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A brief survey for crested gibbons in Bach Ma National Park, central Vietnam

Gibbn Jurnal Nr A brief survey fr crested gibbns in Bach Ma Natinal Park, central Vietnam Thmas Geissmann 1, Trinh Dinh Hang 2, La Quang Trung 2, and Lucy Tallents 2 1 Anthrplgical Institute,
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Gibbn Jurnal Nr A brief survey fr crested gibbns in Bach Ma Natinal Park, central Vietnam Thmas Geissmann 1, Trinh Dinh Hang 2, La Quang Trung 2, and Lucy Tallents 2 1 Anthrplgical Institute, University Zürich-Irchel, Winterthurerstr. 190, CH 8057 Zürich, Switzerland 2 FFI (Fauna & Flra Internatinal), Indchina Prgramme, Hani, Vietnam We carried ut a shrt survey fr gibbns in the Bach Ma Natinal Park (Thua Thien Hue Prvince) f central Vietnam. During eight survey days, eight different grups (including slitary males) were heard. All gibbns appeared t live in lwland evergreen frest at altitudes between 400 and 800 m, althugh the park area als includes frest areas at higher altitudes. Mst gibbn sngs (53%) started at dawn, between 05:00 and 06:00 hurs. Our preliminary density estimate f abut 1.3 gups/km 2 cmpares well with estimates f suthern Nmascus ppulatins and appears t be higher than at least sme estimates frm nrthern ppulatins. We als carried ut tape-recrdings f the gibbns sngs. A cmparative analysis f these recrdings will be helpful in reslving the uncertainties abut the taxnmic status f gibbns in central Vietnam and adjacent parts f Cambdia and Las. Intrductin Bach Ma Natinal Park f central Vietnam is nt nly lcated in a transitin zne between the suthern white-cheeked crested gibbn (Nmascus siki) t the nrth, and the yellw-cheeked crested gibbn (N. gabriellae) t the suth (Geissmann, 1995; Geissmann et al., 2000), but als in the vicinity f the type lcality f N. siki (see Delacur, 1951). This makes the gibbns in the Bach Ma a particularly imprtant key ppulatin in ur cmprehensive study n the vcal diversity and systematics f the crested gibbns (genus Nmascus). Therefre, we carried ut a brief survey f the gibbns in Bach Ma Natinal Park, in rder t tape-recrd their calls, but als t cllect sme preliminary data n the status f the gibbn ppulatin in the park. The mst recent published surveys f crested gibbns in Bach Ma Natinal Park date back t 1990/1 (Eames and Rbsn, 1993; Rbsn et al., 1991). Althugh survey wrk has been cnducted by the park staff since then, n results appear t have been published. Gibbn ppulatins thrughut Vietnam are threatened by hunting and habitat lss, and unfrtunately natinal parks are n exceptin. Therefre, lng-term mnitring f the gibbns in Bach Ma is vital t ensure cnservatin measures are adequate. The Bach Ma Natinal Park is situated n the suthern edge f Thua Thien Hue Prvince in central Vietnam, abut 40 km suth-east f the ld imperial city f Hue (Fig. 1). The area f the park is lcated within the crdinates f N and E. Gulf f Thailand Las Mekng River Thailand Vietnam Cambdia Hani 18 Suth Dng Hi China Sea Hue Bach Ma NP Da Nang Saign Da Lat China Hainan Fig. 1. Map shwing the lcatin f the Bach Ma Natinal Park in Vietnam. Die Karte zeigt die Lage des Bach Ma Natinalparks in Vietnam. Na Trang km 2007 Gibbn Cnservatin Alliance, Switzerland, 44 Gibbn Jurnal Nr The natinal park was created in 1991 with the aim t cnserve the nly green transect left in Vietnam, stretching frm the Suth China Sea t the brder with Las (Le Van Lan et al., 2002). The misty muntain peak f Bach Ma is als a turist attractin and the numbers f visitrs t the park is steadily increasing with 15,000 visitrs in 2001 (ICEM, 2001). Bach Ma Natinal Park is situated in the central Annamite Muntains and lies n a high muntain ridge that runs west-east frm the Latian brder t the East Sea. This ridge interrupts the castal plain f Vietnam, and, therefre, is believed t frm a bigegraphical bundary between the faunas and flras f nrthern and suthern Vietnam. This ridge als affects the lcal climate at the natinal park, which is prbably ne f the wettest places in Vietnam: the mean