Laonastes aenigmamus, Jenkins, Kilpatrick, Robinson & Timmins, 2005

Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Diatomyidae, Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona: Lynx Edicions, pp. 300-303 : 303

Kha-nyou

Laonastes aenigmamus

French: Kanyou / German: Laotische Felsenratte / Spanish: Rata de roca de Laos

Other common names: Annamite Rat, Laotian Rock Rat, Truong Son Rat

Taxonomy. Laonastes aenigmamusJenkins et al., 2005 ,

“ Vicinity of Ban Mauang and Ban Doy , Thakhek District, south eastern edge of Khammouan [sic] Limestone [= Phou Hin Poun] National Biodiversity Conservation Area , Khammouan [sic] Province, Lao People’s Democratic Republic, 17°33’45"N 104°49'10”E, altitude 160 m asl.”

Recent molecular analyses strongly indicate the presence of a complex of subspecies or species that require additional morphometric analysis. Monotypic.

Distribution. C Laos (Nam Kading and Phou Hin Poun national biodiversity conservation areas in Bolikhamsai and Khammouane provinces) and C Vietnam (Phong Nha-Ke Bang National Park in Quang Binh Province).

Descriptive notes. Head—body 213-300 mm,tail 123-161 mm; weight 309-414 g. Head of the Kha-nyouis elongated with numerous very long, robust mystacial vibrissae. Ears are rounded, medium-sized, covered with short hairs but with a fringe of longer hairs along ear margins. Abdominal region is large to accommodate capacious stomach and intestines, estimated to comprise 25-27% of body mass. Dorsal pelage is moderately long and soft, and individuals vary in color from gray to very dark gray-black. Ventral pelage is similarly variable in color, usually lighter gray, orsilvery gray; some individuals have a distinct transition between dorsal and ventral pelage, but in others, lighter coloration is confined to midline. Some male Kha-nyou have noticeably longer guard hairs, forming a slight crest from crown of head onto shoulders. Tail is densely haired, c.50% of head-body length (46-59%), and similar in color but more grizzled than the body. Dorsal surface of feet is well haired, with fringe of hairs overlapping claws; those on hindfeet are particularly long, stout, and bristly; soles of feet are naked, and pads are large, rounded, and closely pressed next to each other. Inner dorso-lateral surfaces of forefeet have contrastingly pale short pelage, with a fringe ofstiff hairs along inner surface of the hallux and first digit. Forefeet have four toes and a moderately welldeveloped hallux but lack a claw; hindfeet have five toes, with short but well-developed pollex and short but stout claws. Females have a single pair of dorso-lateral thoracic mammae. Males have inguinal testes; in adults, epididymides descend partially into paired sacs lying postero-laterally to penis, which is posteriorly directed with an S-bend; and sacculus urethralis is present. Perineal region is sparsely haired and glandular in both sexes. Rostral region of skull is deep and moderately elongated, with a long diastema between incisors and premolars; infraorbital foramen is expanded, with a separate infraorbital neurovascular canal; and nasolacrymal foramen leads into a shallow groove on ventral surface of zygomatic branch oflachrymal. Zygoma has a dorsolateral process on jugal; jugal fossa is lacking; lower branch of maxillary portion of the zygoma is dorso-ventrally flattened and broadened with a ventral sulcus; squamosal is expanded postero-ventrally; and alisphenoid is constricted. Pterygoid fossa does not open into orbit. Coronoid process of mandible is absent; angular process is slightly divergent; ventral groove is absent; superficial masseter pars reflexa is inserted on condyloid ridge that has a short groove from low on condylar process to the area ventral to M,; and mandibular foramen is within condylar fossa. Incisors have multiserial enamel microstructure, molars and premolars are bilophodont and moderately high-crowned, and premolars and third molars large.

Habitat. Restricted to limestone karst in tropical deciduous, semi-evergreen, and evergreen forest in Laos and Vietnam, at elevations of 160-400 m above sea level.

