Vol. 8, pp. 102-106

Asiatic Herpetological Research

1999

Rhacophorus leucomystax in Vietnam with Acoustic Analyses ofCourtship and Territorial Calls

Tanya L. Trepanier
11 -2

Amy Lathrop 2 and Robert W. Murphy 2 3
1 ',

1 --

Department of Zoology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5, e-mail:tanyat@rom.on.ca; 'Centre for Biodiversity and Consenation Biology, Royal Ontario Museum, 100 Queen'sPark, Toronto, Ontario, Canada M5S 2C6;

Corresponding author: e-mail: drbob@rom.on.ca

Abstract.- Acoustic parameters of both courtship and territorial calls were analysed fortwo populations ofVietnamese treefrogs, genus Rhacophorus. These treefrogs from Ba Be National Park and nearby Na Hang
Nature Reserve were identified as R. leucomystax as opposed to R. megacephalus, based on an acoustic analysisof courtship calls. They represent the first confirmed record of this species outside of Borneo and suggest that thespecies may also occur in China. The courtship call, composed of a long note of similar pulses and pitch, has amean dominant frequency of 1940 ± 154 Hz at Ba Be National Park and 1950 ± 70 Hz at Na Hang NatureReserve. The territorial call, a two to three note call, has a mean dominant frequency of 1940 ± 124 Hz at Ba Be
National Park and 2190 ± 256 at Na Hang Nature Reserve. No significant differences were found between thecall charactersof these two populations of Vietnamese R. leucomystax. There was no significant association

between snout- vent length and dominant frequencies.

Key words.- Amphibia, Anura, call analysis, Rhacophoridae, Rhacophorus leucomystax, Vietnam, vocalizations.
also known as the mating or breeding call, isemitted by males and has two functions: the attraction

Introduction

call,

Until recently, the amphibian fauna of Vietnam has
been based on the works of Bourret (1942), andof conspecific females and the announcement of an

accounts from neighbouring China (e.g., Yang, 1991;

Zhao and Adler, 1993: Zhao,1995).

The Chinese

occurrence of one species of treefrog, Rhacophorus
leucomystax, was recently placed into doubt by Matsui et al. (1986) based on chromosomal, morphologicaland acoustic evaluations. These authors reported

leucomystax was restricted in distribution toBorneo whereas a similar species, R. megacephalus.
that R.

occurred in Taiwan. They stated that mainland Chi-nese populations of these frogs required further study,

mainland Chinese populations
should be referred to as R. megacephalus. Zhao andbutin

theinterim,

Adler (1993) reported that R. leucomystax did notoccur in China, but rather that R. megacephalus
occurred throughout the country. Our recent

field

work in northern Vietnam revealed the presence of
two apparent forms of treefrogs similar in appearance
megacephalus and/or R. leucomystax. We successfully recorded vocalizations of one form from twoto R.

allopatric populations. Herein, we report our analysisof the acoustic parameters of both courtship and territorial calls,

including the dominant frequency, whichis species specific.

Amirans are capable of different types of vocalizations

which serve different functions. The courtshipoccupied territory to other males of the same or different species. There are three types of courtship calls:
the courtship call produced by males in attempt toattract a conspecific female, a territorial call produced

by a resident male in response to an courtship callreceived above a critical threshold of intensity, and anencountercallinteractions

evoked during close range agnostic

between males (Duellman and Trueb,1994). The courtship call acts as a courtship isolating
mechanism (Duellman and Pyles, 1983). A second

type of call, the territorial call, is comprised of acoustic signals and is accompanied by corporal vibrations

produced by a male or an unreceptive female inresponse to amplexus. Other types of calls include thereciprocationcallwhichisgiven by a receptive

female, and the distress call which is delivered
response to an enemy or predator for defence.

inSignals are found to vary between and within individuals and between geographically separated popula-and Ryan, 1995).
Anurans use these differences in call characteristics totions of a single species (Cocroft

identify individuals of thesame or different species

and to signal intent. Frost and Platz ( 1983) proposedthat these interspecific and intraspecific differences infundamental call characteristics such as pulse rate,duration of call, dominant frequency, or a combina-

Asiatic Herpetological Research1999

Vol. 8, p. 103

tion of these parameters, permits females to reduce

nised, preserved and deposited in the herpetology col-Anurans recog-

lections of the Royal Ontario Museum, Toronto,
Canada. Calls were transferred from the cassette

the likelihood of error in mate choice.

