Life In A Rotting Log

LIFE IN A ROTTING LOG

Wednesday, July 04, 2007 (Napanee Beaver)

Friday, July 06, 2007 (Picton Gazette)

There is an old log on one of the hiking trails at Algonquin Provincial Park that dates back to 1890. Loggers back then had felled a giant white pine, and after taking off the top and all the limbs, they discovered some defect in the trunk. Taking the good part, they left the defective section to rot in the woods. Even after more than 110 years, the log still retains its shape, but is slowly on its way to becoming part of the forest floor. Dozens of seedlings, some of them conifers, have taken root atop the moss covered log, hastening its decay.

I came upon a similar log one recent weekend while wandering around Macaulay Mountain in Picton. It was difficult to determine what the fallen tree might have been, as it was like a corpse – so far advanced in decomposition that nothing was visible that might offer a clue as to its identity, except for guessing it might have been any one of several different species that were thriving beside it.

An old log is a cool place to find things, for while life appears to be over, life continues on within its rotting mass. A log whose breakdown is well under way is porous and spongy, and readily absorbs moisture from the ground. Even if the log is unable to absorb water from the ground, there is always an internal source of water. The fungi that are always present in logs actually produce water as a result of their functioning. Those animals that live in a log require moisture since they lose it rapidly through evaporation from the body surface under dry conditions. This is especially true for millipedes and slugs.

A log represents a sort of controlled atmosphere. This is important since many of the animals that live in a log are unable to control their body temperature. Salamanders and snakes are occasional visitors to logs. In fact, this is most likely where you would find the retiring little brown snake. Some animals live their entire lives in logs – winter as well as summer.

Most of us are familiar with the pill bug, wood louse or sow bug. Look for them in your basement near the sump pump, or wherever it may be damp. You will not see them right away, as they hide under damp boards and other objects. It is a scavenger common to decaying logs, and is unusual in that it is actually a crustacean. This makes it a close relative to the shrimp, lobster and crab.

But what are they doing away from the usual habitats of shrimps, lobsters and crabs? Well, at some point, these small oval bugs apparently gave up the watery habitat of their close relatives and has succeeded on land. They have not, however, given up their need for moisture. The air around these bugs must be moist in order for the blood running through the gills – and they do have gills, like their relatives – to absorb oxygen. Hence, their fondness for rotting logs as well as damp basements. In the logs, these little pill bugs provide important items in the diets of salamanders, frogs, spiders and foraging birds. I poked around in the log at Macaulay and several of these flat, brownish bugs tumbled out into my hand.

I mentioned millipedes earlier; one can also find centipedes too. Both are arthropods, also related to the crabs and lobsters. Although dubiously blessed with many legs, they don’t have nearly as many as their names suggest. A millipede, however, might beg to disagree as he has to move his in careful sequence lest they become entangled. It has as many as 50 segments with two pairs of legs per segment, for a grand total of 200 legs. We found numerous millepedes along the trails at Deroche Lake, east of Thomasburg three weekends ago, and still wonder why there were so many.

Centipedes on the other hand seldom have more than 15 segments, and only one pair of legs per segment, for a total of 30 legs. While millipedes are largely vegetarian, consuming rotting leaf matter, thus turning organic materials into usable compost, centipedes are carnivores, feeding on larvae. They lost their sense of sight and smell many years ago and rely entirely on their sensitive antennae.

Centipedes have developed the ability to secrete and inject prussic acid into their victims, a poison so lethal that even a small amount if ingested, can kill a human being as one researcher almost found out. She was studying centipedes in Africa and finding no shortage of specimens, began collecting them in a plastic bag. As she worked she began to experience nausea, particularly when she opened the bag to pop in a few more specimens. As it turned out, the centipedes were poisoning one another by secreting the poison, the centipedes’ natural defense, and they had come close to poisoning their collector as well.

It is all these little creatures, working harmoniously together, that will one day return these logs I found to the earth, enriching the soil, and benefitting the trees and other vegetation that have located nearby. For the log at Algonquin Provincial Park, its days are numbered, and in another hundred years, or less, Park staff will have to remove the interpretive sign as there will be nothing to see but a slightly raised knoll of powdery soil.