Summary

Northern yellow-cheeked crested gibbons (Nomascus annamensis) are present in Dakrong Nature Reserve.
The population size is unknown.
The gibbon population trend is unknown.
The site has a total size of 376.18 km².
Key threats to gibbons are illegal logging and exploitation of non-timber forest products.
Conservation activities are not documented.

Site characteristics

Located in Quang Tri Province, in the center part of the Annamite Mountain Range, Vietnam, the Dakrong Nature Reserve was established in 2001(Vu & Doherty 2021). Approximately half the area is covered by rich and medium evergreen forest; the rest is covered by poor, regrowth forest, plantations, or bare land. The terrain of the reserve consists of low and medium hills, with the highest peak reaching 1410 m above sea level (Vu & Doherty 2021).

Table 1. Basic site information for Dakrong Nature Reserve

Area	376.18 km²
Coordinates	16.625414 N, 106.893379 E
Designation	Nature Reserve
Habitat types	Subtropical/tropical moist lowland forest, Subtropical/Tropical Heavily Degraded Former Forest

IUCN habitat categories Site designations

Ape status

The northern yellow-cheeked crested gibbon only occurs in the Central Annamite mountain range along the borders of Vietnam and Laos, and Vietnam and Cambodia. No complete survey for the species has been conducted (Vu & Doherty 2021). A survey was conducted in the reserve in 2019 using passive acoustic monitoring. Gibbon calls were detected in 39 out of 95 recording sites (Vu & Doherty 2021). Assuming a 600 m detection distance, the model-averaged occurrence probability for the nature reserve was 0.44 (SE=0.06). The area of rich and medium evergreen forests within a km of the recording posts was the most important predictor of occurrence (positively correlated). Detection probability was estimated to be 0.52 (SE=0.04) per day (Vu & Doherty 2021).

Table 2. Ape population estimates in Dakrong Nature Reserve

Species	Year	Total number indiv. (95% CI)	Total number groups (95% CI)	Density [groups/km²] (95% CI)	Area	Method	Source	Comments	A.P.E.S. database ID
Nomascus annamensis	2019				Dakrong Nature Reserve	Passive acoustic monitoring	Vu & Doherty 2021

Threats

Most hunters active in the region are thought to come from other provinces, more than 100 km away from the reserve. Similar to other studies, a 2021 study showed a higher occupancy of gibbons in high vs low quality forest (Vu & Doherty 2021). Generally, northern yellow‐cheeked gibbon populations have dramatically decreased in Vietnam due to hunting, habitat loss, and the wildlife trade (Vu & Doherty 2021). The site has been selectively logged in the past, and timber and NTFP exploitation still occurs in the reserve. In addition, local communities live in villages near the nature reserve boundary (Vu & Doherty 2021).

Table 3. Threats to apes in Dakrong Nature Reserve

Category	Specific threats	Threat level	Description	Year of threat
1. Residential & commercial development		Unknown
2. Agriculture & aquaculture		Unknown
3. Energy production & mining		Unknown
4. Transportation & service corridors		Unknown
5. Biological resource use	5.1 Hunting & collecting terrestrial animals	Present, but threat severity unknown	Signs of wildlife hunting and trappings are recorded in the nature reserve (Vu & Doherty 2021).	Ongoing (2021)
	5.2 Gathering terrestrial plants	Present, but threat severity unknown	Illegal exploitation of non-timber forest products (Vu & Doherty 2021).	Ongoing (2021)
	5.3 Logging & wood harvesting	Present, but threat severity unknown	Illegal timber exploitation, in the past and ongoing (Vu & Doherty 2021).	Ongoing (2021)
6. Human intrusion & disturbance		Unknown
7. Natural system modifications		Unknown
8. Invasive & other problematic species, genes, diseases		Unknown
9. Pollution	9.2 Industrial & military effluents	Medium	Forest cover has been reduced by the spraying of chemical defoliants during the Second Indochina War (BirdLife International 2022).	1955-1975
10. Geological Events		Absent
11. Climate change & severe weather		Unknown
12. Other options		Absent

IUCN Threats list

Conservation activities

Table 4. Conservation activities in Dakrong Nature Reserve

Category	Specific activity	Description	Year of activity
1. Residential & commercial development	Not reported
2. Agriculture & aquaculture	Not reported
3. Energy production & mining	Not reported
4. Transportation & service corridors	Not reported
5. Biological resource use	Not reported
6. Human intrusion & disturbance	Not reported
7. Natural system modifications	Not reported
8. Invasive & other problematic species, genes, diseases	Not reported
9. Pollution	Not reported
10. Education & Awareness	Not reported
11. Habitat Protection	Not reported
12. Species Management	Not reported
13. Livelihood; Economic & Other Incentives	Not reported

Conservation activities list (Junker et al. 2017)

Challenges

Table 5. Challenges reported for Dakrong Nature Reserve

Challenge	Source
Not reported

Research activities

Documented behaviours

Table 6. Ape behaviors reported for Dakrong Nature Reserve

Behavior	Source
Not reported

External links

Relevant datasets

A.P.E.S Portal

References

BirdLife International (2022) Important Bird Areas factsheet: Dakrong. Downloaded from http://www.birdlife.org on 31/01/2022.
Vu, T. T., & Doherty, P. F. (2021). Using bioacoustics to monitor gibbons. Biodiversity and Conservation, 30(4), 1189-1198. https://link.springer.com/article/10.1007/s10531-021-02139-1

Page completed by: A.P.E.S. Wiki team Date: 28/01/2022

Dakrong Nature Reserve

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