Abstract
Thomas langur ( Presbytis thomasi ) is endemic Sumatran primates. Its distribution is limited in Aceh and small areas of North Sumatra. The population of this species is very threatened because its habitats has been disturbed, especially by forest fires. This study aimed to determine the sustainability of the thomas langur in Pinus Jantho Nature Reserve (PJNR). Observations were conducted from December 2017 to September 2018 in rehabilitation and protection block, with an area of 184 ha of research sites. The research method used the strip transect sampling and questionnaire. The numbers of observation transects are 23 strips which differ strip lengths. The results shows that there are several various sizes of thomas langur groups. The seven groups consists of from two to seven individuals per group, with a composition of six groups of one male multi female group and all male groups. The total population size with 34 individuals consists of eight adult males, nine adult females, 12 subadult and five infant. The age structure is categorized as stable age structure that evidenced by the age of young Thomas langur, the total numbers of infant and subadult, the same as adult thomas. The sex ratios of adult thomas langur is 1:1,12, and young ages including infant and subadult, with adults 1:1. The sustainability prospect based on indicators of group size and population size does not continue in the PJNR, however it can develop naturally in the PJNR because it has a group composition Keywords: Presbytis thomasi, Population, Nature Reserve. DOI: 10.7176/JNSR/12-8-04 Publication date: April 30 th 2021
Highlights
Thomas langur in the local name is kedih (Presbytis thomasi) is one of Indonesia's non-human primate species, endemic to northern Sumatra, namely Aceh and Langkat, North Sumatra Province
The results show less sustainable, the Thomas langur population in NRPJ can still grow and develop in the future because it has a complex group composition, with the number of adult females slightly more than adult males
The age structure of the population as a whole shows that the condition of the developing population is characterized by a higher number of infant and subadult or young people (56.47%) compared to the www.iiste.org number of adult classes (43.33%) which is expected to be quite productive in the protection block
Summary
Thomas langur in the local name is kedih (Presbytis thomasi) is one of Indonesia's non-human primate species, endemic to northern Sumatra, namely Aceh and Langkat, North Sumatra Province. Based on the records form 1980 to 2000, roughly 20% of the total forest canopy cover has been opened in the Pinus Jantho Nature Reserve especially wood species that have the potential to have high economic value (Ilhartuti, 2014) This condition would result in the loss of feed and sleeping trees and their playground. With the addition of adult females to the NRPJ, in the 8 year, Thomas langur population can reach in the same amount in kedih population of the Ketambe Research Station. It requires less period time than natural process.
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