Natural History Notes on Two Pilbara Endemic LIzards, Diporiphora Valens and Varanus Bushi, With Brief Comments on Survey Methodology

2012·2.6 MB·English

by  Brad Maryan

NATURAL HISTORY NOTES ON TWO PILBARA
ENDEMIC LIZARDS, DIPORIPHORA VALENS AND
VARAN US BUSH I, WITH BRIEF COMMENTS ON
SURVEY METHODOLOGY
By BRAD MARYAN
63 Wallaby Parade, Baldivis 6171
and
JEFF TURPIN
6 Mount Dale View, Roleystone 6111
INTRODUCTION history observations on two
Pilbara endemic lizards, that are
The descriptions of new species
the Southern Pilbara Spinifex
continually adds to Australia’s
Dragon Diporiphora valens and the
incredibly diverse herpetofauna
Pilbara Mulga Goanna Varanus
as shown by the increase in
bushi.
number of species in the three
revised editions of Wilson and
Swan’s “A Complete Guide to
DIPORIPHORA VALENS
Reptiles of Australia’ since 2003.
Despite this increase in taxon¬ The Southern Pilbara Spinifex
omic information, we know very Dragon Diporiphora valens (Figure
little about even the basic 1) is almost entirely endemic to
natural history of many species, the Hamersley Range, with
including those that we another discrete population
encounter on a regular basis. For occurring north of the Fortescue
this reason, it is important to Basin recently described as D.
record observations of specific vescus (Doughty et al. 2012). In
ecology, behaviour and habitat various publications, D. valens is
preference. Regarding the latter, documented as being found in
many species, especially those various shrublands and low
that are found in a particular woodlands with an understorey
region, in this case the Pilbara, are of Triodia hummock grass
documented as being ‘wide¬ (Wilson and Knowles 1988;
spread’ or ‘generalist’. They are Ehmann 1992; Wilson and Swan
widespread but not necessarily 2010) or in stands of Acacia and
continuous throughout the from spinifex bushes (Doughty et
Pilbara and appear to be patchily al. 2012) which more or less
distributed in discrete habitats describes a large proportion of
and/or microhabitats. In this the vegetation structure in the
paper, we present basic natural Pilbara. In this region, there are
274
Figure 1. Adult female Diporiphora valens.
Figure 2. Survey site where Triodia melvillei is the dominant ground cover and
Diporiphora valens are observed active between and perched atop clumps.
275
up to sixteen species of Triodia notable for their absence of T.
(Florabase Database, Department melvillei, we did not record D.
of Environment and Conser¬ valens. Individuals were either
vation 2011) of which some are caught in funnel or pit-traps.
‘hard’ while others are ‘soft’, and When observed active, have been
our observations suggests that D. mostly breeding males (develop¬
valens in the central Pilbara (east¬ ment of reddish hues in groin
ern Hamersley Range) appears to and along base of tail) perched
favour areas that support certain atop clumps that they quickly
species of hummock grass. With ‘dive’ into when disturbed. This
regards to fauna surveys, even perching behaviour has been
some species of typically-diurnal similarly observed in other
dragon lizard that are readily Diporiphora spp. where the main
observed or caught in traps, can ground cover is also Triodia or
go undetected simply because a other grasses (pers. obs.).
specific habitat has not been
investigated.
VARANUS BUSHI
A series of surveys by environ¬
mental consultancy companies, Another endemic Pilbara lizard is
mainly Biologic Environmental the Pilbara Mulga Goanna
Survey, have observed a strong Varanus bushi, which was only
association between D. valens in described recently (Aplin et al.
areas where Triodia melvillei pro¬ 2006). Similar to its closest
vides the main ground cover relatives V. caudolineatus and V.
(Figure 2). T. melvillei is a ‘soft’ gilleni, this species is arboreal
species of hummock grass that often being found behind bark
occurs on plains, rocky hills and on Mulga (Acacia) trees and
sand dunes across Western occasionally inside hollow tree
Australia from the Pilbara south limbs (Wilson and Swan 2010 and
to the Murchison and east to the pers. obs.). Observations of these
central deserts. Our capture small tree-climbing Varanus spp.
records of D. valens in 2010-11 active on the ground are in¬
from a total number of 45 survey frequent, despite them being
sites named Area C West A, Area occasionally caught in funnel/
C West B and Mudlark in the pit-traps, found sheltering under
vicinity of Mount Robinson and ground debris and seen as road-
The Governor approximately kill (pers. obs.).
100km WNW Newman, indi¬ During a series of surveys in 2011
cated that D. valens was recorded by Biologic Environmental
from 9 sites that supported T. Survey in the central Pilbara we
melvillei as the main understorey have recorded V. bushi from most
or it was in association with sites supporting Mulga wood¬
either T. pungens or T. wiseana. At lands and on two occasions in
23 other survey sites named close sympatry with V.
Marillana and Mindi Mainline, caudolineatus. During one winter
276
survey between the 9-10th July adequate shelter, a virtually
one of us (BM) and Matthew inexhaustible food supply for
Johnston found ten (one juven¬ many small species, especially
ile, nine adults) V.bushi inside geckos, and a very temperature-
unused termite mounds in stable environment for egg
Mulga woodland near Mount deposition which has been
