Why You See Earthworms After Heavy Rains (Lumbricus terrestris)

September 29, 2015

Gondwana recently experienced heavy rains which flooded allot of the reserve. With this, allot of earthworms have made their way to the surface and can be seen on the jeep tracks.  

If you pick up an earthworm you’ll feel a slimy mucus surrounding them. This mucus makes moving around in the soil a lot easier. The moister also helps them to breathe through their skin. If the soil is very saturated or an earthworm is submerged in water, it can still survive as long as there is enough oxygen.

According to different research articles a few theories have concluded as to why earthworms appear on the surface after heavy rain. The one theory states it’s for migration. With all the water at the surface it gives the earthworms a chance to move greater distances across the soil surface than they could do through soil.

Another theory is that rain drops make vibrations on the soil surface that can cause similar vibrations to predator vibrations, like that of moles. Earthworms will often move to the surface to escape moles.

A third theory is that Different earthworm species consume oxygen at different rates, sometimes at different times during the day, so some are more at risk of running out of oxygen in wet soil than others. (Matt Soniak, internet article in May 31, 2013). In 2008, zoologists in Taiwan looked at two earthworm species, one that will surface after heavy rains and one that doesn’t. They concluded that the worm surfacing after rain consumed oxygen a lot quicker, mainly at night-time. This specie could also stay underground for a little while when it rained during the day, but had to come up sooner if it rained at night. The other worm specie consumed oxygen at a lower rate and could live underground absorbing less oxygen. This then only counts for some earthworms. Mating reasons has also been mentioned, but only for some species.

By Lizaan Claassen




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