Sternotherus depressus - "Flad" moskusskildpadde.

Denne side er opdateret d.16. april 2019

English text at the bottom of the page.

Habitat 
S. depressus foretrækker  klart-, lavt-, strømmende vandløb (op til 1,5m dybde), med klippe-, og sandbund. På sådanne steder gemmer skildpadden sig om dagen i klippesprækker og under sunkne træerstykker eller de begraver sig i sandet. Fordi skildpadden befinder sig mest på bunden, kan dens skjold være angrebet af igler og overgroet med alger.

Fysiske kendetegn
Sternotherus depressus bliver 8 - 13cm lang. Individer af S. depressus har overlevet, i mere end 20 år, i fangenskab. Deres hoveder er trekantede, med en spids snude og et skarpt næb. Sammenlignet med andre moskusskildpadder, har S. depressus en rygskjold der er helt flad. Toppen af rygskjoldet er brun og det lille bugskjold er enten rosa eller gulbrun. Skildpadden har gul-grønne striber fra spidsen af næsen og ned over halsen, med et netværk af mørke linjer omkring. De har føletråde på hagen. 

Opførsel 
Sternotherus depressus er inaktiv i vintermånederne, men dens dvale vaner er ukendte. Ungerne er mere aktive i løbet af dagen end de voksne. De voksne skildpadder er oftest set aktive i løbet af natten i sommersæsonen. Det menes, at der er en vis sammenhæng mellem, hvor mørkt der er og hvor aktive moskusskildpadderne er. Det er almindeligt at se skildpaddeunger fourager først på aften, men som mørket sætter ind, begynde de lidt ældre skildpadder deres fouragering, og det er først i nattens mulm og mørke, at de voksne skildpadder begynder deres fouragering. Tidligt på sæsonen, hvor temperaturen endnu er kølig, så er S. depressus normalt dagaktiv. Når temperaturen gradvist bliver varmere, ændrer deres aktivitet fra dagaktiv til overvejende nataktive. 

Føde. Den flade moskusskildpadde æder under vandet, hvirvelløse dyr som snegle og muslinger. De voksne moskusskildpadder har udviklet kraftige kæber, de kan bruge til at knuse snegle med. 

Husk. Moskusskildpadder spiser helst fra bunden. Vil du kun fodre dine ny-anskaffede Moskusskildpadder, med foderpiller. Så kan det tage nogle dage, inde de finder fodret.

Læs her mere om fodring af moskusskildpadder

Læs også. Generelt om Moskusskildpadder

Ung Flattened musk turtle - Sternotherus depressus.

Hunnen kommer op af vandet og lægger sine æg, i lavvandede reder, gravet ned i jorden, i nærheden af vandet.

Fælles reder, er ikke set inden for denne art.

Skildpadden lægger mellem 1-4 æg, to æg rappoteres som en redefuld. Dens æg er aflange, ca. 32 mm lange, med skøre skaller. Udrugningstiden er formentlig afhængig af temperaturen og måske andre fysíske faktorer, men varierer fra 45 til 122 dage.

Når klækningen begynder, tager det fra 12 timer til to dage, før ungerne er helt ude. Skildpaddeungerne har en rygskjolds længde på ca. 26 mm. Det tager fra fire til seks år for hannerne af blive kønsmodne, og seks til otte år for hunnerne.

Flattened Musk Turtle i Nord Amerika.

Den flade moskusskildpadde findes kun i en enkelt stat i USA.

Det er i staten Alabama, hvor den Flade moskusskildpadden kun udbredt i en lille del af staten, fra midten og op i statens nordlige område, der hedder the Black Warrior River drænings område.

Foto Bill Hughes.

Denne sjældne skildpadde S. depressus, er følsomme overfor ændringer i deres levesteder, og især ændring af vandkvaliteten.

Disse moskusskildpadder kan kun leve i rent vand. Der har været et kraftigt fald af denne skildpadde, i de seneste årtier. Dels på grund af en stigende forureningen i deres levesteder. Dette skyldes hovedsageligt minedrift efter kul, i skildpaddens leveområder.

S. depressus er også blevet indsamlet i stort antal, til den kommercielle kæledyrs handel.

I februar 1986 ved en offentlig hørring i Birmingham, holdt af Fish and Wildlife Service, kom der forslag til, at optage de flade moskusskildpadder under den "truede" Endangered Species Act. Repræsentanter fra kulmineindustrien mente, hvis skildpadden bliver godkendt som "truede"! det kunne betyde en ende på minedriften efter kul i området. Men US Fish and Wildlife Service vidnede, at kulminedrift ikke ville blive påvirket, hvis statens og de føderale mineloven blev overholdt.

Tidligere er disse bestemmelser ikke blive overholdt, og det er det, der har ødelagt forholdene for moskusskildpadden og drikkevandet i Birmingham og det nordlige Alabama. I juni 1986 blev loven om bevarelse af moskusskildpadden godkend.

Foto af Peyer Prachag.

Distribution
The flattened musk turtle was once found in the upper Black Warrior River system of Alabama, upstream from Tuscaloosa, which is on the fall line between the Piedmont Plateau and the coastal plain. Since 1930, several dams have been built on the river and near the fall line. The resulting reservoirs were more favorable for another turtle, Sternotherus minor peltifer. Where the ranges of the two turtles overlapped, interbreeding occurred to the detriment of the flattened musk turtle population.

Genetically pure populations of this turtle are now believed to exist only in the Black Warrior River system, upstream from Bankhead Dam in Blount, Cullman, Etowah, Jefferson, Lawrence, Marshall, Tuscaloosa, Walker, and Winston Counties of north-central Alabama.

Habitat.
This turtle is mostly found in clear, shallow streams above the fall line. Rocky to sandy-bottomed streams are preferred.

Description.
Sternotherus depressus ranges from about 3 to 5 inches (7.5 - 13 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.

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.

Food Habits.
This turtle feeds primarily on freshwater mollusks andmussels. Large adult musk turtles have expanded jaws for crushing mollusks.

Flattened musk turtle - Sternotherus depressus ung skildpadde.

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.

Flattened Musk Turtles. Foto Sherry Rogers

Sternotherus depressus is primarily threatened by habitat degradation and loss, and secondarily by collection and possibly disease. Siltation, from coal strip mining and improper runoff and stream bank management associated with forestry, agriculture and construction, eliminates the essential rock crevice hiding areas, reduces or eliminates molluscan prey, and may contain toxic compounds.

While the species is legally protected from collection, illegal collection for pets remains a concern.

A severe disease outbreak swept through the Sipsey Fork population in 1985-1986, more than halving its population in one year; disease was also recorded at other streams but its impact was not quantified. The diseases has been speculated to involve a compromised immune system. By 1995 the Sipsey Fork population had not yet recovered to pre-disease levels. 2003 documented that a short-term modest reduction in survivorship created serious long-term consequences for the population. Leech infestation rates are inversely correlated to environmental pollution levels

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.

S. depressus, fotograf JOEL SARTORE/National Geographic Creative.

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