Robinson. In two separate documented for other varanid
mounds we found three indi¬ species (King and Green 1993;
viduals, which were all in a Gaikhorst 2002). it is unknown
torpid state and occupied the at this stage whether V. bushi
cavities within the highest point utilises termite mounds for egg
of the mounds, where it is deposition.
assumed they would obtain
maxi-mum indirect exposure to
the sun. in July 2011 the average DISCUSSION
minimum and maximum temp¬
Specimens of D. valens at the WA
eratures recorded at Newman
Museum suggest that the main
have been 9.6° and 22.8° re¬
centre of distribution for this
spectively. Due to the cool
species is the Hamersley Range
temperatures experienced at this
extending southeast to Kuma-
time of year we assumed the V.
rina in the Gascoyne region and
bushi we found had ‘vacated’ the east in the Little Sandy Desert
more typical retreat of the trees
(Doughty et al 2012). The
to take-up winter residence
Hamersley Range is a regionally
inside the mounds as they
unique area consisting of a large
provided a very stable temper¬
elevated range and plateau that
ature and secure environment.
contains some of the highest
We also speculate that predation
peaks in the Pilbara, including
on the torpid and more
the highest in Western Australia,
vulnerable V. bushi would be less Mount Meharry at 1200 metres.
due to the cold conditions. This
As a result of the elevated top¬
is reinforced by us only a finding
ography, the Hamersley Range
a single V. bushi behind bark on a receives a higher amount of
tree in the vicinity of the
rainfall (both average annual
mounds. However, this seasonal
rainfall and annual average
movement ‘en masse’ to termite
number of days with rainfall
mounds is clearly presumptuous,
greater than 1mm) when com¬
as further visits to the same area
pared to the surrounding area
would have to be made during
such as at Newman. Conse¬
the warmer months.
quently the range supports a
it is well known that termite high level of endemism with
mounds are occupied by a wide flora (eg. Pilbara trudgenii and
variety of animals, particularly Acacia hamersleyensis), inverte¬
reptiles, in the arid regions of brates such as snails and spiders
Australia as they provide (B. Durrant pers. comm.), and
277
vertebrates (eg. Underwoodisaurus quate trapping methodology
seorsus and Lerista zietzi) and there and/or time restraints as stated
still remain undescribed species by Doughty et al. (2011). This is
of reptiles. Contrary to popular evidently clear with the arboreal
belief, not all of the Hamersley species of reptiles such as V. bushi
Range occurs within the bound¬ that are infrequently trapped
aries of the Karijini National compared to active searching
Park, which only statutory ‘pro¬ (pers. obs.). From a total of 297
tects’ a small area. Large areas of survey quadrats, the captures of
the Hamersley Range remain un¬ small to medium-sized arboreal
protected and are as equally goanna species in the Pilbara
scenic and biologically/geo¬ resulted in V. caudolineatus and V.
logically diverse as the national bushi being recorded from only 17
park. and V. tristis from two (Doughty
et al. 2011).
Despite the Pilbara region being
one of the most intensely Surveys that combine trapping
collected areas in Western with active searching by ex¬
Australia (How and Cowan 2006) perienced field naturalists is
the paucity of D. valens records important and play a crucial role
strongly suggests a patchy in specific areas resulting in an
distribution and that it is not as increased knowledge of local
widespread as general distri¬ distribution, relative abundance
bution statements imply. Natu¬ and habitat preference. The
ral history observations such as importance of active searching
those reported here are generally should never be underestimated,
not documented during larger, as demonstrated by the recent
broad-scale surveys that are rediscovery of Aprasia rostrata on
heavily reliant on a presence v. the Montebello Islands (Maryan
absence trapping result metho¬ and Bush 2007) and the first
dology. This survey focus tends Pilbara mainland record of
to negate the time available to Ctenotus angusticeps (Turpin and
actively forage, observe and Ford in press), both species of
record. To downplay the which are listed as vulnerable
importance of active searching under state legislation.
for reptiles by suggesting it con¬
tributes little towards the
ACKNOWLEDGEMENTS
outcomes of the study (Rolfe and
McKenzie 2000) is funda¬ We thank Michael Brown,
mentally wrong. A survey that Stewart Ford (formerly), Ray
does not employ all available Lloyd, Morgan O’Connell, and
sampling techniques, including Thomas Rasmussen of Biologic
active searching, is flawed and Environmental Survey for their
will always contribute to the company, laughs, enthusiasm
exclusion of reptile groups from and regular discussions about the
a survey analyses due to inade¬ diverse Pilbara herpetofauna. We
278
also thank Thomas Parkin HOW, R.A. and COWAN, M.A.
formerly of the Western Aus¬ 2006. Collections in space and
tralian Museum for providing us time: geographical patterning of
with D. valens records. We also native frogs, mammals and
thank the anonymous referee for reptiles through a continental
their suggested changes. gradient. Pacific Conservation
Biology 12:111-33.
MARYAN, B. and BUSH, B. 2007.
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