|Red List Category & Criteria:
||Cordeiro, J. & Thoma, R.F.
||Collen, B. & Richman, N.
||Livingston, F., Livingston, F., Soulsby, A.-M., Batchelor, A., Dyer, E., Whitton, F., Milligan, H.T., Smith, J., Lutz, M.L., De Silva, R., McGuinness, S., Kasthala, G., Jopling, B., Sullivan, K. & Cryer, G.
Cambarus zophonates has been assessed as Critically Endangered under criterion B2ab(iii). This species has an area of occupancy of less than 0.5 km2 and occurs at just two localities which are severely fragmented. In 2006, 23 individuals were recorded, 14 at Hell's Creek and nine at Nesbitt Cave. Extensive searches have been conducted to locate other populations of this species in the area, but so far none have been recorded. This species is threatened by a variety of factors, namely groundwater pollution, vandalism, trespassing, collectors and a reduction in nutrient availability. The US Fish and Wildlife Service (USFWS) has put in place an Action Plan for Hell's Creek Cave including the installation of cave gates, fences and a monitoring programme. However, even with these preventative measures in place, human disturbance continues to occur and degrade this species habitat. No action plan has been initiated for Nesbitt's Cave. Ground water pollution continues to occur, with no measures in place to prevent refuse dumping, the repairing of septic tanks or sewage contamination. Due to the delicate environment that this species inhabits, its access to sufficient nutrients is limited, and reliant on Grey Bat guano and leaf litter from flood waters. However, Grey Bats have not been recorded in Hell's Creek Cave for some time, thus limiting nutrient intake of this species. So far, it is unknown what impact this reduction in nutrients is having on this species. Even with an Action Plan in place, this species continues to be susceptible to habitat degradation and human disturbance.
|Previously published Red List assessments:|
- 1996 – Critically Endangered (CR) –
- 1994 – Endangered (E) –
- 1990 – Endangered (E) –
- 1988 – Endangered (E) –
- 1986 – Endangered (E) –
|Population:||This species was previously known from one pool, at one cave. Recent survey work has located an additional population, also in Stone County, Arkansas (Graening et al. 2006). An additional 29 cave streams in Stone County revealed no additional populations beyond this one and it was also not found in another 50 caves outside this area.|
Up until recently, the total population of this species had been estimated at fewer than 50 individuals (US Fish and Wildlife Service 1988) from a single cave at the type locality. Historically published observed specimens from this locality include 5 specimens in 1961, two in 1972, 15 in 1983, 13 in 1990, 6 in 2000 (two in the first pool and four more in non-submerged passages), 8 in 2001 (most upstream to 300 m in unmapped passages), and 6 in 2003 (Graening et al. 2006). In 1992, several stygobitic crayfish were reported from the second locality and later censuses confirmed the identity of two specimens in 2002 and 14 in 2005 (Graening et al. 2006).
|Current Population Trend:||Unknown|
|♦ Population severely fragmented:||Yes|
This species is threatened by groundwater contamination, vandalism, collectors, trespassing, and the removal of the Grey Bat population. The two caves where this species is located are in an area characterized by sinking streams. These streams are vital for the transition of nutrients to the caves. However, these also cause pollutants to be easily introduced to the groundwater system through the recharge zone (Natural Heritage 2009). The caves are downstream from Mountain View City and a major highway resulting in the introduction of sewage, siltation from construction, and chemicals from spills into the recharge system (Natural Heritage 2009). Illegal refuse dumping, salvage yards and malfunctioning septic tanks are also polluting the groundwater system (Graening et al. 2006). An electrical transmission line also crosses the recharge area, and herbicides have been used to clear the right-of-way (Natural Heritage 2009). Vandalism, trespassing and collectors are also major threats to C. zophonastes. Due to its sensitivity to water disturbance and turbidity, and due to its low population numbers, it is susceptible to the removal of individuals and human disturbance (Graening et al. 2006). Once, 16,000 grey bats roosted in the caves, but for several years they have not been recorded. The loss of nutrients from the guano may have limited the population size of C. zophonastes and is now reliant on leaf litter nutrients which are brought in from floodwaters.
The federal recovery plan (US Fish and Wildlife Service 1988) cited limiting factors such as destruction of habitat, scientific collection, disturbance by amateur cavers, and lack of reproduction. Updated threat information can be found in Graening et al. (2006). Although over-collection may have been a significant mortality factor in the past, scientific collection has ceased and no amateur collection is known. Recreational caving impacts and habitat destruction continue to be potential factors threatening the viability of this species.