Biodiversity research and monitoring for conservation

INVESTIGATING THE UNKNOWN: DISTRIBUTION OF THE SOUTHERN WHITE-CHEEKED GIBBON NOMASCUS SIKI AND THE NORTHERN WHITE-CHEEKED GIBBON N. LEUCOGENYS IN CENTRAL LAOS

Nomascus gibbons are the most threatened of the four Hylobatidae genera. The Northern N. leucogenys and the Southern White-cheeked Gibbon N. siki are both classified as Critically Endangered. They have a restricted global range and are endemic to Laos and Vietnam. It is currently speculated that the Nam Kading-Nam Theun (river) represents the major geographical barrier between N. leucogenys and N. siki (ranging north and south of the river, respectively). However, in central Laos the distribution range limit between the two species remains uncertain, preventing appropriate conservation planning. Gibbon songs are taxonomically distinct between species. To investigate the distribution of N. siki and N. leucogenys, we collected and obtained from partner institutions a total of 896 gibbon songs from sites in central Laos and Vietnam. We compared these recordings with 213 vocal recordings of genetically-screened gibbon individuals of both species from zoological facilities in Europe. Our dataset contains 674 records from males and 222 records from females. We performed the Kruskal-Wallis test to select acoustic parameters. We used cluster analysis to identify differences in vocalisation among the gibbon populations. Cluster analysis is a multivariate method useful for identifying the same individuals based on the acoustic parameters they assign into clusters. The preliminary results showed that in the area north of the Nam Kading-Nam Theun are groups similar to N. siki while groups south of the river show a mixture of the two species. The results of our research will lead to re-evaluating the global distribution of both species and adapt national conservation prioritisation.

This research is conducted in collaboration with Dr. Hradec from the University of Life Science, Czech Republic.

We are currently working on data analysis and publication of our research.

To learn more about White-cheeked Gibbon singing patterns in Laos, read our publication

GIBBON SURVEYING IN THE DIGITAL AGE

Gibbons are difficult to see and easy to hear, so the best way to detect them is to listen for them. It is easy to establish gibbon presence this way, but not so easy to estimate gibbon density and abundance, which requires information on their locations when calling. Humans doing the listening can estimate directions to calls, and gibbon locations can be estimated by triangulation (although this can be labour-intensive and error-prone). Digital recorders are better listeners than humans in that they are cheaper and don’t get tired. Currently available recorders don’t estimate directions to calls but it turns out that accurate directions to calls is important for accurate density estimation. We introduce new digital recorders with synchronised clocks and multiple microphones which are able to provide estimated directions to sound sources accurately, and show how this improves density and abundance estimation, using acoustic spatial capture-recapture methods. We briefly discuss survey design, how calls can be efficiently extracted from acoustic files, and summarise results from initial field testing. These confirm that use of the new digital recorders with angle estimation substantially improves density estimation as well as provides much better information on sound source locations. They will undergo full field testing in Laos late this year. We hope their use will improve gibbon population monitoring and conservation planning in the near future.

This project is conducted in collaboration with the University of St Andrews, Aarhus University, and Rainforest Connection

Very little is known of otter throughout Southeast Asia. Three species have been confirmed to occur in Laos (all listed in the IUCN Red List of Threatened Species): Vulnerable Asian Small-clawed Otter Aonyx cinereus, Smooth-coated Otter Lutrogale perspicillata and Near Threatened Eurasian Lutra lutra, but their distribution and conservation status remains unknown. Otters are declining across their range due to precipitous loss of habitat, illegal trade, and decreasing prey base. Information is urgently needed on their distribution, habitat use and local threats to plan conservation actions.

We are collecting data on the distribution and taxonomic status of otter species in Nakai-Nam Theun, in order to adopt long-term effective, on-the-ground conservation strategies for the species occurring in this area.

The Annamites ecoregion harbors exceptional levels of species richness and endemism, but intensive snaring has decimated populations of terrestrial mammals. Ungulates, such as muntjacs, are susceptible to snaring, and in need of effective conservation action. At least three muntjacs occur sympatrically in the region: the Annamite dark muntjac species complex Muntiacus rooseveltorum/truongsonensis, the northern red muntjac Muntiacus vaginalis, and the large-antlered muntjac Muntiacus vuquangensis. We conducted a landscape-scale systematic camera-trapping survey in Nakai-Nam Theun National Park to gather information on the ecology and distribution of these muntjacs. We analyzed camera-trap records within an occupancy framework to evaluate responses to environmental and anthropogenic variables, and to predict distributions across the protected area. We found varying responses to the covariates, indicating complex drivers of occurrence, though all three muntjac had higher occupancies in more inaccessible areas. Mean (95%) PAO in the protected area was higher for large antlered muntjac (0.33 [0.22–0.49]), followed by Annamite dark muntjac (0.28 [0.18–0.39]), and then northern red muntjac(0.27 [0.15–0.42]). Large-antlered muntjac and northern red muntjac were widespread, while dark muntjac was restricted to a single high elevation area. Overall, our results provide new insights into muntjac ecology, distribution, and population status, and we discuss how this information can be used to inform conservation efforts. Given the high occupancies that we found for the Critically Endangered large-antlered muntjac, we argue that Nakai-Nam Theun National Park may be vital for the long-term survival of the species.

Our research and analysis main observations and conclusions are:

• The three species of muntjac show varying responses to the variables, indicating complex drivers of occurrence
• Annamite dark muntjac was predominantly found at higher elevations, consistent with previous qualitative assessments that the species complex is more common in highland areas across its range
• Northern red muntjac occupancy peaked at approximately 1250 m asl., but declined at elevations above this, consistent with previous assessments that in Laos the northern red muntjac may be uncommon above 1500 m asl
• Large-antlered muntjac was predicted to range at higher elevations: contradicting previous speculations that the species predominantly occurs below 1000 m asl due to ecological habitat associations
• All three muntjac had higher occupancies in more inaccessible areas, as their populations are likely depressed by hunting pressure in less remote areas. From a conservation perspective, such a finding is more worrisome for large-antlered muntjac, given its Critically Endangered conservation status (the species is endemic to the Annamite Mountains: a restricted world range)
• The mean Percentage Area of Occupancy across the national park was higher for large-antlered muntjac, followed by Annamite dark muntjac and then northern red muntjac
• Large-antlered muntjac and northern red muntjac were distributed more widely across the national park, while Annamite dark muntjac was restricted to high elevation areas
• Given the high occupancies that we found for the Critically Endangered large-antlered muntjac, we argue that Nakai-Nam Theun National Park may be vital for the long-term survival of the species. Securing large-antlered muntjac, as well as other Annamite endemic species that are still present in Nakai-Nam Theun NP, is critical for the conservation of these species in the Annamite mountains.
• Assessing population changes over time is an integral part of adaptive management: Percentage of Area Occupied (PAO), occupancy estimates, and predictive maps all provide information that can be used to inform conservation decisions in Nakai- Nam Theun NP.
• Our occupancy estimates provide a robust conservation baseline for each muntjac and management zone, which can, in turn, be used to assess population trends and, ultimately, the effectiveness of conservation interventions.

Read ou publication: Alexiou, I., Abrams, J.F., Coudrat, C.N.Z., Nanthavong, C., Nguyen, A., Niedballa, J., Wilting, A., Tilker, A. (2022) Camera‐trapping reveals new insights in the ecology of three sympatric muntjacs in an overhunted biodiversity hotspot. Mammalian Biology. https://doi.org/10.1007/s42991-022-00248-0