Fauna
Invertebrate

Calico Crayfish

Faxonius immunis

Also known as Papershell Crayfish

Calico crayfish inhabit slow-moving or stagnant waters, including muddy ponds, ditches, and floodplain wetlands across central and eastern North America. Known as papershell crayfish due to their thin, flexible carapaces, these hardy crustaceans burrow deeply into mud banks to survive dry summers and freezing winters. Introduced populations in European river systems now occupy warm, low-oxygen aquatic habitats where native species struggle.

FreshwaterCrustaceanBurrower
Calico Crayfish reference1 / 7
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Least ConcernConservation statusIUCN Red List categoriesLCNTVUENCREWEXLeast ConcernRed List categories, explained →
Key facts
Diet & preyAquatic Vegetation, Detritus, Small Invertebrates
Predators
  • Great Blue Heron
  • Largemouth Bass
  • Raccoon
ThreatsPollution, wetland drainage, intense invasive competition
HabitatsPonds, marshes, sluggish streams, agricultural ditches, mud banks
Life span2–3 years
Classification
  1. FamilyCambaridae
  2. SpeciesFaxonius immunis
Range & activity
Range data is not available yet.
Safe observation
Interaction riskLow
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is low
Pincers can deliver a sharp pinch if handled; observe quietly from the water's edge.
Why it is dangerous
Capable of delivering a painful pinch with its chelae when cornered or grasped.
How to recognize a risky encounter
Look for a brownish-tan carapace with a pale central stripe and thin pincers.
What to do
Observe in the water without picking up; avoid touching pincers directly.
Responsible observation
  • Finding them: Look along muddy edges of quiet ponds or ditches near dusk.
  • Burrow chimneys: Look for small mud tubes constructed over subterranean burrows.
  • Safe viewing: Avoid picking them up directly to prevent being pinched by claws.
Related species
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