Sternotherus odoratus

Geographic Range

Common musk turtles ( Sternotherus odoratus ), also called stinkpots, are found throughout the eastern and central United States, with the exception of higher elevations areas such as the Blue Ridge Mountains. Their geographic range extends as far north as parts of south Maine, Michigan, and Wisconsin, as well as parts of south Ontario, Canada. Their range includes the East Coast, as far south as south Florida. Their range continues along the Gulf Coast and the western bounds of their range include east Texas, east Oklahoma, southeast Kansas, south-central Arkansas, and Illinois.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Stinkpots seldom stray far from water, except for females when they are laying eggs. Stinkpots are most often found in permanent wetlands such as ponds, lakes, or human-made impoundments where aquatic plants can provide sufficient food. They are also found frequently in streams, rivers, and swamps. They typically rest in shaded areas that are low enough for their carapaces to touch the ground. Most of their time is spent on the bottom of bodies of water, searching for mates or for prey in the sediment, giving them the nickname "bottom walker".

Stinkpots are known to return to the sites where they were born when they are displaced. Stinkpots tend to be more active in new areas compared to their natal areas. Males move more than females, on average, likely in an attempt to mate with multiple females. Stinkpots have been observed basking in trees up to 2 m above water. They are found more frequently in shallow water, and are rarely discovered at depths greater than 2 m.

The highest elevation for a known population of stinkpots is 1,170 m in Lake Ravenel of Macon County, NC.

• Habitat Regions
• terrestrial terrestrial
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Wetlands
• swamp swamp

Physical Description

Stinkpots have brown carapaces with small, yellow plastrons. Their carapaces are elongated, narrow, and rounded with irregular patterns of black streaks or spots. Their skin is typically greyish-black, with multiple patterns of yellow spots and streaks on their legs and lower necks. Stinkpots have a pair of dark or pale yellow stripes on each side of their heads: one above and one below each eye. These facial stripes distinguish stinkpots from other species in the genus ( Sternotherus ). They have white or yellow skin, which is visible between the seams of their plastrons. Their plastrons have a single, nonfunctional hinge. Stinkpots also have elongated, pointed snouts and have barbels on their chins and necks. For some individuals, these barbels are reduced in size. It is common for algae to grow on parts or all of their shells.

Males have larger tails and heads compared to females. Males also have differently shaped tails, which go from wide at the base to very thin at the end. The average length for adults is between 100 to 127 mm. Average adult body mass is 100 g.

Stinkpot hatchlings are the smallest turtles in North America, with an average carapace length of 25 mm and a weight range of 1.6 to 3.2 g. Hatchlings resemble adults with the exception of their carapaces, which have noticeably higher midline keels compared to adults. Adults also have noticeable midline keels, but they are much smaller than the keels of hatchlings. The yellow head stripes of juveniles are more distinct compared to adults.

Stinkpots are often mistaken for striped mud turtles ( Kinosternon baurii ) and eastern mud turtles ( Kinosternon subrubrum ), especially since all three species have overlapping ranges. However, stinkpots are distinguishable by the presence of skin visible between the scutes of their plastrons. The other two species also have two hinges on their plastrons and their carapaces are never keeled

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes shaped differently

Development

Stinkpot eggs are thick, but brittle-shelled. On average, eggs are 1.9 cm wide by 2.5 cm long. As female size and clutch size increase, egg width increases and egg length decreases. Yolk development occurs between August and December, and takes place in the ovarian follicles of females. Egg yolk ranges in diameter from 14.7 to 16.8 mm. Stinkpots exhibit indeterminate growth, meaning they do not cease growing throughout their lifetime. However, growth rates are fastest for hatchlings and juveniles, and slower after stinkpots reach adulthood.

Female stinkpots lay 1 to 4 clutches of eggs per season, with a total of 1 to 6 eggs per clutch. Females excavate burrows where they lay their eggs, which typically incubate for 65 to 86 days. Stinkpots exhibit temperature-dependent sex determination. At temperatures greater than 28 °C, nearly all eggs develop into females, whereas temperatures below 25 °C produce nearly all males. Most hatchlings leave their nests in late summer or fall, but others stay in their nests throughout winter, only leaving to seek bodies of water in the spring.

• Development - Life Cycle
• temperature sex determination
• indeterminate growth indeterminate growth

Reproduction

Stinkpots are polygynandrous, and it is possible for clutches of eggs to have multiple paternities. During breeding season, males move around frequently and attempt to mate with multiple females. Females can store sperm from fall through winter and have also been observed mating with multiple males during same breeding season.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Stinkpots mate in the water. In the southeast United States, stinkpots breed throughout the year, although breeding activity peaks in spring and fall. Females lay 1 to 4 clutches per year, with 1 to 6 eggs per clutch. The maximum recorded number of eggs laid in a single breeding season was 9. Clutch size and egg size are positively correlated.

