Next time you walk through a mature forest, try to guess the most abundant vertebrate animal in the woods. Chickadees, chipmunks, garter snakes, and woodland voles would be reasonable suggestions, but all fall short. A pair of chickadees requires a territory of three to 17 acres; chipmunk population densities range from 10 to 18 per acre; under the best of circumstances a diligent search might find 35 garter snakes per acre; and after a population explosion vole densities reach 300 per acre.
Impressive as these numbers may be, they pale when compared with the most common vertebrate in the eastern woods -- the red-backed salamander.
I can't walk the woods without flipping rocks and rolling logs. (I always return them to their original position.) I never know exactly what I'll find -- earthworms, beetles, grubs, millipedes, slugs, snails, snakes -- but I almost always find red-backed salamanders.
Often I find two or three under a single rock or log. Just the other day I found three under a rock in the front yard. I've always known these lizardlike amphibians were abundant, but when I checked some references, I was stunned to learn just how common they are. Population densities of red-backed salamanders can range from 800 to 8,000 per acre!
Red-backed salamanders measure 3 to 4 inches from snout to tip of tail and are found from Minnesota eastward to the Maritime Canadian provinces and south to North Carolina. Two color forms or & quot;morphs & quot; occur in most populations. The red-backed morph has a broad reddish-orange stripe extending from the neck to the base of the tail. The lead-back morph lacks the red stripe but is often found with red-backed morphs.
Active at night
Like most salamanders, red-backs are active at night and commonly roam the forest floor on rainy nights, so they're seldom seen except by rock flippers and log rollers. And though red-backs are easy to find under rocks and logs, on any given day most are below ground. In four consecutive weekly populations surveys in Michigan, for example, the number of red-backs collected each time did not decline over time. This suggests that most of the time most red-backs are under ground.
Because red-backs are so abundant, they play an important role in forest food chains. They're active predators and eat just about anything they can catch. Their menu includes ants, termites, beetles, earthworms, spiders, snails, slugs, mites, centipedes and millipedes. On the other hand, red-backs are important food items for small forest snakes and birds that forage in the leaf litter. Towhees come immediately to mind.
Breed in the fall
Surprisingly, red-back salamanders usually breed in the fall. Though males breed every year, females in the northern part of their range breed every other year. Apparently it takes northern females more than a full year to generate energy-rich yolks for a full clutch of eggs.
Males find females by following pheromone trails. After some ritualistic posturing, the male deposits a spermatophore -- a package of sperm -- on the ground. The female then straddles the spermatophore, picks up the sperm, and stores it in a specialized chamber called the spermatheca, where she can store the sperm for months. In the spring or early summer when the female lays her eggs, she releases the sperm and fertilizes the eggs as they are laid.
The eggs, usually six to eight, are laid in grapelike clusters in natural cavities and crevices under rocks and logs. They are pale, less than a quarter-inch in diameter, and enveloped in gelatinous material. The female coils around the eggs to protect them from predators and prevent them from drying out during the six-week incubation period.
After hatching, juveniles remain in the nest with the female for several weeks before dispersing.
To observe red-backed salamanders in the field, flip a few rocks and roll a few logs. But be careful where you put your hands if you live in rattlesnake or copperhead country. Use a walking stick or an old putter to keep your hands out of harm's way.