nize individuals of the same and different species by
their dominant frequencies.

recorder to a Macintosh computer using a Macrore-

Duellman and Pyles (1983) discovered that
smaller frogs tend to call at higher frequencies andcorder™ digitizer. Sound Edit Pro™ version 2.0.5 forhave a reduced auditory sensitivity compared withlarger frogs. They concluded that an upper limit ofapproximately 5000 Hz is most common. Furthermore, the reception of acoustic signals is affected byhabitat and interferencespecies.

from synchronously callingwhich are complex
were found to produce sounds at

In rainforest habitats,

habitats, anuranslower frequencies because the dense vegetation attenuates sound waves, notably those at higher frequencies. Therefore, transmission frequencies of less than4(X)0 Hz would be most effective for anuran communication in such complex habitats.

Partitioning of theacoustic community can be affected by several factors

such as type of call produced, oviposition site, envi-ronment and the onset of the breeding season (Duell-man andBut

1983).

titioned distinctly based

recognition, acoustic

factors of the physical habitat

interference fromand from community

members also operates to minimize acoustic variability. This implies that members of the same breedingfauna

havevoiceswithcommonusingcharacteristics(Duellman and Pyles, 1983).

Excel™

all

5.0courtship and territorial(Microsoft).

Snout-vent

length (SVL) was measured for all specimens to thenearest 0.1
using digital calipers.

mmResults
Of the 24 specimens recorded and digitized at Ba Be
National Park. 42 courtship calls were analysed from

22 individuals, and 33 territorial calls from 18 individuals. Table

1summarizes measurements of callparameters for all mating calls.

most cases, the fundamental frequencies over-lapped the dominant frequencies, rendering it impossible to obtain exact measurements. However, in thosewerethat

Althoughselection may operate to maximize acoustic properties
for species

ses were performed forcalls,

In

on its particular ecologicaland geographic assemblage of anurans.

Note duration, dominant frequency, fundamental

frequency, notes per call, pulses per note and time
between segments were measured. Descriptive analy-within

any givencommunity, the available acoustic environment is parPyles.

Macintosh computer systems was used for call analyses.

observed,

thefundamental

frequency

appeared to be approximately one half the value of thedominant frequency (900-1000 Hz). Air temperatures
did not vary significantly, with a mean of 26.2°C for
territorial

effectand courtshipcalls,

thereby having

littleon call characteristics. All courtship calls had

one note, and pulses ranged from 2 to 17 per note. In
contrast,

all territorial calls

were either 2 or 3 notes

most common being the former, withinnumbersof pulses in all three notes (Figvariability

per call, theMaterial and Methods

ure 1).

Frog calls were recorded and calling specimens collected from two different localities in northern Viet-nam. Approximately 24 frogs of the R. leucomystax
complex were recorded and collected in Ba Be
National Park (22°24'N 105°37'E) from 15 to 29 May
1995. Five R. leucomystax were recorded and collected in the village of Pac Ban (22°21'N 105°23'E)

located in Na Hang Nature Reserve, from the 23 May
to 3 June, 1996. In both locations, frogs were selectedatrandom and a sufficient call sample was recorded

using a Realistic™ unidirectional microphone and aMarantz™
201 portable cassette recorder. AirPMD

temperatures were recorded in degrees Celsius at Ba
Be National Park at the time of capture, using a ther-mometer; each specimen was collected during
evening hours from a concrete pool adjacent to thePark's research centre. In Pac Ban, frogs were collected from various locations, including in rice patties,

on trees, andinponds. All specimens were eutha-

Of the 5 specimens recorded and digitized in PacBan, 2 courtship calls were analysed from 2 individuals,

and 21

territorial callsfrom 5 individuals. Callparameters are summarized in Table

1. Fundamental
wereobtainedfromthefrequencies
sonograms, wherevalues were noted as approximately one half the valueof the dominant frequency (800-900 Hz). All courtship calls had one note, and pulses ranged from 4 to
16 notes per call. In contrast, all territorial calls wereeither 2 or 3 notes per call, themost common being

the former, with variability in numbers of pulses in all

three notes.

The courtship call resembled the sound of a trill,
or long sequence of pulses of similar pitch, whereas
the territorial calls were more similar to the sound ofclicks.