annual rainfall at the summit f Munt Bach Ma is 7,977 mm (BirdLife Internatinal and MARD, 2004). The tpgraphy f the natinal park is generally steep and rugged, with several peaks abve 1,000 m, the highest f which is Munt Bach Ma at 1,448 m. The park cvers an area f abut 220 km 2, f which 51 km 2 have n frest cver. The frested area cnsists f 27 km 2 rich frest, 59 km 2 medium frest, 65 km 2 pr frest and 17 km 2 yung frest (Van Ngc Thinh et al., 2001). As a result f human disturbance, n primary frest nw remains in Bach Ma Natinal Park, and the dminant habitats at the natinal park are scrub and grassland (Van Ngc Thinh et al., 2001). Yet, the Bach Ma area has lng been nted fr its rich bidiversity (BirdLife Internatinal and MARD, 2004). One reasn is that, within a relatively small area, the area supprts a wide range f habitat types, frm castal lagns t mntane frest. Additinally, Bach Ma is situated at a bigegraphical bundary between nrthern and suthern Vietnam, and between the Annamite Muntains and the castal plain. Bach Ma Natinal Park has als been identified as ne f the Vietnamese regins that supprt imprtant ppulatins f primates that are f natinal imprtance (Van Ngc Thinh et al., 2006), such as the crested gibbns and red-shanked duc langurs (Pygathrix nemaeus) and an unidentified crested gibbn (Nmascus sp.) (Rbsn et al., 1991). Hwever, the current status f many f these species at the natinal park is unclear. Materials and methds Our survey was carried ut during eight days between 5 and 12 April The survey itinerary is shwn in Table 1. The auditry survey technique was emplyed t assess the gibbn ppulatin size (see Brckelman and Ali, 1987, fr details). The survey team split int tw pairs, statined rughly 500 m apart, in rder t accurately lcate the calling grups by mapping the angle and estimated distance t grups frm tw knwn lcatins. Table 1. Survey itinerary. Ablauf der Feldstudie. Date Activity 5 April Survey alng the rad t the summit (km 9 and 10) April Survey alng the Pheasant Trail April Survey alng the rad (km 13 and 14) April Survey in camp area 12 April Survey alng the rad (km 14) in rain Surveys began at 05:00 and ended at 11:00 hurs, in rder t be in psitin during the peak singing time f the gibbns. The lcatin f bservatin psts was determined by a cmbinatin f knwledge f the psitin f grups frm previus surveys, and terrain; ideally, listening psts were lcated n a ridge frm which several valleys culd be surveyed at nce. Because wrkers n the summit rad insisted that gibbns in Bach Ma frequently call in the evening, we als carried ut tw surveys in the evening hurs between 15:00 and 18:00 hurs. Mst bservatin psts were lcated n the rad frm the park ffice t Bach Ma summit. Tw mrnings near the beginning f the survey were spent n the Pheasant Trail, and tw mrnings near the beginning f the survey were spent in the area f ur frest camp ( N, E), lcated n the ridge trail leading dwn frm the summit rad at kilmetre 14 (Fig. 2) ' 1170 Vegetatin: Rich frest Medium frest Pr frest Yung frest Park brderline Buffer zne brderline ' Pheasant trail Camp 1200 Summit rad Park Office Bach Ma summit ' km Fig. 2. Map f the Bach Ma Natinal Park. The black frame indicates the survey area. Frest types after Van Ngc Thinh et al. (2002). Karte des Bach Ma Natinalparks und Lage des Untersuchungsgebietes (schwarzer Rahmen). Waldtypen nach Van Ngc Thinh et al. (2002) ' 16 10' 16 05' Gibbn Jurnal Nr The fllwing infrmatin was recrded: Time f arrival at, and departure frm, the bservatin pst; time f dawn as judged frm when the bserver culd see the green f leaves; lcal time f sunrise (i.e. the time at which the sun was visible ver the hrizn); Gibbn sng buts: start and end time f sng buts, number f males and great-calling individuals, cmpass bearing and estimated distance t grup, and visual infrmatin n grup lcatin when the terrain was visible frm the bservatin pst. Sng buts were recrded using tw sets f taperecrders fr future analysis f sng characteristics: (1) Sny WM-D6C tape-recrder equipped with a JVC MZ-707 directinal micrphne; (2) Sny TC- D5M