Mammoth Spring Crayfish

Photo of a Mammoth Spring crayfish.
Species of Conservation Concern
Scientific Name
Faxonius marchandi (formerly Orconectes marchandi)
Cambaridae (freshwater crayfish) in the order Decapoda (shrimp, crabs, and lobsters)

The Mammoth Spring crayfish is a reddish-brown crayfish with broad, powerful pincers. The pincers have numerous blackish specks on their basal parts. The abdomen is dark rusty red without specks. The carapace is light tan, with a dark brown band crossing the back of the head and another at the junction of the carapace and abdomen. This crayfish bears a striking resemblance to the Ozark crayfish, and both species occur in the Warm Fork. Males of the two species are easily distinguished by the shape of the reproductive structures (gonopods). The gonopod tips are long and slender in the Ozark crayfish, short and blunt in the Mammoth Spring crayfish. The Ozark crayfish is lighter tan and less reddish, especially on the pincers.


Adult length: about 1½ to 2½ inches.

Where To Find
mammoth spring crayfish dist map

The Mammoth Spring crayfish has a very localized distribution near Mammoth Spring in the Spring River of Arkansas and Missouri. In our state it has been collected only from the Warm Fork (and two of its tributaries) of Spring River near Thayer.

The Warm Fork of the Spring River, where this species is found in our state, is a medium-sized, clear Ozark stream with well-defined riffles and runs. This species occurs on riffles over gravel or rubble substrate.

Crayfish are generally omnivores, eating a wide variety of plant and animal materials.

This may be Missouri’s rarest crayfish. It is a Missouri species of conservation concern. Because of its small numbers and very limited range, within a single drainage system, the species could easily be extinguished from the face of the earth. Thus it is considered critically imperiled.

Life Cycle

Like many other Ozark stream crayfish, this species apparently breeds in early fall, generating eggs and hatching young in the spring.

In addition to feeding many types of wildlife, crayfish provide food for many species that humans hunt and fish. Crayfish are fascinating, colorful creatures and are part of our rich native heritage. Many people enjoy spying them through the clear water of Ozark streams.

Crayfish are an important link in the food chain between plants and other animals, breaking down plant materials that are resistant to decay. Crayfish in turn are an important food for many other animals. Presence of crayfish in a stream or pond usually indicates good water quality.

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Similar Species
About Aquatic Invertebrates in Missouri
Missouri's streams, lakes, and other aquatic habitats hold thousands of kinds of invertebrates — worms, freshwater mussels, snails, crayfish, insects, and other animals without backbones. These creatures are vital links in the aquatic food chain, and their presence and numbers tell us a lot about water quality.