June 26, 2012
According to the oral stories and traditions of the Great Lakes Woodland Indians, the turtle is a powerful symbol. One legend details how the turtle’s back provided a base for the first land that was formed in the midst of the great waters. Mackinac Island takes its name from a word in the Ottawa language meaning “Great turtle”.
So begins the Michigan DNR’s Turtle page. I found it fascinating reading, and I hope you enjoy it as well.
The earliest fossil remains of turtles date back about 225 million years to the late Triassic period. For millions of years they shared the planet with the dinosaurs. Unlike the dinosaurs, turtles survived the ecological and climatic changes that caused the extinction of many forms of life. All this was accomplished with little change to their anatomy: early fossils still closely resemble today’s turtles. Soft bodies were covered by a bony shell, with an oval shaped skull and beaked mouth; however these early turtles had teeth and had not yet evolved a way of pulling their heads into their shells. Today some 260 species of turtles (including the terrestrial tortoises) are found worldwide in nearly all temperate and tropical habitats.
The protective shell is one key to the turtle’s survival. Unlike the turtles in children’s cartoons, real turtles cannot climb out of their shell: A turtle literally wears part of its skeleton on the outside of its body. A turtle’s shell is composed of two parts. The upper portion, or carapace, is formed from the flat dermal bones covered by broad scales (scutes) and is connected to the backbone and ribs. The lower shell is the plastron and includes the abdominal ribs and portions of the shoulder girdle.
The shape and weight of a turtle’s shell can provide clues to its lifestyle. Shells can be helmet shaped, like the Blanding’s and eastern box turtle shells, for better protection against predators. A further adaptation of hinges in the middle of the plastron allows these turtles to partly or fully close their shell, offering even more protection for the head and legs. Shells can also be soft and rubbery like the pan caked shaped shell of the fast swimming spiny soft shell turtle, which is covered by skin instead of hard scales. Snapping and Musk turtles have very small, cross shaped plastrons, probably adapted to facilitate walking on pond and lake bottoms. Land living turtles have heavier shells – while these shells offer extra protection from land predators, their weight makes it more difficult to move quickly. The shell of a turtle that spends most of its life in a water environment is lighter in weight and more streamlined in shape.
Read on for more. Regarding the Eastern Box Turtle, they say that its high, domed carapace is dark with a radiating pattern of yellow or orange. The plastron has a flexible hinge that allows the turtle to completely close its shell. Box turtles are Michigan’s only true land-based turtle. They prefer open woodlands and adjacent meadows, thickets, and gardens, often near shallow ponds, swamps, or streams and eat plants, berries, worms & insects and carrion.
Box turtles’ home range is less than five acres, and they routinely live for several decades, occasionally a century or more! One important note is that the turtle’s life in captivity is MUCH shorter, so please enjoy them in their natural habitat! The box turtle is uncommon to rare in southern and western Lower Peninsula and the southern & eastern UP, and they are protected by Michigan law as a special concern species.
Here’s a (pdf) map of Eastern Box Turtle occurrences and you can get some more info and photos from Wikipedia’s Box Turtle entry and also get some really great information & photos about the Eastern Box Turtle and conservation efforts from the Herping Michigan blog!
More of Michigan’s animals on Michigan in Pictures!