The dusky leaf monkey (Trachypithecus obscurus), also known as the spectacled langur, or the spectacled leaf monkey is a species of primate in the family Cercopithecidae. It is found in Peninsular Malaysia, Myanmar and Thailand, and can occasionally be found in Singapore. During the day, these small, folivorous primates divide in sub-groups and forage for vegetation and fruit throughout the tropical forests. According to the IUCN, the dusky leaf monkey's population is declining due to habitat loss, poaching, and anthropogenic land use, which prompted the IUCN to classify the species as endangered in 2015.
Within the Cercopithecidae family, the dusky leaf monkey is a member of the lutung taxonomic group. Although most researchers agree with this classification, others believe that this primate should be categorized under the genus Presbytis. Researchers have also disputed the number of subspecies that exist, with some claiming that there are 11, while others claim there are seven. Currently, the following seven subspecies are officially recognized:
The dusky leaf monkey can appear in different colour variations, depending on the sub-species. While dusky leaf monkeys are born with an orange coat, the colour of their fur changes as they mature into adulthood. Along the abdominal area, their fur is often several shades lighter than that of their dorsal area, which can develop in shades of brown, black, or grey. Surrounding their eyes are circular patterns of bright white fur.
The dusky leaf monkey is a rather small primate. In a study conducted by G. J Burton, the average weight of the 25 male dusky leaf monkeys that were sampled was 7.39 kilograms, while that of the 44 female dusky leaf monkeys that were sampled was 6.47 kilograms. These results suggest that dusky leaf monkeys are sexually dimorphic species, as the females were found to be, on average, 12% smaller than the males sampled. Burton's study also revealed that, among the 25 male primates, there was a direct correlation with the weight of one testicle with the weight of the other, suggesting that one testicle may be used to estimate the weight of the other. However, the female ovaries were found to not be statistically significant enough to predict the weight of one ovary with the other.
While the dusky leaf monkey's fur can develop into shades of grey, brown, or black, they are born with an orange coat.
The dusky leaf monkey can be found across Malaysia, Myanmar, and Thailand, where they inhabit tropical forests.[2] However, these primates have occasionally been spotted in Singapore. Research conducted within the country between 2019 and 2020 revealed that three dusky leaf monkey individuals were located in August 2019 within the northern region of the island, near the body of water that borders Singapore and Malaysia. While dusky leaf monkeys are not native to the region, researchers speculate that they are able to swim to the country. Researchers are concerned about these migratory patterns because these foreign primates can increase competition for resources, such as vegetation, and transfer diseases and pathogens to other native species that are not equipped to recover from them
The below gallery has images of Peninsular Malaysia individuals.