Dominant frequencies were consistent withinmean dominant frequency in courtship calls
were 1940 Hz for the Ba Be population and 1950 Hz

all calls;

Vol. 8. p. 104

Asiatic Herpetological Research

1999

Table 1 Call measurement summary of note duration, notes/call, pulses/note and dominant frequencies for Rha.

cophorus leucomystax in Ba Be National Park and Pac Ban in Na Hang Nature Reserve.

Ba Be National Park
Courtship

Note duration (sees)

Territorial

Na Hang Nature Reserve
Courtship

Territorial

Asiatic Herpeiological Research

1999

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Vol. 8, p. 105

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Time (sec)Time (sec)Figure 1 Call characteristics for Rhacophorus leucomystax as illustrated through audiospectrograms (frequency.

vs. energy) and sonograms (frequency vs. time). An expanded oscillogram (above) shows finer details of the call.
Territorial calls from A) Babe(ROM 19334); B) Pac Ban (ROM 6514), and courtship calls from C) Babe (ROM19486); and D) Pac Ban (ROM 6514).

and the concomitant northward movement of anuran
populations.

The possibility for divergence in mating

University of Toronto, Dr. M. Richardson and K.
Beckley, and S. Bain to R. W. Murphy. For assistancequency of mismatching and nonviable offspring. Like
Victoria, it is not known what the future beholds forwith field work, we are extremely grateful to B. Nupponen for her encouragement and support during thedata collection and analyses of these calls, as well as

the relatively fragile, undiscovered and endemic spe-

A. Cox, L. Ensor, M. Hanson. B. Kus, J. Rhydderchcies of Vietnam.

and M. Theberge.

callstructure could then result increasing the fre-Therefore, identification of species

G. Hochachka and K.

Littlecal and evolutionary fields, will be critical in the next

recorded the calls and captured the frogs at Ba Be
National Park during May of 1995. Phan Van Mach,for many areas of study, such as behavioural, ecologi-few years so that as many species as possible can be

Pham Due Tien, and Cao Kim Thu of IEBR assisted

studied, identified and conserved.

inAcknowledgments

fauna would be possible without the assistance,constant encouragement, and guidance of Prof. Dr.
Cao Van Sung, Director of IEBR. Le Thi Quang,

many ways with on-site arrangements.

None of our efforts to document Vietnam's fantasCollecting and export permits were made available
through Vietnam's Institute of Ecology and BiologicalResources (IEBR), Hanoi. This study was supportedby the Natural Sciences and Research Council(NSERC) of Canada grant A3 148, by the generous
assistance of theSciences Fieldwork Fund, theROM

ROM Future Fund, the ROM Foundation, the Department of ROM Volunteers, the Department of Zoology,

tic

Chairman of the Na Hang District Peoples' Committee, graciously approved the collaborative biodiversity

survey work. Le Hong Binh, Director of Na Hang
Nature Reserve, provided much guidance and expertise

about the resources of the Reserve, and the TayMinority peoples. Our heartfelt thanks go to the Tay

Minority families of Pac Ban

who not only shared
For this we are

their houses, but also their lives.

grateful to1999

Asiatic Herpetological ResearchVol. 8, p. 106

Luong Thi May and Le Van Duy ("thekitchen"). Ma Van Tung and Dinh Thi Thang ("men'sDunlap. D. G., and J. E. Platz. 1981. Geographic
variation of proteins and call in Rana pipiens from thenorth central United States. Copeia 1981: 876-879.
Frost.

J.

S.,and1983.

E. Platz.

J.

Comparativeroom"), and Ma Thi Nguy ("womens' house") for
putting up with a bunch of, at times rowdy, Canadi-

assessment of modes of reproductive isolation amongans.

Evolution 37: 66-78.

Cathay Pacific Airlines significantly contributed tofour species of leopard frogs (Rana pipiens complex).

Littlejohn, M. J., and J. D. Roberts.

1975.

our efforts by providing free excess baggage during
international travels. Magnalight, Coleman, Johnson

analy

Wax, Tilley Endurables, and Benjamin Film contributed significantly to the success of our Vietnam biodi-Leptodactylidae) in south-eastern Australia.
lian Journal of Zoology 23: 1 13-122.

versity project. This is a contribution from the Centre
for Biodiversity and Conservation Biology, ROM.

1942.

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Seto.

andT.

Utsunomiya.

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Acoustic and karyotypic evidence for specific separation of Polypedates megacephalus from P. leucomys-

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