A different fauna?: captures of vertebrates in a pipeline trench, compared with conventional survey techniques; and a consideration of mortality patterns in a pipeline trench

11 Pages·2000·2 MB·English

by  J. C. Z. Woinarski

A different fauna?: captures of
vertebrates in a pipeline trench,
compared with conventional survey
techniques; and a consideration of
mortality patterns in a pipeline trench
J.C.Z. Woinarski, M.Armstrong, K. Brennan, G. Connors,
D. Milne, G. McKenzie and K. Edwards.
Parks and Wildlife Commission of the Northern Territory
PO Box 496 Palmerston NT, 083 1
email: [email protected]
We sampled the vertebrate fauna caught in a pipeline trench near Daly
Waters, Northern Territory in the mid Dry season of 1999, and compared
the species composition with that of a standardised quadrat-based survey
protocol (using pitfall traps, Elliott traps and nocturnal and diurnal active
searches). The proportion of records of snakes, pygopodids, frogs, two
dragon species, the gecko Diplodactylus ciliaris and the rodent Pseudomys
delicatulus was markedly greater in the pipeline than in the quadrat-based
survey; this disparity was also evident in a pronounced size difference in the
reptile species composition of the two techniques. The comparison
demonstrates that the standard survey protocol has substantial biases against
some species and groups of species and that additional sampling effort or
specific new trapping techniques may be required for these taxa.
The species composition of captures in this pipeline study differed
I-
substantially from the results from a larger section of this pipeline route
3
constructed in 1994, possibly due to differences in season, habitats spanned,
construction procedure or differences between years in climate. Mortality
of animals recorded in this pipeline study was I I% , substantially less than that
recorded in other pipeline studies. We suggest operational procedures to
I-
minimise wildlife mortality in pipeline construction, including construction
V) during the most benign season; minimising the distance and time the trench
is kept open; interrupting the trench with frequent escape ramps; and
frequent inspection of trenches for captured wildlife.
Key words: Northern Territory, mammals, reptiles. frogs, sampling. impact
INTRODUCTION adequate protocol should ensure that there is a
reasonable probability of detection of the taxa
Across Australia, as elsewhere (e.g. Heyer et al.
chosen for sampling. This probability clearly
1994), several agencies have attempted to
varies substantially according to sampling
develop standard protocols for wildlife surveys
techniques (e.g. Friend 1984; Catling et al. 1997;
(e.g., McKenzie et al. 1991; NPWSISFNSW
Pa& et al. 1999).
1994; Woinarski 1994; Robinson et al. 2000).
Such consistency facilitates monitoring and the In the monsoonal tropics of the Northern
collation and subsequent comparative analysis of Territory, a standardised procedure for vertebrate
geographically separate data sets and it can also survey has become widely adopted (e.g., Griffiths
provide a mechanism for accreditation of et al. 1997; Woinarski et al. 1999a,b,c), although
sampling associated with impact assessment. An there has been no fonnal assessment of its biases.
Australpfa3
oo ogist volume 3 I (3)
December 2000 42 1
Woinarsk et c/.
Here, we take an opportunity to compare Tiench constructiono ccurredo ver a sevenw eek
detection usingt his standardp rorocolw ith a very period (lateM ay to earlyJuly 1999).T1picaol f this
different samplingr echnique,i ncidental caprures early to mid dry season period, there was
of vertebrates in a pipeline trench. \fildlife effectively no rainfall during the construction
caught has been investigated for several such perioda nd temperaturesw erer elativelyl ow (mean
trenches in Australia, although only one formal daily maximum and minimum temperaturesi n
publication (Ayers and Wallace I99T) has June at Daly Waters are 28.80Ca nd 13.10C
documentedt he results.
respectively:D ames and Moore 1994). These
As wildlife mortaliry may be substantial in conditions tend to depressr eptile and, especially,
trenches( Ayersa nd Wallace 1997) and sincet he frog activity in this region (Fisher 1999).
construction of such trenchesi s becomingm ore Mechanical problemsl ed to somei nconsistencies
widespread in Australia, we also investigated in trenching procedured uring this operation. In
patternso f mortaliry associatedw ith trenching general,o ne or two specialisedd iggingm achines
and suggeswt ayso f minimising this mortaliry. constructeda vertical sheer-walledt rench of 1.1
METHODS to 1.5 m depth, extendingu p to about 5 km per
day. Prior to pipe laying a heavy mechanical
This study was conducted along part of a leveller was run along the bottom of the trench.
