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Socotra Karst Crab
Socotra pseudocardisoma
Abstract
Socotra Karst Crab Socotra pseudocardisoma has most recently been assessed for The IUCN Red List of Threatened Species in 2024. Socotra pseudocardisoma is listed as Endangered under criteria B1ab(iii,iv)+2ab(iii,iv).
The Red List Assessment
Van Damme, K. 2025. Socotra pseudocardisoma. The IUCN Red List of Threatened Species 2025: e.T134433A258464616. Accessed on 13 December 2025.
Last assessed
20 September 2024
Scope of assessment
Global
The Green Status Assessment
Van Damme, K.
2024. Socotra pseudocardisoma (Green Status assessment). The IUCN Red List of Threatened Species 2024: e.T134433A13443320252.
Accessed on 13 December 2025.
Population trend
Decreasing
Number of mature individuals
Species recovery score
25% (25% - 25%)
Geographic range
-
Extant (resident)
Assessment Information
Global Assessment
IUCN Red List Category and Criteria - Global Assessment
Endangered B1ab(iii,iv)+2ab(iii,iv)
Date assessed
20 September 2024
Year published
2025
Assessment Information in detail
Green Status Assessment Information
IUCN SPECIES RECOVERY CATEGORY
Species Recovery Score
25% (25% - 25%)
Date assessed
Year published
2024
Conservation impact metrics
Green Status Assessment Information in detail
Geographic Range
Native
Extant (resident)
Yemen (Socotra)
Number of locations
4
Upper elevation limit
740 metres
Lower elevation limit
40 metres
Upper depth limit
Lower depth limit
Geographic Range in detail
Indigenous and Expected Additional Range
Benchmark Year
1750
Expected Additional Range
No
Indigenous and Expected Additional Range in detail
Population
Current population trend
Number of mature individuals
Population severely fragmented
No
Continuing decline of mature individuals
Population in detail
Spatial Units
Spatial Units
Global population (Socotra Island)
Number of Spatial Units
1
Spatial Units Definition Method
Biological
Spatial units description
The entire range of Socotra pseudocardisoma is considered a single spatial unit, comprising a large limestone area with several sub-areas (each part containing different major catchment areas). The species could theoretically migrate (by night, on land) between these areas, though several large dry areas may act as barriers.
It would be possible to split the species' current range into three spatial units corresponding to threat-defined locations, which in turn correspond to geological features (several major limestone areas in Socotra Island). However, it is uncertain whether the current range represents the indigenous range; the species may have formerly occurred in limestone areas in the west of Socotra (with similar habitats), where it is now absent. Deciding to include or exclude this additional spatial unit risks introducing bias to the assessment, and the simplest way to avoid this is to treat the whole of Socotra Island as a single unit. The estimated past, present, and future status of the species does not differ between the three limestone areas where it is found, so treating them as a single unit does not mask any important spatial variation.
Spatial Units in detail
Habitat and Ecology
Generation length (years)
Congregatory
Movement patterns
Not a Migrant
Continuing decline in area, extent and/or quality of habitat
Yes
Habitat and Ecology in detail
Ecological Function
Functionality description
Very little is known about the functionality of Socotra pseudocardisoma prior to human impacts, as the population is most likely already reduced compared to the past (before the arrival of humans, livestock, and invasive species such as civet cats, rats, and domestic cats). The species has also been consumed by local people in the past. Field observations suggest that current densities during the rainy season do not exceed two individuals per 4 km2 grid, indicating very low population levels. However, this estimate is based on limited field data, and local accounts mention much higher densities at night in the past, albeit without specific numbers. Thus, a Functional spatial unit would need to have two individuals per 4 km2 at the very least, though this remains a rough estimate due to the lack of studies; the species' cryptic behaviour during the day, hiding in rock holes and caves, complicates data collection. Regarding its ecological role as a predator, insufficient information exists to define clear indicators, but a fully Functional spatial unit would likely include a population with a healthy age structure capable of foraging on a diverse diet of plants and animals. At present, young individuals are rarely found during the wet season.
Ecological Function in detail
Threats
Residential & commercial development
- Commercial & industrial areas
Agriculture & aquaculture
- Livestock farming & ranching
Transportation & service corridors
- Roads & railroads
Biological resource use
- Hunting & trapping terrestrial animals
Invasive and other problematic species, genes & diseases
- Invasive non-native/alien species/diseases
Threats in detail
Use and Trade
Food - human
Local:
✔
National:
✘
International:
✘
Use and Trade in detail
Conservation Actions
In-place research and monitoring
- Action Recovery Plan : No
- Systematic monitoring scheme : No
In-place land/water protection
- Conservation sites identified : No
- Area based regional management plan : No
- Occurs in at least one protected area : Yes
- Invasive species control or prevention : No
In-place species management
- Harvest management plan : Unknown
- Successfully reintroduced or introduced benignly : No
- Subject to ex-situ conservation : No
In-place education
- Subject to recent education and awareness programmes : Yes
- Included in international legislation : No
- Subject to any international management / trade controls : No
Conservation Actions in detail
Acknowledgements
Acknowledgements in detail
Bibliography
Red List Bibliography
Green Status Bibliography
External Data
Images and External Links
Images and External Links in detail
CITES Legislation from Species+
Data source
The information below is from the Species+ website.
CITES Legislation from Species+ in detail
Ex situ data from Species360
Data source
The information below is from Species360's Zoological Information Management System (ZIMS)
Ex situ data from Species360 in detail
Studies and Actions from Conservation Evidence
Data source
The information below is from the Conservation Evidence website.