Primates in Peril

Pig-tailed Snub-nose Langur
Simias concolor Miller, 1903
Indonesia
(2002, 2004, 2006, 2008, 2010, 2012, 2014)
Lisa M. Paciulli, Jatna Supriatna & Christian Roos
The two color forms of the Pig-tailed snub-nose langur (Simias concolor concolor) above, and the Siberut subspecies
(Simias concolor siberu), below (Illustrations: Stephen D. Nash)
The Pig-tailed snub-nose langur (Simias concolor) is
again serving as the flagship species for the six Mentawai
Island primates. The other five species inhabiting the
7,000-km² archipelago west of Sumatra are Kloss’s
gibbon (Hylobates klossii), the Pagai surili (Presybtis
potenziani), the Siberut surili (P. siberu), the Pagai
macaque (Macaca pagensis), and the Siberut macaque
(M. siberu). Simias is a monotypic genus with two
subspecies: S. c. concolor / masepsep (Miller, 1903) that
inhabits Sipora, North Pagai Island, and South Pagai
Island; and S. c. siberu / simakobu (Chasen and Kloss,
1927), which is restricted to Siberut Island (Zinner et
al. 2013).
Simias concolor is classified as Critically Endangered on
the IUCN Red List (Whittaker and Mittermeier 2008),
and is threatened mainly with hunting, commercial
logging, and human encroachment (Whittaker 2006).
The Pagai Island populations have to contend with forest
conversion to oil palm plantations, forest clearings,
product extractions by local people (Whittaker 2006),
and opportunistic hunting (Paciulli 2004). Where
hunting occurs on the Mentawai Islands, it has
50
devastating effects on Simias, as it is the preferred game
species (Mitchell and Tilson 1986; Fuentes 2002; Paciulli
and Sabbi 2016). Entire groups can be eliminated in a
single hunting excursion (Hadi et al. 2009a). On the
Pagais, few men report actively hunting (Paciulli 2004),
but on Siberut, 24% of the men still hunt, with 77%
targeting pig-tailed snub nose langurs (Quinten et al.
2014). On Siberut, hunting reduces group size, and
appears to significantly affect adult sex ratios and the
number of immatures in groups (Erb et al. 2012a).
Simias numbers also decline significantly after timber
removal. On the Pagai Islands, densities averaged 5.17
individuals/sq km (13.4/sq mi) in unlogged forests and
2.54/sq km (6.6/sq mi) in forests that had been logged
approximately 20 years earlier (Paciulli 2004). It is
estimated that on the Pagais, there are approximately
3,347 pig-tailed snub nosed langurs, 1,049 Kloss’s
gibbons, 1,545 Pagai surilis, and 7,984 Pagai macaques
(Paciulli and Viola 2009). All of the primate species
seem to reach their highest known densities in the
Peleonan Forest, site of the Siberut Conservation Project
in northern Siberut (Waltert et al. 2008). In Peleonan