The Laotian rock rat (Laonastes aenigmamus) is an endemic rodent species native to Southeast Asia. Researchers identified the species in 2005 from specimens found in a traditional market in Khammouan Province, Laos. The people of Laos call the animal kha-nyou.
The anatomical features of the kha-nyou differ from those of modern rodent groups. Scientists initially suspected that the animal formed a new family named Laonastidae. However, bone and DNA analyses proved that the species belongs to the family Diatomyidae, an ancient rodent group previously known only from fossils.
The Last Remnant of an Ancient Rodent Family
Taxonomically, the Laotian rock rat belongs to the family Diatomyidae. Fossils of the rodent family indicate that the group was thought to have gone extinct 11 million years ago. The discovery of a surviving population led to the kha-nyou being categorized as a living fossil taxon.
The Laotian rock rat has a medium-sized body with a thickly furred tail. Its appearance resembles a blend between a rat and a squirrel. Its fur is dark blackish-gray, providing camouflage against rock surfaces.
When walking on flat ground, its hind feet point outward, resulting in a waddling gait. Nevertheless, the shape of its claws and feet enables the animal to climb steep limestone cliffs.
The hypsodont molar teeth of the mammal function to chew high-fiber vegetation. Its skull structure and dental arrangement distinguish the species from other rodent groups in Southeast Asia.
Adaptating to Limestone Cliff Habitats
The Laotian rock rat is strictly confined to limestone or karst formations. Narrow crevices between large boulders serve as the main shelter for the mammal.
The rocky slopes it inhabits are covered with trees but feature little ground vegetation. The animal does not occupy open landscapes or lowland paddy fields. Its lifestyle is inextricably tied to karst environments.
The species is nocturnal, active primarily at night. During the day, the kha-nyou hides in cave crevices or rock passages to avoid terrestrial predators.
The animal is a herbivore, which feeds on leaves, grasses, and seeds. Its digestive system features a large caecum and appendix, which function to ferment and digest plant fibers.
Population Distribution in Karst Landscapes
The geographic range of the Laotian rock rat encompasses the karst regions of Khammouan and Bolikhamxai Provinces in Laos. Populations of the species are also recorded in Phong Nha-Ke Bang National Park, Viet Nam.
The International Union for Conservation of Nature (IUCN) classified the species as Least Concern in 2016. The category was assigned because its population is distributed across several large karst blocks isolated from human settlements. National protected areas in Laos, such as Phou Hinpoun and Hin Namno, serve as natural refuges for the mammal.
Threats to the population occur along the margins of the karst areas. Limestone mining for cement manufacturing degrades its habitat. Additionally, local hunting for meat reduces population numbers in several smaller karst pockets.
The isolation between limestone cliffs also poses a distinct risk to the survival of the species. Unable to cross open areas, kha-nyou populations remain trapped within individual karst blocks without connectivity. Such condition leaves small populations on narrow karst cliffs highly vulnerable to localized extinction if their habitat is degraded.
Reference:
Duckworth, J. W. (2016). Laonastes aenigmamus. The IUCN Red List of Threatened Species 2016, e.T136474A22199035. https://dx.doi.org/10.2305/IUCN.UK.2016-2.RLTS.T136474A22199035.en
