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Kangaroos: boom, bust)
and blatant ballyhoo |
By GRAEME O'NEILL
DESPITE the well-intentioned
and very public international
campaign to conserve it, Aus
tralia's eastern grey kangaroo is not
endangered, nor is its larger cousin, the
red kangaroo. In fact, the two big
marsupials arc probably the least en
-dangered of all Australia's distinctive
mammals. •
Many conservationists have already
accepted the scientific cvidcnce that the
eastern grey and the red kangaroo are
not endangered, despite a spectacular
population crash during the severe
drought of the early 1980s, which vir- -
tually halved kangaroo numbers from
a 1982 peak estimated at 19 million
animals.
Yet some still argue for a halt to
culling of the eastern grey. The argu
ment is now based more on cthical
grounds, but its proponents arc quite
prepared to cite the population crash
and the cull of hundreds of thousands
of kangaroos to support claims that
Australia's kangaroos arc vulnerable to
the threat of extinction. It is an ap
proach that does the conservation
movement little credit, and risks un
dermining the more tenable ethical
arguments — which are not without
their own problems.
No argument that is based upon raw
figures of kangaroo populations can
succeed unless it takes into account the
unique biology of red and grey
kangaroos. In the boom-and-bust
cycles that Australia's erratic climate
induces in nature's economy, red and
grey kangaroos have seen it all before.
Good times, bad times, they are con
summate survivors, whose reproduc
tive strategies are wonderfully adapted
for rapid recovery in the wake of dis
aster.
The red kangaroo is a reproductive
machine gun — almost unique among
the world's larger mammals, its repro
duction rate goes up, not down, during
bad season. If it loses a joey, an im
planted embryo that has been held in
a suspended state of development in
the uterus is released, to be born little
more than a month later, and is itself
replaced by another embryo in the
womb. The species is "shooting" at the
erratic target ofa favourable rainfall
event; many of its shots go astray
because ofthe almost complete un?
predictability of rainfall in the semi
arid and arid zones.
The eastern grey also possesses the
delayed embryo development techni
que — but it applies the one-up-the
spout, one in the pouch strategy more
sparingly, waiting for good conditions
to arrive instead of firing in
discriminately.
All along the way. the two kangaroos
are beautifully adapted to perpetuate
their species. In a large mob with no
young, most breeding-age females will
have a joey developing in their pouches
little more than a month after the first
green grasses appear.
Dr Graeme Caughley. a CSIRO wild
life researcher who is regarded as one
of the world's leading authorities on
animal census techniques, said ex
perienced overseas biologists shared •
conservationists' difficulty in grasping
the idea that massive population fluc
_ tuations among Australia's kangaroos
were quite normal.
"I keep on getting letters from
biologists in the Northern Hemisphere
who were used to relatively constant
environments. In constant environ
ments, really big population fluctua
tions arc unnatural, so they think the
big crashcs wc get here must also be
unnatural," he said.
"They think that because kangaroo
numbers crashed in the big drought, it
must have been a disaster. But it's an
integral part of the ecology of the arid
zone.
"They simply have no understanding
of what the Australian arid zone
climate is all about. And it's difficult
to explain. In a constant environment,
whether you are dealing with desert or
a high rainfall area, you can talk about
the land having a fairly fixed capacity
to carry a certain density of animals.
"But in three years out of 10 in
Australia's arid zone, rainfall is either
50 per cent below average or 50 per cent
above average. You have to trade off
droughts, against good conditions, in
stead of thinking in terms of "normal"
conditions interspersed with devas
tating droughts. "Normal" ceases to be
a useful concept, and the same applies
to the kangaroo populations.
Dr Caughley said the 1970s was the
wettest decade on record in the western
rangelands. Kangaroos began building
up from about 1973, and by the early
1980s, densities per square kilometre
were as high as they had ever been since
European settlement — over large
areas, there were as many kangaroos as
there were sheep.
"At the beginning of the 1982-83
drought, kangaroo numbers were quite
extraordinary, so that peak of density
cannot be used as a reference point
when talking about kangaroo num
bers," he said.
"There was approximately a 50 per
cent crash across South Australia, NSW
and southern Queensland, but in
Western Australia, numbers actually
went up.