pipeline route between Daly Waters and Pipe was then placed in the rrench, which was
Borroloola (Fig. 1). This 330 km gas pipeline then immediatelyf illed in, but the time from the
was originally laid in 1994 (Dames & Moore trench opening to rhe pipe laying varied from
1994), but a 60 km section had to be re-laid several hours to several days, depending upon
in 1999. The route traversesp astoral lands, equipment (mal)function. The trench lay within
with vegetation comprising mostly bloodwood- a broader area of disturbance (Fig. 2), which
eucalypt woodland (typically dominated provided a range of obstacleso r disincentivesf or
by Eucalyptus pruinosa and Cor"tmbia wildlife to reach the trench. In the months before
dichromophloia)o r lancewood Acacia shirleyi - trench construction a corridor of about 10 m
bullwaddy Macropteranthekse kwickjjo pen forest width was cleared (or re-clearedf ollowing initial
or tall shrubland. clearancei n 1994), an easement (with narrow
13{ t36 r?n
Figurel . Generallo cationo f studyThicbkr ackli nei ndicatepsi pelinero r-rte.
AustrafjaSlogist
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A different fauna?
dirt track) associated with the previous pipeline Over the same period as the trench sampling,
was situated on one side of the trench, and a new we also surveyed wildlife using a standard
access track (which during trench placement quadrat-based protocol (Woinarski et al. 1999a,
carried a stream of heavy construction and other
1999b). For each 50 m x 50 m quadrat, this
vehicles) was located on the other side of the
comprised a) pitfall trapping, using four pitfall
trench. Whiie digging, the trenching machine
traps (two 20 litre buckets (41 cm deep x 28 cm
also placed earth from the trench into a set of
wide) and two 10 litre buckets (26 cm x 25
parallel continuous mounds immediately
alongside the trench. cm)), each with 10 m of 30 cm high flywire
driftline, b) live mammal traps (20 Elliott traps
We searched the trench for wildlife over 12 days
and four cage traps, baited daily with a peanut
in the period from 1-18 June 1999. Searching
comprised walking along the entire length of the butter-honey-oats mixture, and arranged
open trench and removing all vertebrates around the perimeter of the quadrat), and c)
encountered, with searches undertaken in early active searching (three diurnal searches and two
morning (from first light) and late afternoon. We spotlight searches, each of 10 min duration). We
recorded the position of each capture (by Global
do not report sampling of birds or bats here. A
Positioning System and reference to locational
total of 15 quadrats was sampled, each for a 72
markings placed alongside the trench by
hr period. These were located within 200 m to 5
construction workers) and whether the animal
km of the trench and in a similar range of
was dead or alive. For each search, we recorded
habitats to those traversed by the trench,
the length of trench open (and searched), the
period over which each trench section had been In addition to the detailed study of the 1999
opened, and the period since that section had
trenching operation, we also here compile and
been last searched. Barring mechanical problems,
compare capture information from the original
the trench construction continued throughout
laying of the pipeline in 1994. During that
day and night, whereas the pipeline laying was
construction (which lasted over at least 6 months
continuous throughout the day. Thus, it was
and extended for several hundred kilometres
difficult to be precise about the actual period
during which any particular trench section had beyond the 1999 study), the trench was searched
been opened. As the trench was (generally) on five occasions (24-30 July, 31 August, 26-30
continuous, there was also some imprecision in September, 1-5 November and 5-30 November).
associating any animal record with a particular Search methods then were not as rigorous, and
period that the trench had been opened, because documentation of the results was patchy.
animals falling into a section of the trench which
Additionally, the 1994 trench was generally
had been opened for several days may then have
markedly less crisp, with less sheer walls, more
moved slong the trench to the most recently
shallow stretches and far more frequent
constructed sections, or vice-versa.
interruptions (soil ramps which provided escape
In addition to animals that we encountered in
routes for trapped animals).
the trench, we also noted prints of animals
We also compare the results from this study with
moving alongside the trench, and documented
some additional records from construction that for two comparable trench sampling studies in
workers reporting captures between our western New South Wales (Ayers and Wallace
trench searches. 1997; Faulkner 1999).
