782 H. Trinh-Dinh et al.
conservation area, gibbon population and habitat monitor- ing, community development, publicity and education, sci- entific research, and transboundary cooperation.
Habitat restoration
Fan et al. (2013) evaluated habitat quality for the cao vit gib- bon population in both contries and suggested that the remaining area of intact forest can support c. 20 groups. However, systematic habitat restoration in disturbed forests could increase suitable habitat to support 26 groups. The current population size of 20–22 groups is approaching the estimated habitat carrying capacity. In saturated habitat with a high density of gibbon groups, transitory individuals are expected to replace resident individuals rather than establish new breeding groups (Brockelman et al., 1998). Two cases of male replacement and one case of female replacement were recorded in two cao vit gibbon groups on the Chinese side of the border, suggesting that this population is approaching habitat carrying capacity (
C.Y.Ma, unpubl. data). To promote population recovery, Fan et al. (2013) sug-
gested habitat restoration. Three transboundary sympo- siums on habitat restoration for the cao vit gibbon were conducted, in 2010, 2011 and 2012, with the support of FFI and the People Resources and Conservation Foundation. A framework for transboundary restoration of cao vit gibbon habitat was published in English in 2013 and Chinese in 2014 (FFI, 2016). Pilot habitat rehabilitation actions under this framework have been implemented at four sites, covering 1.3 ha in China. Food trees for the gibbon have been planted in abandoned fields (32.3 ha in six valleys) in the protected area in Viet Nam (Uong Sy Hung, People Resources and Conservation Foundation, pers. comm., 2016). Despite these initial successes, the situation remains challenging because habitat restoration requires time and continued funding. Progress and effectiveness of habitat restoration and reforestation programmes need to be systematically evaluated. Livestock grazing continues inside protected reserves in China, and future research should examine the potentially adverse effects of grazing on habitat restoration and gibbon recovery. In summary, our results from two transboundary surveys
of the only known population of the Critically Endangered cao vit gibbon indicate that previous surveys conducted sep- arately in VietNamand China have underestimated the glo- bal population of this species. According to the latest survey (2016), this population is increasing slowly and has 20–22 remaining groups containing c. 107–136 individuals. The gibbon population and its habitat in both countries are legally protected and hunting and charcoal making have been eliminated in the past decade. As habitat carrying capacity is a limiting factor, habitat restoration needs to be expanded, but lack of sufficient funding remains a major challenge.
Acknowledgements This work was carried out under the auspices of the Primate Conservation Projects of Fauna & Flora International (FFI) with funding from the FFI Species Fund and Arcus Foundation. The long-term field study in China was supported by the National Natural Science Foundation of China (#30900169; #31822049), the One Hundred Talent Program of Sun Yat-Sen University, and the National Program for Support of Top-Notch Young Professionals in China. We thank Paul A. Garber for editing the text, Liang Gang for supporting the surveys, and all survey participants for their contribution.
Author contributions Study design and fieldwork: HTD, CYM, VTN, TDL, TCN, VDL, HOL, JY, ZJZ, PFF; data analysis and writing: HTD, CYM, PFF.
Conflicts of interest None.
Ethical standards This research abided by the Oryx guidelines on ethical standards. The research did not involve human subjects, experimentation with animals and/or collection of specimens.
References
BARTLETT, T.Q. (2011) The hylobatidae: small apes of Asia. In Primates in Perspective. 2nd edition (eds C.J. Campbell, A. Fuentes, K.C. MacKinnon, R.M. Stumpf & S.K. Bearder), pp. 300–312. Oxford University Press, New York, USA.
BROCKELMAN,W.Y.&ALI,R.(1987) Methods of surveying and sampling forest primate populations. In Primate Conservation in the Tropical Rain Forest (eds C.W. Marsh & R.A. Mittermeier), pp. 23–62. Alan R. Liss, Inc., New York, USA.
BROCKELMAN,W.Y., REICHARD, U., TREESUCON,U.&RAEMAEKERS, J.J. (1998) Dispersal, pair formation and social structure in gibbons (Hylobates lar). Behavioral Ecology and Sociobiology, 42, 329–339.
BRYANT, J.V., BRULÉ, A.,WONG, M.H.G., HONG, X., ZHOU, Z., HAN, W. et al. (2016) Detection of a new Hainan gibbon (Nomascus hainanus) group using acoustic call playback. International Journal of Primatology, 37, 534–547.
CHAN, B.P.L., TAN, X.F. & TAN,W.J. (2008) Rediscovery of the Critically Endangered eastern black-crested gibbon Nomascus nasutus (Hylobatidae) in China, with preliminary notes on population size, ecology and conservation status. Asian Primates Journal, 1, 17–25.
FAN, P.F., JIANG, X.L., LIU, C.M. & LUO,W.S. (2006) Polygynous mating system and behavioural reason of black crested gibbon (Nomascus concolor jingdongensis) at Dazhaizi, mt. Wuliang, Yunnan, China. Zoological Research, 27, 216–220.
FAN, P.F., FEI, H.L., XIANG, Z.F., ZHANG,W.,MA, C.Y. & HUANG,T. (2010) Social structure and group dynamics of the cao vit gibbon (Nomascus nasutus) in Bangliang, Jingxi, China. Folia Primatologica, 81, 245–253.
FAN, P.F., FEI, H.L., SCOTT, M.B., ZHANG,W. & MA, C.Y. (2011) Habitat and food choice of the Critically Endangered cao vit gibbon (Nomascus nasutus) in China: implications for conservation. Biological Conservation, 144, 2247–2254.
FAN, P.F., FEI, H.L. &MA, C.Y. (2012) Behavioral responses of cao vit gibbon (Nomascus nasutus) to variations in food abundance and temperature in Bangliang, Jingxi, China. American Journal of Primatology, 74, 623–641.
FAN, P.F., REN, G.P.,WANG,W., SCOTT, M.B., MA, C.Y., FEI, H.L. et al. (2013) Habitat evaluation and population viability analysis of the last population of cao vit gibbon (Nomascus nasutus): implications for conservation. Biological Conservation, 161, 39–47.
Oryx, 2020, 54(6), 776–783 © 2019 Fauna & Flora International doi:10.1017/S0030605318001576
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164
