Sternotherus depressusFlattened Musk Turtle

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Geographic Range

These turtles are currently only found in the Black Warrior River watershed above the Bankhead Dam, in Alabama. The ten Alabama counties included in this range are Blount, Cullman, Etawah, Fayette, Jefferson, Lawrence, Marshall, Tuscaloosa, Walker and Winston.

Habitat

This turtle is mostly found in clear, shallow streams above the fall line. Rocky to sandy-bottomed streams are preferred (Ernst, Lovich, and Barbour 1994).

  • Aquatic Biomes
  • rivers and streams

Physical Description

Sternotherus depressus ranges from about 3 to 4 inches (7.5 - 10 cm) in carapace length; record in 4.6 in (11.7 cm). When compared with other musk turtles, Sternotherus depressus has a carapace that is quite flattened. The top of the carapace is brown and the small plastron is either pinkish or yellowish-brown. The head and neck are greenish with a network of dark lines around them, and there are barbels located on the chin (Conant and Collins 1998).

Reproduction

Females come out of the water and deposit their eggs in shallow nests dug into the ground near the stream. Each female chooses a different site. Clutch size appears small; two eggs are reported in one clutch. Eggs are oblong, about 32 mm long, with brittle shells. The incubation period is probably dependent on temperature and perhaps other physical factors, but ranges from 45 to 122 days. Once hatching begins the actual emergence from the egg takes anywhere from 12 hours to two days. The hatchling has a carapace length of about 26 mm. Growth to maturity may take four to six years for males, and six to eight years for females (Ernst, Lovich, and Barbour, 1994).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)

Behavior

Sternotherus depressus is inactive during the winter months, but its hibernation habits are unknown. Juvenilles are more active during the day then adults are. Adults are most often seen active during the night during the summer season. It is thought that there is some correlation between the amount of darkness and the size of the active musk turtle. It is common to see juveniles foraging in the early evening, but as darkness sets in, foraging activity is seen mostly in young adults, and it is not until the dead of night that the very large adults emerge for feeding. Early in the season when temperatures are cool, S. depressus is normally diurnal. As the temperature gets progressively warmer however, the dirunal activity becomes less obvious and nocturnal behavior becomes dominant. (Ernst,Lovich,and Barbour, 1994)

Food Habits

The flattened musk turtle feeds underwater on invertebrates such as snails and mussels. Large adult musk turtles have expanded jaws for crushing mollusks.

Economic Importance for Humans: Positive

The presence of this species is a good indication of the condition of the streams, as it requires clear, relatively unpolluted habitat.

Unfortunately, the Flattened Musk Turtle has had value in the pet trade, and has been heavily exploited for that reason in some parts of its small range..

Economic Importance for Humans: Negative

This turtle is of no concern to fish management and is harmless to human interests.

Conservation Status

These animals are sensitive to changes in streambed habitats, and especially to water quality. These musk turtles can only survive in pure waters. Sharp declines in recent decades have occurred due in part to an increase in pollution levels in their aquatic habitat. This is mainly due to coal strip mining. These turtles have also been collected in large numbers for the commercial pet trade. In February of 1986, at a Birmingham public hearing about the Fisheries and Wildlife Service's proposal to list the flattened musk turtle as "threatened" under the Endangered Species Act, representatives of the coal industry claimed that listing the turtle as 'threatened" could mean an end to coal mining in the area. But the U.S. Fish and Wildlife Service testified that coal mining would not be affected if the State and Federal strip-mining laws were obeyed. Strip miners are required to control discharges, and mining is barred within a certain distance of rivers. It is the lack of attention to these rules that has destroyed the flattened musk turtle's habitat as well as the valuable drinking water. Protecting the turtle would therefore also protect the quality of water for the citizens of Birmingham and northern Alabama. In June 1986 the proposal to list the Flattened Musk Turtle as threatened was accepted and became law. (Environmental Defense Fund, 1986)

Contributors

Katie Kiehl (author), Michigan State University, James Harding (editor), Michigan State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

threatened

The term is used in the 1994 IUCN Red List of Threatened Animals to refer collectively to species categorized as Endangered (E), Vulnerable (V), Rare (R), Indeterminate (I), or Insufficiently Known (K) and in the 1996 IUCN Red List of Threatened Animals to refer collectively to species categorized as Critically Endangered (CR), Endangered (EN), or Vulnerable (VU).

References

Conant, R., J. Collins. 1998. Field Guide to Reptiles and Amphibians of Eastern and Central North America (Third Ed., expanded). Boston: Houghton-Mifflin.

Environmental Defense Fund, 1986. "Turtles Future Tied To Clean Water" (On-line). Accessed November 17, 1999 at http://www.edf.org/pubs/EDF-Letter/1986/May/c_alturtle.html.

Ernst, C., J. Lovich, R. Barbour. 1994. Turtles of the United States and Canada. Washington, D.C.: Smithsonian Institution Press.