River Cooter (Pseudemys concinna) — identification, habitat & look-alikes

The river cooter is a big, plant-eating turtle of eastern U.S. rivers, often seen basking on logs and sliding into the water at the first sign of trouble. Look for the yellow C-shaped marks on the side of its shell. Released pets have also turned up far from home, including in California and Washington.

Appearance

Appearance: The upper shell is olive-brown to nearly black with swirling yellow lines and backward C-shaped marks on the side scutes. The lower shell is usually plain yellow. Each side of the head and neck usually has a yellow Y-shaped mark. Old adults can turn so dark that the pattern fades.
Growth form: Adults usually have a shell 9–13 in (23–33 cm) long, rarely up to about 16.5 in (42 cm). Females are larger than males.

Look-alikes

Red-eared SliderTrachemys scripta

Sliders have a red stripe behind each eye and a dark smudge on each scute of the lower shell. River cooters lack the red stripe and usually have a plain yellow lower shell.

Why they get mixed upThey bask side by side in the same rivers and lakes.

Yellow-bellied SliderTrachemys scripta scripta

No red ear stripe, like a cooter, but its yellow lower shell has black spots along the edges.

Why they get mixed upIt lacks the slider's red ear patch, so it looks more cooter-like.

Northern Red-bellied CooterPseudemys rubriventris

Has a single wide vertical bar on each side scute instead of a C-shaped mark, and two prominent tooth-like points on the upper jaw.

Why they get mixed upIn Virginia, this is the turtle most often mistaken for a river cooter.

Where it lives

Typical habitats: Rivers
Lakes and reservoirs
River sloughs
Range: Native from Virginia south to central Georgia and west to eastern Texas and Oklahoma, reaching north to southern Indiana, with isolated populations in West Virginia, eastern Kentucky, and north-central Tennessee. The Suwannee cooter subspecies lives in rivers of northern Florida. In Missouri it lives across the southern half of the state.
Preferred conditions: Prefers slow pools with lots of underwater plants and plenty of logs or rocks for basking.
When to see it: In Missouri
Breeding May–Jun · Active Apr–Oct

Behavior

Diet: Mostly aquatic plants and algae—in one Missouri reservoir study, green algae made up as much as 90% of the diet. Also eats fallen mulberries and, now and then, crayfish, mussels, and insects. Young turtles eat more animal food.
Activity: Active by day, mostly April through October in Missouri. In cooler areas it spends winter buried in mud underwater, though it may come out to bask on warm winter days. It can stay underwater a long time, which helps explain why it is often overlooked.

Life cycle

Breeding season: Mates in the water in spring; in Missouri, females nest from late May through June.
Nest: Females dig nests in soil on land near the water.
Clutch size: 4–30 eggs (about 15 on average); several clutches a year
Incubation: About 70–96 days; in Missouri most hatch in August–September, and some hatchlings wait in the nest until the next spring.
Time to maturity: Males likely start breeding around age 6, females around age 10 or older.
Lifespan: 40 years or more in the wild

Conservation

IUCN Red List: LCLeast ConcernLow risk of extinction
Status: Listed as endangered in Illinois and Indiana, at the northern edge of its range. Threats include pollution, drained backwaters, road deaths, and collection for food and the pet trade; Missouri has ended commercial harvest of the species.