River cooter (Pseudemys concinna)

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Florida cooter, head detail
IUCN Red List species status – Least Concern LEAST
CONCERN

Top facts

  • The river cooter is the largest North American member of its family.
  • The temperature at which river cooter eggs are incubated determines the sex of the hatchlings.
  • River cooter hatchlings are omnivorous, eating a variety of plant and animal matter, but adults of this species tend to be primarily herbivorous.
  • The river cooter is threatened by collection for the Asian food market.
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River cooter fact file

River cooter description

KingdomAnimalia
PhylumChordata
ClassReptilia
OrderTestudines
FamilyEmydidae
GenusPseudemys (1)

The river cooter (Pseudemys concinna), a freshwater turtle (2), is the largest North American member of its family (3). This species has a narrow, oval-shaped carapace which is slightly serrated and flared towards the rear (2) (3) (4).

The carapace is green or olive to dark brown in colour (2) (3) (4) (5) with an intricate reticulated pattern of yellowish markings (2) (3) (5). These markings are relatively variable and may be thinner or absent in older individuals (2) (3). Each scute along the margin of the river cooter’s carapace has a wide, yellow bar running down the centre, while the lower parts of each of these scutes are patterned with blotches or rings (3). The underside of the shell, known as the plastron, is yellow to orange in colour (2) (3) and may occasionally be marked with a black pattern (3) which fades with age (2) (3).

The neck, limbs and tail of the river cooter are olive to brown or black (2) with cream, yellow or orange stripes noticeable on the head, chin and legs (2) (3) (4). Wide yellow stripes can be seen on the underside of the neck, with the most central stripe branching to form a Y-shaped mark (2).

The adult female river cooter tends to have a higher, more domed carapace than the male (2) (3), and lacks the straight, elongated foreclaws present in the male (2) (3) (4) (5). Hatchlings of this species differ from the adults in being more brightly coloured with a greener shell, brighter markings (2) (3) and a keel running down the centre of the carapace (2).

Also known as
Suwannee cooter.
Synonyms
Emys hieroglyphica, Emys mobilensis, Pseudemys concinna subspecies metteri, Pseudemys floridana subspecies suwanniensis, Pseudemys suwanniensis, Ptychemys hoyi, Testudo concinna, Testudo floridana.
Size
Male carapace length: up to 32 cm (1)
Female carapace length: up to 40 cm (1)
Hatchling total length: 27 - 39 mm (1)
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River cooter biology

Across much of its range, the river cooter is active from April to October, hibernating in the mud or on the bottom of its watery habitat during cold winters. However, in warmer winters this species may remain active year round (2). The river cooter is mostly diurnal, foraging underwater in the early morning and late afternoon (2) and spending much of the rest of its day basking in the sun with other individuals of its kind (2) (3) (4) (5).

The adult river cooter is a primarily herbivorous reptile, eating a variety of plants and algae (1) (2) (3) (4) (5), while the young of this species are omnivorous (5), also feeding on snails, crayfish, insects, tadpoles and small fish (2). However, adult river cooters may occasionally supplement their diet with animal prey (2). As an adult, the river cooter has very few natural predators, but nests are often raided by fish crows (Corvus ossifragus), raccoons (Procyon lotor) and grey foxes (Urocyon cinereoargenteus) (2).

The age and size at which maturity is reached in the river cooter varies slightly with location (1) (2), although typically males become sexually mature at about 6 years old and females between 13 and 24 years old (1). Mating in this species occurs in the spring (2), and courting involves the male swimming with and above the female, vibrating its claws in her face (5). The nesting season lasts from May through to the end of June (2) (3), with nesting typically taking place during the day (3), usually not far from the river (2) (3).

The female river cooter digs a flask-shaped nest cavity using only her hind feet (2), within which around 20 eggs are laid (2) (4) (5). The eggs are incubated for a period of between 70 and 96 days (1) (2) depending on the temperature of the soil (2), typically hatching in August or September (2) (5). The temperature of the soil also determines the sex of the hatchlings. At incubation temperatures of between 22.5 and 28 degrees Celsius, the clutch will contain mostly males, whereas at temperatures of 29 degrees Celsius and above, females will be produced (2). Female river cooters produce up to six clutches per year (1) (2), although two is most common (2), and individuals of this species are thought to live for up to 40 years (1).

