Friends of Myles Standish State Forest

East Head Reservoir Eco Tour




The northern red-bellied cooter ("cooter") is a large basking turtle.

Size Wise

By the Seat of your Chair - Charlie Pye

The cooter is the second largest turtle in the forest, next to the snapping turtle.  While the males may grow up to twelve inches long, females may be a little longer, at up to thirteen and a half inches and weigh up to thirteen pounds.

Shining Shells 

Just Hanging with Friends - Michele Wood - 2016

On cool days, cooters often climb into the sun to warm up. Look for their shiny shells on hammocks, islands and on downed trees. Cooters can't come out of their shells. The shells are part of them. 


A Long Name Tells a Story

The northern red-bellied cooter (Pseudemys rubriventris) (“cooter”) has a long name. “Northern” is to discriminate it from nine other species of cooters, whose ranges are up and down the east coast as for west as Texas.  Cooter comes from kuta a name for large river turtles in the nations of Mali, Gambia, and Guinea, brought to this country by enslaved people from southwest Africa, the derivation of cooter is from their languages. Pseudemys, the genus name, derives from the Greek pseudes meaning false or misleading, and emydos, which is a genus of freshwater turtle. Thus, the genus name means they look like, but are not from the genus Emys. The species name, rubriventris, means red belly and is named for the female’s underside, as below.

Red Belly Basking

Rubriventris -  Linda Howes - 2017

Note how large the back foot is. Not only does it propel the turtle quickly through the water it also acts as a solar panel absorbing heat as the cooter basks. All extremities are spread and the neck is extended to increase the surface area in the sun. Mature females begin nesting activity from late May to early June.  They typically nest within 300 feet of the water's edge.  Nest holes are dug about 4 inches deep, where the females typically lay 10–20 eggs. Red-bellied cooters have temperature-dependent sex determination.  Nests with warmer temperatures produce females, while cooler nests produce males. This is a concern because of a warming planet.

Incubation lasts 73–80 days.  Plenty of time for the eggs to be eaten by skunks, who are the main predator, plus racoons, foxes, coyotes, cats and dogs (human sponsored predators) and many others. In fact, predation of eggs is one of the main reasons the numbers of cooters have crashed from their height. While most hatchlings emerge from late August through October, if late summer weather is unseasonably cool, some eggs may overwinter and hatch the following spring. New hatchlings are eaten by herons, crows, bullfrogs and fish. When growing, the young cooters eat aquatic vegetation, mostly Myriophyllum sp., which is a kind of milfoil. Cooters also eat any bite-sized snack that they see; insect larvae, tadpoles, snails, worms, etc.

Females reach maturity at 13–20 years, while males reach maturity at a younger age. Life expectancy is believed to be more than 50 years. This extended juvenile time-frame, especially for the females, means that they may not reach breeding age. But once they are too big for anything to swallow they have few predators, mostly humans.

Butt Breath- Underwater Respiration

Near the end of the GI tract is the cloaca (Latin for sewer), an all purpose place for the products of digestion, elimination and reproduction. Cloacae are present in sharks, amphibians, reptiles and birds. The cooter pumps water into the cloaca through the vent to act as a flush. But this does much more. The rich blood vessels in the walls of the cloaca absorb oxygen while releasing co2, like another lung. This allows the cooter to stay underwater for long periods of time, depending on the temperature of the water. The hotter it is the faster the metabolism and the more often the cooter must surface to breath. Oppositely, the colder it is the longer a cooter can stay underwater. During a long cold winter a cooter may stay under the ice for many months, as all metabolism slows to a crawl.

Bright Future

Now, a restocking program by MassWildlife’s Natural heritage program has been raising cooters to about the size of a human hands before releasing them. Once they are fist size they become too large for a bullfrog to swallow, which is their major predator. More than 4000 red-bellied cooters have been released.

All line drawings by: Patricia J. Cassidy