Signs of Spring 4: Earthworms on the Sidewalk!

NASA, Wikimedia Commons

The full moon of March (which this year will occur on March 12) has many names. The Algonquin’s called it the “catching fish” moon, while the Omaha and the Cree called it the “little frog” or just the “frog” moon (we will have to wait a few weeks more, though, before the frog choruses begin to grace our evenings!). The Kiowa called it the “bud” moon, and several other tribes referred to it as the “crow” moon after the increased vocal activity of the flocks of crows as they sorted out their social and reproductive hierarchies after the long and stressful winter. A number of the northern tribes called the March full moon the “crust” moon after the icy snow crusts that form on the persisting snowpack due to the daytime thawing and nighttime re-freezing of the surface. They also called it the “sap” moon after the rising sap of the trees (especially the sugar maples!) which, interestingly, is caused by the same daytime warming and nighttime freezing cycles that cause the snow crusts.

The name most frequently applied to the full moon of March today, though, and attributed to Native American sources (although never in my readings to a specific tribe), is the “worm” moon.

Photo by H. Casselman, Wikimedia Commons

Walking out on last week’s warm, wet mornings, the “worm” moon appellation seems quite appropriate. On almost every sidewalk, driveway, or parking lot a significant number of “earthworms” of various species were wiggling along on the wet surfaces, moving in apparently random directions out from their former burrows in the surrounding grass. Why are so many worms emerging all at once? The emergence is probably a behavioral response to moisture and temperature variables that helps to disperse and expand the boundaries of an earthworm population (no, they are not drowning in the wet soil!). As earthworms reproduce and their clustered cocoons hatch the new worms tend to be clumped together, the spring dispersion helps to spread their numbers out across a soil habitat.

Photo by R. Bushby, Wikimedia Commons

The arrival of the migratory flocks of robins is coincident with this worm emergence event. Watching the foraging robins voraciously eating worms really gives you a good idea of how many earthworms are actually slithering along on or just hiding beneath the soil surface. Many bird species (including the grackles that just showed up under my bird feeder last week!) also opportunistically, and with less time and effort investment than the robins, catch and consume earthworms. European starlings, an alien invasive bird species, have even been known to follow the hunting robins at a distance and then, on seeing a robin grab a worm, dive at them noisily so that the worm is dropped when the startled robin flies away. The starlings, then, get a stolen, protein-rich, meal. This is only one of the ecologically disrupting things that starlings do, but that’s a topic for another essay.

As many of you know, I studied earthworms very intensively in my Ph.D. research and in a variety of studies here at Penn State back in the 1980’s and early 1990’s.  A “worm” moon, then, should have some special meaning to me, and, I admit, it does. It is not at all clear to me, however, how Native Americans could have had any ecological or historical connection to these earthworms! Almost all of the organisms we call “earthworms” are, like the European starling and the gypsy moth and Colt’s foot and so many other species of plants and animals around us, organisms that were introduced to North America by European settlers as they spread across the forests and plains of the continent. Earthworms are a group of alien, invasive species!

Photo by S. Shepherd, Wikimedia Commons

Earthworms do many important things in their soil habitats. They improve the stability of a soil’s structure and its drainage properties, and they accelerate rates of leaf litter decomposition and nutrient cycling. Aristotle called them “the intestines of the Earth,” and Charles Darwin spent many years of his life intensively observing and describing their activities and their extremely positive influences upon soil fertility. My own research described the immense benefits that robust populations of earthworms could have on leaf litter decomposition in established forests ecosystems and on re-forested strip mines, and in the cycling and rehabilitation of sewage sludge.

A few years ago, though, an article in the Science section of the New York Times described some of the more negative consequences of the extremely active shredding and burying of leaf litter in worm rich soil ecosystems. Earthworm activity leads to the loss of leaf litter habitats for a wide variety of other invertebrates. It also leads to the loss of the protective, soil covering leaf litter “blanket” and changes the nature of the soil community’s nutrient and energy webs. Earthworm activity also changes the way that organic materials are distributed through the soil profile. The soils of what seem to be undisturbed ecosystems are, in fact, irrevocably changed from their original conformations by the actions of the introduced earthworms.

So, how could Native Americans describe the mass emergence of earthworms in the spring and relate it to the March moon if these earthworm species didn’t arrive in North America until possibly the Seventeenth or even the Eighteenth Centuries? I don’t think that they could or did, and careful examination of lists of specific tribal moon names backs up this idea. No specific tribal designation for the March moon includes the “worm” moon.  Fish, frogs, buds, crusts, crows and more are listed, but no worms. My feeling is that the “worm” moon is, like the worms themselves, an imported thing brought by the settlers from their European homes that quickly became incorporated into the structure and perceived history and ecology of their new environment.

Did the increased abundance of the earthworms lead to increases in American robins and other earthworm eating birds? Did earthworm activity change forest soil properties to favor different tree species? Did the cleared land plowed into farm fields become more productive because of the swelling numbers of earthworms? Did the earthworms cause the extinction of some litter dwelling beetles and other insects? Did the activities of these extremely active earthworms drive native annelid species into their very restricted present day distributions?

What interesting ideas! Something to look at in my retirement!

Happy worm moon, everybody!

 

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One Response to Signs of Spring 4: Earthworms on the Sidewalk!

  1. Jennifer Wood says:

    Thanks for the reminder that the “worm moon” is nearly upon us, Bill! Fascinating!

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