I have always been a log flipper. Every time you flip a log you never know what treasures you may find. First and most important is that there is a whole ecosystem under a log and when it is turned over it does disrupt the system. When flipping logs we need to be as gentle as possible and return the log as best as we can to the original placement. With that understanding, let’s flip some logs to take a closer look at life under a log!
A log lying on the forest floor is a microhabitat that provides all the necessities for life. Water, shelter, food are all present and allows a vast and complex system to exist. Probably the most important characteristic is that the log regulates temperature and moisture keeping them relatively constant even as the temperature and humidity above is constantly changing. The salamander is one of the most abundant vertebrates in a forest ecosystem. Feeding on mostly small invertebrates the redback salamander plays a very important role in nutrient recycling. These salamanders belong to a group of lungless amphibians that absorb oxygen and water through their moist skin. They need to keep their skin cool and moist and the log on the forest floor accomplishes this for them.
Similar to the salamander, the potato bug, pill bug, rolly-polly, woodlouse, isopods or whatever name you have learned for these small critters need a moist environment to survive. They belong to the group Isopoda, which most are aquatic and breathe through gills. Underneath logs they are busy eating dead plants and play a role in recycling nutrients in the forest. They are very abundant in Ohio with over a dozen described species. The majority of species are introduced, but there are two native species that are listed as endangered in the state of Ohio and can only be found in cave environments. They are food for other animals found under the log as well.
Other common critters found under a log are the gastropods. These are the snails and slugs utilizing the shelter and dampness that the log provides and venture out at night to feed on vegetation. I remember growing up, my father used to put boards down in the garden so that the slugs could be found there during the day. Their fate was usually a saltshaker which of course pulls all the water out of the slug and is fatal. This process was an attempt to keep the slug damage in the garden to a minimum. While there are some native slugs, most of the ones that damage crops are of European descent. In the autumn and winter when flipping logs you may see a small pile of little white round eggs. These are slug eggs that will overwinter under the log and hatch in the spring. Slugs are hermaphrodites being both male and female and determine sex during mating. They locate a partner by following trails of slime left behind and curl into mating ball. The tentacles of a slug have light sensing eyes on the upper pair and a chemical or smelling organ on the lower set of tentacles, all of which are retractable. Their snail cousins support a shell can be found hiding under and log waiting for the cool damp night to go about snail activity.
Millipedes and centipedes are often encountered but their identification is often confused. Millipedes are more rounded in shape and have two legs per body segment. They are decomposers; eating mostly dead vegetation, compared to centipedes which are predators. Centipedes have flattened bodies with only one pair of legs per body segment. Plus, centipedes are fast! This allows them to capture their prey and utilize venom that is delivered from large venom claws directly behind their head.
A variety of insects can be found under a log, from the very small springtail to larger beetles. Even in winter, under a log is a great place to find hibernating insects. One on the most famous hibernating insects in our area is the wooly bear caterpillar. This amazing insect has been documented to hibernate up to twelve years in colder climates before forming its pupa and cocoon, which can also be found under logs. Many bees, hornets and wasps utilize logs for their hibernation as fertilized queens. They will emerge in the spring to start their own colony and begin their annual cycle again.
Small mammals can also be found under logs on forest floor and if you are lucky you may run across a short-tailed shrew as they tunnel under the logs on their endless search for food. They have extremely high metabolisms and need to eat an extremely large number of calories daily to fuel themselves. This translates into about 3 times their weight in food each day! They do have toxins in their saliva that is used to help subdue prey, sometimes even prey much larger than themselves.
While logs do provide habitat for this diverse assemblage of organisms, without fungus to break down the wood, our forest would be piled high with dead trees. Fungi release nutrients in the wood fiber and are a food source for many of the animals we have already mentioned. Cleveland Metroparks does have a policy to leave fallen trees in the forest. For some this may look cluttered, but the life that abounds under a log is fantastic and is a very important piece of the forest ecosystem.
Join me on a hike; I am sure we will flip some logs to see what treasures we can find!