Distribution of Trachypithecus barbei
The type locality of both Presbytis barbei Blyth, 1863 and Pithecus pyrrhus atrior Pocock, 1928 is Ye, Tenasserim. The distribution is limited to a small area of far western Thailand and adjoining parts of Burma, between about 14° and 15°30’N and from the Bay of Bengal as far east as 98°30’E in the northern end of the range and 99°E in the southern end. To the north occurs T. phayrei, to the south T. obscurus, to the southeast T. germaini. Fooden (1976, Fig. 4) mapped these species’ ranges (including them all in Presbytis),but included both T. barbei and T. germaini under Presbytis cristatus. In Fooden’s map, the three westernmost localities of “cristatus” (localities 13, 14 and 18 in his earlier publication (Fooden, 1971) represent T. barbei. They have been depicted as such in our Fig. 3.
Fig. 3. Distribution range of four Trachypithecus species in the southern parts of Burma and central Thailand.
Black circles: localities for Trachypithecus barbei.
BURMA: 1 – Ye Forest, Ataran Division; 2 – Nwalabo Taung (= Mt. Nwalaboo). THAILAND: 3 – Khao Yai, Huay Kha Khaeng Game Reserve; 4 – Ban Kerng Chada; 5 – Ban Tamrong Phato; 6 – Phlu, Khao; 7 – Ban Huai Maenam Noi, and Huai Mothimo (= H. Maw Tee Maw).
Open circles: localities for T. phayrei.
BURMA: 1 – Lampha; 2 – Mulayi Taung. THAILAND: 3 – Mae Sot; 4 – Ban Mae Lamao; 5 – Tha Chang Tai; 6 – Ban Pong Nam Rong; 7 – Khlung, Khlong; 8 – Ko Keow; 9 – Wong, Nam Mae, 40 mi E of Um Pang; 10 – Wong, Nam Mae, 53 mi E of Um Pang; 11 – Ban Pak Nam Pho; 12 – Phetchabun; 13 – Kata Taek; 14 – Ban Muang Baw Ngam; 15 – Chongkrong; 16 – Khao Kamphaeng; 17 – Lat Bua Khao.
Squares: localities for T. germaini.
THAILAND: 1 – Khao Yai, Huay Kha Khaeng Game Reserve; 2 – Lat Bua Khao; 3 – Pak Chong, Sathani; 4 – “Siam”, 13°45‘, 99°25‘; 5 – “Siam”, 13°40‘, 99°25‘; 6 – Phachi, Mae Nam; 7 – Nakhon Pathom; 8 – Tahkamen, Bang Pakong R.
Triangles: localities for T. obscurus.
BURMA: 1 – Tavoy. THAILAND: 2 – Phet Buri. The Huay Kha Khaeng Reserve, where T. barbei may be affected by gene-flow from T. phayrei, is well to the east of Ye, and not far southwest of Kata Taek, one of Fooden’s (1976) localities for T. phayrei, and not far northeast of Fooden’s localities 15 and 16 for the same species.
This study for the first time accurately assesses the geographical distribution of T. barbei, although the data were available in various previous reports. From this it becomes clear that the distribution range is indeed extremely restricted, somewhere between 10,000 and 12,000 km2 (possibly larger if the species’ range extends north- and/or southwards). This may be the smallest distribution range of any Trachypithecus species. Because species with small distribution areas are more vulnerable than species with large distribution areas, and because the range of T. barbei is located in the centre of the Indo-Burmese region – a biodiversity hotspot which has already lost 95.1% of its primary vegetation (Mittermeier et al., 1999; Myers et al., 2000) – an evaluation of the species’ conservation status should urgently be carried out.