A
1
? o i l
Old pi@ine II &rs Swlh eap Cleared m l Consbudbnvehde Dozed Dead, pusted over has
lm [cleandeanageway) we heap major aaerr track m*
mound
Treneh
0 5rn
b-+++i
Hokontal Scale
Figure 2. Schematic cross-section of distubance matrix around trench. Horizontal and vertical axes not at same scale.
Australfaono, o gist volume 3 I (3)
December 2000
Analysis RESULTS
Tallies for individual species were recorded for We recorded a total of 349 individual vertebrates
each section of the trench searched, where a of 40 species from the trench, from a total
section is defined as a length searched at a distance of 74.2 km searched (Table I), with
particular time (i.e. date and morning or track records of a further five species.
afternoon), which had been left open for the
Capture rates of nocturnal animals in the trench
same time (with a precision of +/- 6 hr), and
were significantly associated with the time since
which had been previously searched at the same
the trench was previously searched (27% of
time (again, with a precision of +/- 6 hr).
deviance explained, p<0.001: Fig. 3), with only
The capture rate of nocturnal animals (no./km of 3% of deviance (p<0.05) additionally explained
tre-n ch searched) was related to the number of by the time the searched section had been
niehts over which the trench section had been opened. No comparable significant relationship
opened and the number of nights since the last was found for diurnal animals, and neither the
search, using generalised linear modelling total number, nor the proportion, of dead animals
(Crawley 1993). Comparable analyses were was significantly related to either the time since
undertaken for diurnal animals, for the number the previous search or the period over which the
(and proportion) of dead nocturnal animals, and trench section had been open.
the number (and proportion) of dead diurnal Comparison with quadrat results
animals. Proportions were arcsine transformed
There was only moderate correspondence
prior to analysis. Analysis included examination
(r,=0.33, p=0.035) between the species
of main effects and interaction tern.
composition of trench captures and those of
The number of captures for each species in the quadrat captures (Table 1; Fig. 4). Twenty of the 39
trench was compared with the numbers recorded species recorded from the trench (excluding the
in quadrat sampling using Spearman rank single bird species and those species recorded only
correlation. A similar analysis was used to from tracks) were not recorded in the quadrat
examine the relative frequencies of captures in sampling; only one species recorded in quadrats
the 1999 and 1994 trench surveys. was not also recorded in the trench. The disparity
The cumulative frequency distribution of size in numbers recorded from trench and quadrats
categories for reptiles was compared between varied among taxonomic groups (Fig. 4). Snakes,
trench and quadrat samples using 2-tail pygopodids and frogs were far more common in
Kolmogorov-Smimov tests (Siegel 1956). We trench samples than in quadrat samples, whereas
used (average) snout-vent lengths as given in, or skinks, mammals and geckces were relatively more
derived from, Cogger (1992). equitably sampled. For some individual species
Table I. Cornpanson of captures of vertebrates in trench in 1999 and resub from simubneous standard survey
quadrats, and captures recorded during the construction of the trench in 1994. 'Y" = recorded by tracks. The no.
recorded in quadrats includes both trapped animals (in brackets) and animals located by active search. For trench
captures,t he number in brackets is the number that were dead when located (=O, unless otherwise indicated)
species no. recorded in no. recorded in trench
survey quadrats in (no. dead)
1999 (no. trapped) in 1999 in 1994
Amphibians
Bufo marinus 0 0 8 (1)
Cyclorana austrolis 0 I 1 (4) 2
Litorio coeruleo 0 0 20 (10)
Reptiles
Geckos
unidentified gecko 0 0 9
Diplodactylus cilioris I(I) 18 30 (8)
D conspicillotus [(I) I 22 (3)
D stenodactylus 3 (3) 5 2
Gehym oustra1;s 2 (0) 13 3
Heteronotia binoei 4 (2) 40 (1) 4
Oedura hornbifer 6 (3) I 0
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Rhynchoeduro ornotus I(I) 2 I
Pygopodids
Delmo boreo 0 4 5
D nosuto 0 0 2
D tincto 0 0 5 (2)
Liolis burtonis I(I) 16 57 (10)
PygoQus nigriceps 0 2 54 (1 7)
Dragons
Diporiphoro bennetti I (1) 5 I
D. rnogna I(I) 19 (1) I
Lophognothus gilbem 2 (1) 22 3
Skinks
unidentified skink 0 0 5
Corlio ornox
C.r nundo
Ctenotus inornotus
Ct pantherinus
Ct pulchellus
Ct. mbustus
Ct schornburgkii
Ct spoldingi
Glophyrornorphus isolepis
Menetio rnoini
Morethio stom
Proablephorus tenuis
Tiliquo rnultifascioto
1 scincoides
I
Vomnus oconthurus 0 0 I2
V gouldii t t 0
Snakes
unidentified snake 0 0 9 (8)
