Have you ever had one of those moments that was so unexpected, so incongruous, that you had a hard time believing it really happened?
I did, just last weekend.
You may remember those recent days, when temperatures topped out in the 60s. That in itself was notable—it was, after all, almost mid-December. But when the rain started to fall on Sunday, the scene progressed from unusual to absolutely uncanny.
I’d spent the day doing housework and errands, and had anticipated a quiet evening of folding laundry. But then the phone rang. It was my friend Tricia calling, and with excitement in her voice she delivered her one-word message: “Worms!”
If you’ve been to Hickory Knolls before, you know that we have quite a number of live animals—our education “team,” so to speak. Several of these critters consume a diet heavy on invertebrates, including insects and, yes, worms.
Over the years we’ve found that bait shop nightcrawlers are not only expensive, but also of varying quality. Besides, I don’t know if you’ve noticed the way we have, but bait shops themselves are today much harder to find than they once were.
At any rate, when you get a magical combination of weather that is not only warm, but also wet, it means easy pickin’s—at least as far as worms are concerned.
Tricia and I hastily made a plan to head to Davis Park, where worms crowd the paved paths like holiday travelers clog O’Hare. And almost for the same reason…
When our airports fill up at Thanksgiving and Christmas, it’s because people have a specific destination in mind. They’re heading out to see friends and/or family, and given the distance they need to cover and the time in which they need to complete it, air travel make the most sense.
When earthworms crowd our rain-slick sidewalks, they too have destinations in mind. Maybe not specific locations, but certain goals nonetheless. Scientists are somewhat divided on the exact purposes of these movements, but several highly touted theories exist.
If you’ve handled an earthworm recently, or in fact ever, you’ve probably taken note of the critter’s clammy—some would say slimy—skin. That slime provides the worm with a vital protective barrier. Without it, the worm would not be able to keep its skin moist. Without moist skin, the worm would not be able to breathe. And without the ability to take in oxygen—well, the hapless creature would end up crisp and dry. And indeed, they often do.
For that reason—self-preservation—some scientists believe worms opt to take advantage of warm, wet weather and literally hit the streets, to migrate to new areas. They can move faster using overland paths than they can by burrowing through the soil. And because everything’s soaking wet, there’s no chance of desiccation and death.
With so many worms in such close proximity, incidental contact is bound to occur. However, some research now indicates that that contact may not be simply by accident. Some worm species use rainy nights to carry out mating functions. (Yes, even though earthworms are hermaphroditic, it still takes “two to tango,” so to speak.)
Then there’s the research indicating that worms actually form herds and swarm an area when conditions are favorable. Using environmental cues, the worms emerge en masse, then use social cues—like touch—to make group decisions on where to move next. Such large numbers, all in one area, give the worms the same protection enjoyed by flocks of birds and hordes of insects: While predators may strike and some individuals may perish, the rest of the group gets to live another day.
Finally, some scientists assert that worms emerging during rains are reacting to the vibrations they sense when the raindrops hit the ground. It has been shown that earthworms will crawl up and out of the way when they perceive the movement of a nearby predator, like a mole. Rain may create similar vibrations and result in similar movements. (Ever hear of “drumming” for worms? It operates on the same principle. Rubbing a ribbed piece of wood against a stake in the ground produces tiny tremors, resulting in worms vacating their burrows to escape what they feel might be danger.)
Regardless of the theories that may or may not have been at work the other night, I know one thing is certain: The Hickory Knolls vermivores—animals that feed on worms—will be eating like kings. Our worm bin (okay, crisper drawer in the work room fridge), is set up with fresh bedding, oak leaves and just a little cornmeal—the perfect combination to keep our worms happy and healthy.
I know a column about earthworms might seem an odd way to wish you all Seasons Greetings. But it’s our sincerest hope that you will—just like the worms in our well-stocked bins—enjoy a happy and healthy holiday season. Merry Christmas to all, and to all a good night…crawler…
Pam Otto is the manager of nature programs and interpretive services at the Hickory Knolls Discovery Center, a facility of the St. Charles Park District. She can be reached at 630-513-4346 or potto@stcparks.org.
December 18, 2015
And to all a good night … crawler
Earthworms and Christmas lights? Normally these two phenomena don’t occur at the same time. But our recent warm weather caused an incongruous confluence.