Why Are Worms All Over the Sidewalk?

Last Updated (Saturday, 02 April 2011 16:39) Written by Raymond Nakamura

Have you ever noticed how some days after a rain, worms literally litter the sidewalk? Are they members of some vermicide cult or can we reconcile this behaviour with a worm's normal life of eating dirt, breathing through their skin, and finding a mate, while not getting eaten, dried out, or cooked by UV rays? I decided to dig a little deeper.

Drowned and Out Explanation

Some argue that water holds less oxygen than air, so when it rains so much that a worm's burrow gets flooded, the worm has to crawl out for a breather. But this explanation may not hold water. For one thing, worms don't seem to be out and about whenever it rains, only sometimes. And if it happened during the day, they would be easy meat for birds, early and otherwise.

Gimme Sweet Lovin' Explanation

Earthworms have male and female bits, but they still need a mate to reproduce. Worms tend to be more active at night and this varies seasonally and may even be influenced by the full moon. I wonder if the scent of worm has anything to do with it. They tend to get in the mood for love in the spring and fall, at about 13 degrees Celsius (55 F), usually after a rain so the ground is wet.

Meet Market

The open space makes it easier to come across a mate. If it's raining, they don't have to worry about getting dried out and if it's at night, they don't have to worry about getting pecked on as much. They can sense the good vibrations of potential mates. Some worms crawl around in search of a worm body, while others just stick their business (anterior) ends out of their burrows and wave them around like they just don't care. In some places, you can find more than 400 worms in a square metre, and since they are not picky, they have a good chance to find that not so special someone to share some mucous, sperm, and good times. Although some marine worms coordinate reproduction with the lunar cycle, earthworms don't seem to bother.

Watching All the Worms Go By

I don't know how much their behaviour varies with species. British Columbia is home to two dozen species of earthworms (only four of them native). perhaps this leads to different behaviours. If you are interested in identifying ones in your neighbourhood, you can find some tips here. And if you're feeling inspired to look at worms more closely, you might also be interested in a joining Wormwatch, an educational Canadian science project on identifying worms and mapping their distribution.

A Hard Place

Whatever their reasons for wriggling about, the problem for worms is that didn't evolve to deal with impenetrable concrete. So they get stranded and then dried out or stepped on. And you think your life is hard.