Countries of Occurrence:
Spain - Canaries
Groh, K. & Neubert, E.
Cuttelod, A. & Bilz, M.
Facilitators / Compilers/s:
Theba grasseti is only known to the Island of Gran Canaria. It is a very rare species probably restricted to a very small area around the capital Las Palmas de Gran Canaria and the northern Peninsula La Isleta. There are only three known locations , and the species is under major threats by increasing urban developments. This species is listed as Endangered (EN) B1ab(ii,iii)+2ab(ii,iii).
Theba grasseti is only known to the Island of Gran Canaria. The species might only be confined to La Isleta and the adjacent extreme northeastern part of Gran Canada near Las Palmas. However, specimens have been observed at locations including La Isleta at an altitude of 50-100 m. La Luz, Las Coloradas, Las Palmas, Santa Catalina and Angostura at an altitude of approximately 300 m. All these sites are situated within La Casleta (= 1 location). Greve et al. (2010) record two locations in total with three specimens, one of them near Las Palmas, the other in the north-west of the island (= two locations).
There is no information available on the population size or trend of this species.
Theba grasseti is a terrestrial gastropod found living apart from the typical T. pisana, being practically confined to the highlands and to the topmost ridges of the barrancos, and is never found naturally below an altitude of 130 m, except on the Isleta, where T. pisana does not exist. Theba grasseti is always found feeding on the Balsamiferous Spurge (Euphorbia balsamifer). This species lives in the dry temperate shrub vegetation (Piso basal).
Almost nothing is known on the threats to this species. The main area of distribution for this species is in the direct vicinity of Las Palmas de Gran Canaria, a flourishing and growing city. Probably, the species is so rare because most of its distribution area is already devastated by urbanisation, road construction, and similar activities. Only La Isleta is currently less affected because it is closed down by the military, the status of the subpopulation there is not clear at the moment. However, in case the area will be released from military purposes, the city will immediately spread to this area and demolish the last probable surviving subpopulations.
There is no conservation action in place for this species.