Rornphotyphlops diversus
R. endoterus
R. ligatus
R. sp.
Liosis childreni
L. olivoceus
Demonsio olivoceo
D. papuensis
D. torquoto
Furino ornato
Pseudonajo nucholis
Rhinoplocepholus pollidiceps
Sirnoselo~sin cinctus
suto pu"ctoto 2 (2)
5. suto
Vermicello rnultifosciato
I
Birds
I
little button-quail Turnix velox 2 0
Tochyglossus oculeotus 0 0 I
Plonigole rnoculoto I(I) 10 0
Srninthopsis rnocrouro 0 I 0
Logorchestes conspicillotus 0 3 0
Onychogoleo unguirosvis t t 0
Mocropus ogilis t 4 0
Macropus robustus t t 0
unidentified rodent 0 0 3
Leggodino lakedownensis 18 (18) 41 (5) 0
Pseudornys delicotulus 0 67 (20) 0
k? nonus 3 (3) 23 (5) 0
Ranus tunneyi 0 I 0
Rottus villosissirnus 0 I 0
Felis cotus t t 0
Conis fornifioris t t 0
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December 2000 oo og~stv olume 3 1 (3) 425
No. captures/km
Figure 3. Relationship between numbers of nocturnal animals encountered per km of trench searched and time
since the section was last searched. Symbols shwv trench '"get': open cirrle=trenh open for 0 previous nights;
open square=trench open for 0.5 previous nights; filled diamond=trench open for I previous night; filled
triangle=trench open for more than I previous night
Quadrat captures (log)
Figure 4. Scattergram showing the number of records in which an individual species was recorded in the trench
and corresponding number of records fmm sampling nearby quadrats. Note that both axes are log-scaled. Key to
symbols: open circle=frogs; open square=geckos; open diamond=pygopodids; open triangle=dragons; filled
circle=sknks: filled square=snakes; filled diamond=mammals.
reptile size (mm)
Figure 5. Histograms of size distribution of all reptiles caught in trench (paler ban) and all reptiles recorded
from quadrat sampling (dark bars).
(notably the gecko DipIodactyluc ciliaris, the Comparison with other trench studies
pygopodid Lialis b u m ,t he dragons Donphora
The capture rate recorded in this study was
magna and Lophognarhus giIbem' and the rodent
greater than that recorded in comparable
Pseudnmys delcaculus), the numbers recorded in studies of other pipelines, including that
the trench was markedly greater than that for recorded in the previous laying of this pipeline
quadrat samples. (Table 2). Species richness in this study was
Considering reptiles only, there was a highly generally less than that reported in western New
significant (D=0.204, p<0.01) difference in the South Wales by Ayers and Wallace (1997), with
size diiuibution of individuals caught in the this difference probably largely due to the
trench and those recorded from the quadrats greater sampling effort and environmental range
(Fig. 5), with proportionally far more larger sampled in that study. Relatively few frog species
reptiles in the trench. were recorded in this study.
Table 2. Comparison of capture rates and mortality between this pipeline and others.Tallies with + indicate
that some specimens were not identified to species. Note that the distance searched was not recorded for
two sampling periods in 1994."mort rate"=% of all animals encountered that were dead
study dist no. total mom
search individs. no. nte no. individuals (no. spp.)
(km) (noJkm) ~PP.
frog reptile bird mammal
This study 74.2 349 (4.70) 40 1 1.1 I I (1) I85(29) 2(1) 151(9)
July 1994 ? 20 fl 10 0 0 20 (10) 0 0
Aug 1994 40 40 (1 .XI) 16 7.5 '(1) 39 (I 5) 0 0
Sept 1994 ? 15 C) 6 26.6 0 15 (6) 0 0
ea+ Nov. I994 103 198(1.92) 25+ 31.3 25(2) 169(2I+) 0 4 (2+)
late Nov. 1994 33 52 (1.58) 17 3.8 4 (2) 48 (15) 0 0
Ayers &Wallace 256 680 (2.66) 64 4 1.8 30 (8) 375 (39) 7 (3) 22 1 (1 4)
Faulkner 255 299(1.17) 27+ 52.5 174(6+) 102(14+) 5(3+) 17(4)
Records in trench 1999
Figure 6. Scattergram showing the number of records in which an individual species was recorded in the trench
in 1999 and corresponding number of records from the trench in 1994. Key to symbols: open circle=frogs and
reptiles: filled square=mammals.
