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Science
Volume 40 Issue 21 • Sept 30-mid-Nov., 2010, now in our 40th season

The Invader Came from Petworld

by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station

Moments earlier, I was walking around Douglas Lake in Northern Michigan (Tip of the Mitt) at the University of Michigan Biological Field Station (http://www.lsa.umich.edu/umbs), and I came across a recent hatchling snapping turtle on the path near the lake. The tiny guy/girl (I did not look that closely) was about the size of a silver dollar and it was struggling across a gravel road to complete its first major journey since escaping its shell. 

This reminded me of the turtle a friend brought to me to care for and to serve as an educational tool for children visiting the field station.  It was hard for him to give up his pet and an unselfish act and as you’ll see it was also the right thing to do as opposed to releasing it into the wild.  It’s a pretty hefty little turtle about 8-9 inches long with expressive eyes and a fair amount of attitude.  He’s an aquatic species, and loves paddling about and occasionally hauling out to warm up under a variety of heat lamps.

Turtle
Photo by Len Germinara

What’s wrong with this little guy?  Where does the conflict come in?  Well, he is non-native to Massachusetts and it used to be frequently sold in pet stores to people who want a low maintenance pet.  Unfortunately, this species has more heating and lighting requirements than one would think.  It’s not necessarily the Jessica Simpson of pets, but neither are they pet rocks, and when people find out there is a lot involved both in time and cost, they tend to start rethinking their investment.  That is when a bad decision starts impacting our local native turtle species.
So what is this evil invader?  It’s called a red eared slider.  The red-eared slider Chrysemys scripta elegans (formerly known as Trachemys scripta elegans) is a semi-aquatic turtle belonging to the family Emydidae.  Emydidae is the largest and most diverse turtle family.  The family Emydidae includes approximately 95 species in 33 genera.  Members are distributed throughout North America, northern South America, Europe, northwestern Africa, and Asia.  Emydids are primarily freshwater species, though some species inhabit brackish waters or are terrestrial.  The "slider" part of their name comes from their ability to slide off rocks and logs and into the water quickly.

Backing up a bit, the term “turtle” is basically a generic name for the group of reptiles which includes tortoises and terrapins whose body is shielded by a special bony shell developed from their ribs.  All extant, or living, turtles are members of the order Testudines, which includes both living and extinct varieties of turtle.  The etymology of the order name Testudines and the family name Chelydridae are intertwined in a strange chicken versus the egg fashion.  The term “chelys” is Greek  (the Latin is “testudo”) for “turtle” and was originally known as a stringed musical instrument that had a convex back of tortoiseshell or of wood shaped like the shell.  The word “chelys” was used to specifically refer to the oldest lyre of the Greeks, which was said to have been invented by Hermes.  According to the Homeric Hymn to Hermes (475), he was attracted by sounds of music while walking on the banks of the Nile, and found they were coming from the shell of a tortoise across which were stretched tendons which vibrated in the wind.  The word “chelys” continued to be used for a variety of stringed instruments.  The term Chelydra was formed by combining “chelys” with  “hydros” for water serpent.

There are two major groups of turtles: sea turtles, which grow to large sizes and live in the oceans in the temperate and tropical regions of the earth, and fresh-water turtles.  Fresh-water turtles which spend the majority of their time on the land are generally called tortoises.  In the United Kingdom, aquatic fresh-water turtles are known as terrapins. Fresh-water turtles are generally much smaller, ranging in size from a few centimeters to a few feet long. All turtles have a protective shell around their bodies. The top part of their case is called the carapace, the underside is the plastron, and the two are connected by the bridge.  Even though they spend large amounts of their lives underwater, aquatic turtles are air-breathing reptiles, and must surface at regular intervals to refill their lungs with fresh air. They also spend part of their lives on dry land.

Back to our little friend paddling about the Nantucket Field Station Lab. Red-eared sliders are natives of the southern United States, but they have become common in various areas of the world due to the pet trade and it has started to become a problem to us here in the Northeast. As you’ll soon see, we are not alone in addressing this issue as this turtle’s superior survivability, toughness, and aggressive nature allow it to outcompete the native species in areas in the U.S. for habitat and resources.

