HABITAT Microbats make up one fifth of all Australian mammals, comprising over 60 species, in 6 families. Mostly roosting in colonies to maintain temperature and humidity, these endearing, but little understood animals roost in caves, mine shafts, tree hollows, cracks in rocks and fence posts, in the walls and roofs of old buildings, and sometimes even turn up in mailboxes. Microbats can be broadly divided into 'cave-dwelling' and 'tree-dwelling'.

NESTING Over 50 percent of Australia's Microbats are 'tree-dwelling', which means they, like many mammals, are very dependent on tree hollows. Breeding normally takes place in autumn to winter, (depending on the climate) mothers usually giving birth to one - sometimes two - babies, which are born around November to December, after a 12 week pregnancy.

After birth, the young 'pup' will attach itself, to a nipple in the wing pit, staying there until old enough to be left in crèche at the roost, with the other 'pups'. Here they remain warm and safe while the mothers are away feeding. On her return, the mother will call to her young which answers back. Young Microbats begin to fly from around 5 to 6 weeks of age.

NOTES Some Microbats are so small that a full grown adult can weigh as little as 3 grams. Feeding mostly on insects such as moths, beetles, and mosquitoes, a single Microbat can consume up to 40% of its own body weight per night - up to an incredible 500 insects per hour. As you can see, there is a distinct advantage to having a healthy population of these little critters around your house or farm.

MYTHS (1) Bats use sophisticated echolocation, and do not get tangled in your hair. (2) Although bats have very small eyes, they are not blind. (3) There are no Vampire bats in Australia.

Natural tree hollows form when fungus and termites eat out the dead centre of old trees. Most Eucalypt species do not form these hollows until they are at least 100 years old. Although there are vast tracts of native plantation timber (particularly on the East Coast), they are typically harvested at around 60 - 80 years old. So of course hollows do not form.

Since European settlement, literally millions of trees (and hollows) have been lost to urbanisation, industry, roads, and agriculture. As if that isn't bad enough, our struggling native animals have to compete with introduced Honey Bees and Common Mynas, which aggressively colonise hollows.

These factors have led to some pretty desperate little critters trying to live in somewhat 'B grade' accomodation. Some examples are: Sugar Gliders trying to live in the fronds of Banana trees, Feathertail Gliders turning up in the electricity boxes on top of power poles, Microbats trying to sleep in mailboxes, and our seldom seen little Antechinus' trying to raise their babies in sock drawers, and even kitchen stoves.

Far from ideal... Many of these animals of course turn up in care.

(2) BENEFITS OF NESTBOXES

Although we cannot possibly hope to replace the countless natural hollows lost in the bush, our towns, cities, and farms were once forest. As a result, there is an awful lot of displaced wildlife competing for an ever decreasing amount of this prized real estate. This is where we can all really make a difference; in our suburban gardens, and rural properties.

A single well placed nestbox which survives say 10 years, can see a pair of Rosellas raise 10 generations of chicks. A slightly different box could provide a secure home to 6 adult Sugar Gliders. Different shape again could provide a luxury home to that 'trouble-some' Possum in your roof. Whilst yet another shape provides five star accomodation for up to 50 Microbats. And, when you consider that a single Microbat can consume one half it's own weight in insects a night. That's an awful lot less crawlies in your veggie patch. And, they provide this service completely free.

Nestboxes also provide priceless education for your children. Watching wildlife on TV is wonderful, but there is something very special about watching native animals coming and going, feeding, and raising their young so close to your home. If you've ever seen a Mountain Brushtail Possum looking out of her box at dusk, Pink nose resting on front paws - you'll know what I mean.

I grew up in the UK. One year my Grandfather decided to put up a nestbox in a pine tree in our garden. Next Spring a pair of Blue Tits moved in, and every year without fail, we used to watch from the comfort (and warmth) of the dining room, as that pair of birds raised 4 - 5 babies. From just 3 metres away, we'd watch the parents feeding the fledgelings every few minutes, and seemingly just days later, watch the youngsters take their first tentative flights. What's more, the box only took 10 minutes to put up.

Nestboxes are fun, easy and cheap to make, and once up will provide a secure home for many years to come.

A word of caution: If you own a cat, putting up nestboxes which attract birds & mammals to your garden, is a recipe for disaster...

