Group Composition and Social Structure of Red-Shanked Doucs (Pygathrix nemaeus) at Son Tra Nature Reserve, Vietnam

Multilevel societies, consisting of multiple one-male multi-female units, are relatively rare among primates, but are more widespread in the odd-nosed colobines than other taxa. Multilevel societies are found particularly in snub-nosed monkeys (<i>Rhinopithecus</i>)<i></i>and have been debated in studies of proboscis monkeys (<i>Proboscis</i>). While it has been suggested that douc langurs (<i>Pygathrix</i>) may also form multilevel societies, the limited data available make the details of their social organization unclear. We aimed to establish a more comprehensive picture of the social organization of red-shanked doucs (<i>Pygathrix nemaeus</i>) and to address the question of whether this species forms multilevel societies, specifically collections of multiple distinct one-male units hereafter termed “bands.” We collected 259 h of behavioral data at Son Tra Nature Reserve in Vietnam from February 2010 to May 2011. The mean band size was approximately 18 individuals. Bands were comprised of approximately 2.7 units, and each unit contained approximately 6.5 individuals. Units had an average sex ratio of 1.0:1.6. We observed fission and fusion behaviors which were not correlated with phenological or weather measures. Activity budget data showed that fission and fusion behaviors between units were positively correlated with activity. Both vocalizations and vigilance increased when units engaged in fission. Based on this evidence, <i>P. nemaeus</i> at Son Tra Nature Reserve appear to engage in daily fission-fusion activity which does not vary between seasons. Additionally, our data suggest that these primates may form multilevel societies made up of distinct units. However, future data including proximity pattern analyses are necessary for confirmation.

Modeling the Red-shanked Douc (Pygathrix nemaeus) distribution in Vietnam using Maxent

The Red-shanked Douc (Pygathrix nemaeus) is the only douc species recorded in all three countries of Indochina. It is classified as Endangered by IUCN, and is believed to have experienced a major drop of more than 50% of its population over the last 40 years. The known distribution of main P. nemaeus populations in Vietnam ranges from Pu Mat National Park, Nghe An Province in the North to the Kon Ha Nung, Gia Lai Province in the South. In this study, we used Maxent, a species distribution modeling approach that is shown to a have high predictive power even with low number of occurrence records, to predict the current distribution of the Red-shanked Douc in Vietnam based on published records. The results show that P. nemaeus inhabits a region from Nghe An to Kon Tum Province, with areas from Ha Tinh, Quang Binh, Quang Tri, Thua Thien – Hue, Da Nang – Quang Nam Provinces exhibiting the highest potential. With all model parameters already listed here, studies in the future may incorporate more occurrence records to develop better models, or other environmental variables to assess the influence of different factors on the species distribution. The results also suggest that species distribution modeling, coupled with a carefully checked and filtered occurrence dataset, as well as species-specific model fine-tuning and evaluating, can help address many conservation issues in Vietnam.

Conservation of the red-shanked douc Pygathrix nemaeus in Lao People's Democratic Republic: density estimates based on distance sampling and habitat suitability modelling

The Endangered red-shanked douc Pygathrix nemaeus is a charismatic Asian colobine endemic to Vietnam, Cambodia and Lao People's Democratic Republic (PDR). The largest population is found in central-eastern Lao PDR but it has never been quantified. We conducted line-transect surveys in Nakai–Nam Theun National Protected Area in 2011–2012. We used distance sampling combined with a habitat suitability model to estimate group density and group abundance in the area. Our analysis yielded a density of 2.8 (range 1.9–4.1) groups per km2 and c. 4,420 groups within the predicted c. 1,600 km2 of suitable habitat in Nakai–Nam Theun. These are the only available data for P. nemaeus in Lao PDR to date. We discuss the limitations of our survey, which involved potential violations of the distance sampling method, and highlight the challenges of using this method for primates. We also consider the importance of assessing limitations in distance sampling studies, to evaluate reliability and facilitate comparisons. The population of P. nemaeus in Lao PDR is under threat from illegal hunting and is not the focus of any specific conservation action. To avoid a repetition of the decline the species has already experienced in Vietnam, and to secure the species' global survival, conservation projects need to target the population in Nakai–Nam Theun. A long-term conservation and research project in this key biodiversity area will also benefit other threatened and unique co-existing species.

DANH LỤC VÀ Ý NGHĨA BẢO TỒN NGUỒN GEN QUÍ HIẾM CÁC LOÀI THÚ Ở KHU BẢO TỒN THIÊN NHIÊN BÀ NÀ, THÀNH PHỐ ĐÀ NẴNG

Trong bài báo này, chúng tôi giới thiệu danh lục gồm 77 loài thuộc 28 họ, 10 bộ ở khu bảo tồn thiên nhiên Bà Nà, thành phố Đà Nẵng thông qua việc điều tra khu hệ thú ở đó từ 31/3 đến 5/4/2002 và từ tháng 3 đến tháng 7/2007 và kế thừa các kết quả của các nghiên cứu trước đây. Trong 77 loài ghi nhận được ở Bà Nà có 27 loài quý hiếm có giá trị bảo tồn cao, trong đó có 25 loài có tên trong Sách Đỏ Việt Nam (2007), 21 loài trong Danh lục Đỏ IUCN (2002), 26 loài trong Nghị định 32/NĐ-CP của Chính Phủ và Chà vá chân nâu (Pygathrix nemaeus nemaeus) là loài đặc hữu của Việt Nam.