tape-recrder equipped with a Sennheiser ME80 (+K3U) directinal micrphne. Results Eight different grups were heard (including slitary individuals). Mst grups cntained ne adult male, and ne t three great-call-singing individuals. The great-call-singers f each grup presumably include adult females and immature grup members f either sex (e.g. Geissmann, 1993). Sngs f ne grup were t far away t determine whether greatcalls ccurred in the sng r nt. Tw slitary males were heard repeatedly. Minimum grup sizes, based n the number f calling individuals, are listed in Table 2. N direct bservatins f gibbns were pssible during this shrt study. All gibbn grups we heard appeared t be lcated at altitudes between 400 and 800 m (Fig. 3). Six grups were lcated in what was classified as rich r medium frest by Ngc Thinh et al. (2001), and tw grups in pr frest. In seven days, a ttal f 17 sng buts were heard by tw bserver teams. We heard ne t fur grups per day and ne t five sngs per days. Single great calls were nt included in the cunt. Three additinal sng buts may have ccurred but were nt heard reliably. The earliest sng but started at 05:22 hurs, the last ne at 08:44 hurs, and a majrity 53% f all sngs started befre 06:00 hurs (Fig. 4). Median sng duratin was 7 minutes (range 1-12 minutes). All days, except the last ne, were sunny with ccasinal intervals f heavy fg (Fig. 5a, b). Gibbns were nt heard t sing in the fg. Heavy rain during the mrning f the last survey day made it impssible t hear any gibbn calls (Fig. 5c). Other primates recrded included ne grup f abut 20 bear macaques (Macaca arctides) which passed near ur camp. In the camp area, we als discvered tw rusty metal bjects that were bviusly relics frm the Vietnam war. One f them appeared t be part f an illuminatin shell, the ther may have been a fragment f a larger shell (Fig. 6). Grup number Table 2. Minimum gibbn grup size, based n the number f audible singers. Mindestgrösse der gehörten Gibbngruppen, basierend auf der Zahl der singenden Tiere. Adult males Minimum number f greatcalling individuals Minimum grup size Number f sngs (sng days) (3) (2) (3) (2) (1) (1) 7 1? 1? 1 (1) (1) Ttal (minimum) (7) Fig. 3. View frm the summit rad t the nrth. Gibbn territries extend up t the crest in the left fregrund and dwn in the valley behind it (left half f the pht), but n gibbns were heard frm the cne shaped hill in the centre. The arc-shaped bay f Phu Lc is visible in the backgrund, right half f the pht. Pht: Thmas Geissmann. Ausblick nach Nrden, vn der Strasse, die auf den Bach Ma Gipfel führt. Gibbn-Territrien erstrecken sich bis auf den Hügelkamm, der links vrne ins Bild ragt, swie ins Tal dahinter (linke Bildhälfte), aber keine Gibbns wurden vn dem kegelförmigen Berg in der Mitte gehört. Die Berge vn Bach Ma erstrecken sich fast bis zur Küste. Im Hintergrund rechts ist die bgenförmige Bucht vn Phu Lc zu sehen. 46 Gibbn Jurnal Nr Number f sung buts (1) (2)?? Time f day, hurs Fig. 4. Frequency distributin f the start time f gibbn sng buts (n = 17). Questin marks indicate three pssible additinal sng buts that were nt heard reliably. (1) dawn (average: 05:22 hurs), (2) sunrise (average: 05:56 hurs) Häufigkeitsverteilung der Startzeit vn Gibbngesängen (n = 17) im Bach Ma Natinalpark. Fragezeichen kennzeichnen drei weitere mögliche Gesänge, die aber nicht verlässlich gehört wurden. (1) Dämmerung (Durchschnitt: 05:22 Uhr); (2) Snnenaufgang (Durchschnitt: 05:56 Uhr).? Discussin All gibbn grups we heard appeared t ccur in lwland evergreen frest at altitudes between 400 and 800 m, althugh the park area cvers altitudes frm m a.s.l. and frest als ccurs at altitudes higher than 800 m. Frest abve an elevatin f 900 m was identified as mntane evergreen frest (Gilmur and Nguyen Van San, 1999). Crested gibbns (genus Nmascus) are knwn t ccur at higher altitudes. Nmascus cnclr fr instance, is knwn t ccur at elevatins f m a.s.l. in Yunnan Prvince, China (Bleisch and Chen, 1991; Bleisch and Jiang, 2000). Other crested gibbns like N. nasutus, N. leucgenys and N. gabriellae have all been reprted