Sternotherus

Genus of turtles

Sternotherus is a genus of turtles in the family Kinosternidae including six species commonly known as musk turtles. The genus is endemic to North America, occurring in the eastern third of the US and southeast Ontario, Canada. Musk glands positioned near the bridge of the shell can produce foul smelling secretions when the turtles are threatened, although gentle handling does not normally provoke a response. Sternotherus are moderately small turtles, with the largest species in the genus, the razor backed musk turtle (S. carinatus), attaining a maximum of 17.6 cm. in shell length. The carapace is characteristically oval and domed (an exception being the flattened musk turtle, S. depressus), with most species having one or three keels on the back which may become smoother and obscure with age in some species. Musk turtles are generally drab in color, mostly black, gray, brown, olive, or ocher, which aid in camouflaging them in their natural habitats. The head is relatively large and stout, marked with spots, streaks, or strips. The plastron has only 10 or 11 scutes, as opposed to 12, a more common condition in North American turtles. The tail is short, with males having a horny claw like tip. Sternotherus are largely aquatic, however some species frequently bask on fallen logs or rocks emerging from the water, and eastern musk turtles (S. odoratus) occasionally leave the water to forage. Sternotherus are omnivorous and opportunistic generalist in their diet, although inclining toward being carnivorous, with mollusks (gastropods and bivalves) and insects making up a significant percentage of their diet. Some older adults develop large musculature on the head and expanded, crushing jaw surfaces aiding in the consumption of mollusk. Musk turtles are oviparous with females producing one to six clutches a year. The typical clutch size is two to four eggs, although clutches may range from one to 13. The sex of the hatchlings is determined by the incubation temperature. The eggs are deposited in shallow nest excavated on the banks or in woodlands a few meters from the water. Eggs may be laid singly, or in groups, and some species are known to share communal nesting areas.

Turtles in the genus Sternotherus are very similar to the American mud turtles in the genus Kinosternon, but tend to have a more domed carapace, with a distinctive keel down the center of it. Sternotherus odoratus typically grows to only in straight carapace length at full maturity, with females often being larger than males.

The genus Sternotherus is endemic to North America. It occurs in the approximant eastern third of the US and extreme southeast Ontario, Canada. The eastern musk turtle (S. odoratus), the most wide ranging species of the genus, occurs in southern Maine, south to Florida, west into eastern Texas, Oklahoma, and Kansas, and north to southeast Wisconsin, southern Michigan, and the Great Lakes region of southern Ontario. It is generally absent from higher elevations in the Appalachian Mountains. The other species in the genus largely occur within the southern regions of the eastern musk turtle's range. Two species have relatively limited distributions, the flattened musk turtle (S. depressus) is endemic to north central Alabama in the Black Warrior River basin above the fall line, and the intermediate musk turtle (S. intermedius) is found in southeastern Alabama and adjacent areas of the Florida panhandle in the Choctawhatchee, Conecuh, Yellow, Pea, Blackwater, and Escambia rivers. The razor backed musk turtle (S. carinatus) occurs throughout Louisiana, and neighboring areas of Mississippi, Arkansas, Oklahoma, and Texas. The loggerhead musk turtle (S. minor) is found in extreme southeast Alabama, Georgia, and northern Florida. The stripe necked musk turtle (S. peltifer) predominantly occurs in Alabama and Mississippi with some peripheral records from Georgia, and Louisiana, and ranging into northern watersheds in eastern Tennessee with marginal records from North Carolina, and Virginia. The razor backed (S. carinatus) and eastern musk turtles (S. odoratus) are known to be bottom feeders, often searching with the neck extended and probing the mud and sand with their heads. Olfaction is probably important in the location and selection of food items. However, musk turtles occasionally feed at the surface and are also known to eat out of the water. Eastern musk turtles (S. odoratus) have occasionally been observed leaving the water at dusk to feed on slugs on land. Some larger adults develop hypertrophied head musculature and expanded crushing surfaces on both the upper and lower jaws that aid in eating mollusk. One study concluded razor backed (S. carinatus) and eastern musk turtles (S. odoratus) were "euryphagous with food preferences directly related to the availability of food." Digestive turnover rates, from ingestion to defecation, of 49 hours (S. odoratus) to 57 hours (S. minor, S. peltifer) have been reported, although temperatures may influence these times. The razor backed musk turtle (S. carinatus) favors the relatively deeper waters of rivers, creeks, bayous, and associated oxbow lakes, backwater swamps, and floodplains where slower currents and soft substrates are found. Behavior: Sternotherus is a highly aquatic genus. But some species, like the common musk turtle, are known to bask on fallen trees and coarse woody debris on shorelines. The thermal activity range and annual activity period was longer for Sternothaerus than Kinosternon