ACKMA 1973 - 2007

A spare (?) Saturday morning and Kent's deadline already passed - sudden panic when the sailing date for Antarctica is brought forward by a week and nowhere near everything on the list even thought about - and away from where I need to be to do it all - what does one do? One sits down and writes an ANDYSEZ, naturally. But on what?

Yesterday I visited the "Bats" special exhibition at the Australian Museum in Sydney which is well worth a look if you are in town (exhibition runs until 13 February) - but it is not quite as good as I thought it was going to be. However, the things for sale in the Museum shop are very comprehensively batty - but the bat tie (for only $69.95) was hideous! This, the exhibition, not the ties, provided an idea.

The diversity of vertebrate fauna in Australasian caves is not particularly high. Certainly, there is a wide range of amphibians, reptiles, birds and mammals that opportunistically use caves, normally in the twilight or near twilight zone. Some may survive happily and may show loss of pigmentation and apparent reduction in the ability to see. However, only two groups appear to be obligate users - teleost fish and microbats.

Australia has only two troglobitic vertebrates. Both of these are from Cape Range and have been known for a number of decades. For an easily accessible account of these species see Knott (1993). The first is the blind gudgeon, Milyeringa veritas Whitely, 1945, which is relatively abundant in the groundwaters of the coastal plain around Cape Range. It is completely eyeless and grows to about 4.5 cm. Little is known about its biology. Its affinities are puzzling but it does have near relatives from Madagascar. I have a very poor photograph of these fish in an open hole reaching down about 50 cm to the watertable! One doesn't expect to see troglobites in broad sunshine - but this is Western Australia, after all.

The second species is an eyeless swamp eel, Ophisternon candidum (Mees, 1962). This is much rarer than M. veritas and is not commonly seen. It grows too as much as 40 cm. It has troglobitic relatives in Mexico and Yucatan and from India.

There are about 90 species of bats in Australia - thirteen of which are the megachiroptera - fruit bats or flying foxes - that don't use caves so we don't have to worry about them! It should be noted that some of the megachiroptereans are smaller than the largest microchiroptera. Of the other 75 approximately, around 25 use caves. Not all of these are obligate cave users.

Bat diversity, like so much else, is higher in the tropical north decreasing as we go south until there are no cave-using bats in Tasmania. There is a story that, many years ago, members of the Tasmanian Caverneering Club found a bat in a cave and subsequently took it outside for its own good! There are more than twenty cave-using bats across the north of Australia, perhaps ten in New South Wales and probably no more than three in Victoria.

Although bats form more than half of Australia's mammalian fauna, their cryptic habits, small size and mobility - plus a variety of taxonomic problems - means that their life cycles, dietary and roost preferences are not well known - which explains the woolly numbers above.

Of NSW's ten, only six are obligate cave users - I visited a cave near Cooktown a few years ago which had nine species in the one cave! Very exciting - especially as one of them was the ghost bat, Macroderma gigas.

As is often the case I have to apologise to our colleagues across the Tasman - I know very little about New Zealand bats - and I have no literature available to dip into. Before the Polynesians introduced Rattus exulans (about 1200 years ago?) bats were the only mammals in New Zealand seals, whales etc excepted. I know that there is at least one species of cave-roosting bat in the North Island. According to the museum exhibition, one of the South Island bats has specially adapted teeth which it bores through trees making tunnels up to 100 metres long - although there can't be much tree left with that much tunnel?

Having now written-off the three major offshore islands - and not knowing anything about Norfolk - I can talk with authority about cave-dwelling bats on Lord Howe Island. A decade or so ago the late Jerry van Tets collected a fresh-looking skull of a bat from a small cave. It was subsequently described as Nyctophilus howensis. No further evidence of this bat has been found and there are no other Nyctophilus species on the Island - it has been pronounced as officially extinct in the new Bat Action Plan produced by Environment Australia.