Stinkpot mating behavior can be grouped into three phases. The first phase involves tactile communication, with males chasing females, nudging their shells, biting their heads, and attempting to mount them. If a female is receptive to mating, the second phase begins. The second phase involves mounting and penetration, with males using all four feet to grasp their mate's carapace. Then, males use the scale patches on their rear legs to clasp their mate's tail, moving it to the side to expose the cloaca, and insert their penis. The third phase involves biting and rubbing, with males biting and rubbing their mate's head and neck during intromission. At the same time, females bite their mate's head and feet. Male ejaculation involves full-body contractions and stiffening. The mating behavior of stinkpots has been called forced insemination.

Stinkpots often make their nests in shady areas less than 46 m away from a body of water. They excavate shallow nests, often under logs, under leaves, or on grassy ground. Multiple females usually nest in the same area.

Stinkpots are independent immediately after hatching. Males reach sexual maturity after 5 to 6 years with an average carapace length of 63.6 mm. Females reach sexual maturity after 8 to 9 years with an average carapace length of 80.7 mm.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• oviparous oviparous

Females exhibit no further parental investment beyond the acts of nest digging and egg deposition. Males exhibit no further parental investment beyond the act of mating. Hatchlings are immediately independent upon hatching.

• Parental Investment
• no parental involvement

Lifespan/Longevity

On average, stinkpots live to be 15 to 19 years old. Mortality rates are high for hatchlings and juveniles, but low for adults. The longest recorded lifespan of a wild individual is 28 years. The longest recorded lifespan of a captive individual is 54.8 years.

Behavior

Stinkpots are mostly aquatic, but will go on land during rainstorms. They often bask on branches or forking limbs overhanging water. They drop into the water from these overhangs, and there are reports of them inadvertently dropping into boats passing under such branches. It is uncommon for stinkpots to move between disjunct bodies of water.

Stinkpots brumate when water temperatures drop below 10°C. They typically enter brumation after burying themselves around 30 cm deep in mud.

Stinkpots are mostly crepuscular, although they are more nocturnal at southern latitudes because nighttime temperatures are warmer than at northern latitudes. Because they are small and ectothermic, environmental temperatures can strongly affect stinkpot activity. They mostly inhabit highly vegetated areas near water or relatively shallow aquatic zones. Stinkpots travel an average of 27 m daily.

• Key Behaviors
• natatorial natatorial
• nocturnal nocturnal
• crepuscular crepuscular
• motile motile
• sedentary sedentary
• hibernation hibernation

Home Range

Aquatic habitat dimensions often influence home range size and shape. Recorded home ranges for stinkpots vary from less than 1 ha to more than 100 ha. On average, males have home ranges that are twice the size of female home ranges. Within their home ranges, stinkpots may use certain areas more often than others, depending on resource distribution. Resources that affect stinkpot activity include basking sites, foraging areas, and areas with microclimates that are suitable for surviving harsh conditions. Stinkpots are not known to defend specific territories.

Communication and Perception

Stinkpots have four glands, located under their carapaces, that discharge an orange fluid when stinkpots are threatened. The fluid is a form of phenylalkanoic acid, which is mostly used to protect themselves from predators. However, it is believed that this fluid could also play a role in mating. Stinkpots get their common name due to the strong, distasteful odor associated with the fluid.

There is limited information on communication in stinkpots specifically. However, the reproductive and mating behavior of other turtles in the genus Sternotherus includes chemical communication. Turtles release chemicals in water to communicate their body size, health status, and whether they are male or female. Aquatic turtles are also sensitive to vibrations in the water, which helps them detect approaching predators and prey. They also use their senses of smell and vision to find prey in the water and on land.

• Communication Channels
• chemical chemical

• Other Communication Modes
• scent marks scent marks

• Perception Channels
• visual visual
• vibrations vibrations
• chemical chemical

Food Habits

Stinkpots are omnivorous, consuming a wide variety of plants and animal prey. Stinkpots mainly eat benthic and neustonic taxa. They eat plants such as algae, water lilies (family Nymphaeaceae ), and seeds of both terrestrial and aquatic plants. They eat dragonflies (family Odonata ), beetles (family Coleoptera ), moths (family Lepidoptera ), and other insects. They also eat mollusks (phylum Mollusca ), crayfish (order Decapoda ), and terrestrial worms (phylum Annelida ). They will also opportunistically eat carrion such as dead fish and mollusks.