Food and Feeding. Tooth morphology, anatomy of the digestive tract, analysis of stomach contents, and information from local people indicate that the Kha-nyouis primarily herbivorous and at least partially folivorous, but there is also evidence of insect consumption. Limited observations of a few captive individuals provide conflicting information. Most consumed a wide variety of leaves, buds,ripe fruits, seeds, roots, and some insects; one individual refused all offers of animal food, and another had an apparent preference for dried, dead leaves over fresh leaves and fruit. Forefeet are used to grasp and manipulate stems and thin branches when feeding. Observations of food remains found in dens in Vietnam suggest that food may be carried back to dens for consumption during the day. In Vietnam, plants identified from dens, in stomach contents, and in the diet of an animal kept in semi-wild conditions included Acanthopanax trifoliatus ( Araliaceae ), Aglaonema simplex ( Araceae ), Alangium ridley: ( Alangiaceae ), Dracontomelon duperreanum ( Anacardiaceae ), Ficus (Moraceae) , Lithocarpus fenestratus ( Fagaceae ), Manihot esculenta ( Euphorbiaceae ), Musa paradisiaca and M. uranoscopus ( Musaceae ), Perilla frutescens ( Lamiaceae ), Pometia (Sapindaceae) , Prunuspersica ( Rosaceae ), Psidium guajava ( Myrtaceae ), Streblus asper ( Moraceae ), and Zea mays ( Poaceae ). Despite its irritating toxic terpenes, Euphorbia antiquorum is apparently eagerly consumed by recently captive Kha-nyou in Laos, and its sap is used to bait traps. Leaves of several ofthe plants included in the diet of Kha-nyou contain toxins, requiring a specialized system for digestion. Insects such as cicadas, mantis, and grasshoppers were found in diets of Kha-nyou in Vietnam.

Breeding. Pregnant female Kha-nyou have only been observed to carry a single fetus, and reports from local people suggest that this is the norm. Nevertheless, there is evidence from local hunters that two young are occasionally born during the rainy season. Activity patterns. Information from local people indicates that Kha-nyou are nocturnal or crepuscular, spending the day in dens within karst and emerging to feed during dusk and early evening. An apparently sedentary lifestyle may be linked to a partially folivorous diet and time needed for digestion.

Movements, Home range and Social organization. Although Kha-nyou are able to move readily on rocky scree, on ledges, and in cracks in karst, they apparently are unable to jump or move rapidly on open ground. Home ranges of individuals are therefore likely to be confined to their daytime occupancy of karst and nighttime foraging and social activity on the forest floor in close proximity to karst. There is no information on social organization, other than one report from local people that Kha-nyoulive in groups of c.10 individuals, mainly females grouped around a dominant male. Kha-nyou are preyed on by nocturnal predators and may also be vulnerable to diurnal predators such as snakes.

Status and Conservation. Classified as Endangered on The IUCN Red List. The Kha-nyou occurs mainly within the Phou Hin Poun National Biodiversity Conservation Area. Its distribution is now known to extend beyond the south-eastern border of the protected region and approaches the western margin of the Hin Namno National Biodiversity Conservation Area, where there is knowledge ofits existence. In 2015, the Kha-nyou was also recorded in Nam Kading National Biodiversity Conservation Area. In 2012, it was recorded from Phong Nha-Ke Bang National Park, Quang Binh Province, central Vietnam, which is adjacent to the Hin Namnoarea. The Vietnamese population requires urgent assessment. Kha-nyou are threatened by high levels of hunting by local villagers, restricted and fragmented habitat, probable genetic isolation of populations, and loss of habitat due to logging and clearance.

Bibliography. Aplin & Lunde (2008a), Clements et al. (2006), Dawson et al. (2006), Flynn (2007), Hautier & Saksiri (2009), Hautier et al. (2011), Herbreteau et al. (2006), Herrel et al. (2012), Huchon, Catzeflis & Douzery (2000), Huchon, Chevret et al. (2007), Jenkins et al. (2005), Keovichit et al. (2011), Landry (1999), Nadler (2010), Nguyen Xuan Dang, Nguyen Xuang Nghia, Nguyen Dinh Duy et al. (2014), Nguyen Xuan Dang, Nguyen Xuang Nghia, Nguyen Manh Ha et al. (2012), Nicolas et al. (2012), Riviere-Dobigny et al. (2011), Scopin et al. (2011), Troscher et al. (2015).

Figures

Kha-nyou

Distribution. C Laos (Nam Kading and Phou Hin Poun national biodiversity conservation areas in Bolikhamsai and Khammouane provinces) and C Vietnam (Phong Nha-Ke Bang National Park in Quang Binh Province).