[In Western Australia, the eastern
grey kangaroo is replaced by its rela
tive, the western grey. There is a zone
of overlap between the two species in
South Australia and western NSW],
"The whole thing was a very stan
dard event for the kangaroos. When the
conditions arc good, their numbers rise
rapidly, and they can fall just as rapidly
in drought.
"In the big droughts, the kangaroos
decline much faster than the sheep. For
example, in western NSW the drought
cut sheep numbers by about 14 per
cent, but the kangaroos went down by
half."
Dr Caughley believes the eastern grey
may not have been a natural tenant of
the central plains of NSW until the
advent of European settlers, who built
dams that offered a reasonably per
manent water supply. The eastern grey
may have been confined to the wetter
eastern tablelands, perhaps extending a
small way into the more favourable
eastern margins of the plains. The spec
ies' range may have been extended up
to 300 kilometres westwards during the
period of European settlement, while in
the original part of its range, its num
bers were many times lower than today.
Thus, kangaroo numbers before the
big drought may actually never have
been higher, at least during the past half
dozen centuries. The conservation
movement's benchmark of 19 million
kangaroos, pre-drought, is untenable as
a benchmark to support arguments that
the specics is in danger of extinction.
Dr Caughley believes there is an
extremely low risk of cither the eastern
grey or red kangaroo being made ex
tinct by deliberate culling or random
shooting by graziers or hunters.
In fact, he knows of^o confirmed
case where an Australian mammal.
large or small, has become extinct
through deliberate or indiscriminate
shooting. One possible case was that of
Toolache's wallaby in South Australia,
a species already rare when Europeans
arrived, but there is evidence that habi
tat disturbance was a more important
factor in its demise.
And habitat disturbance, says Dr
Caughley, has been the major factor in
the extinction of Australian mammals.
The far western plains of NSW once
had abundant animal life; within a few
decades of the advent of European
settlers with their sheep, only the most
resilient animals remained — among
them grey and red kangaroos.
Habitat disturbance continues apace
today. It is not a term that finds its way
into headlines, because it is a more
subtle, non-violent assault on animal
species than people with guns or traps-.
As television footage, it is far less
dramatic than joeys being skinned
alive. The species simply fade away;
your grandfather saw them, your father
reported seeing them once or twice, but
you can search in vain for them today.
In the clamour for a halt to havesting
kangaroos, the smaller and very much
rarer species that are at real risk of
extinction are being overlooked. The
very success of those diehard factions
in the conservation movement —
Greepeace among them — in placing
kangaroos on the front pages of our
newspapers and on our television
screens, heightens the risk that public
and political attention will be dis
tracted while genuinely endangered
species arc lost.
If Dr Caughley is right, and
kangaroos have invaded parts of the
semi-arid and arid zone where there
were none before European settlement,
the kangaroos themselves have almost
certainly contributed to the extinction
of the original small species of the arid
zone through habitat disturbance and
the direct impact of competition.
CSIRO recently initiated a major
survey of800 landholders in a huge
region from Longreach in Queensland
to Esperance in WA, to determine the
impact of kangaroos and wallabies on
agriculture and pastoral production. It
will provide the most reliable figures
yet of the impact of these large
marsupials on the grazing industry.
If there are sustainable arguments for
halting the killing of kangaroos, they
now derive from an ethical base. The
conservation movement must be
scrupulously honest instead of seeking
to cloak an essentially emotional argu
ment with selective figures that wilfully
ignore the unique biology of red and
grey kangaroos.
And in spite of attempts to link the
plight of the grey kangaroo with that of
young harp seals, there is a fundamen
tal difference between the two issues.
The harp seal is culled predominantly
for profit, to satisfy the ghastly interna
tional market for furs — a market
which threatens many unique mammal
spccies around the world.
But kangaroos are culled principally
because they arc competing with
domestic livestock for food and water,
even though there is a second, un
deniably commercial aspect to the cull.
Australia cannot prevent interna
tional outrage at the culling of
kangaroos. But ifGreenpeaceand
others arguing for a halt to the kill
choose to occupy the high moral
ground, there is a most immoral aspect
to fanning that outrage with selective
facts and bald statistics which offer a
patently one-dimensional view of the
problem.
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