Wood Turtle on West Virginia Forest Road - Wm. Needham

Common Name: Wood Turtle, Sculpted tortoise, Red-legged tortoise, Red-legs – The protruding, distinctive scales called scutes that make up the dorsal shell or carapace have the appearance of having been carved from wood.

Scientific Name: Glyptemys insculpta – The generic name is derived from the Greek glyptos which means ‘carved’ and emys which means ‘fresh-water tortoise.’ The species name is Latin for ‘engraved.’ Both terms emphasized the sculpted shell.

Potpourri: The conical segments called scutes that make up the outer shell of the Wood Turtle almost appear to have been glued on to a smooth substrate; the conveyed appearance is that of an imbricated wood sculpture. Even though the wood turtle lives in the woods, it is named for its wood-like carapace as the most obvious attribute and not for its wooded habitat. There is a good reason for the protuberant ruggedness of the pyramidal shapes; it is the result of the continuous concentric growth of each individual scute over the fifty-plus years of the turtle’s life. Unlike most other turtles that replace the scales over time to account for growth, the wood turtle never sheds its keratinous armor; you can even estimate the age of a wood turtle by counting the concentric scute growth rings - at least up to the age of about 20 years when full adult size is achieved. The mobile fortress of the shell affords a Palladium against most predation and the wood turtle accordingly has no apatetic features to dissuade its adversaries. On the contrary, the bright red-orange legs and limbate head markings are hard to miss. The wood turtle’s roseate hues are likely an adapted display for sexual species identification; they certainly do not contribute to crypsis.

Wood Turtle_Tundra_Jun2010.jpg
The Red Legs and Head are not cryptic - D. Tundra
The peculiar physiology of turtles attests to their primordial provenance, appearing on the tellurian scene about 225 million years ago, long before the breakup of Pangaea. Turtles have no cranial fenestration (holes in the temple area of the skull) and are hence thought to have evolved from reptiles of the Carboniferous Period called anapsids that also lacked the temporal penetrations. Turtles are in the class Reptilia and order Testudines (from the Latin testudo meaning tortoise) as a taxonomic grouping for animals that have an external, or exoskeleton; they are more closely related to dinosaur-cum-birds and crocodilians than skinks and snakes. The backbone and ribs of the turtles evolved into a protective bony carapace covered with impact-absorbing cartilaginous scales, a design so intelligent that it has resisted significant evolution for eons. The fusion of the carapace resulted in the loss of the intercostal muscles between the ribs that supplement the abdominal muscles in the control of breathing in almost all other vertebrates. Recent archaeological research revealed that abdominal muscle breathing in turtles evolved very slowly, beginning with a broadening of the ribs in an ancestor 50 million years before the first fully encapsulated turtle. As turtles are monophyletic - having a single ancestor – their taxonomic classification should be fairly well settled. The wood turtle, for reasons that are somewhat obscure, has had twelve different scientific names that have ranged from Testudo insculpta when first designated by the American Naturalist John Eatton Le Conte in 1830 through intermediate and mellifluous genera Emys, Clemmys, and Geoclemmys, finally settling into the current genus Glyptemys in 2001 when DNA analysis provided the first true taxonomic basis; the genus is shared with only one other species, the bog turtle (G. muhlenbergii). The biological revisionism enabled by the gene sequencing technology polymerase chain reaction (PCR) invented in 1983 has rewritten the taxonomic textbook to the point that many former siblings have become distant cousins.

The wood turtle, like its fellow testudines, is very adaptable to habitat and environmental changes, a fact confirmed by the fossil record. While it’s current range extends from Virginia north to Nova Scotia, skeletal remains have been found in northwest Georgia from the Pleistocene Epoch, the southern migration having been necessitated by the climate changing advance of the glaciers of the last ice age. While changing temperatures is a slow process on the geologic time scale, the extinction of many plants and animals due to these changes implies a survival of the fittest persistence to those that endured. The wood turtle is fast (for a turtle); its movement has been measured at a third of a kilometer an hour with average movement of over 100 meters a day – and smart (for a reptile); a 1932 study revealed that wood turtles out-performed rats in mazes in which food was the reward. It is not unlikely that its mobility and intelligence are a result and not a cause of its continuance into what is now frequently called the Anthropocene Epoch (vice the traditional Holocene Epoch) to account for the dramatic impacts of Homo sapiens on nearly everything in nature.

Moving at what would be fast only when compared to a snail’s pace (.05Km/Hr.) the forest is a smorgasbord for the omnivorous wood turtle; it will eat most anything that it can catch. According to Turtles of the U. S. and Canada by Ernst and Lovich, an analysis of the stomach contents of wood turtles in West Virginia, revealed that 68% had consumed vegetation, 46% earthworms, 38% beetles and slugs, and 23% carrion. Perhaps more surprisingly, fungi can comprise over 30% of a turtle’s diet; six species including Amanita muscaria (the North American variant is poisonous to humans) and Russula aeruginia have been specifically identified. In fact, Ernst and Lovich warn that “the wood turtle’s consumption of the toadstool Amanita muscaria may cause poisoning of anyone who eats G. insculpta;” not an atypical caveat in the mycophobia of the English-speaking countries. But the mainstay of the wood turtle’s diet is earthworms; they have even learned to hunt them. It is an established fact that earthworms rapidly evacuate their hypogeal burrows when the plangent noises of burrowing moles (their nemesis) are emulated. Wood turtles have learned to alternate stomping with their two front feet at a frequency of about one beat per second for an average of about 8 thumps; they then pause to observe for the emergence of their vermicular refection. Using this technique, a consumption rate averaging 2.4 worms per hour can be sustained - pretty clever for a cold-blooded reptile.

The virtual indestructibility of the adult wood turtle is offset by the tenuous survivability of turtle eggs and hatchlings. After aquatic mating, which cannot occur until both the male and female become fertile at 14 -18 years of age, the female wood turtle swims ashore and lays about seven eggs in a shallow nest of soft soil near to the water, covers them with earth and trundles off leaving them unattended to await discovery by a passing carnivore. Raccoons are the most notorious of the egg-robbers; coyotes, skunks and corvids also play a role. The predation problem has been exacerbated by the proliferation of these animals with the environments that result from human habitation. The indirect effect on wood turtle populations is bad enough, but the real problem is the direct human effect. Wood turtles are classified as endangered according to the International Union for the Conservation of Nature (IUCN) red list and is in Appendix II of the Convention for the International Trade in Endangered Species (CITES); Appendix II is for the current 1,400 animal species “not necessarily threatened with extinction, but in which trade must be controlled in order to avoid utilization incompatible with their survival.” Humans are the direct proximate cause for wood turtle declines due to habitat destruction, collection for the pet trade, agricultural accidents and road kill. While there has been progress in habitat restoration with a reduction in tilled family farms and wildlife corridors, the pet trade is insidious. Adult breeding pairs are sold on the internet for about $500; one wood turtle will fetch almost $4000 in Japan. As Walt Kelly’s Pogo famously mused: “we have met the enemy and he is us.”