Animal
Red swamp crayfish
The red swamp crayfish is a dark red animal with big claws. It lives in swamps and ponds and digs holes in the mud.
The red swamp crayfish is a dark red freshwater crustacean with long claws covered in bright red bumps. It comes from the swamps and streams of the southern United States and northern Mexico, where it digs burrows in the mud. People have carried it around the world for food, and in many new places it harms the plants and animals that already live there.
Procambarus clarkii, of the family Cambaridae, is native to the Gulf coastal plain and the southern Mississippi basin of North America. Tolerant, fast-growing and widely farmed, it has been introduced to Europe, Africa, Asia and South and Central America, where the Global Invasive Species Database records severe impacts, including the spread of crayfish plague to native crayfish.
Photo: Juan Emilio Prades Bel, CC BY 4.0, via Wikimedia Commons
Meet the red swamp crayfish
The red swamp crayfish is a dark red animal.
It has two big claws with red bumps. It lives in water and walks on the bottom.
The red swamp crayfish looks like a small lobster that lives in fresh water. It is usually dark red, with a long head and long claws dotted with rows of bright red bumps. Adults are 5.5 to 12 centimeters long.
In the southern United States it is a popular food called crawfish. It grows very fast and can live in many kinds of water, so people farm it in many countries. But those same skills make it a problem in places where it does not belong.
Procambarus clarkii belongs to the family Cambaridae (order Decapoda, class Malacostraca). The U.S. Geological Survey identifies it by its typically dark red color, elongate claws and head, a triangular rostrum without a central keel, and bright red rows of tubercles on the claws; juveniles are not red and are hard to tell from related species. Adults measure 5.5 to 12 centimeters.
The IUCN calls it a major commercial crayfish widely introduced into culture ponds around the world, and the Global Invasive Species Database (GISD) says its rapid growth and tolerance of seasonal waters made it the dominant freshwater crayfish in the world.
Quick facts
- Group
- Invertebrate
- Length
- 5.5 to 12 cm
- Weight
- from 50 g
Where it lives
Red swamp crayfish come from the southern United States and Mexico.
They live in swamps, ponds, ditches and rice fields.
The red swamp crayfish comes from the warm, low lands near the Gulf of Mexico, from the Florida panhandle to Mexico, and up the Mississippi River valley as far as Illinois.
It lives in swamps, marshes, wet meadows, ponds, lakes and streams, and it does well in rice fields and irrigation ditches made by people. People have carried it to many other parts of the United States and to Europe, Africa, Asia and South and Central America.
The USGS gives a native range on the Gulf coastal plain from the Florida panhandle to Mexico and in the southern Mississippi River drainage north to Illinois; the IUCN describes it as ranging from northern Mexico to Escambia County, Florida, and north to southern Illinois and Ohio. The sources disagree about Mexico: the IUCN assessment's own country list marks Mexico as introduced, while the USGS and a 2008 study of the crayfish's spread in Mexico (Hernández and colleagues) treat northeastern Mexico as native and the populations farther west, in Baja California, Durango and Sinaloa, as introduced. The map follows the USGS. Habitats include wet meadows, karst systems, seasonal swamps and marshes, permanent lakes and streams, rice paddies, and irrigation channels and reservoirs.
It tolerates low oxygen and high temperatures (IUCN) and wide ranges of salinity and pH (USGS). Outside its native range it has been introduced across the United States and to Europe, Africa, East Asia and South and Central America; in central and southern Europe it has established in warm, shallow natural and agricultural wetlands.
Continent
Its habitat
Where can you find this animal?
- Brought here by people · Countries and seas named by a scientific source
- Lives here naturally · Countries and seas named by a scientific source
- Sightings recorded · Records of wild sightings (GBIF)
Brought here by people · Countries and seas named by a scientific source
Countries where the IUCN lists the red swamp crayfish as introduced and established (30 besides Mexico), across Europe, Africa, Asia and South and Central America. It has also been introduced to many U.S. states outside its native range and to western Mexico.
Places: Belgium, Belize, Brazil, Chile, China, Colombia, Costa Rica, Cyprus and 22 more places.
