Order

Rodentia

Key region

N/A

Range

Lao PDR

How this species is doing

The Kha-nyou (Laonastes aenigmamus) was first described in 2005, after specimens purchased by scientists visiting a local food market in Lao were shown to be unique. It was subsequently shown to be the sole surviving member of the ancient and morphologically distinct rodent family Diatomyidae. The kha-nyou is known only from Khammouan Province in Lao People’s Democratic Republic (PDR). It was thought to be largely confined to the Phou Hin Poun National Biodiversity Conservation Area (formerly known as Khammouane Limestone National Biodiversity Conservation Area) but recent reports suggest it may be more widespread. These need verifying.. The majority of specimens were collected in the vicinity of Ban Mauang and Ban Doy villages in Thakhek Distric in areas with large limestone boulders, on steep slopes surrounding karst formations. Slopes in these areas are covered in both evergreen and deciduous trees, but have little ground vegetation. Classified as as Least Concern on the IUCN Red List of Threatened Species, although current losses on population and range may warrant consideration of Near Threatened status in the future.

Pressure

The limestone karst in which the species is found is fairly resilient to degradation. However, more accessible areas of the karst are vulnerable to logging and firewood removal. The species is also targeted by local hunters who sell it for food at bushmeat markets. While the precise impact of these threats is unclear, it is likely that the current level of offtake is unsustainable given the species’ small range (less than 5,000km2).

Responses

The species occurs in the Phou Hin Poun National Biodiversity Conservation Area. Further research is needed to assess the current population status of this species, and the relative importance of the suspected threats.

Knowledge level

The Kha-nyou is believed to be nocturnal. The structure of the teeth together with analysis of stomach contents from two specimens indicates the species has a primarily vegetarian diet, consisting of leaves, grass and seeds and possibly the occasional insect. Females are thought to give birth to a single young. Kha-nyou are squirrel-like in appearance, with an elongated head, small rounded ears and a long bushy tail. The compact body is covered in long, soft, dense fur that varies in colour from dark grey to black. Individuals have padded feet to provide grip on steep rocky slopes and long whiskers that act as a sensory aid to movement in rock crevices. Species in the Diatomyidae family were thought to have lived from 33.9 Mya (Early Oligocene) to 11.6 Mya (Late Miocene), and, until the discovery of the kha-nyou, to have been extinct for 11 million years. The discovery of living examples of taxa that were previously thought to be extinct is a very special case of the “Lazarus effect”, one that has only rarely been documented among mammals and other vertebrates. Molecular studies have revealed that the kha-nyou’s closest living relatives are the five surviving species of gundi (family Ctenodactylidae), all of which are currently confined to Africa. However, these two families diverged around 44 million years ago, making Laonastes the sole representative of 44 million years of unique evolutionary history.