Vertebrate fauna in Queensland’s
tropical savannas is largely unknown and unsurveyed—a concern
given the mounting need to find a balance between economic and
environmental sustainability in managing the land. JCU–CRC
PhD student Alex Kutt has completed a baseline survey of the
region, identifying new and existing species and impacts such as
fire and grazing. Photos and story by Alex Kutt.
Above left, the inland forest bat,
Vespadelus baverstocki, one of the smallest mammal species in
Australia, if not the world. It weighs between 3-5 grams, and is
found in south-western parts of the Desert Uplands. It can consume
1-1.5 times its body weight in insects per night. Above right, the
Julia Creek dunnart, Sminthopsis douglasi, furious at being
handled; restricted to cracking grey clays typical of the Mitchell
Grass Downs, its discovery in outlying grasslands in the Desert
Uplands extended its known range.
Survey aims and outcomes | Using regional ecosystems to identify biodiversity
| Impact of fire and grazing | More than a snapshot needed | Getting the cat into the bag: just what toll are feral cats
exacting on wildlife? |
The Desert Uplands (DEU) is one of Queensland’s six
tropical savanna bioregions, covering more than six million
hectares and sharing boundaries with the Mitchell Grass Downs to
the west, the Brigalow Belt to the south and east, and the
Einasleigh Uplands to the north. The DEU has a semi-arid climate
with vegetation consisting mainly of Acacia and Eucalypt woodlands,
ephemeral lake habitats and grasslands. It straddles the Great
Divide between Charters Towers, Hughenden and Blackall and it is
this division between the wet east coast and the dry interior which
makes this area of biological and biogeographic interest.
Unlike Queensland’s coastal zone and Cape York Peninsula,
there is almost no baseline data on fauna that would allow
landholders and managers to create a landscape mosaic that
maintains the balance between economic viability and biodiversity
conservation.
The survey, undertaken between 1997-2000, was designed mainly to
identify fauna of the regional ecosystems (the lowest level
bioregional planning unit used in Queensland), describe the
patterns of the variation in distribution, diversity and abundance
of these groups, and characterise the region’s biogeographic
position within the Queensland landscape.
So after three years and 23,000 Elliott and cage trap nights,
4200 pitfall trap nights, the installation of more than 7 km of
drift fence and the equivalent of almost seven weeks at 24
hours-a-day of active searching, the field survey was completed.
The primary outcome is a database of more than 35,000 records
(24,000 from field survey), representing more than 400 species.
As one would hope for in a predominantly unsurveyed bioregion,
there were a number of unexpected finds of animals outside their
previously known ranges (some by many hundreds of kilometres)
including Spinifexbird and Painted finches, rodents such as the
Lakeland Downs mouse Leggadina lakedownensis, the Desert Mouse
Pseudomys desertor and Pebble-mound mouse Pseudomys patrius, and
dasyurids (marsupial mice) such as Common Dunnart Sminthopsis
murina and the Julia Creek Dunnart Sminthopsis douglasi. Reptiles
included the Brigalow Scaly-foot Paradelma orientalis and the
Centralian Blue-tongue lizard Tiliqua multifasciata.
Highlights were the discovery of two new species, both reptiles:
Ctenotus rosarius sp. nov, (the rosarius referring to the blotches
along its flank that resembles a string of rosary beads), currently
being described in conjunction with the Queensland Museum; and
Lerista sp. nov., still awaiting a formal classification, but this
time a collaboration with the Queensland and South Australian
Museums. As an adjunct to the trapping survey, the stomach contents
of feral cats were examined to gain an insight into how these pests
are affecting native fauna in the region—see boxed story below .
Besides the value of providing new information, this survey will
also produce a range of useful outputs for stakeholders interested
in the project. These include government agencies, the Desert
Uplands Build-up and Development Strategy Committee, the local
Shire Councils, Landcare groups and most importantly the
landholders in the region.
Fauna patterns in the Desert Uplands
The Desert Uplands’ bioregion is an area of
‘interchange’ between the Torresian (north-east
Queensland and New Guinea origin) fauna of the coast and the Eyrean
fauna (arid central Australia) of the inland. Unlike the wet
tropics and Central Australian Deserts which have large numbers of
endemic and specialised animals, the Desert Uplands has neither the
tall mountains nor expansive deserts that act as refuges to allow
unique species to evolve. However as the climate shifts, coastal
and desert species expand, contract and interact across the Desert
Uplands, leaving behind elements of both faunas, but not many of
its own unique species—in effect the bioregion is a jack of
all trades, but a master of none.
