Saturday, October 31, 2015

[Mammalogy • 2015] New Data on Limestone Rat Saxatilomys paulinae Musser, Smith, Robinson & Lunde, 2005 (Mammalia: Rodentia) from Central Indochina Limestone


Paula's Limestone Rat | Saxatilomys paulinae 
Figure 1. Living specimen of Saxatilomys paulinae from Quang Binh province
 (the nose is wounded by trapping). DOI:  10.3897/BDJ.3.e4961 

Abstract
Background
Paul[in]a's Limestone Rat Saxatilomys paulinae Musser et al., 2005 was first discovered by Musser et al. (2005) based on specimens from the Khammouane Limestone National Biodiversity Conservation Area (NBCA) in Khammouane Province in central Lao People's Democratic Republic (PDR). This tower karst landscape is part of the Central Indochina Limestone massif, which extends eastward into north-central Vietnam in Quang Binh and Quang Tri Provinces.

New information
In April 2014, we conducted a rodent survey and collected four (4) whole specimens of Saxatilomys paulinae in Quang Binh province. This is the first record of Saxatilomys paulinae in Vietnam. External and craniodental characteristics of all specimens clearly exhibit the characters of Saxatilomys paulinae as described in Musser et al. (2005)​. The rats are of medium size (HB: 160.3 ± 2.03 mm, T: 192.3 ± 6.69 mm) with some specific morpological characteristics. The external and craniodental measurement of the specimens from Vietnam tend to be larger than those of specimens from Lao. However, this needs to be verified by more studies in future. The habitat of Saxatilomys paulinae in Vietnam is characterized by complicated terrain comprising low karst towers (around 400 m) with steep slopes covered under limestone humid evergreen forest. The forest has been affected by selected timber logging in the past, but still has a complex 4-layer structure. The population of Saxatilomys paulinae in Vietnam is threatened by rodent trapping/snaring and habitat disturbance. More status surveys should be conducted to assess the species distributional range and its population status for undertaking relevant conservation measures.

Keywords: Rodent, morphology, Quang Binh, Khammouane, karst limestone forests, Central Indochina Limestone



Discussion
Simple comparison of external and craniodental measurement of specimens from Vietnam with those of specimens from Lao indicates that specimens from Vietnam are generally larger than specimens from Lao (Table 1​). However, due to very small number of specimens examined, this needs to be verified by more studies in future.

In Lao, Saxatilomys paulinae was reported to inhabit steep rocky slopes with large limestone boulders covered in heavily degraded deciduous forest mixed with scrub and bamboo at the base of the surrounding massive karst (Musser et al. 2005). Vietnam's population of Saxatilomys paulinae was found in rocky slopes with large limestone boulders, under the limestone humid evergreen forest which is different from the deciduous forest type in Lao. This indicates Saxatilomys paulinae can tolerate different limestone forest habitats existing in the Central Indochina Limestone landscape.

Before this study, Saxatilomys paulinae was recorded only in the Phoun Hin Poun NBCA in Khammuoane province of Lao (Musser et al. 2005). Our records of Saxatilomys paulinae in Quang Binh province expand global distribution range of this species into Vietnam's part of Central Indochina Limestone for about 100 km east-ward. However, the range of the species distribution remains restricted by only five known localities (four localities in Lao and one locality in Vietnam), while trapping and habitat disturbance remain as current threats to the species survival. More surveys need to be conducted to assess the species distributional range and the status of its populations for undertaking relevant conservation measures.

It is interesting that both Saxatilomys paulinae and Laonastes aenigmamus share the same limestone forest habitat in Central Indochina Limestone. The Laonastes aenigmamus is the only surviving member of the otherwise extinct rodent family Diatomyidae, that was formerly believed to have been extinct for more than 11 million years (Dawson et al. 2006). Both species are currently known only from few localities in Central Indochina Limestone. This again indicates high importance of the Central Indochina Limestone for the global biodiversity conservation.

Figure 1. Living specimen of Saxatilomys paulinae from Quang Binh province 
(the nose is wounded by trapping). DOI:  10.3897/BDJ.3.e4961 

Nghia Xuan Nguyen, Dang Xuan Nguyen, Tuong Xuan Ngo and Duy Dinh Nguyen. 2015. New Data on Recently described Rodent Species, Paulina's Limestone Rat Saxatilomys paulinae Musser, Smith, Robinson & Lunde, 2005 (Mammalia: Rodentia).
Biodiversity Data Journal. 3: e4961. DOI:  10.3897/BDJ.3.e4961

Musser, G.G., Smith, A.L., Robinson, M.F. & Lunde, D.P. 2005. Description of A New Genus and Species of Rodent (Murinae, Muridae, Rodentia) from the Khammouan Limestone National Biodiversity Conservation Area in Lao PDR.  American Museum Novitates 3497: 1–31.  DOI: 10.1206/0003-0082(2005)497[0001:DOANGA]2.0.CO;2

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