By Greg Calvert, James Cook University
Landscape and fauna
The spectacular emerald python is found only in
the Iron Range/McIlwraith Range district of Cape York Photo: Greg
Calvert.
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From a zoologist's point of view, Cape York Peninsula is
somewhat like an island. It has animals from surrounding regions
such as Arnhem Land, North East Queensland and Papua New Guinea, as
well as its own endemic fauna that are found nowhere else. The
peninsula is not an island of course, since it is connected to the
Australian continent, however, there are barriers to the movement
of animals that are just as significant as if it was surrounded by
water.
A broad, low-lying dry belt stretches across the bottom of the
peninsula, through the Laura Basin and extending north towards Cape
Melville and Princess Charlotte Bay. In terms of rainforest
species, this effectively prevents Cape York species from spreading
south into the wet tropics, while also stopping wet tropics species
from moving north.
It is presumed that it is this dry belt which excludes from the
Peninsula many savanna and woodland animals such as koalas,
bettongs and most species of kangaroos, wallabies, possums and
gliders. Cape York Peninsula has no highland connections with the
rest of the Great Dividing Range and this may prevent
cool/temperate dependant taxa from migrating from the wet tropics
or the Einsleigh Uplands bioregions. This would apply regardless of
whether or not the taxa are dependent on rainforests, and may
explain the absences of dry/open savanna taxa.
Historical effects on fauna
Cape York Peninsula was not always its present shape. During the
last Ice Age (some 12,000 years ago) sea levels were much lower.
Cape York was connected to Papua New Guinea via the Torres Strait
and the Gulf of Carpentaria was also above sea level.
The east coast extended much further than it does today,
allowing strong south-easterly winds to form huge, spectacular sand
dunes along the present coast. During this time, it was possible
for many animals to migrate and settle new areas.
At the same time, the Ice Age meant that rainforest areas were
contracting and that the plants and animals that depended on these
areas were becoming extinct.
(Click here to go to an
overview of the geology of the Tropical Savannas.)
In the parts of the Iron Range with high mountain ranges and a
relatively high rainfall, animals were better able to find refuges.
However even these refuges would not have been enough for animals
such as tree kangaroos which have disappeared from this area. (This
is why there are tree kangaroos in Papua New Guinea and the wet
tropics, but not in between).
In the Lockerbie scrub at the tip of Cape York, there are no
mountain ranges and so refuges would have been even smaller. This
meant that even more animals disappeared from here than from the
Iron Range. When the sea levels rose and stabilised 6000 years ago,
many Australian species remained in Papua New Guinea and many
animals from Papua New Guinea remained on Cape York Peninsula.
Amphibians
Frith and Frith records 31 species of frogs on the Peninsula,
five of which are endemic and two that are found only on the
Peninsula in Australia but also in Papua New Guinea. Many postcards
show the giant white-lipped tree frog ( Litoria infrafrenata
) which also occurs through the wet tropics and in Papua New
Guinea.
One of the most interesting recent discoveries is that of the
Cape Melville frog ( Litoria andiirrmalin ) which was only
described in 1997. Unfortunately, the introduced cane toad (
Bufo marinus ) can also be added to the list. Its spread to
the tip of Cape York in about 1994 is having disastrous
consequences.
Reptiles
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Estuarine crocodile Photo: Greg Calvert
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Frith and Frith record a total of 133 reptile species (excluding
sea snakes) as being found on Cape York Peninsula, although the
actual number could be higher. By far the best known is the
saltwater or estuarine crocodile which has significant breeding
populations throughout the region and is seen by many as the symbol
of the wild, untamed wilderness. (click here to see research papers
on the estuarine crocodile ( Crocodylus porosus
)
Many of the isolated beaches on the Peninsula are also nesting
beaches for several species of marine turtle. Many of these turtles
and crocodiles are widely distributed across tropical Australia and
extend north into South East Asia, unlike the 18 species of
reptiles known to be endemic to Cape York Peninsula.
There are a further 14 species which are found in Papua New
Guinea, but nowhere else in Australia outside the Peninsula.
Many of the endemic reptiles are small skink species, which,
because of their small size, limited mobility and low resource
requirements, were able to evolve separate species in isolation
from each other in response to the incredible patchwork of habitats
that occur within the region.
