The Indochinese Silvered Leaf MonkeyTrachypithecus germaini (Sensu lato) in Lao PDR

Abstract

The Indochinese silvered leaf monkey Trachypithecus germaini (perhaps comprising two species, T. germaini [sensu stricto] and T. margarita) is probably the rarest and most threatened monkey in Lao PDR. It has received less conservation-related attention in the country, however, than have the primates endemic to Indochina east of the Mekong because until recently it was generally considered conspecific with the widespread T. cristatus of Sundaic South-east Asia. All Lao records with firm locality details are from south of 16°23'N (in Dong Phou Vieng National Protected Area) and in lowland forests (up to 550 m above sea level), with many from near waterbodies. The predominant habitat seems to be semi-evergreen forest as patches and strips within a mosaic of more deciduous forest types, especially semi-evergreen forest in riparian and other waterside situations. Occupied semi-evergreen forest seems generally at the dry end of its spectrum, with a high deciduous tree component (this is the predominant type in interior plains-level Indochina), where this forest type grades to what some call mixed deciduous forest. Few if any records come from the interior of extensive unbroken semi-evergreen forest, or from highly-deciduous mixeddeciduous forest. Occupied areas include narrow stands flanking watercourses in deciduous dipterocarp forest, but there are no records from the more extensive deciduous dipterocarp forest matrix itself. Vague reports suggest occurrence up to 1,200 m, but given the high survey effort in such habitat, the species is at best very rare above the lowlands. Lao villager reports, and comparison with its status in similar habitats in adjacent Cambodia, suggest steep declines in Lao PDR. Suitable habitat (as profiled above) naturally covers only a small part of the southern Lao landscape, is among Lao PDR’s most threatened habitats, and bears heavy hunting. Hence the great rarity of Indochinese silvered leaf monkeys compared with sympatric monkeys and gibbons, which inhabit the more extensive hill forests. There are records of the Indochinese silvered leaf monkey from only one Lao site since 2001. Although appropriate surveys during the 2000s have been limited, the species may now be extremely rare in the country and should join other, better publicized, bird and mammal species of these southern lowland plains landscapes as in need of urgent conservation action.