Limestone Rat (Niviventer hinpoon)
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.
samples were trapped from
two locations. One adult male of
was captured in the cave at
Wat Tham Prathat in Lop Buri province (14˚ 48’ 15” N 100˚ 49’ 30” E),
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
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.
was first trapped by
William Neil in 1973 from the areas close to the entrance of the bat cave at
Tham Prapothisat, Saraburi province (14˚ 34’ 31” N 101˚ 08’ 43” E) (Lekagul and
McNeely, 1988). The second location of
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
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
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
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,
was not found in places
Wat Khudkham (Dondung). The results indicated that the local
geographical ranges of
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
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
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,
rats in the area were
relatively under the pressure of the predators and under the serious situation
of local extinction.
It is patchily distributed, being tied to karst habitats, but
there is no current information on population status.
Population Trend: Unknown
The external measurements ofNiviventer 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
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.
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.