aerate the soil, make nutrients more accessible to your plants, and even fertilize the substrate with their “by-products” resulting from feeding on dead organic matter.

Even if when we say “earthworms,” we all have a specific picture in mind, the truth is that there are more than 6,000 varieties of these invertebrates. In the United States alone, you can find about 180 species of earthworms.

And among those varieties, there are the “nightcrawlers” varieties, who feed above ground at night. If you have crossed your yard at night and noticed them, you shouldn’t be surprised.

But have you ever wondered why do earthworms come out at night? Well, you are in the right place to find out!

Why Do Earthworms Come Out At Night?

Why Do Earthworms Come Out At Night?

Earthworms don’t have eyes but have photoreceptors in their body that detect light (and distinguish it from the dark).

But when exposed to the sunlight and warmth, these invertebrates can die, meaning they will never venture out under the sun. So, their survival depends on staying deep in moist soil.

Because of the threat to their life, earthworms will only come out to the surface at night and feed on grasses and other detritus they might find in the vicinity.

Don’t forget that earthworms breathe through their skin, which needs to stay moist to keep exchanging oxygen. Coming out of the soil might cause them to dry and suffocate. For this reason, they will rarely venture out of their burrows.

Nightcrawlers, in particular, are worms you can find at night when the grass is wet with dew (and so easier to digest). These species are much bigger than the typical earthworms and greyish, so you shouldn’t have problems recognizing them. You may easily spot them in areas of the yard where the grass is scarce or cut very short.

Why Do Earthworms Come Out After it Rains?

Why Do Earthworms Come Out At Night?

You might know how earthworms seem to become more visible after rain. Some of us are so used to this that we don’t even pay attention to them anymore.

And some know that these invertebrates come out after heavy rain because they are drowning. But drowning refers to the lungs filling with water, and earthworms don’t have lungs, so how can they drown?

It seems that earthworms need moisture for breathing. But there are many species of earthworms, and not all present the same behavior. For instance, some species are more susceptible to water immersion and will come to the surface when they need oxygen.

And this might explain why earthworms come out at night. But other species never come to the surface, as they are used to lower intakes of oxygen and don’t need more.

Most garden worms will survive underwater for long periods if there is enough oxygen to breathe. So, they will come out after it rains because the humidity in the air helps them move around without worrying about suffocating or drying out.

So Why Do Earthworms Prefer the Dark?

Why Do Earthworms Come Out At Night?
Earthworms need moisture and darkness to survive. Because they breathe through their skin, they cannot risk getting dry under the sun, as it might cause them to suffocate.

Crawling out of their tunnels and making small holes in the ground at night minimizes the chances of putting their lives at risk. Plus, they have fewer predators to worry about during the night.

Related Article: Do Earthworms Eat Plant Roots?