t ccur at altitudes f well abve 1000 m (see review in Geissmann et al., 2000), althugh they seem t prefer lwer frest if available. Our findings suggest that gibbns in Bach Ma prefer lwer altitude frest. Althugh lcal peple insisted that gibbns in Bach Ma als exhibit a secnd preferred calling time in the evening hurs, we heard n gibbns after 09:30 hurs. What ur infrmants identified as gibbn calls in the evening were, in all prbability, calls f the crested Argus pheasant (Rheinardia cellata). This bird is very cmmn in Bach Ma Natinal Park, and its calls exhibit a bimdal frequency distributin with elevated calling frequency bth in the early mrning and early evening hurs. a b c Fig. 5. (a, b) Phases with heavy fg were cmmn during ur survey. (c) Because f heavy rain we did nt hear any gibbns during the last survey day. Phts: Thmas Geissmann. (a, b) Phasen mit dichtem Nebel waren häufig während unserer Studie. (c) Heftiger Regen am letzten Tag der Studie machte es unmöglich, Gibbngesänge zu hören. Gibbn Jurnal Nr Fig. 6. Relics f the Vietnam war are still t be fund in the frest f the Bach Ma NP. The left item apparently was part f an illuminatin shell, the pyrtechnic cntent f which was still functinal when we fund it. The scale is 15 cm. Pht: Thmas Geissmann. Nch immer finden sich Überreste aus dem Vietnamkrieg im Wald des Bach Ma Natinalparks. Die Hülse links war ffensichtlich Teil eines Beleuchtungsgeschsses, dessen Inhalt nch funktinstüchtig war, als wir sie fanden. Der Massstab unten im Bild misst 15 cm. Althugh we did nt find these pheasant calls very similar t thse f the crested gibbns, they can be cnfunded. This is als cnfirmed by the very first field study n calls f gibbns in Vietnam (Rznv et al., 1986). Examinatin f the published snagrams and the riginal tape-recrdings revealed that the early study unfrtunately did nt examine gibbn calls but cnsists f a detailed analysis f the calls f crested Argus pheasants (Geissmann, unpublished data). During ur survey, we mnitred a frested area f abut 6 km 2 and we heard eight gibbn grups (including sl singing males). Based n this data, we estimate a density f abut 1.3 gups/km 2. Because f the shrt duratin f ur study, this is a very preliminary estimate, but it is very similar t estimated ppulatin densities f N. gabriellae and N. siki in eastern Cambdia which range frm 0.0 t 3.73 grups/km 2 (n = 15), with an average f 1.47 grups/km 2 (Traehlt et al., 2005). These estimates appear t be higher that thse f crested gibbns frm mre nrthern latitudes. Density estimates fr N. cnclr in Yunnan Prvince range frm 0.43 t 0.82 grups/km 2 (review in Chan et al., 2005), with a mean f 0.6 grups/km 2 (n = 4 reprts). Density f N. hainanus was estimated as grups/km 2 (Zhang et al., 1995). Only N. cnclr at Che Ta, nrthern Vietnam, may exhibit higher grup densities f 1.6 grups/km 2 (Tallents et al., 2000). Several hyptheses culd explain this general trend. It is pssible that the nrthern Nmascus species are mre heavily thinned ut as a result f particularly severe hunting pressure r habitat degradatin, r these species may need larger territries because the mre seasnal climate may cause fd surces t be less cmmn during dry seasns. Rbsn et al. (1991) recrded gibbns calling frm nine lcatins in Bach Ma Natinal Park. Their nrthern-mst tw grups were nt detected during ur survey and may have disappeared r remained silent when we were surveying the area. These tw grups were lcated in what was identified as pr quality frest in the maps prvided by Van Ngc Thinh et al. (2001). The nrthernmst tw we heard als appear t live in pr frest. All ther gibbn grups were lcated in rich r medium quality frest. Althugh an earlier survey carried ut by the Park Frest Prtectin Department in the year 2000 recrded nly five grups in the park (Van Ngc Thinh, persnal cmmunicatin), we fund eight grups during ur shrt survey. Cnsidering that we nly surveyed less than 10% f the park s strict prtectin area f 71 km 2, and ur survey had a duratin f nly seven days (excluding the rainy day), there may well be mre gibbns living