This 'holy' crab species (Karstama balicum & emdi, or Sesarmoides balicum), first found in Nusa Penida in 1994, was identified by P. Ng Kee Lin in 2002, after it was realized that the type series of crabs described as K. emdi (Ng and Whitten 1995) contained this additional species.
The species was reassigned from Sesarmoides to Karstama by Davie and Ng (2007). IUCN warned that two species of crab (Karstama balicum and Karstama emdi), found only in a single cave on the island of Bali, are now considered 'critically endangered', as they have been increasingly threatened by growing tourism and numerous religious ceremonies held in the cave.
Image: Karstama balicum & emdi, or Sesarmoides balicum (Tony Whitten, 2015)
This species meets the criteria for listing as Critically Endangered because its area of occupancy is about 0.003 km², only one locality is known, and the habitat is imminently threatened by uncontrolled and increasing tourism/religious practices. This species is known from only a single cave on the east coast of Nusa Penida: Goa Giri Putri in the hamlet of Karangsari, Suana Village. This cave is 276 m long. It may also be present in the adjacent small cave, Gua Paon, where Karstama emdi is also found. A pamphlet was distributed across the island's villages in 2012 asking villagers to contact a local conservation non-Government organisation (NGO) to report any other sites, but there were no reports. No estimate of the population size has been made.
Habitat & Ecology
This crab is found on the muddy floor and lower walls of the cave. It shelters both in small (less than 7 cm diameter) drip pools in the floor when these are wet, or in clefts in the wall. It has relatively long legs, a common morphological adaptation for living in caves. The cave floor is the path used by the many pilgrims and worshippers at the cave's temples.
Image: Goa Giri Putri (Tony Whitten, 2015)
The primary threat to this crab is the increasing use of the cave by pilgrims at worshippers at Goa Giri Putri. In 1994 when the crab was first collected the infrastructure was minimal, but now there are walkways and seating across part of the cave floor, and electric lights. Six visits since the original discovery have noted a decline in the abundance of this crab, although some of that may have been caused by visits being undertaken in relatively dry periods when free water on the floor of the cave was less available. It is possible that the crabs benefit from food offerings left and spilled on the ground but this is not yet confirmed.
There are no conservation actions in place. The most effective feasible action is the cooperation of the temple authorities to allow a degree of precautionary management and monitoring of crab numbers and ecology/behaviour.
- Whitten, T. & Ng Kee Lin, P. (2015) - Karstama balicum. The IUCN Red List of Threatened Species, iucnredlist.org/details/62082915/0, iucnredlist.org/details/62082915/0