The mortality rate recorded in this study DISCUSSION
(11.1%) was substantially less than those from
This study has demonstrated that our standard
the two previous studies in western New South
quadrat-based sampling protocol has some
Wales, and that from the combined sampling of
substantial biies in species detection and the
this same pipeline in 1994 (24.9%) (Table 2).
assessment of the relative abundances of different
Nonetheless, mortality rates for some individual
species. Our quadrat sampling techniques appear
species in this study were substantial (e.g., 30%
to substantially under-represent snakes,
for P s e h y s d elicatulus) (Table 1).
pygopodids, frogs and some individual species,
Species composition of captures in the trench most notably the mouse Pseudomys delicatulus,
during this study varied considerably (I,= -0.14,
the dragons Diporiphora magna and Lophognathus
pz0.05 for all species, and r,= 0.002, p>0.05 if gilberti and the gecko Diplodacrylus cihtis.
mammals excluded) from that recorded over a
The inadequate sampling of these taxa by our
greater length of this pipeline during its initial
laying in 1994 (Table 1; Fig. 6). The most marked standard quadrat protocol appears to relate mostly
differences were the absence of rodents and to behaviour (e.g. I! deLcanJus appears to be trap-
dasyurid mammals, and relatively low abundance shy for Elliott traps) and size (most of the larger
of the gecko Hetermria binoei, the dragons reptiles can climb out of the pitfall traps we used).
Diponphora magna and Lophognuthus gilberti, and Conversely, comparison between trench and
the elapid snake Furina omata in the 1994 quadrat results also suggests some biases in trench
sampling, and the much greater reporting rate
captures. The most notable of these is the apparent
then of the amphibians Litotia cneruka and Bufo
under-representation of the smallest reptiles, which
malinus, the gecko Diplodatylus cmpicillrtus, the
may be due to the substantial manix of disturbance
pygopcdid F'ygopus W e p s and the large skinks
surrounding the pipeline trench, including a series
T i e s pp. Eighteen species were recorded in
of spoilheap rows which may provide an effective
1994 but not 1999, 17 species in 1999 but not
barrier for smaller reptiles.
1994, and 22 species in both years.
A
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volume 3 1 (3) December 2000
The low detectability of some of these species by "abundance" between the two samples. The 1999
our standard quadrat protocol may be a problem survey sampled relatively small sections of the
for monitoring and measurement of trench intensively, and generally relatively soon
environmental impacts. This may be serious for (<5 days) after the trench was established. In
groups such as snakes and other larger reptiles, contrast, the 1994 sampling was far less intensive
for which substantial decline has been suggested and, in many cases, searches were made at long
following spread of cane toads (Covacevich and intervals and long after the trench had been
Archer 1975; Burnett 1997; Catling et al. 1999). opened. A biased selection of species may have
escaped the trench or been eaten during such
This study suggests that our quadrat sampling
relatively long intervals. With regard to
protocol will need to be modified to include more
predation, it is notable that there were many
effort andlor different sampling techniques for
reports in the 1994 survey of cat, dog and goanna
such species. This modification should include
tracks in the trench, and records of raptors
greater effort devoted to searching for such
patrolling along the trench: there was little sign
species and/or the use of traps more specifically
of this in the 1999 sampling, almost certainly
designed to sample the currently under-
because the trench was being constructed and
represented taxa.
filled far more rapidly, and inspected more
The low level of correlation between trench freauentlv. than in 1994.
captures in 1994 and 1999 suggests that a range
On a broader scale, marked differences in
of factors may make samples from trenches highly
habitats, sampling methods and construction
variable. In this case, some of the variation may
protocol influenced the contrast between the
be due to different locations and habitats being
results from this study and those of the two
sampled (although there was substantial overlap
pipeline studies in New South Wales (Ayers and
in both of these), some seasonal influence (again,
Wallace 1997; Faulkner 1999), although there
although there was substantial overlap), and
possibly differences bemeen years in animal are some notable similarities in all studies. The
most marked contrasts are that our study had a
populations (which may contribute some
explanation of the extraordiary difference in very low representation of frogs (which is a simple
rodent captures between the two trenching seasonal factor), and a substantially lower
events). However, as well as these factors, mortality rate. To some extent, the latter may
differences in sampling regime and differences in also be a seasonal factor, as the timing of pipeline
trench construction may also have contributed to construction in our study coincided with the
the contrasts in species composition and relative season of least stressful climate.