in Bach Ma than the eight grups recrded by us, even if frest areas abve 900 m are discunted. The identity f the gibbns f Bach Ma Natinal Park is still nt fully reslved. Fllwing ur survey, the calls we tape-recrded were cmpared with gibbn calls frm varius mre suthern lcalities in Cambdia, suthern Las and Vietnam, suggesting gibbns in nrth-eastern Cambdia, suthern Las and in Quang Nam Prvince (Vietnam) prduce the same sng type as the gibbns f Bach Ma. In cntrast, the yellw-cheeked gibbns (N. gabriellae) in suthern Cambdia prduce a distinct sng type (Knrad and Geissmann, 2006; Geissmann, unpublished). In a next step, we will cmpare the calls f these gibbns t thse frm areas nrth f Bach Ma (Ruppell and Geissmann, in prep.). Acknwledgements We wuld thank Mr. Huynh Van Ke, Directr f Bach Ma Natinal Park, fr allwing us t carry ut this survey. Our thanks als g t Mr. Nguyen Vu Linh fr his help in arranging the lgistics f the survey, and t the park Frest Prtectin Department rangers fr the help and infrmatin they prvided. We wuld als like t acknwledge the assistance f the lcal peple and turism staff f the park. This survey was part f FFI Indchina s Gibbn Cnservatin Prject, and as such was funded by the Walt Disney Fundatin. We are grateful t Julia Ruppell fr reading and cmmenting n ur manuscript. References BirdLife Internatinal and MARD (2004). Surcebk f existing and prpsed prtected areas in Vietnam: Secnd editin, BirdLife Internatinal in Indchina and MARD. Dwnladable frm 48 Gibbn Jurnal Nr Bleisch, W. V., and Chen, N. (1991). Eclgy and behavir f wild black-crested gibbns (Hylbates cnclr) in China with a recnsideratin f evidence fr plygyny. Primates 32: Bleisch, W. V., and Jiang, X. (2000). Actin plan fr cnservatin f the gibbns f the Wuliang Muntains, Sin-Dutch Frest Cnservatin and Cmmunity Develpment Prject, Kunming, Yunnan, China. Brckelman, W. Y., and Ali, R. (1987). Methds f surveying and sampling frest primate ppulatins. In Marsh, C. W., and Mittermeier, R. A. (eds.), Primate cnservatin in the trpical rain frest, Alan R. Liss, Inc., New Yrk, pp Chan, B. P. L., Fellwes, J. R., Geissmann, T., and Zhang, J. (2005). Hainan gibbn status survey and cnservatin actin plan, versin 1 (last updated Nvember 2005). Kadrie Farm & Btanic Garden Technical Reprt N. 3, Kadrie Farm & Btanic Garden, Hng Kng, 32 pp. Dwnladable frm Delacur, J. (1951). La systématique des Gibbns Indchinis. Mammalia 15: (French text). Eames, J. C., and Rbsn, C. R. (1993). Threatened primates in suthern Vietnam. Oryx 27: Geissmann, T. (1993). Evlutin f cmmunicatin in gibbns (Hylbatidae), Ph.D. thesis, Anthrplgical Institute, Philsph. Faculty II, Zürich University, 374 pp. Dwnladable frm Geissmann, T. (1995). Gibbn systematics and species identificatin. Internatinal Z News 42: Geissmann, T., Nguyen Xuan Dang, Lrmée, N., and Mmberg, F. (2000). Vietnam primate cnservatin status review Part 1: Gibbns (English editin), Fauna & Flra Internatinal, Indchina Prgramme, Hani, 130 pp. (Dwnladable frm Gilmur, D. A., and Nguyen Van San (1999). Buffer zne management in Vietnam, IUCN Vietnam, Hani. ICEM [Internatinal Centre fr Envirnmental Management] (2003). Field study: Vietnam. Thua Thien Hue Prvince. In: ICEM (ed.), Field Studies: Ecnmic benefits f prtected areas. Lwer Mekng Prtected Areas and Develpment Review, Indrpilly, Queensland, Australia, pp Dwnladable frm Knrad, R., and Geissmann, T. (2006). Vcal diversity and taxnmy f Nmascus in Cambdia. Internatinal Jurnal f Primatlgy 27: Le Van Lan, Ziegler, S., and Grever, T. (2002). Utilizatin f frest prducts and envirnmental services in Bach Ma Natinal Park, Vietnam, Prtected Areas and Develpment, 9 pp. Dwnladable frm Rbsn, C. R., Eames, J. C., Newman, M., Nguyen Cu, and Trung Van La (1991). Vietnam frest prject: Frest bird surveys in Vietnam 1989/90, final reprt, Internatinal Cuncil fr Bird Preservatin, Cambridge, 71 pp. Rznv, V. V., Niklski, A. A., and Kuznetsv, G. V. (1986). [Vcal activity f gibbns n the Tainguen-Plateau]. In Sklv, V. E. (ed.), [Fauna and eclgy
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