The normal range for the red-eared slider in the United States is from Illinois to the Gulf of Mexico, and the East Coast to western Texas.

It has been found in other regions, presumably because people released their pet turtles into those areas.  It spends most of its time in or around water. Although it can be found in lakes and rivers, the red-eared slider prefers marshes, ponds, and slow-moving waters that supply food and basking areas. In northern areas it will hibernate (well, technically brumate, i.e., becoming less active but occasionally rising for food or water), which means interlopers on Nantucket will burrow in the mud or somewhere else warm and stay put during most of the winter.  Hatchlings are approximately 1 inch in diameter.  The red-eared slider can grow up to 12 inches in length.  Red-eared sliders are omnivores and eat a variety of animal and plant materials in the wild including, but not limited to fish, crayfish, carrion, tadpoles, snails, crickets, wax worms, aquatic insects and numerous aquatic plant species.

Red-eared Sliders kept as pets generally reach sexual maturity between 2-4 years of age. In the wild, females may not mature until 5-7 years of age. Females are generally larger than males, though males have longer tails and very long front claws.

The skin of a red-eared slider is green with bright yellow stripes.  A patch of red behind each eye gives the red-eared slider its common name, although some sliders may be missing this color.  Some turtles may also have a small patch of red on top of their heads.  The Red-eared Slider has webbed feet and strong claws.  The shell of hatchlings is green with a fine pattern of yellow-green to dark green markings. As the turtles mature, the carapace may become yellow or olive green, with the fine pattern changing into dark lines or patches on each scute.  Portions of the shell may be white, yellow, or even red. As the turtle ages, even the lines and patches may slowly disappear until the shell is a uniform dark olive green or greenish-brown. Some male turtles will become "melanistic" which means will develop a uniformly dark gray or black color as they age. The red-eared slider can live up to 40 years with some individuals reaching 50 or 60 years of age.

Students at the University of Toledo in Dr. Daryl Moorhead’s lab in the Environmental Sciences’ department have done research evaluating the danger to local native turtles species that is posed by the cute red eared gate crasher.  They found that the turtles expand into their range quickly when released and that their aggressive nature and toughness give the turtles a genetic advantage over the smaller cousins.

We have three different species of turtles on Nantucket who all love to be near freshwater, the spotted turtle (Clemmys guttata), the painted turtle (Chrysemys picta), and the common snapping turtle (Chelydra serpentina).  There is some discussion as to whether we have any of the states’ other species (ten in total) such as the eastern box turtle; but we’ll concentrate on the aquatic species for now.

Our red eared slider has very special needs not the least of which is space. This web site: http://redearslider.com/ offers some basic information for those of you who have adopted this pet. So in a manner that is identical to our elbowing each other for a spot of land, turtles too fight for space and breeding area.

The truth is that many of this country's non-native invasive wildlife species were brought to the state through the pet industry. There are invasive parrots and African clawed frogs in Los Angeles County, snakehead fish in several states, a plethora of invasive fish and reptiles in Florida, and so on. When possible it is ideal to have laws in place to limit bringing in species that are simply too easy to release. In the United States, it is illegal for pet stores to sell a red-eared slider that has a carapace (shell) less than 4 inches in diameter. This is because of the risk of salmonellosis and due to the invasive nature of these turtles when released into the wild. As of July 1, 2007, it is illegal in Florida to sell any wild type red-eared slider, as they interbreed with the local yellow-bellied slider population – Trachemys scripta scripta which is another subspecies of the same species. In case you are in doubt, if you have a pet turtle or a pet of any aquatic nature from koi to alligator, once you have decided you no longer can care for it, it is best to escort it to the river Styx.

Our little red eared slider will be a good teaching tool for many years. As this is the Fall issue, I’d like to remind folks to come visit the Nantucket Field Station at 180 Polpis Road and to come to the Nantucket Conservation Foundation Cranberry Festival on October 9th from 11-4 at the Milestone Cranberry bog.

 

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