CAVERNICOLOUS OF CAPE RANGE
Abstract
A look at the subterranean fauna of North West Cape and some of the factors affecting its continued existence. The purpose of this paper is to bring attention to the richness and diversity of the subterranean fauna of the North West Cape peninsula and to highlight the possible threats to its continued existence. For the purpose of simplicity the fauna has been divided in two components. The coastal plain community and the Cape Range community.
The coastal plain fauna is totally marine and contains the only known troglodytic vertebrates in Australia. The blind gudgeon Milyeringa veritas and the cave eel Ophisternan candidum. There are also two species of Atydid shrimps, Stygiocaris lancifera and Stygiocaris stylifera and a recently discovered unnamed amphipod. The Cape Range fauna is more diverse with one aquatic amphipod (unnamed), the arachnid Schizomus vinei, a highly adapted troglodytic millipede, a cockroach that has a few experts baffled and a number of other cave adapted species.
To date only one cave (C215) has been found which contains populations of both communities. That cave is on the west side of the range in the vicinity of the Milyering Complex.
In a paper presented to Dave Leeuwin 1991, Dr W.F. Humphreys of the W.A. Museum describes in greater detail the range of known fauna and discusses the climate of the cave environment in relation to that fauna.
In his paper, Humphreys points out that the Cape Range community only occurs in caves with a high relative humidity and a soil moisture content greater than 92%. If the cave dries out the fauna apparently moves into areas, possibly lower levels, inaccessible to cavers. It is logical therefore to assume that any action or activity which affects the long term climate of the cave or caves will also affect the cavernicolous existing within the system.
One system under possible threat is Cl63 (Wanderers Delight). This is the longest known cave in the Cape Range with some 4.3km of surveyed passage and new leads still unexplored. This cave contains populations of almost all the Cape Range community faunal types. It also contains several subterranean fresh water lakes although these may be all part of one water body.
Very little is known about the water table beneath the range or even in fact whether cavers have actually reached water table at all, but only elevated pools.
At present a limestone mining lease exists to the south east of Cl63, and extends to within 1500 metres of the known system. It is not inconceivable that quarrying may breach a water table, draining the system and destroying the fauna by permanently drying the cave.
Also, because of the flatness of the coastal plain and the low nature of the native vegetation any mining of the face of Cape Range will constitute an eyesore to anyone travelling along the Minilya - Exmouth road.
An even greater threat exists to the coastal plain community by way of the leaching of toxins from the Exmouth rubbish tip only a few hundred metres from C23 (Dozer Cave) and Cl05 (Gnamma Hole), a linked system containing blind fish eels and shrimp.
Added to this a proposed marina to the south east of the Exmouth townsite could result in the partial drainage of the ground water and its possible replenishment by sea water. This could also have affect on the town water supply which comes from bores to the west.
Efforts are being made to monitor and protect what is already known and to further our knowledge of the subterranean aspect of North West Cape. Advice and if possible assistance with this project would be greatly appreciated by the members of the Exmouth Cave Research Group.