Table 3. Summary of measures which reduce capture and mortalty of uildlife during trench construction.
type of measure recommended procedure e.x planation
construction undertake operations in the most benign wildlife mortalii is likely to be highest in
operational season hot (or very cold) weather;
wildlife activty may also be higher in warm
weather than cool weather;s o capture
.r ates then would be greater
intempt trench with frequent "escape ramps" exit points from the trench will enable
for captured wildlife trapped animals to leave the trench: sloping
ramDs away from the trench everv 2M) -
503'm sho"ld be sufficient for mist species
minimise the time the trench is opened, fewest animals will be trapped if pipe laying
through careful planning of construction and (and immediately thereaftertrench filling)
oioe lavine occun within 24 hr of trench ooenino
site pipeline route to avoid areas of
exceptional consewdon mlues (e.g. remnant
bushland, essential habit for threatened
species, etc.) .
inspection ensure that trenches are inspected kquentty mortality is likely to be minimised if all
trench sections are checked at earlv
morning and late afternoon
Austral$q
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December 2000
This influence of seasonality on mortality decrease mortality include rapid construction
patterns may provide one mechanism for linked with rapid filling of trenches (such that
minimising the impact of pipeline construction. only small extents of trench are open at any time)
Our results failed to reveal any clear pattern and the provision of escape ramps at frequent
connecting mortality with either trench age or intervals (e.g. every 200 to 500 m). A summary of
frequency of trench inspection. These these mitigation measures is presented in Table 3.
(non)results are a little surptising, and may be Generally similar measures were proposed by
explained by a) the relatively narrow range of Ayers and Wallce (1997) and Faulkner (1999).
both of these variables in this study, b) the Faulkner (1999) recommended that such
imprecision in our estimation of these ages in this measures be explicitly incorporated into the
study, c) the possibility that build-up in numbers Environmental Management Plan or
of captured animals with increasing nench age is Environmental Impact Statement governing the
compensated for by an increased likelihood of construction project. These measures should also
dead animals being consumed or taken away by be included within an environmental code of
scavengers, and/or d) unavoidable error in practice by the pipeline constmction industry.
relating the location of animals found in the
Somewhat conversely to impact minimisation, in
trench with their point of entry. We strongly some cases it may be most productive (in terms of
suspect that we would have had substantially
gathering information on wildlife dii&ution and
higher mortality rates if the period between our
abundance, and especially for species which may
inspections was increased beyond the maximum
otherwise be cliffcult to detect), to use sampling
we used. Variation in trench construction
and construction techniques which maximise
techniques may also substantially affect capture
captures. This study suggests that capture rate, at
and mortality rates. Narrow deep trenches may
least for nocturnal animals, is largely a function of
be relatively cool and shady, but may make
frequency of inspection (at least, over the limited
escape less likely. Other procedures which will
range of inspection intervals that we used).
Acknowledgements and Murray Ellis for access to unpublished infomation
on pipeline surveys in NSW, and Mark Elliot, Cranston
This study was initiated by the pipeline contruction
Tumer (both of Macmahon), Kurt Tschirner, Nic
company, Macmahon, and we are most grateful for
Gambold, Dave Hooper, Tun Hutton, Richard Baket,
their interest, encouragement and information. We
Rowena Arthur, Paul Homer, Dave Farlam, Danielle
particularly thank Peter Miller for his help and
Barrow and Murray M i f or their involvement in
hospitality, but all workers involved in the pipeline
samphg the pipeline in 1994. We are grateful to Alaric
placement were exceptionally helpful to our work. We
Fisher for comments on a previous draft, and to the
also thank Paul Homer for assistance in the
Tropical Savannas CRC for research support.
identification of some specimens, Dani Ayers
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