American Mud and Musk Turtles: Kinosternidae
AMERICAN MUD AND MUSK TURTLES: KinosternidaeSTINKPOT (Sternotherus odoratus): SPECIES ACCOUNT
American mud and musk turtles have glands, or sacs, along their sides that produce a musky substance that smells like the spray of a skunk. The upper shell, or carapace (KARE-a-pays), is rather tall, giving each turtle the outline of half a flattened ball when viewed from the side. The lower shell, or plastron (PLAS-trun), looks different in separate species. In some species the plastron has one or two hinges reaching from the left to the right side of the shell, but in others the shell has no hinges. The hinges allow the plastron and carapace to pull tight against one another after the turtle pulls its head, neck, legs, and tail into the shell. Some mud and musk turtles have a plastron that covers only part of the lower body, while others have a quite large plastron that almost entirely conceals the undersides.
All of these small to medium-sized turtles have barbels (BAR-buhls), which are small bits of flesh that dangle from the chin. A few have very large heads. Most of the species in this family have a carapace that is less than 8 inches (20 centimeters) long and in some cases grows to just 4 inches (10 centimeters) in length. The largest species, called the Mexican giant musk turtle, has a carapace that reaches 15 inches (38 centimeters) long. Males and females look quite similar. Males, however, usually have thicker and longer tails that are tipped with a spine. Males also have two rough, scaly patches on each hind leg.
Members of the American mud and musk turtle family live in North and South America.
American mud and musk turtles are freshwater species. Most live in still or slow-moving waters and prefer lakes and ponds that are filled with water all year long. A few make their homes in shallow, seasonal ponds, which have water only a few months a year, usually during the spring season. American mud and musk turtles are found mainly in eastern and southern North America and as far south as Argentina in South America.
American mud and musk turtles are mainly meat eaters. They eat snails, clams, insects, worms, leeches, and sometimes freshly killed fishes they come across. Turtles that have large heads typically prefer snails and clams, which the turtle can easily open with its massive jaws. Turtles in seasonal ponds may also eat a large number of seeds.
BEHAVIOR AND REPRODUCTION
Although most American mud and musk turtles stay in the water for most of their lives, these turtles are only fair swimmers and move rather slowly. In the rainy season, some turtles may crawl onto land and look for food there, but for the most part, most of the trips to land are for nesting. Some turtles are active only during the day, and some only at night. Others may be up and about at any time of day or night. Those that live in warm, wet climates are active all year. In areas with cold winters and in deserts with long stretches of dry weather, the turtles may be active only a few months a year and spend the rest of the year underground, where they wait for better conditions. This period of inactivity in the winter is called hibernation (high-bur-NAY-shun). A period of inactivity in dry summers is called estivation (es-tuh-VAY-shun). In both cases, the turtle enters a state of deep sleep.
THE LONG SLEEP
The yellow mud turtle holds the record among turtles for the amount of time it spends in a deep sleep every year. In very dry years this small, yellow-throated reptile buries itself in the ground and waits for the rains to come, even if that means the turtle has to stay underground up to ten months of the year. While underground the turtle enters a deep sleep. Usually this period of inactivity is called estivation if it occurs during the summer and hibernation if it occurs in the winter. Yellow mud turtles, however, are inactive from summer through fall and winter to the following spring. In other words, they both estivate and hibernate. When the spring rains flood the ground, the turtles crawl out of their slumber to mate, eat, and prepare for another long sleep.
During breeding season, males and females have no real courtship, or mating, rituals. They mate in the water. The females scramble onto land to make their nests. Some dig holes, lay their eggs at the bottom, and then bury them. Others bury themselves first and then dig a deeper hole for their eggs. Still other species skip the hole and simply lay their eggs among leaves on the surface of the ground. Females usually lay three to six eggs in each clutch, or group of eggs, although some clutches have as few as one egg or as many as twelve eggs. The female may lay up to six clutches a year. The oblong eggs range from 0.9 to 1.7 inches (2.3–4.3 centimeters) long and from 0.6 to 1.0 inches (1.5–2.5 centimeters) wide. The eggs hatch seventy-five days to a year after being laid. The nest temperature controls whether the eggs in most species hatch into males or females. Very warm or very cold temperatures produce females, and medium temperatures produce males. In a few species, such as the Mexican giant musk turtle and Pacific Coast giant musk turtle, the nest temperature has no effect on whether the eggs become males or females.
