Scientific Name: Pyrgacris relictus
Species Authority: Descamps, 1968
Assessment Information [top]
Red List Category & Criteria: Critically Endangered B1ab(iii,iv)+2ab(iii,iv) ver 3.1
Year Published: 2014
Date Assessed: 2014-05-29
Assessor(s): Hugel, S.
Reviewer(s): Hochkirch, A., Odé, B. & Bushell, M.
Justification:
This species is assessed as Critically Endangered, because it is restricted to a single locality (40 ha) that was recently badly modified. The only food plant, an endemic palm species, is also Critically Endangered.
Geographic Range [top]
Range Description: This species is endemic to Mauritius. It represents one of the two species belonging to the Mascarene endemic family Pyrgacrididae.
Countries:
Native:
Mauritius
Range Map: Click here to open the map viewer and explore range.
Population [top]
Population: Pyrgacris relictus is now restricted to a single population at a single locality. This locality has been badly modified over the past months to construct a golf course. Many Acanthophoenix palm trees (the only food plant of the species) of that locality have been destroyed due to this. A drop in the population size is therefore expected to occur in the near future.
Population Trend: Decreasing
Habitat and Ecology [top]
Habitat and Ecology:
Pyrgacris relictus strictly feeds only on palm trees endemic to Mauritius. These palm trees are critically endangered, most being almost extinct in the wild. The only locality harbouring Pyrgacris relictus harbours a population of few hundred Acanthophoenix rubra palm trees. Also, this is probably the only wild locality where this palm tree reproduces. In-situ experiments indicate that Pyrgacris relictus feeds also on another palm species endemic to Mauritius (Dictyosperma album) which is virtually extinct in the wild, but widely cultivated.
Systems: Terrestrial
Use and Trade [top]
Use and Trade: This species is not utilized.
Threats [top]
Major Threat(s): Past threats of this species were illegal harvesting of palm species native to Mauritius (these are the only food plant). Present threats are the loss of habitat for tourism and recreational activities, human intrusions and disturbances, and Acanthophoenix spp. palm harvesting.
Conservation Actions [top]
Conservation Actions: The genus Pyrgacris is the only member of the family Pyrgacrididae. It includes only two species: Pyrgacris relictus (in Mauritius) and Pyrgacris descampsi (la Réunion). If the habitat of the only locality of Pyrgacris relictus is not restored quickly this endemic species will be forced into extinction. The only locality is a slope surrounding a river dominated by exotic plant species, mostly Traveller's Palm (Ravenala madagascariensis). Before 2013, numerous scattered Acanthophoenix rubra were present in the undergrowth and in the canopy. This site was probably the only place in Mauritius with natural regeneration of this Critically Endangered palm tree (Page 1998 in IUCN 2013). By the end of 2013 the site was badly modified to build a large golf course (the site being on the side of the course): all the Ravenales have been clear-cut, leaving standing the tall Acanthophoenix rubra and Pandanus sp. and on the ground a mess of Ravenales trunks and leaves together with crushed Acanthophoenix rubra.
The most urgent problem is the food supply as the few Acanthophoenix remaining are tall and not reachable from the bare ground where the grasshopper lays its eggs. To overcome this urgent problem, Dyctiosperma album, another endemic palm widely cultivated, can be planted on the site as ex-situ experiments (Hugel unpublished) show that Pyrgacris relictus can feed on it. Besides this urgent point, the site should be restored with native species of plant. Importantly, the few small spots of Combo-Bois Sec that have not been damaged should be kept as is, with a very progressive removal of exotic species (including control of rats to allow regeneration of Acanthophoenix). In addition, it would be worthwhile to translocate recently hatched nymphs found to a locality where non-treated Acanthophoenix are cultivated.
www.iucnredlist.org/details/55929685/0