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River cooter range

The river cooter occurs in the eastern and central United States (1), from eastern Texas eastwards through Oklahoma and Tennessee to Virginia, as far south as the panhandle of Florida and as far north as southern Illinois, Indiana and Ohio (1) (2).

At least three subspecies of river cooter are currently recognised, and these all vary in their distribution (1).

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River cooter habitat

The river cooter is typically found in medium to large rivers and streams (1) (2), particularly those with clear water (1) (3), moderate to fast currents (2) and extensive aquatic vegetation (1) (2) (3). Stretches of river 100 centimetres or more deep are ideal for this species (3), which tends to prefer areas with abundant basking sites such as rocks and partially submerged logs (2) (3). The river cooter also occurs in oxbow lakes, reservoirs, impoundments (2) (5), ponds (1) (2) and swamps (1). In these habitats, this species is typically found in shallower areas (2).

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River cooter status

The river cooter is classified as Least Concern (LC) on the IUCN Red List (1).

IUCN Red List species status – Least Concern

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River cooter threats

Although not currently considered to be at risk of extinction, the river cooter faces a variety of threats, including over-exploitation for human consumption (1) (2) and use in the pet trade (2). In North Carolina, South Carolina and possibly Georgia, this species is known to be collected for the Asian food market (3).

The river cooter is also negatively affected by pollution and activities such as dredging and mining which alter and degrade its habitat (1) (2) (5). As well as affecting the river cooter directly, pollution of its habitat may impact the aquatic vegetation upon which this species feeds (1). In addition, this reptile is frequently involved in collisions with vehicles (1) (2), and is known to be used as a target in a sport known as ‘plinking’, whereby turtles are shot off their basking sites (1) (3).

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River cooter conservation

The river cooter is known to occur in a number of protected areas, and receives additional protection through a variety of State legislation and regulations (1). For example, this species is classified as State Endangered in Illinois (5), while a subspecies is considered to be a Species of Concern in Georgia where it has an extremely limited range (3). However, it has been recommended that this legislation needs to be properly enforced and even strengthened and expanded (1).

In addition to safeguarding the river cooter’s habitat from pollution and degradation, population monitoring is required to properly assess the status of this species and record population trends. In Leon County, Florida, the river cooter is thought to have benefitted from the creation of a special ‘Ecopassage’ which enables the turtles and other species to move across their habitat without having to traverse a busy road. Efforts to raise awareness of the plight of this reptile have also been suggested as necessary future conservation measures (1).

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Find out more

Find out more about the river cooter:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Algae
Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
Carapace
The top shell of a turtle or tortoise. In arthropods (insects, crabs etc), the fused head and thorax (the part of the body located near the head), also known as the ‘cephalothorax’.
Diurnal
Active during the day.
Herbivorous
Having a diet that comprises only vegetable matter.
Hibernation
A winter survival strategy in which the animal passes the winter in a resting state. This period of inactivity is characterised by specific biological and biochemical changes including lowered blood pressure and respiration rate. In reptiles, this is also known as brumation.
Incubate
To keep eggs warm so that development is possible.
Incubation
The act of incubating eggs; that is, keeping them warm so that development is possible.
Keel
A projecting ridge along a flat or curved surface, particularly down the middle.
Omnivorous
Feeding on both plants and animals.
Plastron
The lower shell of a turtle or tortoise.
Scute
A large scale on the shell of a turtle or tortoise.
Subspecies
A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
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References

  1. IUCN Red List (April, 2014)
    http://www.iucnredlist.org/
  2. Ernst, C.H. and Lovich, J.E. (2009) Turtles of the United States and Canada. Johns Hopkins University Press, Baltimore, Maryland.
  3. Jensen, J.B. (2008) Amphibians and Reptiles of Georgia. University of Georgia Press, Athens, Georgia.
  4. Savannah River Ecology Laboratory - Herpetology Program: River Cooter (April, 2014)
    http://srelherp.uga.edu/turtles/psecon.htm
  5. Illinois Natural History Survey - River Cooter (April, 2014)
    http://www.inhs.uiuc.edu/animals_plants/herps/species/ps_concinn.html
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Image credit

Florida cooter, head detail  
Florida cooter, head detail

© Todd Pusser / naturepl.com

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