Habitat

Historically, the PCC inhabited natural and often temporary bodies of shallow fresh water within open pine flatwoods and prairie-marsh communities (Hobbs 1942). However, most of these communities have been cleared for residential or commercial development or replaced with slash pine plantations. Thus, the PCC currently is known to inhabit the waters of grassy, gently-sloped ditches and swales, slash pine plantations, and utility rights-of-way (Keppner and Keppner 2001). Several conservation easements within their range are under management for the PCC. These easements are largely wet pine flatwoods and wet prairie habitats. Other private lands are inaccessible to surveyors although, lacking significant disturbance, are likely occupied by PCC given the appropriate soil types discussed further below.

The highest densities of PCC have been recorded in areas with little to no shrub or tree cover. Suitable habitat is normally dominated by herbaceous vegetation such as redroot (Lachnanthes caroliniana), beakrushes (Rhynchospora spp.), pitcher plants (Sarracenia spp.), sundews (Drosera spp.), butterworts (Pinguicula spp.), and lilies (Hymenocallis spp.) (Keppner and Keppner 2004, Keppner and Keppner 2005). Lowest population densities have occurred in small, open sites where shrubs or trees were present, or in the furrows between bedding rows in some pine plantations (Keppner and Keppner 2005). When encountered in dense titi (Cyrilla racemiflora and Cliftonia monophylla) swamps, the species was associated with temporarily inundated areas open to the sun with some herbaceous vegetation. Such sites may be considered secondary or suboptimal habitat for PCC. On sites where mixed habitat features are present (e.g., partially wooded sites or sites with permanent, deep-water ponds), PCC appear to select favorable areas dominated by herbaceous vegetation, with shallow or fluctuating water levels (Keppner and Keppner 2005). The overall value of mixed-habitat sites for conservation of PCC depends on the extent and quality of suitable wetland habitats restored or maintained on a given site. Removal and control of nonnative plants is an important part of ongoing and future PCC habitat restoration efforts.

PCC are rarely collected from water bodies that lack vegetation. Vegetation is likely important for sheltering while in water given their small size as well as for food. Observations on PCC that were held in aquaria spanning 1.5+ years (Keppner 2014) indicate that they are detritivores and herbivores. Specimens were offered dead animal material, but they avoided it in favor of processing the substrate for particles of prepared fish food and the fresh aquatic vegetation that were provided as primary food sources.

Shelters are an important resource for crayfish as some species build burrows and others use natural substrates for protection. Shelters are used for protection against conspecifics, extreme conditions, environmental changes and predators, during vulnerable stages such as molting, as well as attracting potential mates. Crayfish will use vegetation, gravel, and large rocks for shelters. Crayfish will compete with conspecifics and other species for use of shelters and often engage in agonistic bouts with conspecifics over shelter usage (Longshaw and Stebbing, 2016).

Hobbs (1942a and 1981) categorized the species of crayfish in the genus Procambarus by their burrowing habits, and provided drawings and a detailed discussion of the types of crayfish burrows (Hobbs 1981). The PCC is a secondary burrower (Figure 2.9 is from Hobbs, 1981). Secondary burrowers are normally in surface water when it is present on the hydric soils they inhabit. They construct burrows that contact the water table as the surface water of their habitat recedes, and they occupy burrows when surface water is absent or during periods of extreme water temperatures. They emerge from the burrows when surface water is present again or water temperatures are favorable. Their burrows are usually rather straight tunnels to the water table, much like a tertiary burrower, but a side chamber may occasionally be present and a second opening to the surface may also be present. These species can often be collected from the surface waters although they may retreat to burrows even when surface water is present. It appears that they can survive significant periods of drought in their burrows when they can maintain contact with the water table.

Crayfish burrows and chimneys.
Figure 2.9. Burrows and Chimneys, Hobbs (1981).

