The flattened musk turtle (''Sternotherus depressus'') is a critically endangered

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of freshwater

turtle Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Kinosternidae The Kinosternidae are a family of mostly small turtles that includes the mud turtles and musk turtles. The family contains 25 species within four genera, but taxonomic reclassification is an ongoing process, so many sources vary on the exact num ...

. The species is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to north-central and west-central

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

.Dodd, C.K., Jr. 2008. ''Sternotherus depressus'' Tinkle and Webb 1955 – flattened musk turtle. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., and Iverson, J.B. (Eds.). Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs No. 5, pp. 013.1-013.7, doi:10.3854/crm.5.013.depressus.v1.2008, //iucn-tftsg.org/cbftt/.

Geographic range

''S. depressus'' is an endemic with a restricted range, historically inhabiting the

Black Warrior River The Black Warrior River is a waterway in west-central Alabama in the southeastern United States. The river rises in the extreme southern edges of the Appalachian Highlands and flows 178 miles (286 km) to the Tombigbee River, of which the ...

drainage of north central

. Conant, Roger (1975). ''A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Second Edition''. Houghton Mifflin. Boston. xviii + 429 pp. + Plates1-48. (hardcover), (paperback). (''Sternotherus depressus'', pp. 42–43 + Plate 4 + Map 9). Serious declines have been observed throughout its range, and it has likely been extirpated from greater than 70% of its historic range, especially in much of the Mulberry Fork and the Locust Fork of the upper Black Warrior River Basin. Sipsey Fork populations have fared significantly better due to protection offered by the Bankhead National Forest.

Description

A small turtle, ''S. depressus'' can have a straight

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

length of as an adult, with a record length of . Both the

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...

and

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

refer to the fact that the species' carapace (upper shell) is much lower and flatter than those of the other members of the genus ''Sternotherus''. In fact the flattened musk turtle looks as if someone had accidentally stepped on it, hence the common name.

Habitat

The flattened musk turtle is a freshwater, stream-dwelling turtle. The ideal habitat for the flattened musk turtle is a clearwater stream or river that has an adequate amount of cover sites to escape to under rocks and crevices. The shape of the flattened musk turtle allows it to fit into confined spaces, such as crevices. In absence of quality cover in rocks and crevices, the flattened musk turtle will dig under logs or brush. Juveniles will often be found in weed beds in shallow water.

Diet

''S. depressus'' are omnivorous and mostly rely on gastropods (snails) and pelecypods (mussels) as a large part of their diet. Crayfish, insects, and seeds are also consumed by ''S. depressus'', but are not a main food item. A greater portion of snails were detected in the feces of denser populations of ''S. depressus.''

Behavior and Movement

''S. depressus'' has an average home range of 332 meters, although home ranges as large as a kilometer were recorded. In areas of poorer habitat, it is possible that ''S. depressus'' may have to move more to fulfill its dietary needs. Light and moderate precipitation was correlated with more overall movement for ''S. depressus'', but not overall activity (i.e. amount of time active during the day). The breeding and nesting season showed more overall activity and movement compared to the brumation season for ''S. depressus''. Basking has been observed in ''S. depressus'' on rocks, trees, and logs, although it is thought to be related to disease or overall poor health.

Captivity

Individuals of ''S. depressus'' have survived for more than 20 years in captivity. Although reproductive rates are low for the species, ''S. depressus'' has been bred infrequently in captivity with relative success. Future propagation efforts may be key to preserving and reintroducing the species once its habitat has been restored.

Threats and causes of decline

The flattened musk turtle is primarily threatened by habitat alteration and habitat destruction. Strip mining for coal has increased the amount of silt and particulates in the waters of the Warrior River drainage system. ''S. depressus'' relies on rock crevices to escape predation, which are easily filled in from silt and sediment. Increased siltation in the streams also decreases the food availability for ''S. depressus'' as mollusk populations decrease. Sewage and other forms of pollution from urban areas near the Warrior Basin have also had an effect on stream biota. Secondary threats to the flattened musk turtle are illegal collection for the pet trade and disease. Habitat fragmentation also poses a significant threat to ''S. depressus''. Isolated populations have the potential to lose genetic viability and threaten normal population structure. Smaller isolated populations also have less resilience to human caused disturbance, and thus are more vulnerable.

Gallery

File:Sternotherus depressus 10037861.jpg, Young turtle File:Sternotherus depressus 10037848.jpg, Young turtle File:Sternotherus depressus 10037837.jpg, Young plastron File:Sternotherus depressus 10037824.jpg, Young carapace

References

External links

*Tortoise & Freshwater Turtle Specialist Group (1996)
''Sternotherus depressus''

2006 IUCN Red List of Threatened Species.
Downloaded on 29 July 2007. {{Taxonbar, from=Q1938586 Endemic reptiles of the United States Sternotherus Endemic fauna of Alabama Reptiles described in 1955 Taxa named by Robert G. Webb Taxonomy articles created by Polbot