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Savanna Explorer > Cape York > Plants and Animals

Plants and animals

By Greg Calvert, James Cook University

Landscape and fauna

Emerald python

The spectacular emerald python is found only in the Iron Range/McIlwraith Range district of Cape York Photo: Greg Calvert.

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

Estuarine crocodile Photo: Greg Calvert

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.

One of the migratory birds, the Torres Strait (Pied Imperial) pigeon Photo: Greg Calvert

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.

Contacts

Dr Greg Calvert
Consultant
ERISS
Tel: 08 8979 9789

Mobile: 0416 360 155

3 Melaleuca Close
JABIRU , NT 0886