DEAR JOAN: Can you explain the behavior of the local population of earthworms that insist on leaving their deep, dark underground abode to explore above ground after a heavy rain downpour?
In our Livermore neighborhood, they will crawl on the grass and ground cover and end up being washed into the curbside rain gutter. As children we would “rescue” the worms floundering in the deep water. We didn’t want them to drown.
The worms will also emerge out of the cracks in the street asphalt after a heavy rain shower. Alas, most are crushed by passing vehicles or eaten by a murder of crows.
— Don Lenkeit, Livermore
DEAR DON: While those goofy worms are always up for rain dancing, the real reason has to do with a basic function necessary to life. They need to breathe.
Worms have neither lungs nor gills. Instead, they breathe through their skin, and although we’d be lousy at it, they breathe quite nicely underground. The soil has plenty of oxygen in it to suit the little squirmy invertebrates, but that changes when it rains.
The water displaces the oxygen in the soil, making it difficult for the worms to get enough air. It’s not so much that they drown, but that they suffocate. So the worms make their way to the surface and fresh air, although breathing above ground isn’t as easy for them as it normally is underground.
Scientists aren’t certain why they don’t return to the soil once the rain has stopped and the ground becomes less saturated. It could be that they lose their way and are unable to locate their dens from on top of the ground. As you can imagine, the above world is a lot different from the below, and they might become so distracted, confused or bothered by traffic, people and predators that they can’t act and become stranded.
While that’s all bad news for the worms, a lot of creatures that feast on worms aren’t complaining.
DEAR JOAN: Given our strange Bay Area weather (maple leaves falling while it’s snowing, nasturtiums are popping up), I wonder if the birds think it’s fall or spring.
Sparrows, juncos, chickadees, wrens are all over our yard. Have they not flown south yet? Will they stay through the winter, if it doesn’t get too cold?
— Pat, Los Altos
DEAR PAT: We’re all unsettled by climate change, so I don’t doubt the birds are a little confused, too. But they aren’t so unsettled that they’d go against their nature and not migrate.
Changes in temperature can either delay migration or send the birds off earlier than normal, but those changes occur more slowly, over many seasons and generations.
The visiting birds you have are among several Bay Area species that remain here year round. Through many generations, they’ve taken a liking to our more temperate climes. That doesn’t mean they don’t migrate. All birds do, but the native populations travel much shorter distances, moving further inland where food, water and shelter are more plentiful, or to traditional breeding grounds that have been established. That’s why at certain times of the year your yard is filled with birds, and at other times, they are few.
Animal Life runs on Mondays. Contact Joan Morris at [email protected]
Comments are closed.