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Broad River Burrowing Crayfish. Photo by Chris Lukhaup. Image may be subject to copyright.
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Distocambarus devexus (Hobbs, 1981)

Broad River Burrowing Crayfish

Federal Protection: No US federal protection

State Protection: Threatened

Global Rank: G1

State Rank: S1

SWAP High Priority Species (SGCN): Yes

Element Occurrences (EOs) in Georgia: 12

Habitat Summary for element in Georgia: Simple and complex burrows adjacent to streams or in low areas where the water table is near the surface of the ground; also found in ephemeral streams and temporary pools


Description

The overall color of the Broad River Burrowing Crayfish is tan to brownish with dark mottling. The areola is fairly narrow and the rostrum is wide, gradually converging anteriorly to a blunt point. The movable fingers of the claws are about the same length as the mesial margins of the palms of the claws. The abdomen appears narrower than the cephalothorax. This species reaches a maximum total body length of about 75 mm (3 in).

Similar Species

Small individuals of the Broad River Burrowing Crayfish may be confused with small individuals of the Variable Crayfish (Cambarus latimanus). Juveniles of the latter usually have red-tipped claws, and a more sharply pointed rostrum. In addition, the movable fingers of the claws are about 1.5 times the length of the mesial margin of the palm rather than about equal in length as in the Broad River Burrowing Crayfish.

Habitat

Simple and complex burrows adjacent to streams or in low areas where the water table is near the surface of the ground. A single specimen was collected from a burrow that did not penetrate the water table and was only damp in the bottom. This species (particularly juveniles) is frequently collected in temporary pools and ephemeral streams in the spring.

Diet

No studies of the Broad River Burrowing Crayfish are known and the diet of burrowing crayfishes in general is poorly understood. Crayfishes are considered opportunistic omnivores and likely feed on a variety of items, both plant and animal, living or dead. Burrowing crayfishes may forage around the mouths of their burrows, eat organisms that crawl or fall into the burrow, or eat worms that inadvertently tunnel through a burrow wall.

Life History

Burrowing crayfishes inhabit a system of tunnels that may be very complex with several openings to the surface. Openings to the tunnels are often marked by piles of dirt or mud pellets (chimneys). Depending on the soil type and moisture content, these chimneys can reach heights of 15 cm (6 inches) or more. These crayfishes are typically confined to their burrows, but a male must leave its burrow to search for females during the reproductive season. As mentioned above, they may also forage near the opening of their burrow. Active burrows with fresh soil are seen from late spring to late fall, particularly after rain events. During the dry part of the summer, burrow openings may be plugged to help conserve moisture in the burrow. Reproduction probably occurs during the spring and fall, but males in reproductive condition may be found at any time during the year. When a female crayfish releases her eggs, she attaches them to her swimmerets and is said to be “in berry.” Upon hatching, the juvenile crayfish are attached to the mother by a thread. After the juveniles molt for the second time, they are free of the mother, but stay close and will hold on to her for some time. Multiple juveniles are occasionally found in a single burrow. Eventually they move off on their own. Crayfishes molt 6 or 7 times during their first year of life and most are probably able to reproduce by the end of that year. They molt once or twice a year for the remainder of their lives. Although it is difficult to study burrowing crayfishes, some researchers believe they may live as long as 10 years. Very little is known about the life history of the Broad River Burrowing Crayfish. Males in reproductive condition have been collected in April and a female with large, bright orange eggs was observed in May. On two occasions, a male and female Broad River Burrowing Crayfish were found in the same burrow.

Survey Recommendations

Burrowing crayfishes may be collected by direct excavation of their burrows, by trapping, and during night surveys. Excavating burrows is time consuming and can be very difficult. It also results in destruction of the animals’ burrow. Traps made with PVC pipes or mist nets can be effective. Burrowing crayfishes are sometimes captured around the openings of their burrows on damp nights. Active burrows are found from about mid-March to mid-November if the water table is within about two feet of the surface of the ground. As mentioned above, the Broad River Burrowing Crayfish may be found in temporary open waters so using a dipnet in woodland pools, ditches, or ephemeral streams may reveal the species.

Range

The Broad River Burrowing Crayfish is currently known from about 17 locations in the Broad River system (Savannah River drainage) and smaller Savannah River tributaries in northeastern Georgia in Elbert, Oglethorpe, Lincoln, and Wilkes counties (Skelton 2016). All of these locations lie within the Piedmont physiographic province.

Threats

The small range of this species makes it vulnerable to land disturbing activities around streams and wetlands that could destroy burrows and alter hydrology.

Georgia Conservation Status

This species is considered to be stable at this time.

Conservation Management Recommendations

Additional surveys and life history studies are needed to better define the range of the Broad River Burrowing Crayfish to help predict its response to environmental change. If possible, areas with burrows should be protected from land disturbing activities. Environmental education programs should include information about burrowing crayfishes and encourage protection of burrows.

References

Hobbs, H.H., Jr. 1981. The crayfishes of Georgia. Smithsonian Contributions to Zoology 318:1–549.

Skelton, C.E. 2016. Status Assessment for 14 Crayfish Petitioned for Listing. Final Report. United States Fish and Wildlife Service, Athens, GA. 71 pp.

Taylor, C.A., G.A. Schuster, J.E. Cooper, R.J. DiStefano, A.G. Eversole, P. Hamr, H.H. Hobbs III, H.W. Robison, C.E. Skelton, and R.F. Thoma. 2007. A reassessment of the conservation status of crayfishes of the United States and Canada after 10+ years of increased awareness. Fisheries 32:372–389.

Authors of Account

Christopher E. Skelton

Date Compiled or Updated

C. Skelton, 2008: original account

C. Skelton, January 2019: general update of account.

D.Weiler, October 2019: added photo

Broad River Burrowing Crayfish. Photo from Chris Skelton. Image may be subject to copyright.
Photo by Georgia DNR – Wildlife Resources