Source: iucn-red-list · checked October 2026
Lives here naturally · Countries and seas named by a scientific source
The Gulf coastal plain from the Florida panhandle to northeastern Mexico, and the southern Mississippi River basin north to Illinois. The map shades whole countries; the native range covers only the south-central United States and northern Mexico. The IUCN country list instead marks Mexico as introduced; the USGS and Hernández and colleagues (2008) treat northeastern Mexico as native.
Places: United States and Mexico.
Source: https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=217 · checked October 2026
Sightings recorded · Records of wild sightings (GBIF)
Counts of GBIF records of wild observations (human and machine) and preserved specimens. Records include introduced populations, vagrants, escaped or released animals and misidentifications, so a country with records is not necessarily part of the native range.
Wild sightings have been recorded in Spain, France, Netherlands, United States, Switzerland, Belgium, Colombia, Italy and 34 more places.
Source: gbif · checked October 2026
Range maps show where scientists say an animal lives, often country by country. An animal may live in only part of a country shown, and sightings records can include animals that wandered far from home.
What it eats
Red swamp crayfish eat almost anything.
They eat water plants, small animals and bits of dead things.
Red swamp crayfish are omnivores, which means they eat both plants and animals. Most of their food is plants, but they also eat insects, snails, small fish, other crayfish and bits of dead material on the bottom.
Because they eat so much and so many different things, large numbers of red swamp crayfish can change a whole pond or wetland.
GISD describes P. clarkii as an opportunistic omnivore with a primarily plant-based diet. The USGS adds that it consumes plant material, animals, detritus and sediment, and that the animal part of the diet is dominated by insects (especially midge larvae), other crayfish, snails and fish.
This broad diet underlies many of its impacts where introduced: GISD reports reduced water-plant (macrophyte) cover and diversity in lakes and wetlands from Spain and Italy to Kenya, and predation on and competition with amphibians, molluscs, other invertebrates and fish.
Did you know?
Young red swamp crayfish are not red.
Young red swamp crayfish are not red yet, so they are hard to tell apart from other kinds of crayfish.
Juveniles lack the adult red coloration and are difficult to distinguish from other Procambarus species (USGS).
A crayfish up close
A crayfish has a hard shell and long feelers.
Its two big claws have red bumps. It has a long, jointed tail.
A crayfish is a crustacean, like crabs and lobsters. Its head and middle are covered by a hard shell called a carapace, and behind that is a long, jointed tail called the abdomen.
At the front are long antennae and two eyes on short stalks. The first pair of legs carry big claws with rows of bright red bumps, and four more pairs of legs are for walking. To grow, a crayfish must molt its whole shell.
The USGS describes elongate claws and head, a triangular rostrum tapering forward without a central keel, reduced or absent spines on the side of the carapace, and bright red rows of tubercles on the claws.
Like other decapods, it has five pairs of walking legs (the first pair modified as claws), long antennae and stalked eyes. Growth is by molting; the USGS notes that because crayfish in shared burrows can be cannibalistic, adults often molt in the open.
Growing up fast
A mother crayfish carries her eggs under her tail.
The tiny babies stay with her in her burrow. They grow up very fast.
A female red swamp crayfish carries her eggs under her tail. A big female can carry up to 500 eggs, and a smaller one about 100. The eggs are tiny, less than half a millimeter wide.
After they hatch, the baby crayfish stay with their mother in her burrow for up to eight weeks and molt twice before they can look after themselves. Red swamp crayfish grow up very fast: some can have young of their own when they are only about two months old.
GISD reports that a 10-centimeter female may produce up to 500 eggs and smaller females about 100, each egg about 0.4 millimeters, smaller than those of European native crayfish. Hatchlings remain with the mother in the burrow for up to eight weeks and molt twice before becoming independent. Populations can contain egg-carrying or young-carrying females all year, with at least two breeding periods where flooding lasts more than six months.
The USGS gives sexual maturity in as few as two months and a generation time of about four and a half months, while GISD gives maturity at 6 to 12.5 centimeters. This fast life cycle helps explain how quickly introduced populations grow.
Burrow builders
Red swamp crayfish dig holes in the mud.
Some holes have a little mud tower at the top, called a chimney.
