Turtles! Yes, it’s World Turtle Day! During my herpetofaunal survey I had been lucky enough to find a spotted turtle (Clemmys guttata) right under foot. In New York, these are a species of special concern. I’ve spotted painted turtles (Chrysemys picta) in my yard and quite frequently while they were sunning themselves along rivers. I even came across a common musk turtle (Sternotherus odoratus) during my last kayaking trip. These quiet animals are more common than you might think, if you take a moment to look around.
What the word “turtle” represents actually depends on who you’re talking to and where. In North America “turtle” typically any reptile with a bony or cartilaginous shell that is developed from their ribs. It doesn’t matter if these animals are on land or in fresh or salt water. In Great Britain, though, a “turtle” is one of the water-dwelling species. A tortoise is a land-dwelling turtle and terrapin is sometimes used to describe small species found in brackish water. This is just English, mind you, so it can get pretty confusing! Many scientists refer to the group as chelonian, given that the scientific superorder is Chelonia, just to avoid confusion. For this post I’ll just stick to “turtle”.
There are over 300 living species of turtles in 14 extant families. The oldest turtle fossil is dated to 220 million years ago and is one of the oldest reptiles.
Turtles, I think, are most well known for their shells, and these shells go back in time a long ways. They evolved from the ribs out into plates, and if you ever look inside the shell of a turtle, you can clearly see this. These shells aren’t always the hard scale covering you’re probably most familiar with though; there are at least 26 soft-shelled turtle species all over the world, in the Trionychidae family. Their hard shells are covered by leathery skin and the outer edges lack the boney shell underneath.
Turtles lay soft, leathery eggs which are laid in sand or mud, and then covered. When the eggs hatch the newborns are on their own; neither parent hangs around after the eggs are deposited. The eggs are susceptible to predation, as are the newly hatched turtles, and some people/organizations collect them for incubation and release, patrol the grounds, and/or protect the newborns as they make their way into the habitat, which is often the oceans, in this case.
While all juvenile turtles are carnivorous, adult turtle diets range depending on the species and habitat. Some eat vegetation, some, algae, while others eat jellyfish, shellfish, fish, invertebrates, and the occasional carcass.
Turtles have a wide ranging life span depending on species but even the ones with shorter life spans still live many years, which is an important consideration for anyone considering a turtle for a pet. Larger species can live more than 100 years. There is some debate as to the oldest recorded animal but Addyaita, male Aldabra giant tortoise, is considered one of the oldest, and he died around the age of 250.
The Speckled Cape tortoise (Homopus signatus) is the smallest turtle, averaging 6-8 cm. An African species, the females lay only a single egg each year. The largest species on record is the leatherback turtle (Dermochelys coriacea), a marine species with an individual that measured almost 3m (9ft) in length and weighed 914 kilos (2,016 pounds). Unfortunately, the animal had drowned in a fisherman’s net..
Not only can marine animals drown in nets but human trash can cause serious problems, such as plastic bags looking like jellyfish and getting caught in a turtle’s throat, or other waste can get caught around their bodies. Wetland habitats such as swamps are commonly filled in for home and commercial “development,” river and lake-side properties are prime spots for homes, water is often contaminated with chemical pollutants, slow moving turtles get hit by cars, and eggs get preyed on by many animals, including invasive and non-native pets.
As today is World Turtle Day, it’s time to keep in mind that you can make a difference! Even something small and, I would hope, common sense, such as not running them over, saves a life!