Factors that determine the presence of animals
Animals can be clustered into different assemblages, or groups,
depending on how often they are recorded in a particular area, and
the climate, vegetation and habitat characteristics of a site. For
example, the types of species found in tussock grasslands on
cracking clays and hummock grasslands on sandy clays are very
different, despite both habitats being grasslands with a similar
overall diversity of species. The former has Julia Creek Dunnarts
Sminthopsis douglasi and Long-haired Rats Rattus villosissimus and
the latter has the Desert Mouse Pseudomys desertor and Delicate
Mouse Pseudomys delicatulus.
Both subtle and stark fauna variations such as this also occur
in open woodlands that have the same broad types of vegetation and
mix of species. Simple things like the density of trees, soil type,
number of logs or litter on the ground and proximity to water cause
significant changes in the number and composition of animals in
seemingly uniform environments. This information is important in
not only providing clues as to the micro-habitat and life-history
controls of these animals, but counters any assumptions that all
habitats type are the same within a small area or across their
geographical range.
Though the subtle variation and environmental control of fauna
assemblages is recognised, the reality is that no one has the
resources or time to survey and describe the range of patterns ad
infinitum. So rather than attempting to make sure individual
species are protected, planners in Queensland try to ensure that
each regional ecosystem is protected. However there has been little
or no examination of the how adequately regional ecosystems
correspond to animal diversity and variation across a
bioregion.
While regional ecosystem types correlated quite well to changes
in animal species diversity across the Desert Uplands (e.g. species
in woodlands were quite different to those in grasslands), within a
large widespread regional ecosystem unit (e.g a single woodland
type) fauna diversity also varies geographically. Therefore
regional ecosystems used as a surrogate to represent the entire
biodiversity within this unit fails, unless one considers the
differences across its range. The implication here is that planning
for biodiversity protection needs to be considered on a variety of
scales.
Fire is an important natural influence on fauna assemblages and
contrary to anecdotal beliefs, some fire patterns can actually
improve biodiversity rather than impede it. Many animals have
different micro-habitat requirements (e.g. levels of ground cover)
and an abundance of biodiversity is achieved by burning patterns
that create a vegetation mosaic in the landscape. However, grazing
complicates the pattern in that it also influences ground cover,
and therefore the composition of animal groups. A range of
moderately grazed and ungrazed quadrats of different fire ages were
sampled in Eucalyptus similis Yellowjack woodlands. Results
indicated that though fire and grazing interacted to affect the
abundance of many species in this community, vertebrates responded
most significantly to the amount of time that elapsed since
fires—species changed in type and abundance as the vegetation
regrew—whereas differences in ant fauna were most notable
between grazed/ungrazed environments.
One of the first tasks on completing the thesis is to return to
the Desert Uplands and present the findings to the stakeholder
groups who assisted over the life of the project. Also a
preliminary atlas of distribution ecology of key species in the
area is being developed. Mapping known and predicted distribution
of significant or indicator fauna is being developed in
collaboration with Greg Connors (PWCNT) and Sharon King (QEPA), and
this will provide the basis to pursue funds to produce a more
permanent, distributable document.
Such a bioregion inventory is just the first step. The reality
is that this survey is a snapshot, and not really of the scope to
extend our understanding of the dynamics of wildlife in rapidly
modifying landscapes. The next phase would be to undertake targeted
follow-up work to examine in detail the interplay between
land-management regimes (fire frequency, stocking rates, tree
clearing) and the best means to balance needs for farm viability
with native fauna protection. The maintenance of healthy
sustainable landscapes is vital for future generations of people in
the bush, and it is also our responsibility to protect the wildlife
with which we share our environment.
Getting the cat into the bag: just
what toll are feral cats exacting on wildlife?
As an adjunct to the trapping survey,
the diets of feral cats were examined via stomach contents, which
were systematically collected across the bioregion and the directly
adjacent areas of the Mitchell Grass Downs and Northern Brigalow
Belt. Samples were obtained by local professional kangaroo and pig
shooters.
A total of 194 cat guts were collected
over two years comprising 1300 prey items. Initial sorting revealed
some broad patterns: of all prey items identified, 16 per cent were
birds, 33 per cent reptiles, 5 per cent amphibians, 25 per cent
mammals, and 21per cent insects.
And volume of prey was frightening:
one cat had consumed two birds, one dunnart, one dragon and seven
geckoes while another, one dunnart, three dragons, eight geckoes
and one tree skink. Multiplied over a year, this translates to a
significant amount.
The influence of feral cats on native
fauna, particularly in recently modified habitats, is not well
understood, and regional information is sorely needed. Hopefully
this data will contribute to the debate on the impact of feral
cats, which currently does not receive nearly enough attention.
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