Vertebrate animals are those with backbones -- fish, amphibians, reptiles, birds and mammals. As a group, they are much less abundant than invertebrates such as insects, spiders, and mollusks. But there is one vertebrate that occurs in stunning numbers, often quite close to home.
Among common vertebrate species, chipmunk population densities can range from 10 to 18 per acre, garter snakes might reach 35 per acre, vole densities can reach 300 per acre. The vertebrate population champ, however, is the red-backed salamander.
Red-backed salamanders spend about 90 percent of their time under rocks, logs, and leaf litter, so they are seldom seen ... unless you look for them.
I flip rocks and roll logs when I walk in the woods. (I always return them to their original position.) I never know exactly what I'll find -- grubs, slugs, earthworms, beetles, millipedes, snails, snakes -- but I almost always find red-backed salamanders. Often I find two or three under a single rock or log.
Population densities of red-backed salamanders can range from 800 to 8,000 per acre. In some Appalachian forests, the biomass of red-backed salamanders exceeds that of all the birds and mammals that occupy the same area.
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. Curiously, they belong to a family of lungless salamanders. They respire directly across their moist skin.
Two color forms or "morphs" occur in most red-back 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.