Yellow mud turtle (Kinosternon flavescens)

Yellow mud turtle basking on log
IUCN Red List species status – Least Concern LEAST

Top facts

  • The sex of a yellow mud turtle is determined by the temperature at which it is incubated when it is in the egg. Higher temperatures yield more females and lower temperatures produce more males.
  • The yellow mud turtle has been known to aestivate underground for up to 24 months.
  • Unlike other turtles, the female yellow mud turtle remains buried with its eggs to protect them.
  • The yellow mud turtle exudes a pungent aroma.
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Yellow mud turtle fact file

Yellow mud turtle description

GenusKinosternon (1)

The yellow mud turtle (Kinosternon flavescens) has a depressed carapace (4), which is olive-brown (2) (4) (5), while the underpart of the shell, known as the plastron, is yellow-brown (2) (5). The colour of its skin can vary between yellow and grey (5), although the head is olive with yellow or cream areas on the chin and throat (2) (4). There are narrow crescent-shaped skin folds over each eye and small barbels on the lower surface of its flattened head (2). The hooked jaws are usually yellow-white, but may occasionally be patterned with dark spots (5). The male yellow mud turtle has a long tail with spines on the upper surface (2), and rough patches of scales on the inner surface of the hind legs. The feet of this semi-aquatic species are webbed (5).

When newly hatched, the female yellow mud turtle is slightly larger than the male (2) (5), although the male outgrows the female after around three years (5), and is larger as an adult. The tail of the female lacks spines on the upper surface, the head is slightly smaller and the lower surface of the shell is less concave than that of the male (2) (5). The underside of the hatchling’s shell is yellow and black (4).

Cinosternon flavescens.
Male carapace length: up to 16.5 cm (2)
Female carapace length: 8.8 - 11.7 cm (3)
Hatchling length: 1.8 - 3.1 cm (1)

Yellow mud turtle biology

The yellow mud turtle spends spring in aquatic habitats, and hibernates in a subterranean burrow during winter (3). Some individuals may also aestivate in summer during hot or dry periods. As it is not freeze-tolerant, winter burrows are built below the freeze line and are often located underneath a plant to provide extra protection from the cold. The annual activity period for most individuals is 140 days per year, with the rest of the time spent aestivating or hibernating. The high fat content of the yellow mud turtle means it is able to sustain itself throughout long periods of dormancy, and the amount of fat held within one individual can sustain it for up to 24 months (2).

The opportunistic yellow mud turtle feeds on a variety of prey (1) (2), including earthworms, leeches, crustaceans, insects, molluscs, fish and amphibian larvae (5), with plant matter being digested secondarily (2) (5).

After becoming sexually mature between the age of 11 and 16 years (1), the female yellow mud turtle produces a single clutch annually (3), which usually contains between four and nine eggs (1). The female digs a hole in the ground down to around 20 centimetres, where it proceeds to remove the earth underneath itself to form a nest cavity, before depositing the eggs (2). Unlike other turtle species, the female shows parental care after the eggs have been deposited, and may remain buried with the eggs for over 38 days (1) (2). The eggs are usually laid in June, and hatch during the autumn (3). The hatchlings then overwinter close to the nest site and migrate away from their natal habitat between May and June (3), although some hatchlings may burrow into the soil beneath the nest cavity and remain there until the following spring (5). The sex of the young is dependent on the temperature at which they are incubated (2) (3) (5), with temperatures above 30 degrees Celsius producing all females and lower temperatures between 25 and 27 degrees Celsius producing mostly males (3). Eggs incubated at temperatures lower than 24 degrees Celsius do not usually hatch (3).


Yellow mud turtle range

The yellow mud turtle is found in disjunct populations (5) from the southern United States in the north to Mexico in the south (1) (2). In the United States, it is found in Arizona, Texas, Oklahoma, Illinois, Iowa, Missouri, Nebraska, Kansas and New Mexico (1) (5).


Yellow mud turtle habitat

The yellow mud turtle typically inhabits the various permanent and temporary waterbodies (1) (3) (4) surrounding desert and prairie areas (1). This species is a poor swimmer, therefore it is usually found in areas with shallow water (2). As well as occurring in aquatic habitats, it is also found in terrestrial areas, including arid and semi-arid grasslands and open woodland. The soil within the habitat of this species is soft and non-rocky, which enables it to dig the subterranean burrows where it spends a vast amount of its life (2).


Yellow mud turtle status

The yellow mud turtle is classified as Least Concern (LC) on the IUCN Red List (1).

IUCN Red List species status – Least Concern


Yellow mud turtle threats

The main threat to the yellow mud turtle is habitat degradation and water extraction, which leads to the reduction of the temporary and permanent waterbodies it requires for breeding (1). Road traffic accidents are also thought to be a main cause of mortality for this species (5).


Yellow mud turtle conservation

In Mexico, all turtles are protected from exploitation by law, although the extent of enforcement of these laws may vary in some areas. In Illinois, the yellow mud turtle has been intensively conserved after there was a decrease in population size due to habitat loss. In the future, more surveying and monitoring of wild populations must be performed to ensure the survival of this unique species and its habitat (1).


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To become dormant during the summer or dry season, comparable to hibernation in winter.
Fleshy projections near the mouth of some aquatic vertebrates.
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’.
Diverse group of animals with jointed limbs and a hard external skeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
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.
To keep eggs warm so that development is possible.
A diverse group of crustaceans, with flattened, segmented bodies, that includes pill bugs and woodlice.
Immature stage in an animal’s lifecycle, after it hatches from an egg and before it changes into the adult form. Larvae are typically very different in appearance to adults; they are able to feed and move around but are usually unable to reproduce.
A diverse group of invertebrates, mainly marine, that have one or all of the following: a horny, toothed ribbon in the mouth (the radula), a shell covering the upper surface of the body, and a mantle or mantle cavity with a type of gill. Includes snails, slugs, shellfish, octopuses and squid.
Of or relating to birth.
The lower shell of a turtle or tortoise.
An extensive area of flat or rolling, predominantly treeless grassland, especially the large tract or plain of central North America.
Living underground, in caves or groundwater.


  1. IUCN Red List (November, 2013)
  2. Degenhardt, W.G., Painter, C.W. and Price, A.H. (1996) Amphibians and Reptiles of New Mexico. University of New Mexico Press, New Mexico.
  3. Iverson, J.B. (1991) Life history and demography of the yellow mud turtle, Kinosternon flavescens. Herpetologica, 47(4): 373-395.
  4. Conant, R. and Collins, J.T. (1998) Reptiles and Amphibians of Eastern/Central North America. Houghton Mifflin Company, New York.
  5. Ernst, C.H. and Lovich, J.E. (2009) Turtles of the United States and Canada. Johns Hopkins University Press, Baltimore and London.

Image credit

Yellow mud turtle basking on log  
Yellow mud turtle basking on log

© Rolf Nussbaumer/Imagebrokers /

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