New species are being found all the time, including a possible
new Lerista skink and dtella gecko ( Gehyra sp.) from
Pajinka. A new, bright pink snake with the humorous name of
Rhinoplocephalus incredibilis has been found on the beaches
of Prince of Wales Island off the tip of Cape York. There is
speculation that it may also occur on the mainland. Of the species
with extra-limital ranges outside Papua New Guinea, none are more
spectacular than the emerald python ( Morelia viridis )
found only in the Iron Range/McIlwraith Range district.
Of the 133 species of reptiles listed by Frith and Frith, there
are two crocodiles, six marine turtles, seven freshwater tortoises,
15 geckos, four legless lizards, five dragons, nine goannas
(monitors), 39 skinks and 46 snakes (only five of which are
dangerous).
Birds
Cape York Peninsula is considered a mecca for bird watchers,
with Frith and Frith recording 321 species for the region,
excluding occasional vagrant species. Of this, the only two that
are truly endemic are the golden-shouldered parrot and the
white-streaked honeyeater. Of these, the golden-shouldered parrot
is considered as threatened by habitat changes from alteration of
fire regimes.
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One of the migratory birds, the Torres Strait
(Pied Imperial) pigeon Photo: Greg Calvert
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A large majority of bird species found on Cape York can also be
found in Papua New Guinea, though there are 18 species whose
Australian distribution is restricted to Cape York. These include
the palm cockatoo, eclectus parrot, red-cheeked parrot,
yellow-billed kingfisher, red-bellied pitta, green-backed
honeyeater, tawny-breasted honeyeater, white-faced robin, frilled
monarch, black-backed butcherbird and fawn-breasted bowerbird.
The northern rainforests of the Peninsula is also home to two
species of birds of paradise from Papua New Guinea. These are the
magnificent riflebird and the trumpet manucode, both of which have
a singular and unmistakable call and are eagerly sought after by
birdwatchers.
There is some difference between the bird fauna at Iron Range
and the Lockerbie Scrub. The eclectus parrots and red-cheeked
parrots are restricted to the Iron Range area, having presumably
disappeared from the Lockerbie Scrub during the last Ice Age. The
southern cassowary has also disappeared from the very northern
forests; however, this is because of recent hunting pressure.
Many of the Papua New Guinea bird species which also call Cape
York home are isolated from their northern populations by the
Torres Strait.
Garnett (1991) lists 31 bird species that are isolated by the
Torres Strait and 11 which make annual crossings. September is
considered an interesting time for bird watching as this is often
the time that these migratory birds arrive from Papua New
Guinea.
Migratory species observed arriving at Pajinka at this time
include mongolian plover, oriental plover, curlew sandpiper,
sharp-tailed sandpiper, grey-tailed tattler, bar-tailed godwit,
pied imperial pigeon, buff-breasted paradise kingfisher and the
common koel. The very elusive red-bellied pitta doesn't arrive
until the wet season is in progress (December-January), whereas the
metallic starling may arrive as early as July before building their
enormous colonies.
Mammals
As previously stated, Cape York Peninsula is as interesting for
the animals it doesn't have as for the animals that it does. The
mammals best illustrate this. Frith and Frith record 72 species of
mammals, four of which are endemic and a further eight of which
also occur in Papua New Guinea. Of the total, there are only three
gliders, three possums, ten macropods (wallabies, kangaroos and
pademelons), and 31 bats. Of the 12 rodents listed, the cape york
melomys and the lakeland downs mouse were noted as being endemic,
however, the lakeland downs mouse has now been found at a site
north of Townsville in north east Queensland.
Of the 72 mammals listed by Frith and Frith as occurring on the
Peninsula, only 25 have actually been recorded on the tip of Cape
York. One of these species, the northern quoll, may be presumed
extinct since the 1994 arrival of the cane toad.
Reflecting the situation with birds, Iron Range has higher
mammal diversity (64 species identified) than found in the
Lockerbie Scrub. Notable amongst these is the grey cuscus. It is
particularly interesting to note that many of the mammal species
present at the tip of Cape York also occur in Papua New Guinea.
These include the echidna, rufous spiny bandicoot, southern brown
bandicoot, striped possum, sugar glider, spotted cuscus, agile
wallaby, water rat and cape york rat. This could be a clue for
biogeographers trying to determine what has influenced the current
distribution ranges for many Cape York Peninsula animals.
