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Western Australias oldest cave system, in Tunnel Creek National Park, is famous as a hideout used late last century by an Aboriginal leader known as Jandamarra. He was killed outside its entrance in 1897.
Tunnel Creek flows through a water worn tunnel beneath the limestone of the Napier Range, part of the 375 to 350 million-year-old Devonian Reef system. You can walk 750 metres through the tunnel to the other side of Napier Range, wading through several permanent pools and watching for bats and the stalactites that descend from the roof in many places.
The tunnel is up to 12 metres high and 15 metres wide in parts. Near the centre of the cave the roof has collapsed and is an excelent place to ovserve the colony of fruit bats. Take a torch, wear sneakers and be prepared to get wet and possibly cold.
Tunnel Creek was once known as the "cave of bats". At least five species of bat are known to use the cave. These include the Western Cave Bat, the common Bentwing bat and the rare Ghost Bat, Australias only carnivorous bat, which preys on frogs, lizards, small birds and mammals including other bats.
The Yellow-lipped Bat, found only in the Kimberley, has been little studied but apears to be a strict cave dweller. The Orange leaf-nose bat named for its golden fur prefers limestone caves which provide warmth and humidity to help maintain its body temperature when resting. Unlike other bats, Orange leaf-nosed bats do not huddle together to keep warm.
Many of these bats are particularly sensitive to disturbance. Ghost bats aand the orange leaf-nosed bat may abandon their refuges if too much artificial light penetrates the cave.
At times a colony of Little Red fruit bats roost where the roof of the tunnel has collapsed. During the day the tunnel provides a protected retreat. At dusk they leave en masse to seek out the blossoms of woodland trees.
Small Freshwater crocodiles are sometimes seen in the tunnel where they feed on small fish, cherabun (a vrustacean), frogs and insects. Rainbow fish, bony bream, spangled perch and fork-tailed catfish are found in the pools.
Birds such as the Black bittern and Nankeen Night Heron are sometimes seen just inside the mouth of the cave, looking for small fish and cherabun. Nankeen kestrels are often seen and heard flying about the cliffs at the entrance to the cave. Tunnel Creek is also home to many other bird species.
The limestone reef is made up of calcium carbonate, which is readily dissolved by rainwater seeping from the surface into the rock. Over many thousands of years, water flowing along cracks, joints and bedding surfaces dissolves the limestone away, opening them out to form caves. Cave systems have formed wherever the reef has been exposed at the Earths surface. This first occurred 250 million years ago, and the present system of active caves may have reused the same channels they created over the last 20 million years or so.
Tunnel Creek follows a prominent joint through the limestone. A old river valley on top of the range formed at a time when the climate was wetter, and the water table (the level to which rock beneath the surface is saturated with ground water) was higher. Erosion has since exhumed the reef, preserving the old river course.
The presence of underground pools along the floors of the cave is due to the water table being just below the present erosion surface. Water only flows through the cave after prolonged heavy rain during the wet season. During the dry season, water dripping from the roof of the caves and onto the floor precipitates calcite to form stalactites and stalagmites, or flows down the walls to form curtains of flowstones.
Things You Need To Know
Where is it?
Tunnel Creek National Park covers just 91 hectares. It is 112 kilometres from Fitzroy Crossing, 180 kilometres from Derby, 36 kilometres south-east of Windjana Gorge.
Two hours from Fitzroy Crossing and two and a half hours from Derby.
What to do
Cave exploration, sightseeing, walking and photography.
Tunnel Creek is a day use area with facilities limited to toilets and an information shelter. There is no camping and pets are not allowed. There are no rubbish bins so please take your rubbish with you.
The best season to visit is between May and September and the park is usually inaccessible during the wet season.
(Information supplied by Parks and Wildlife Services)