Sternotherus carinatus is the sister species of S. odoratus, and those two species are sister to the clade including the remaining Sternotherus species (Thomson et al. 2021). Hybridization of S. carinatus and S. peltifer has been observed in the area of sympatry at the western extent of the range of S. peltifer (Brown 2021).

While traditional population assessments for Sternotherus carinatus are lacking, the species is generally regarded as widespread and locally abundant. Though no recent threat assessments have been conducted for S. carinatus, there are no known specific significant threats affecting the species in a major way. Sternotherus carinatus occurs in extensive portions of protected areas and are commonly found outside of protected areas. Therefore, its future survival does not currently appear to be a matter of significant concern. Therefore, we assess S. carinatus as Least Concern (LC) at this time. The species was also previously assessed as Least Concern in 2011 (van Dijk 2011).

Sternotherus carinatus inhabits the south-central United States (primarily the lower Mississippi Valley region), from central and eastern Texas through southeastern Oklahoma, southern Arkansas, most of Louisiana and Mississippi to extreme southwestern Alabama (Webb 1975, Dundee et al. 1989, Iverson 1992, Trauth et al. 2004, Lindeman 2008, Guyer et al. 2015, TTWG 2021, Franklin et al. 2023). The species has been introduced to areas of southern Florida (Powell et al. 2016). The estimated historical indigenous range (area of occupancy, AOO) for the species was ca 328,143 sq. km and the historical extent of occurrence (EOO) was ca 512,687 sq. km (TTWG in press). Rangewide, S. carinatus is found at elevations ranging from 0–310 m asl (average: 66.3 m ± 6.78; n = 81) (USGS 2023). Oklahoma records exist in the upper Little River at elevations of at least 335 m asl (M. Howery, unpubl. data).

While traditional population surveys are lacking for Sternotherus carinatus, it is considered common throughout its range; the main exception is the population of the Pascagoula River, Mississippi, where a combination of pollution and habitat modification have reduced populations of this and other turtle species (Lindeman 2008).

Sternotherus carinatus typically inhabits deeper waters of medium to large flowing rivers and streams with limited vegetation and sand, gravel or cobble bottoms, but also occurs in lakes, oxbows, swamps, and urban city ponds (Lindeman 2008, Dixon 2013, Powell et al. 2016; current authors, unpubl. data). The species has been found cohabitating urban ponds with Sternotherus odoratus and Kinosternon flavescens (Ricardez and Franklin, unpubl. data). The presence of deadwood, both above water for basking and underwater for retreats, appears to be a significant factor determining habitat suitability (Lindeman 2008).

Sternotherus carinatus is carnivorous, feeding on aquatic insects, mussels, snails and crayfish, with molluscs increasing as a proportion of diet as individuals grow (Mahmoud 1969). The species typically reaches 13–16 cm straightline carapace length (SCL), with the record size being 20.9 cm SCL for males, and 15.5 cm SCL for females (TTWG 2021). Females reach maturity at 8.5–9.5 cm SCL at 4–8 yrs of age. As such, if we assume sexual maturity at ca six yrs, then generation time can be estimated as ca 12 yrs (Iverson 2024). Two to three clutches of 1–7 eggs per year are typical. Hatchlings measure about 25–28 mm SCL and weigh 3–4 g (Iverson 2002).

These small turtles are susceptible to a range of predators at different life history stages. Predators include diving beetles (Family Dytiscidae; C.J. Franklin, unpubl. data), fish, water snakes (Nerodia) (Ernst and Lovich 2009), Alligator Snapping Turtles (Macrochelys temminckii) and American Alligators (C.J. Franklin, unpubl. data). Potential for mortality has been documented for a specimen falling from a basking site and becoming stuck between branches (Franklin et al. 2022). When hooked by fishermen this species is sometimes killed in great numbers (Mahmoud 1969).

Some populations, particularly in the Pascagoula River drainage in Mississippi, are under potential threat from or have been impacted by toxic pollutants, removal of deadwood and snags for navigation purposes, and from sand and gravel mining (Lindeman 2008). Specimens coincidentally caught during fishing may be killed (Mahmoud 1969). Some specimens, mainly hatchlings, are traded as pets. None of these threats are so far considered to be sufficiently severe or extensive enough to threaten the species’ survival for the foreseeable future.

Hatchlings of Sternotherus carinatus are traded as pets in some numbers, being particularly sought after in Europe and East Asia as well as the US pet trade. Their small size has become a trait sought after by pet turtle enthusiasts. Various website searches yielded prices from $30 USD for a captive bred hatchling to $114 USD for older or yearling turtles. Searches via iNaturalist resulted in reports of released pet S. carinatus in California, Florida, Italy, China, and Republic of Korea. Adults have been documented in the European pet trade since the early 1990s (Becker 1992, 1995; Felsner 2001).

Sternotherus carinatus is confirmed or presumed to occur in a substantial number of National Wildlife Refuges (NWR), National Preserves (NP), National Forests (NF), and state Wildlife Management Areas (WMA) throughout its range. These properties include, but are not limited to: Catahoula NWR (Louisiana), Dale Bumpers White River NWR (Arkansas), Upper Ouachita NWR (Louisiana), Sam D. Hamilton Noxubee NWR (Mississippi), Tensas River NWR (Louisiana), Big Thicket NP (Texas), Davy Crockett NF (Texas), Sam Houston NF (Texas), Sabine NF (Texas), Delta NF (Mississippi), Ouachita NF (Arkansas), Angelina NF (Texas), Kisatchie NF (Louisiana), De Soto NF (Mississippi), Bayou Macon WMA (Louisiana), Longview Saline Natural Area WMA (Arkansas), Winona WMA (Arkansas), Old River WMA (Mississippi), Sunflower WMA (Mississippi), and Ouachita WMA – McCurtain (Oklahoma). The species was included in CITES Appendix II as Sternotherus spp. in 2023. Sternotherus carinatus is generally considered secure throughout much of its geographic range and no specific conservation actions appear necessary at present (Lindeman 2008). It is listed as a Species of Greatest Conservation Need in the Oklahoma Wildlife Action Plan, and its commercial harvest is prohibited there (M. Howery pers. comm.). Studies documenting population status, structure and dynamics, habitat usage, and other ecological information on the species would be desirable, in addition to monitoring of the pet trade, which may be increasing.