Striped Mud Turtle
Kinosternon baurii

Common Name:

Striped Mud Turtle

Scientific Name:

Kinosternon baurii



Kinosternon is derived from the Greek word kineo which means "move" and sternon which means "chest". This refers to the hinged plastron.


baurii was assigned to honor Georg Hermann Carl Lugwig Baur a vertebrate morphologist and turtle expert.

Average Length:

3 - 4 in. (7.5 - 10 cm)

Virginia Record Length:

4.8 in. (12.3 cm)

Record length:

5 in. (12.7 cm)

Systematics: Originally described by Samuel Garman in 1891 as Cinosternon baurii, based on 11 specimens from Key West, Florida. The genus Kinosternon was first used for this turtle by Lonnberg (1894). No subspecies are currently recognized.

Description: A small freshwater turtle reaching a maximum carapace length (CL) of 127 mm (5.0 inches) (Conant and Collins, 1991). In Virginia, known maximum CL is 123.0 mm, maximum plastron length (PL) is 115.5 mm, and maximum body mass is 337 g.

Morphology: Carapace rounded, smooth, and without keels in adults; no serrations posteriorly; carapacial scutes may be translucent in some individuals; 1st vertebral triangular and not in contact with 2d marginals; usually marginals 11/11, pleurals 4/4, and vertebrals 5; marginal 10 on both sides counting anterior to posterior larger than others; plastron hinged anteriorly and posteriorly and slightly notched posteriorly; bridge consists of only axillary and inguinal scutes; plastron 82- 95% of CL; pectoral scute triangular in shape; width of posterior plastral lobe >50% of carapace width. The lower beak is sharply curved, especially on old adults.

Coloration and Pattern: Carapace brown to nearly black, with or without 3 light-tan or cream stripes; plastron olive to mahogany in color, sometimes with dark borders along seams; skin dark brown to black; 2 distinct yellowish to cream stripes on head usually present, one above and one below tympanum; stripes may be broken or continuous; each stripe extends to tip of snout; light specks may occur on dorsum and lateral surfaces of head; tomial surfaces of upper and lower jaws may be edged in black.

Sexual Dimorphism: Average adult male CL (88.1 ± 8.6 mm, 71.1-114.7, n = 48) was less than that in adult females (96.0 ± 12.4 mm, 70.2-123.0 mm, n = 40). Sexual size dimorphism index was 0.09. Similar differences existed between sexes in PL (males 77.1 ±6.7 mm, 62.7-94.4, n = 48; females 90.5 ± 11.9, 67.0-115.5, n = 40) and body mass (males 117.7 ± 31.5 g, 63-221, n = 48; females 165.0 ± 60.3, 68-337, n = 40). The precloacal distance was longer in males (7-16, ave. = 12.2 ± 1.9, m = 20) than in females (0-5, ave. = 0.9 ± 1.8, n = 17) and the cloacal opening extends beyond the posterior margin of the carapace. Males possess a patch of rough scales behind the thigh and crus of each rear leg.

Juveniles: Juveniles have a carapacial keel that becomes rounded with age and an orange plastron with black smudges along the midline. Head stripes are prominent at hatching, and carapacial stripes are visible in most individuals at this age. The size of hatchlings in Virginia is unknown. Hatchlings from northern Florida were 17.6-25.0 mm CL (ave. = 22.5) and 15.5-22.0 mm PL (ave. = 19.2) (Iverson, 1979).

Confusing Species: Sternotherus odoratus has squarish pectoral scutes on the plastron and skin visible between the plastral scutes. Kinosternon subrubrum lacks the 3 light stripes on the carapace. The light stripes on each side of the head, if present at all, do not occur on the snout. The plastron in juveniles is reddish. See "Remarks" for additional comments.

Geographic Variation: None known in Virginia, and no distinctive variation is known throughout the range of this species. Striped Mud Turtles in Florida possess faint dorsal stripes on translucent carapacial scutes, distinct stripes on the carapace, or no stripes at all (Iverson, 1978b).

Biology: In Virginia, Striped Mud Turtles inhabit primarily blackwater swamps and rivers, permanent ponds and small lakes, ditches, and temporary ponds. They are known to enter brackish water (Ernst and Barbour, 1989a). Preferred habitat appears to consist of dark water with an organic substrate. Aquatic vegetation may or may not be present. These turtles seldom bask, but spend considerable time on land. Kinosternon baurii is active all year in Florida (Iverson, 1977c). Available records from Virginia suggest an activity period of late March through October.