During these dry periods the PCC excavates and lives in unbranched burrows up to three feet long that extend down to the water table, thereby enabling the PCC to remain adequately hydrated and survive. When surface water is absent, the entrance to PCC burrows can usually be detected through identification of small, distinct balls of mud that are deposited on the surface during burrow excavation, forming a chimney. It should be noted that other crayfish within the range of the PCC also build chimneys, so a given chimney cannot be assigned to a particular crayfish species unless the burrow is excavated and its occupant identified.

Hobbs (1981) discussed the “function” of the chimney and provided information from others who either believed the chimney was of no purpose or that it was deliberately constructed by the crayfish to serve a purpose. Hobbs (1981) proposed that the chimney is above the ground surface to provide a vent for air flow in the burrow (oxygen in the water in the tunnel system is often less than 2 mg/l).

Keppner and Keppner (2004) provided the number of occurrences of P. econfinae in the various occupied soil types and provided the following table of soils that supported P. econfinae locations during their surveys (Table 2.3). Core soils were those soil types that supported the PCC during the drought period of 1998-2003 and during the normal dry seasons (Table 2.3). The locations in Albany sand and other less hydric soil types are in ditches or in small depressions in these soil types. They are not considered to be core soils at this time, because return visits to a few of these locations, after the initial observations of the PCC at the locations with surface water, revealed the absence of surface water and absence of burrows (Keppner and Keppner 2014).

Table 2.3. Soil types supporting P. econfinae within their known Range (* = considered “core soils”).
Soil #
Soil Name
Characteristics
1 Albany Sand Somewhat poorly drained along defined drainageways and on areas leading to lower wet areas, water table at depth of 18-30 inches for 1-3 months.
12 Leefield Sand Somewhat poorly drained nearly level soil in wet areas along drainageways in flatwoods. Water table at 18-30 inches for about 3-4 months. Irregularly ponded.
13 Leon Fine Sand Poorly drained, nearly level soil in flatwoods, water table within a depth of 10 inches for up to 4 months each year, 10-40 inches the remainder of year.
22* Pamlico- Dorovan Complex Very poorly drained, depressional areas along low gradient drainages, ponded after flooding for 4-8 months, water table at 10 inches each year.
29* Rutlege Sand Very poorly drained, level to slightly depressional areas along drainages, ponded 4-6 months, water table at or near surface 4-6 months each year.
31 Osier Fine Sand Poorly drained, nearly level or slight depressions and flatwoods slopes, ponded 2-4 months, water table within 10 inches 3-6 months each year.
32* Plummer Sand Poorly drained, low-lying areas and poorly defined drainages, ponded for brief periods, water table within 10 inches 3-6 months each year.
33* Pelham Sand Poorly drained, slight depression, flats along poorly defined drains, brief periods of flooding, water table within 15 inches 3-6 months each year.
36 Alapaha Loamy Sand Poorly drained, nearly level in wet depressions along poorly defined drainageways in flatwoods. Water table less than 15 inches for 3-6 months, brief flooding when water table is high.
39* Pantego Sandy Loam Very poorly drained in wet depressions and poorly defined drainageways in flatwoods and moderately well-defined drainageways in uplands. Water table at less than 15 inches for 3-6 months, depressional areas ponded for 1-3 months.
51* Rutledge- Pamlico Complex Very poorly drained, frequently flooded, drainage ways and wide depressional areas, flooded about 3-6 months each year, water table within about 20 inches of surface.

Essentially, the “core soils” acted as long hydropattern wetlands as defined by Acosta and Perry (2001), with a water table that remained sufficiently close to the surface during drought for the crayfish to maintain contact with it (Table 2.3). The long hydropattern wetlands provided for survival during drought and provided juveniles for dispersion under normal and increased annual precipitation patterns. The secondary soils acted as short hydropattern wetlands as defined by Acosta and Perry (2001) and acted as sinks during drought and sustaining habitat only during normal or higher than normal annual precipitation patterns (Table 2.3).