Stinkpots use visual and olfactory cues to detect prey. Adults mostly feed in the water, whereas juveniles and subadults (1 to 12 years old) more frequently feed on land. Stinkpots can have difficulty quickly capturing or transporting prey compared to other freshwater turtles. This is because their jaw and hyoid movements have a low integration (connection). When stinkpots are in the water, prey has to be directly in front of their mouths, because they are not able to create suction forces.

Stinkpot diets fluctuate seasonally and vary between sexes. Females consume more food than males due to the higher energetic demands of gestating and laying eggs, as well as locating nest sites and excavating nests.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods
  • molluscivore molluscivore
  • vermivore
  • scavenger scavenger
• herbivore herbivore
  • folivore folivore
• omnivore omnivore

• Animal Foods
• fish
• eggs
• insects
• mollusks
• terrestrial worms
• aquatic or marine worms
• aquatic crustaceans

• Plant Foods
• seeds, grains, and nuts
• algae

Predation

Juvenile and adult stinkpots serve as prey for a variety of predators in their communities. Mammalian predators include raccoons ( Procyon lotor ), striped skunks ( Mephitis mephitis ), gray foxes ( Urocyon cinereoargenteus ), and North American river otters ( Lontra canadensis ). Avian predators include bald eagles ( Haliaeetus leucocephalus ), red-shouldered hawks ( Buteo lineatus ), boat-tailed grackles ( Quiscalus major ), and large wading birds, such as herons and egrets (family Ardeidae ). Reptilian predators include common snapping turtles ( Chelydra serpentina ), northern water snakes ( Nerodia sipedon ), and cottonmouths ( Agkistrodon piscivorus ). American bullfrogs ( Lithobates catesbeianus ) and largemouth bass ( Micropterus salmoides ) also prey on stinkpots.

Humans ( Homo sapiens ) intentionally and unintentionally kill stinkpots during fishing activities. If they are caught on fishing lines, humans often decapitate them. Also, stinkpots can get caught in fishing traps and they drown if the traps are not checked frequently.

Terrestrial predators of eggs and hatchlings include raccoons, grey foxes, striped skunks, Virginia opossums ( Didelphis virginiana ), kingsnakes ( Lampropeltis getula ), and scarlet snakes ( Cemophora coccinea ). Crows (genus Corvus ) will also eat eggs and hatchlings. Raccoons will follow the tracks of female stinkpots to find their nests. Some nest predators will also opportunistically kill nesting females.

Stinkpots have a tough shell that protects them and dark coloration that helps them camouflage with their environment. They release a foul-smelling, orange fluid from specialized glands when they are threatened, and will also bite in defense.

Ecosystem Roles

A study on a stinkpot population in southern Pennsylvania found that 86% of individuals had algal colonies on their carapace. The algae was identified as either Basacladia chelonum or Cladophora kuetzingiana . Stinkpots have a mutualistic relationship with these algae, with stinkpots providing a protected substrate and algae providing natural camouflage for stinkpots. In the same study in southern Pennsylvania, a leech species, Placobdella parasitica , was observed actively feeding on 33% of the stinkpots surveyed.

Stinkpots are important bioindicators for freshwater habitats. Water pollution and other disturbances can negatively affect body mass and shell quality, which in turn can impact population size, reproductive fitness, and susceptibility to disease.

Economic Importance for Humans: Positive

Stinkpots are occasionally eaten by humans, but are more commonly owned as pets. However, they are not a popular species in the pet trade and so their economic benefits to the pet trade are likely negligible.

• Positive Impacts
• pet trade pet trade
• food food

Economic Importance for Humans: Negative

Stinkpots have no known negative impacts on humans.

Conservation Status

Stinkpots are considered a species of "least concern" on the IUCN Red List. In Canada, stinkpots are listed as a species of special concern. There is no known conservation status for populations in Mexico. Stinkpots have no special status on any other national or international conservation lists. They do not often venture far from bodies of water, which makes them less vulnerable to road mortality compared to other freshwater turtle species. Stinkpots have a large geographic range and are abundant throughout its entirety. Although water pollution and anthropogenic development near bodies of water can negatively impact their populations, they are unlikely to be considered threatened or endangered in the near future. In general, effective freshwater turtle conservation methods require protection of both terrestrial and aquatic habitats. There are no known conservation practices in place for stinkpots specifically.

Stinkpots are occasionally kept as pets, but are not currently at risk of over-collection.

Additional Links

Encyclopedia of Life

Contributors

Katelyn Lowery (author), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Emily Clark (editor), Radford University, Cari Mcgregor (editor), Radford University, Jacob Vaught (editor), Radford University, Galen Burrell (editor), Special Projects.

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