(3) CONSTRUCTION

Below is a plan for the construction of a roosting box suitable for most Australian Microbats. Materials used, and notes are below the plan. Please note that all sizes marked are for EXTERNAL DIMENSIONS.

The best materials for construction are either; 3 cm thick plantation pine (hardwood is a product of native forest), or structural pine plywood. There is of course no need to use expensive dressed timber. Rough sawn or even second hand timber is ideal. Just make sure if using second hand, that it is free of nails, and any unknown paint.

Your box is best screwed and glued, rather than nailed together, and may be finished off with filler in any gaps. The roof can either be hinged conventionally, or simply make an outside hinge out of a piece of old rubber, which also helps to make it weatherproof.

A couple off offcuts on the inside of the roof to prevent slippage, and (unless you roughen the wood), shadecloth stapled to all inner surfaces will allow the residents to grip securely.

Microbat roostboxes are best left with a rough finish to allow them to crawl about the outside to investigate.

(4) INSTALLATION

So you're now the proud owner of a new Microbat roostbox. Where to place it?

Choose your position carefully. Make sure that the box will have plenty of shade during the hottest part of the day (ie; foliage cover), but not where it will be in full shade all day either. Clear and trim a few branches in the immediate vicinity of the box/es to allow an uninterupted flight path, leaving branches above the box/es for shade.

Better still - make 3 boxes, and place them at the same height on 3 different sides of a tree. Bats will actually move from one to the other if one box becomes too hot or cold.

Hang from the chosen tree by a piece of wire threaded through a scrap piece of garden hose (so that it doesn't cut into the tree), or alternatively, nailed to the tree using 2 strips of galvanised steel. The strips need only go halfway round the tree to allow for growth, and to prevent ringbarking.

FOR MICROBATS, you need to position the box 3 - 5 metres above the ground.

OK. So your new roostbox is in place, and you're sitting back with a beer, or a cup of tea waiting for the homeless critters to move into their new home. Don't be dissapointed or surprised if no one takes up residence immediately. It can sometimes take weeks, or even months, for someone to show some interest. There are many reasons for this:

The box is 'too new', unfamiliar. It looks and smells new and out of place. Give it time to 'weather in'. To become part of the local landscape.

Most birds for instance, nest in the Spring. Birds don't normally live in nests, only requiring them for breeding. If your box went up in May, it may not be required until say October.

Mammals such as Possums do live in hollows all year round, but it's not until the parents actually kick the youngsters out of home, that junior will go in search of a new home.

Microbats are notoriously slow on the uptake. they may take 6 months to 3 years to discover there are new 'tree hollows' in the neighbourhood.

While you're waiting for the box to be occupied, please resist the temptation to keep looking inside. You don't know who's checking the box out when you're not looking, and constant disturbance will only discourage them. You'll know when the locals move in by watching, listening, and by looking for droppings underneath.

(5) MAINTENANCE

To finish off, just a few words on maintenance. Once a year, just have a quick look to see if any repairs need to be done, such as filling any gaps, a quick re-paint, or making sure the box is still securely fastened to the tree. Also, watch that the growing tree doesn't pull apart the fastening.

BIRDS: Some introduced birds such as Sparrows, Starlings, and Mynas have become a menace; driving native birds away, or even building their own nests on top of existing eggs or young. This of course should not be a problem with a batbox having its very narrow opening at the base.

BEES: The introduced honey bee has also become a serious problem in some areas. They will readily colonise tree hollows (real or artificial). If you have a problem with bees, look up bee keepers in your Yellow Pages.

If you've taken the time to build and place a box like this... Pat yourself on the back. YOU WILL have made a difference to YOUR local environment. Congratulations.

A FINAL WORD: Once your new box is occupied, please resist feeding. Feeding native wildlife is not a good idea. It fosters familiarity with humans and domestic animals. It encourages a dependency on an artificial food source, which will stop if you go on holiday, get sick, or move away. And lastly, your feeding routine is soon 'sussed out' by local cats and dogs. Animals are at their most vulnerable whilst feeding, and are particularly at risk when instead of feeding high up in the canopy, they are encouraged down to your level. You just don't know who is watching from the bushes. (This includes bird baths placed near cover). Please don't encourage your new residents to become 'cat-bait'.