Red swamp crayfish are great diggers. They dig burrows with a single opening, sometimes topped with a little tower of mud called a chimney, which helps keep the burrow damp. When the weather is hot and dry, they dig down to the water underground, sometimes almost a meter deep.
They have two ways of living. Sometimes they wander and move quickly from place to place. At other times they stay put, hiding in their burrows by day and coming out at dusk to feed.
The USGS calls P. clarkii a physical ecosystem engineer: it builds simple burrows with one opening, sometimes capped with a mud plug or chimney that reduces water loss, leading to an enlarged chamber, and in drought or heat burrows can extend 40 to 90 centimeters down to the water table. Burrow density is highest in fine sediments.
GISD describes a wandering phase with bursts of fast movement and no daily rhythm, and a longer stationary phase in which crayfish hide in burrows by day and emerge at dusk to forage. GISD lists damage to irrigation systems and changes to water quality and sediments among its impacts in invaded areas.
Did you know?
Red swamp crayfish grow up very fast.
Some red swamp crayfish can have babies when they are only about two months old.
Sexual maturity can arrive in as few as two months, with a generation time of about four and a half months (USGS).
A problem far from home
At home, red swamp crayfish are doing well.
In other countries they can hurt the animals that already live there. People should never let pet or bait crayfish go into the wild.
In its home range the red swamp crayfish is not in danger; the IUCN lists it as Least Concern. Far from home, it can be a very harmful invader. In Europe it carries a disease called crayfish plague, which it can resist but which kills Europe's own crayfish. It also eats water plants, snails and other small animals, harms frogs and other amphibians, and changes the water it lives in.
Some red swamp crayfish spread when people use them as fishing bait. Never releasing crayfish into rivers and ponds is one of the best ways to help.
The IUCN (assessed 2010, flagged as needing updating) lists P. clarkii as Least Concern with an increasing population, noting it is highly invasive. As an introduced species, GISD reports aggressive competition with native crayfish, introduction of the crayfish plague (Aphanomyces astaci), reduction of water plants, altered water quality and sediments, predation on and competition with amphibians, molluscs and invertebrates, and harm to agriculture and fisheries.
In Europe, GISD notes that P. clarkii resists the plague while native crayfish are susceptible, contributing to the decline of species such as the endangered white-clawed crayfish and the noble crayfish. Management options it lists include trapping, barriers, banning the transport of live crayfish and public education; it can spread when anglers use it as bait.
IUCN Red List
How is the red swamp crayfish doing in the wild?
- Least Concern (this animal)
- Near Threatened
- Vulnerable
- Endangered
- Critically Endangered
- Extinct in the Wild
- Extinct
Least Concern
Not at risk of disappearing from the wild right now.
See the IUCN Red List assessment · The IUCN Red List of Threatened Species 2022.2
Amazing facts
-
Some crayfish build little mud towers.
Red swamp crayfish sometimes build a chimney of mud on top of their burrow, which helps keep it damp.
Burrow openings may be capped with a mud plug or chimney that reduces evaporative water loss (USGS).
-
Baby crayfish stay with their mother.
Baby red swamp crayfish stay in their mother's burrow for up to eight weeks before going off on their own.
Hatchlings remain with the mother for up to eight weeks and molt twice before becoming self-sufficient.
-
Red swamp crayfish grow up very fast.
Some red swamp crayfish can have babies when they are only about two months old.
Sexual maturity can arrive in as few as two months, with a generation time of about four and a half months (USGS).
-
Young red swamp crayfish are not red.
Young red swamp crayfish are not red yet, so they are hard to tell apart from other kinds of crayfish.
Juveniles lack the adult red coloration and are difficult to distinguish from other Procambarus species (USGS).
Words to know
- crustacean
- an animal with a hard outer shell and jointed legs, such as a crab or crayfish
- burrow
- a hole or tunnel an animal digs to live in
- omnivore
- an animal that eats both plants and animals
- invasive
- a living thing brought to a new place where it causes harm
- native range
- the places where a living thing lived before people moved it
- molt
- to shed an old shell or skin so the body can grow
Discovery challenge
-
What color is a grown-up red swamp crayfish?
