IUCN SSC Mid-Atlantic Island Invertebrates Specialist Group

Species

BackBenoitodes caheni

Benoitodes caheni

Cahen’s Ground Spider

  • Kingdom: Animalia
  • Phylum:
  • Class: Arthropoda
  • Order: Arachnida
  • Family:
CR Critically Endangered
IUCN Red List Status:

Countries of Occurrence:
Portugal - Azores

Archipelago(s):
St. Helena

Assessor/s:
Amy Dutton
David Pryce
Vicky Wilkins
L. White

Reviewer/s:
S. Henriques & P. Cardoso

Contributor/s:

Facilitators / Compilers/s:


Assessment Rationale:

This species is endemic to the small and remote island of St Helena, in the South Atlantic Ocean, where it has only been found at Prosperous Bay Plain in the east of the island. The species was discovered in 1965, and a total of 91 specimens were collected: however, the species has not been found since this time, despite two invertebrate surveys on the Plain itself in 2003 and 2005-6 and another survey of the area to the east of the Plain in 2014. Removal of surface rocks in the past will probably have negatively affected the species and the construction of a new airport along the eastern edge of its presumed range may also have negatively impacted the species. Current threats are invasive non-native species, particularly predators that will compete with, or potentially predate the species, such as the centipede Scolopendra morsitans. The species has a very low extent of occurrence (EOO) and area of occupancy (AOO) each 4 km², is only known from one locality and has not been recorded since March 1967 despite several surveys at its known range. The species is therefore assessed as Critically Endangered (Possibly Extinct). Date last seen: 12-19 March 1967

Geographic Range:

This species is endemic to the island of St Helena, in the South Atlantic Ocean, where it is restricted to the Prosperous Bay Plain area in the east of the island.

Regions:
Saint Helena - British Overseas Territory
Extent of Occurrence (EOO):
4 (km2)
Area of Occupancy (AOO):
4 (km2)
Elevation Lower Limit:
(m)
Elevation Upper Limit:
(m)
Biogeographic Realms:
Presence:
Extant
Origin:
Endemic Azores
Seasonality:
Resident

Population:

This species was first collected during the two expeditions from the Royal Museum for Central Africa (Tervuren, Belgium) in 1965-6 and 1967 when a total of 91 specimens were collected (Benoit 1977). No specimens have been collected since, despite more recent survey work in this area in 2003 (Ashmole and Ashmole 2004), 2005-6 (Mendel et al. 2008) and 2014 (Pryce and Paajanen 2014). The precise localities where this species was originally found were not recorded and it is probable that the recent construction of an airport at the eastern edge of this area will have impacted the habitat of this species, and non-native predatory animal species are an ongoing threat to this species, see threat section for more details. Current Population Trend:  Decreasing 

Habitat and Ecology

This species is restricted to Prosperous Bay Plain, an arid desert area to the east of the island. Spiders in this family do not produce prey-capture webs; They usually run prey down on the ground. Systems: Terrestrial

Major Threat(s):

Habitat decline and destruction are major threats to this species. The eastern edge of the area that this species inhabits has recently been impacted by the construction of a new airport, was completed in 2016. Past threats to its habitat have also involved removal of surface stones for building material. Current threats include that of invasive non-native predator species such as rats, mice other spiders and the centipede Scolopendra morsitans Linnaeus, 1758.

Conservation Actions

Further research to determine if this species is still present is of key importance. Should the species be found again, its distribution, abundance and habitat should all be carefully recorded. Further survey work using the same techniques should then be used in similar areas of habitat to further clarify its status. The species is protected under the island's 2016 Environmental Protection Ordnance and is it is covered by the 2016-21 St Helena Invertebrate Conservation Strategy (Cairns-Wicks et al. 2016).