The Foundation for National Parks & Wildlife is urgently seeking funds to study the impact of logging on native wildlife following the next round of logging in the South East Forests in 2008.

The past two decades have seen great changes to logging practices in Australia, and while modern day prescriptions are more sympathetic to wildlife, there is still concern for the impact of logging on the habitat of many forest-dwelling animals.

The South East Forests of NSW have been at the centre of a long-standing debate between forestry and conservationists, with the Foundation funding research into the matter to gather the facts for the development of more sustainable practices.

To monitor the success of the new logging prescriptions, studies should be undertaken immediately after logging and build on previous surveys.

For over twenty years scientists from the Department of Environment and Conservation (DEC) have studied the impact of logging on forest-dwelling bats. Two protected species, Gould’s long-eared bat – Nyctophilus gouldi and the Little forest bat – Vespadelus vulturnus were the focus of this study in the Mumbulla State Forest near Bega.

The outcome of this important research reveals that specific logging prescriptions are required to ensure the survival of these forest-dwelling bats. This is due to the bats’ highly selective criteria for roosting sites; preferring the complex characteristics of old, large growth trees (many of them hundreds of years old) with open cavities and decaying matter, to the twenty-five year old eucalypt regrowth in the same area.

Scientists go where bats go
Starting in 1983 members of the Biodiversity Conservation Science Section of the DEC headed by Dan Lunney, glued radio transmitters onto the back of the small Gould’s long-eared bats. This study was a first; successfully undertaking a previously impossible task of investigating roosting and foraging habits of bats. Now twenty-three years on giant advances in technology have enabled the group to fit transmitters weighing less than five hundred milligrams, onto Little forest bats. Quite an achievement; at four and a half grams these little critters are one of the smallest bats in the world!

Size and age do matter
As part of the research, tree characteristics (age, size, type, condition, presence of hollows, loose bark) and environmental elements (aspect, topography, logging history) from roosting sites were compared with the range of trees present in the study area.

In the 1980s Gould’s long-eared bats showed clear preferences in tree selection for roosts. The study was recently repeated to determine any consistencies in roosting behaviour, and to see if the bats’ selection criteria had expanded to include the regrowth.

The comparison of this repeated study and the first study of the Little forest bats have shown that:
• Both species are highly selective, preferring large trees (50cm diameter minimum) with hollows located on south or east facing slopes.
• Maternity roosts, occupied by female Gould’s long-eared bats and their young, are similar to many chosen by males. However, the males were found to also roost under dead wattle bark.
• The Little forest bats prefer dead Stringybark trees, while Gould’s long-eared bats prefer live trees of species other than Stringybark.

While the roosting preferences of bats are complex, varying from species and sex, their dependence on cavities in dead and decaying large growth trees is consistent. No evidence to date has been found of tree dependent bats, roosting in eucalypt regrowth.

Tuning commercialism towards nature
Although forest management practices have improved and are more sympathetic to wildlife, the outcomes of this study show further improvement is required to conserve forest-dwelling bat habitat. It is also clear a better understanding of the highly specific habitat requirements of forest bats is needed.

To monitor the success of the new logging prescriptions, studies should be undertaken immediately after the next round of logging in 2008. It is important the study repeat the work of the Gould’s long-eared and Little forest bat and include other species of micro-chiropteran bats (of which there are sixteen in the study area). The impact of fire, drought and climate change also needs to be considered.

This study of forest-dwelling bats proves that size does matter and that their habitat of old forest giant trees needs to be intelligently managed. These tiny critters have their unique role in maintaining the complex ecosystems of our forests – as do all creatures great and small.

The research team from DEC is indebted to the Foundation for National Parks and Wildlife for its support of this project.