What color are adult red swamp crayfish usually?
What is the typical color of adult Procambarus clarkii?
- Bright blue
- Dark red
- Green with yellow stripes
Show the answer
Dark red
It is dark red, with red bumps on its claws.
Adults are usually dark red, with bright red bumps on the claws. Young ones are not red yet.
Typically dark red, with bright red tubercles on the chelae; juveniles are not red.
-
Where do red swamp crayfish come from?
Where is the red swamp crayfish's native home?
What is the native range of Procambarus clarkii?
- Australia
- The southern United States and northern Mexico
- Japan
Show the answer
The southern United States and northern Mexico
They come from the southern United States and Mexico.
They come from the Gulf coast from Florida to Mexico and up the Mississippi valley to Illinois.
The Gulf coastal plain and southern Mississippi River drainage; Japan is part of its introduced range.
-
Why are red swamp crayfish a problem in Europe?
Why is the red swamp crayfish a problem in Europe?
Which impact has contributed most to the decline of Europe's native crayfish?
- It spreads a disease that kills Europe's own crayfish
- It eats trees
- It blocks out the sun
Show the answer
It spreads a disease that kills Europe's own crayfish
It carries a sickness that hurts the crayfish that already lived in Europe.
It carries crayfish plague, which does not harm it but kills Europe's native crayfish.
Transmission of the crayfish plague, Aphanomyces astaci, together with direct competition.
-
Where do baby crayfish stay at first?
Where do young red swamp crayfish live after they hatch?
Where do P. clarkii hatchlings spend their first weeks?
- In a bird's nest
- In the burrow with their mother
- Up in a tree
Show the answer
In the burrow with their mother
They stay with their mother in her burrow.
They stay in their mother's burrow for up to eight weeks.
In the maternal burrow, for up to eight weeks and two molts.
Places where you might see it
-
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United States
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Country
Spain
Spain covers most of the Iberian Peninsula in southwestern Europe. Its middle is a high, flat plateau, the Pyrenees mountains stand between it and France, and almost 50 million people live there, with Madrid as the capital.
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For parents & teachers
What children will learn
- Identify the red swamp crayfish's main body parts and how it differs from crabs.
- Describe its burrowing behavior and fast life cycle.
- Explain what makes an invasive species harmful, using the crayfish plague as an example.
- Understand why people should never release pets or bait animals into the wild.
Recommended ages: 3 to 17 · About 15 minutes
Talk about it
- Which of the red swamp crayfish's traits help it succeed in new places?
- Why might a disease that does not harm one crayfish be deadly for another?
- What rules could stop people from spreading crayfish by accident?
Try at home or in class
- Build a small mud chimney from damp soil and compare how fast it dries with a flat patch of the same soil.
- On a map, mark the crayfish's native home and three countries where it has been introduced.
Key vocabulary: crustacean, burrow, omnivore, invasive, native range, molt
Where these facts come from
- The IUCN Red List of Threatened Species , International Union for Conservation of Nature (IUCN terms of use (no redistribution of Red List data or range maps))
- GBIF Backbone Taxonomy and GBIF Occurrence Search , Global Biodiversity Information Facility (CC0 1.0 (backbone); occurrence counts are facts derived from records under CC0, CC BY and CC BY-NC)
- Procambarus clarkii (Red Swamp Crayfish), 2010 global assessment , IUCN Red List of Threatened Species
- Red Swamp Crayfish (Procambarus clarkii) - Species Profile , U.S. Geological Survey, Nonindigenous Aquatic Species program
- Procambarus clarkii , Global Invasive Species Database, IUCN SSC Invasive Species Specialist Group
- Geographic expansion of the invasive red crayfish Procambarus clarkii (Girard, 1852) (Crustacea: Decapoda) in Mexico (Hernández et al. 2008, Biological Invasions 10: 977-984) , Biological Invasions (Springer)
- Wikidata , Wikimedia Foundation (CC0 1.0)
- Wikimedia Commons , Wikimedia Foundation (Per file: Public domain, CC0, CC BY or CC BY-SA only (credited on each page))
Checked, not yet human-reviewed. Last updated October 28, 2026. Spotted a mistake? Tell us.