AMERICAN MUD AND MUSK TURTLES AND PEOPLE
Other than once in a while collecting a turtle for the pet trade or for its meat value, people generally leave mud and musk turtles alone.
Most species of American mud and musk turtles are quite common in their habitats, but according to the World Conservation Union (IUCN), four species are Vulnerable, which means they face a high risk of extinction in the wild. Three of the four live in very small areas, and the fourth lives in a disappearing habitat. The U.S. Fish and Wildlife Service lists one species, the flattened musk turtle, as Threatened, or likely to become endangered in the near future.
Physical characteristics: As its name says, the stinkpot can give off quite an odor. This odor comes from a substance known as musk, which comes from sacs, or glands, on the sides of the turtle's body. The stinkpot is small, has a somewhat rounded upper shell, or carapace, and a small lower shell, or plastron, that covers only the center of its underside. The plastron has one side-to-side hinge near the front. The turtle's head typically has two yellow stripes on each side that run backward from a pointy snout. The stinkpot also has at least two barbels, or bits of hanging flesh, on its chin and neck. Stinkpots, which are also known as common musk turtles, grow to about 5.4 inches (13.7 centimeters) in carapace length, although some adults only reach about 3 inches (7.6 centimeters) long.
Geographic range: Stinkpots are found in Canada and the United States.
Habitat: The stinkpot is a small freshwater turtle most at home in mud-bottomed, weedy lakes and ponds in southeastern Canada and through much of the eastern half of the United States.
Diet: Stinkpots eat a variety of animals and plants. Their diet includes worms, snails, clams, crayfish, insects, tadpoles, fishes and their eggs, and even bites of flesh they take from dead animals. Stinkpots are also fond of seeds, tiny aquatic plantlike growths called algae (AL-jee), and pieces of plants that grow in the water.
Behavior and reproduction: Like other members of their family, stinkpots stay in the water much of their lives but are poor swimmers and often simply walk along the water bottom looking for food. Although they are small, stinkpots can put up quite a fight if an animal attacks them or if a human tries to pick one up. Often a turtle that feels threatened ducks its head, legs, and tail as far as possible into the shell. At other times, however, the stinkpot snaps out with its mouth wide open, sometimes taking a firm bite at the attacker.
Stinkpots sometimes sunbathe, or bask, on land. Turtles that live in a warmer area may stay active all year long. Turtles that live in an area that has cold winters may hibernate for a few months.
Most musk turtles mate in the spring or fall, but some mate at other times of the year. The male may try to attract the female by biting at her shell or nudging her, but these turtles often mate without much fuss. The females lay their eggs from spring to midsummer, sometimes as early as February in warmer areas. Some female stinkpots simply drop their eggs among leaves, but others dig a hole, lay the eggs inside, and then bury them. The white, oblong eggs range from 0.9 to 1.2 inches (2.3–3.0 centimeters) long and from 0.5 to 0.7 inches (1.3–1.8 centimeters) wide. The female usually lays a clutch, or group, of two to five eggs at a time but sometimes lay as few as one or as many as nine eggs. The stinkpot may lay one or two clutches a year in colder areas and up to four clutches a year in southern climates. The eggs hatch in about sixty-five to eighty-five days. Very warm and very cool nest temperatures produce females, and temperatures in between produce males.
Stinkpots and people: Some people collect stinkpots for the pet trade, but this practice is not very common.
Conservation status: Neither the World Conservation Union (IUCN) nor the U.S. Fish and Wildlife Service consider the stinkpot threatened. ∎
FOR MORE INFORMATION
Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Knopf, 1979.
Burnie, David, and Don E. Wilson, eds. Animal: The Definitive Visual Guide to the World's Wildlife. London: Dorling Kindersley, 2001.
Conant, Roger, and Joseph T. Collins. A Field Guide to Reptiles and Amphibians of Eastern and Central North America. 3rd ed. Boston: Houghton Mifflin, 1998.
Harding, J. H., and J. A. Holman. Michigan Turtles and Lizards. East Lansing: Michigan State University, 1990.