More species of nocturnal primates are now recognized than in the past, because many are cryptic species. Subtle morphological disparities, such as pelage pattern and color variation, vocal cues, and genetics have aided in elucidating the number of diagnosable species in a genus. The slow lorises (genus Nycticebus) once included only two species, but recent taxonomic studies resulted in the description of three additional species; further incompletely explored variability characterizes each of the currently described species. The Bornean loris in particular is characterized by pelage and body size variation. In this study, we explored facemask variation in the Bornean loris (N. menagensis). Differing facemask patterns, particularly inﬂuenced by the amount of white on the face, signiﬁcantly clustered together by geographic regions, separated by notable geographic boundaries. Our results support the recognition of four species of Bornean lorises: N. menagensis, N. bancanus, N. borneanus, and N. kayan. Genetic studies are required to support these ﬁndings and to reﬁne further our understanding of the marked variability within the Bornean loris populations.
Key words: Nycticebus menagensis; Nycticebus bancanus; Nycticebus borneanus; cryptic species; morphology; sympatric, allopatric
Etymology: The speciﬁc name kayan comes from the Kayan River, which ﬂows through the range of the species, close to the type locality of Peleben.
Distribution: Nycticebus kayan is located in central and northern Borneo (Sarawak, Sabah, and East Kalimantan). Its southern range extends to the Mahakam River in East Kalimantan and the Rajang River in Sarawak. It is found as far north as the base of the southern part of Mt. Kinabalu in Sabah. It spans the width of Borneo, east to west, but unlike its neighbor (N. menagensis), it appears not to be found along the coast. It is sympatric with N. menagensis in East Kalimantan and Sabah.
Discovered: The new species of Borneo's enigmatic primate with a toxic bite
An international team of scientists studying the elusive nocturnal primate the slow loris in the jungles of Borneo have discovered an entirely new species. The team's analysis of the primate's distinctive facial fur markings, published in the American Journal of Primatology, reveals the existence of one entirely new species, while two of species, previously considered as possible sub-species, are being officially recognized as unique.
"Technological advances have improved our knowledge about the diversity of several nocturnal mammals," said Rachel Munds from the University of Missouri Columbia. "Historically many species went unrecognized as they were falsely lumped together as one species. While the number of recognized primate species has doubled in the past 25 years some nocturnal species remain hidden to science." The slow loris (Nycticebus) is a primate genus closely related to the lemur. Found across South East Asia, from Bangladesh and China's Yunnan province to the island of Borneo, the slow loris is rare amongst primates for having a toxic bite, and is rated as Vulnerable or Endangered on the IUCN Red List.
Slow lorises are recognized by their unique fur coloration on the body and face, yet while traits such as fur patterns are often used to distinguish between species; nocturnal species are cryptic in coloration and have less obvious external differences. The team's research focused on the distinctive colorings of Borneo's slow loris, whose faces have an appearance of a mask, with the eyes being covered by distinct patches and their heads having varying shapes of caps on the top.
Differences among these facemasks resulted in recognition of four species of Bornean and Philippine lorises, N. menagensis, N. bancanus, N. borneanus and N. kayan. Of these Nycticebus kayan is a new group unrecognized before as distinct. This new species is found in the central-east highland area of Borneo and is named for a major river flowing in its region, the Kayan.
The recognition of these new species strongly suggests that there is more diversity yet to be discovered in the jungles of Borneo and on the surrounding islands, including the Phillipines. However, much of this territory is threatened by human activity so the possibility that more slow loris species exist in small and fragile ranges raises urgent questions for conservation efforts.
"The pet trade is a serious threat for slow lorises in Indonesia, and recognition of these new species raises issues regarding where to release confiscated Bornean slow lorises, as recognition by non-experts can be difficult," said co-author Professor Nekaris, from Oxford Brookes University.
"In the first study to quantify facial mask differences we have recognized three new species of slow loris, two of which were recognized as subspecies at some point in the past, but are now elevated to species status, and one previously unrecognized group." concluded Ms Munds. "This finding will assist in conservation efforts for these enigmatic primates, although survey work in Borneo suggests the new species are either very difficult to locate or that their numbers may be quite small."
R. Munds, S. Ford, K.A.I. Nekaris. 2013. Taxonomy of the Bornean Slow Loris, with New Species Nycticebus kayan (Primates: Lorisidae). American Journal of Primatology. 75 (1); 46-56 DOI: http://dx.doi.org/10.1002/ajp.22071