Logging and lunaphobes
by Linda Vergnani

Miniscule "lunaphobic" beasts that emit sounds at a frequency so high they cannot be detected by the human ear are the subject of a long-term study funded by the Foundation for National Parks & Wildlife.

The Chocolate wattled bat Chalinolobus morio is aptly named for its chocolate-coloured fur and wattle (or lobe) near the corners of its mouth. It is 1 of 16 species of small insectivorous bats recorded in Biamanga National Park and Mumbulla State Forest. Photo: Dan Lunney, DEC

The small insectivorous bats constitute one-third of the mammals in the Mumbulla State Forest near Bega. Now zoologist Dan Lunney, a principal research scientist in the Department of Environment and Conservation (DEC), is about to complete a 21-year study of how logging is affecting these minute but critically important creatures.

This autumn, Dan and his colleague Alison Matthews will begin a year-long programme of attaching radio transmitters to around 25 to 30 bats of different species and sexes to find out where the creatures roost.

The area where they are doing the study is a like a chessboard of logged and undisturbed forest, according to Dan. The trees have been felled primarily for wood chipping and the remaining areas of indigenous forest will be logged soon.

Disappearing fauna

Dan has long been researching the impact of logging on native mammals ranging from koalas to gliders. "I've been working on bats since 1980. I work on forest mammals like koalas, possums, gliders, antechinuses, dunnarts, wombats and bats. I look at how logging, bush clearing, land development and fire make our native fauna disappear, vanish, vaporise." He also looks at factors that can help fauna recover.

He says the difficulty is trying to convey to people what is being lost and what can be done to save the fauna. While the public is concerned about large creatures like koalas and kangaroos, people usually need high technology to spot the insect eating bats which weigh between four and 30 grams and fit in the palm of a person's hand.

"The bats don't go out until it's dark and then they avoid the lights," says Dan. They spend their time seeking the shadows and if there is a full moon they fly far less or fly in the shadows. They are lunaphobes."

Injured microbats

This large old hollow-bearing tree provides a crucial roosting place for forest-dwelling bats. Photo: Dan Lunney, DEC

His early research showed that these microbats, as some people describe them, roosted in big trees in unlogged forest. At one stage during his 1983 survey in Mumbulla forest, a logging crew reported that dozens of tiny bats had flown away from the hollow branch of a white stringybark that split open when felled.

Other injured bats were found lying around the stringybark, one of the largest trees remaining in the forest. Among the injured bats were 15 Chocolate Wattled Bats (Chalinoloblus morio), some of which had young, and seven greater broad-nosed bats.

In the 1983 survey, Dan and his colleagues found the insectivorous bats were flying through and being caught in logged areas but were roosting in big trees in unlogged forest.

Last year Dan and Alison repeated part of the 1983 study, trapping 210 microbats with harp traps in logged and unlogged areas of Mumbulla. In addition they counted bats by recording and analysing the bats' sonar signals on the new Anabat digital system.

Devised by Australian researcher Chris Corben, the Anabat detector records the frequencies of bat calls. The microbats use sonar signals, which are beyond the range of human hearing, for navigation and hunting insects. The signals are emitted from the microbat's nose or mouth and bounce off their prey and the surrounding vegetation. Through this echolocation the bats can detect exactly where their insect meal is situated.

Counting fly pasts

Geoff Ross of the DEC radiotracked the bats with Dan Lunney in the early 1980s. Results showed for the first time that bats can fly long distances between foraging areas and their roosts. The presence of bats in logged forests is therefore no evidence that these modified areas provide for all the bats' habitat needs. Photo: Dan Lunney, DEC

Each species of microbat has a different frequency pattern. The Anabat digital recorder switches on only when the bats call. Using this method the researchers counted 6,500 overpasses of bats. Chris Corben took part in the survey, fine-tuning his system to better detect the sonar calls and identify which species were flying past.

The next phase of the survey, which has been allocated $11,000 of Foundation funding, involves putting radio transmitters on a group of bats and tracking where they roost. Dan says unlike in the 1980s, when the first study was done, radio transmitters are now so tiny that they can be fitted on even the smallest bats weighing just four grams.

On the basis of their findings Dan and his colleagues intend to get a long-term picture of the impact of logging on the little lunaphobes and to make recommendation for conserving the microbats.

Dan says: "About one third of the forest in the region has been transferred to national parks. What people have to be concerned about are the bats and other creatures that live in the two-thirds of forests that remain to be logged. The real question at Mumbulla is what will happen when they log every remaining forest, resulting in wide areas of young regrowth with few old trees."

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