Pachnodus fregatensis


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Pachnodus fregatensis
Species Authority: Van Mol & Coppois, 1980

Assessment Information [top]

Red List Category & Criteria: Endangered A1a ver 3.1
Year Published: 2009
Date Assessed: 2006-01-11
Assessor(s): Gerlach, J.
Reviewer(s): Miller, R.M., Pollock, C.M. & Seddon, M.B.
Secondary poisoning with rodent poison (Brodifacoum) in the year 2001 led to a decline in the popualtion of about 87%, relative to the population size in 1999. The causes of this decline have ceased and future population increases are expected.

Geographic Range [top]

Range Description:This terrestrial snail is endemic to Fregate island, Seychelles. It occupies a single, continuous range of only 2 km² (extent of occurrence (EOO) and area of occupancy (AOO) both calculated at 2 km²).
Seychelles (Seychelles (main island group))
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: Eradication of rats using Brodifacoum poisoning was associated with an 87% population decline in this species between 1999 and 2001. In 2005, the population was estimated to be 7,700 individuals.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: This snail, the only surviving terrestrial Pachnodus species, is found under logs in lowland woodland, from 1-100 metres above sea level.
Systems: Terrestrial

Threats [top]

Major Threat(s): Predation by rats was speculated to be a threat in the 1990s. Eradication of rats using Brodifacoum poisoning was associated with an 87% population decline in this species between 1999 and 2001. The successful completion of the rodent eradication means that neither of these threats remain. Currently no active threats are known. Large-scale agro-industry farming and plantations caused some habitat degradation in the past.

Conservation Actions [top]

Conservation Actions: A captive assurance colony is maintained by the Zoological Society of London, and habitat restoration is in place. Continued monitoring of the population status is necessary.

Bibliography [top]

Gerlach, J. 2005. The impact of rodent eradication on the larger invertebrates of Fregate island, Seychelles. Phelsuma 13: 20-27.

Gerlach, J. 2006. Terrestrial and Freshwater Mollusca of the Seychelles Islands. Backhuys, Leiden.

Gerlach, J., Matyot, P. and Samways, M.J. 2005. Developing strategies for invertebrate conservation, the case of the Seychelles islands. Phelsuma: 9-12.

IUCN. 2009. IUCN Red List of Threatened Species (ver. 2009.2). Available at: (Accessed: 3 November 2009).

Citation: Gerlach, J. 2009. Pachnodus fregatensis. In: The IUCN Red List of Threatened Species. Version 2015.2. <>. Downloaded on 28 August 2015.
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