Kinosternon baurii is an omnivore, consuming leaves and seeds of plants, algae, snails, insects, and dead fish (Ernst and Barbour, 1989a). Nothing is known of its diet in Virginia. Striped Mud Turtles have an extended reproductive season. Females in Florida have been found to possess oviductal eggs or corpora lutea in all months of the year (Iverson, 1977c). I found oviductal eggs in females from Virginia 29 July to 4 October. Richmond (1945b) reported egg laying in mud turtles from New Kent County in March through September, the latter 3 months probably pertaining to K. baurii. His description of nest construction behavior (summarized in the K. subrubrum account) may also pertain to K. baurii. In northern Florida, females reached maturity at 70- 75 mm CL and 5-6 years of age (Iverson, 1979). Clutch size in Virginia females was 5-6 (ave. = 5.1 ± 0.4, n = 7) compared with 2.6 ± 1.0 in Florida (Iverson, 1979). Eggs from Virginia females measured 27.1 ± 1.4 x 18.5 ± 0.4 (length 25.4-29.5, width 17.8-19.4, n = 36) in size and weighed5.0- 5.9 g (ave. = 5.5 ± 0.4, based on means of seven clutches), similar to those reported from Florida by Iverson (1979). None of the eggs from Virginia females hatched in the laboratory. Eggs collected by N. D. Richmond in New Kent County that may have been in embryonic diapause (see K. subrubrum account) may have also included those of K. baurii.

The population ecology of this species has been studied only in Florida. In a population inhabiting a forested swamp ecosystem in central Florida, Wygoda (1979) found an adult sex ratio of 1:2 (males to females) in a pond and a 1:1 ratio in the adjacent swamp. He also found that turtles spent 1-50 days in terrestrial, shallow burrows ( = forms); forms were usually under a thin layer of soil and leaf litter. Wygoda observed that seasonal activity was bimodal, with emergence from drying ponds to terrestrial sites in February-July and the return to ponds with swamp drying in September-December. Dunson (1981) determined that Kinosternon baurii individuals not only are faithful to their home ponds, but also repeatedly utilize the same terrestrial retreats to avoid periods of dryness or high salinity in ponds. Salinities above 15 ppt are avoided, suggesting that these turtles will not be found in coastal aquatic systems in Virginia that routinely experience salinities well above that level. Population sizes were estimated to be 219-274 on Summerland Key and 42-52 on Johnston Key (Dunson, 1981).

Like other mud turtles, K. baurii is a bottom walker and seldom basks. It will attempt to bite when handled.

Remarks: Although I had been aware of baurii-like variation in mud turtles since the early 1980s, it was not until Trip Lamb and Jeff Lovich conducted their morphometric study (1990) that K. baurii became a confirmed member of Virginia's reptile fauna. Using multivariate statistics, they determined that the following equations separate K. baurii from K. subrubrum: for K. baurii males, the ratio PH/PL (the length of the right humeral scute along the midline divided by the plastron length) was 0.29-0.33 and the ratio FL/PL (the plastral forelobe length divided by the plastron length) was 0.35-0.38; for females PH/PL was 0.28-0.35 and FL/PL was 0.32-0.35. ForK. subrubrum males, PH/PL was 0.25-0.28 and FL/PL was 0.39-0.42; for females PH/PL was 0.24-0.28 and FL/PL was 0.36-0.39. The inclusion of K. baurii in Virginia is based on the above analysis, and on the occurrence of individuals that match the description of typical baurii from Florida (see Conant and Collins, 1991). The systematic relationship of K. baurii and the closely related K. subrubrum has not been completely explored, leaving open the question of whether these are separate species as currently understood (J. B. Iverson, pers. comm.). The presence of K. baurii in Virginia should, therefore, be con- sidered putative until the systematics have been resolved. Mitchell and McAvoy (1990) determined that none of the eight individuals of K. baurii in a Virginia Beach population contained Salmonella bacteria.

Conservation and Management: Although we know little about the population status of K. baurii in Virginia, the number of locations known and the occurrence of appropriate wetlands in the Coastal Plain suggest that this turtle is not endangered or threatened. However, because of our lack of knowledge, it should be listed as status undetermined and records should be maintained until such time as an informed decision can be made. Kinosternon baurii inhabits shallow and ephemeral wetlands, the types most likely to be lost to development activities. This species also utilizes terrestrial habitats. Thus, maintenance of all wetlands and a substantial surrounding buffer is essential to the long-term survival of this turtle in Virginia.

References for Life History


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