Yellow mud turtle

Kinosternon flavescens




Platythyra flavescens Agassiz, 1857, Rio Blanco, near San Antonio, Texas.


English: Illinois mud turtle; Spanish: Tortuga-pecho quebrado amarilla.


This is a small kinosternid turtle (maximum shell length 6 in [16 cm]) with a yellowish chin and throat and a low carapace, with the ninth marginal scute raised distinctly higher than the eighth but equal to the height of the tenth. The plastron has two hinges and is not greatly reduced and the pectoral scutes are triangular in shape and are only narrowly in contact.


Ranges nearly continuously from southern Nebraska to southern New Mexico and to northeastern Mexico, with relict populations known in northwestern Nebraska, Iowa, Illinois, Missouri, Kansas, and east Texas.


An inhabitant of grassland habitats, preferring still water, this turtle also is found in permanent to very temporary pools, even those created by humans (e.g., ditches and cattle ponds). It is only rarely found in streams or rivers, and then only in backwaters or cutoffs.


This turtle spends the majority of each year inactive, buried underground (hibernating or estivating). Activity is stimulated by warm rains (and filling ponds); these turtles will migrate considerable distances from emergence sites to bodies of water, and hence are most often seen moving terrestrially.

The activity season for some populations is as short as for any known turtle—as little as two months in very dry years. As ponds dry up these turtles again bury terrestrially and estivate and/or hibernate until the next warm rainy season. Yellow mud turtles are also frequently seen basking at the edge of the water, even in subtropical locations.


This species is decidedly carnivorous, and plant matter found in their stomach was probably only accidentally ingested when foraging for small animals such as snails, clams, insects, crustaceans, earthworms, tadpoles, and fish. They often forage on carrion.


Yellow mud turtles mate rapaciously when they emerge from dormancy and reach the water. Warm rainfall escalates courtship behavior; in captivity males can be induced to court females simply by changing the water in their containers. Females leave the water and may migrate considerable distances to nest in May and June. In Nebraska, gravid females bury themselves completely underground 6—10 in (15-25 cm) and deposit their eggs while buried at these depths. Females remain buried for variable periods once the eggs are laid. Some females may dig out and return to the water the next day after nesting, but some apparently remain in estivation with the eggs through the summer and then dig deeper in the autumn to hibernate for the winter. The eggs are small and elliptical (0.9-1.2 X 0.6-0.7 in [23-31 X 14-18 mm]) with white, brittle eggshells. The clutch size ranges from one to nine (typically four to six), with larger females producing larger clutches. A maximum of a single clutch is produced per year in most populations, and some females do not nest every year. However, two clutches per year may be produced in southern populations. Eggs hatch after 90 to 118 days; at least in Nebraska, hatchlings then dig straight down as much as 3 ft (1 m) below the nest to avoid freezing temperatures during the winter. They dig back out and head for the water during the following spring.


Not threatened. This species has a wide distribution and exhibits high densities in many populations, and so is not in need of protection over most of its range. However, most relict populations in northwestern Nebraska, southeastern Iowa, western Illinois, and northeastern Missouri are small, vulnerable to extirpation, and hence in great need of protection.


Exploited only minimally by humans for the pet trade. ♦

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