Why Do Earthworms Surface During Rainy Weather?
On a rainy day, you’ll often see lots of earthworms on sidewalks and roads. But what makes the worms crawl away from the safety of the soil when it’s raining? Some people assume worms come to the surface so they do not drown in their burrows. However, according to Thea Whitman, a soil scientist at the University of Wisconsin-Madison, worms absorb oxygen through their skin and can do so from water as well as from air. Earthworms can survive in water for days as long as there is oxygen present.
The Oxygen Mystery
A 1956 study found that earthworms can live for extended periods in water-saturated soil as long as there is oxygen available. However, a 2008 study suggested that oxygen consumption might influence why some earthworm species surface during rainy weather. Some species that require higher oxygen levels are more likely to come to the surface, while others that do not need as much oxygen remain belowground.
The Predator Perception
Another theory suggests that vibrations from the rain may be perceived by worms as a predator approaching, prompting them to surface to escape. However, Kevin Butt, an earthworm ecologist at the University of Central Lancashire in England, finds this idea unlikely, as predators like moles would produce distinguishable vibrations. It is more probable that earthworms surface on rainy days to move more quickly on wet ground, possibly for mating or migration purposes.
Worm Grunting and Charm
The tradition of “worm grunting” or “worm charming” involves generating vibrations in the soil to entice worms to the surface, where they are gathered for various purposes, including bait for fishing. This practice is now used competitively in events like the annual “Worm Gruntin’ Festival” in Florida.
In conclusion, the reasons why earthworms surface during rainy weather remain a subject of scientific intrigue and cultural fascination. Whether it is to escape low oxygen levels, perceived predators, or simply to navigate wet environments more efficiently, these humble creatures continue to surprise and captivate us with their behavior.
