Limestone Rat (Niviventer hinpoon)

Range Description:

This species is currently known only from the Korat Plateau in South East Thailand (Musser and Carleton 2005). It is likely to be confined to this karst area of Thailand, but is currently known only around the immediate vicinity of the type locality. Six N. hinpoon samples were trapped from two locations. One adult male of N. hinpoon was captured in the cave at Wat Tham Prathat in Lop Buri province (14˚ 48 15 N 100˚ 49 30 E), and five N. hinpoon samples (two adult males and three adult females) were captured from the mixed deciduous forest at the foot hill of Wat Khudkham (Dondung) in Lop Buri province (15˚ 08 35 N 100˚ 36 44 E). In these areas, limestone rat has never been reported of its occurrence before. Therefore, Wat Khud Kham (Dondung) is a new distributional range of limestone rats and becomes the largest population site in this study. During the field survey, the number of N. hinpoon was extremely small. After the physical measurements of 4 samples were performed on N. hinpoon, Only  one adult female rat was instantly released to minimize biological and physiological impacts that might be arising in the rats.  N. hinpoon was first trapped by William Neil in 1973 from the areas close to the entrance of the bat cave at Wat Tham Prapothisat, Saraburi province (14˚ 34 31 N 101˚ 08 43 E) (Lekagul and McNeely, 1988). The second location of N. hinpoon was discovered in 1976 at Wat Tham Prathat, Lop Buri province (14˚ 48 15 N 100˚ 49 30 E), 43 kilometers northwest of Wat Tham Prapothisat. The specimen was captured by Mr. Songsakdi Yenbutra, a former mammalogists of the TISTR, from inside the cave.  The survey results revealed that the current distributional ranges of N. hinpoon were geographically restricted. N. hinpoon samples were trapped from two sites in Lop Buri province, at Wat Tham Prathat, and Wat Khudkham (Dondung) (15˚ 08 35 N 100˚ 36 44 E), the new distributional range of N. hinpoon (Figure 4). However, it was unsuccessful to trap N. hinpoon from its type locality at Wat Tham Prapothisat, Saraburi province. The results indicated very small ecological ranges of the species . The geographical distances of these three habitat sites were considerably adjacent. Therefore, it was expected that new locations of N. hinpoon on the limestone hill were situated along the ranges of the current and former distributional sites in Saraburi and Lop Buri provinces. At Wat Tham Prathat, Saraburi province, one adult male was captured inside the cave on the last night of 4-night trapping with 0.5% of the successful rate. Previously, 50 live traps were placed around the cave entrance and adjacent areas for three consecutive nights where none of N. hinpoon was found. This indicated an extremely low number of its population and restricted local distribution. At Wat Khudkham (Dondung), five rats were captured with 2.5% of the successful rate. Moreover, some pieces of its skull were found inside the bat cave near the temple. In addition, N. hinpoon was not found in places away from Wat Khudkham (Dondung). The results indicated that the local geographical ranges of N. hinpoon were very narrow and relatively small as its type locality (Lekagul and McNeely, 1988). It was likely that they lived on the foot hill near the temple. Many factors such as the availability of food may influence the home range size of the rodents (Boutin, 1990). In Panama, the resource availability was related to the home range sizes of the spiny rat (Proechimys semispionosus), an endemic rodent (Endries and Adler, 2005). Nonetheless, it was uncertain about the biological and ecological factors that might influence the distribution ranges of N. hinpoon in the study sites. N. hinpoon lived in the temple areas which appeared to have a good protection from illegal poaching. At Wat Tham Prapothisat, Saraburi province, a type locality of N. hinpoon, total of 400 live traps were placed around the areas of its habitats but none of them was caught. It was possible that the rats might be extinct from the area or its population was too small to detect. The study was not focused on identifying the causes of vanishing. However, it was observed that there were about 80 domestic dogs and 30 cats living in the temple. Some cats returned to the wild and became free-living animals. Both dogs and cats were high potential predators, especially for the rats. Therefore, N. hinpoon rats in the area were relatively under the pressure of the predators and under the serious situation of local extinction.
Countries: Native:
Thailand

Population:

It is patchily distributed, being tied to karst habitats, but there is no current information on population status.
Population Trend: Unknown

Description

The external measurements of Niviventer hinpoon captured from Watt Khud Kham (Dondung), Lop Buri province, a new distributional range, compared to two specimens in CTNRC. Niviventer hinpoon (n=4) External measurements Head and body length (mm.) 129.25 122.80-142.00 8.67 144 138 Tail length (mm.) 136.05 132.40-139.40* 3.51 141 131 Tail length (% of head and body) 104.98 98.17-111.03* 6.47 97.9 94.9 Ear length (mm.) 18.23 17.80-18.60 0.39 28 18 Hind foot length (mm.) 23.83 23.00-24.80 0.75 20 24 Weight (g) 65.00 59.00-65.00 7.79 54.5 60 The limestone rat N. hinpoon is a small rat with the spiny upper-part, dark belly and Bicolored tail. Its tail length is relatively equal to its head and body length. Belly dull duff with grey bases; back very spiny, coloured dull Buffy grey like the dullest of R.bukit . Tail relatively short, sharply bi-coloured for its entire length. Skull undistinqshable  from that of R.bukit. Feet smaller than that of  R.bukit.  There are 46 chromosomes of which  the 6 smallest are metacentric, 2 of the largest are subtelocentric and the rest are telocentric.

Habitat and Ecology:

This species is closely associated with limestone cliff habitat. It was collected halfway up the face of a forested limestone cliff outside the entrance to a cave, while another record is from "high above the valley floor, in scrubby vegetation at the base of vertical limestone cliffs" (Lekagul and McNeely 1988).  It has a very narrow ecological range, shared with a very endemic species of bird, the limestone babbler, Napothera crispirons calcicola and with Rattus neilli
Systems: Terrestrial

 Major Threat(s):

The major threat is likely to be habitat loss and degradation, particularly of the limestone forest, although it may be shown to occur in the nearby Khao Yai National Park where there is improved habitat protection.

Conservation Actions:

It may occur in Khao Yai National Park, but as far as is known it has not yet been recorded. This species is in need of further survey work to establish whether it really is endemic to, and more widespread on, the Korat Plateau.

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