Using microbat roosting boxes to manage mozzies
Tuesday, 27 October 2015
The mosquito season is about to begin. I'm one of those fortunate people that mosquitoes don’t like the taste of. My husband isn't so lucky. A husband bothered by mozzies isn't much fun – so I'm preparing our natural mosquito control arsenal.
Mosquito coils aren't part of our mozzie control kit.
Smoke from mosquito coils contains carcinogens and fine particles that can damage your lungs.
Studies investigating the harmful components of mosquito coil smoke suggest that sitting in a closed room with a burning mosquito coil is equivalent to smoking anywhere from 51 to 137 cigarettes.
Popping a mosquito coil by your table while enjoying a barbecue is as hazardous as having a chain smoker sit at your table.
Thankfully there’s a less toxic way to reduce mosquito numbers – tiny, cute microbats.
In contrast to their larger fruit-eating cousins (flying foxes or fruit bats), microbats eat only insects.
They have a voracious appetite.
One microbat can eat thousands of mosquitoes in a night.
The benefit of microbats doesn’t stop at mosquito control – they also eat many garden pests including moths, beetles, aphids, weevils and crickets.
You can encourage microbats by providing them with roosting habitat.
Most microbats roost in trees – in cracks, fissures, hollows and under bark.
Trees with cavities suitable for microbat roosts are typically old or dead.
If you have an old hollow-bearing tree in your neighbourhood consider yourself fortunate because it’s likely to house any one of Australia’s 80 species of microbats.
The trouble is, old or dead trees are often removed from residential areas for safety and aesthetic reasons.
Combine targeted tree removal with large-scale clearing of native vegetation, and microbats are running out of places to roost.
Thankfully, many microbats don’t mind living in artificial roost boxes.
We've made one roost box so far and plan to make many more.
It’s a good idea to install multiple boxes because microbats prefer to move between multiple roosts to confuse predators.
If you want to specifically encourage mosquito-eating microbats (rather than larger microbats that eat larger insects like moths), you need to ensure the entrance to your microbat box is no more than 12 millimetres wide.
Microbats prefer entrances that are only just big enough for them to squeeze through – larger entrances are also likely to let predators inside.
Different-sized entrances will attract different species. The smaller microbat species are more likely to feed on mosquitoes – whereas larger species feed on larger insects like moths.
Microbat roost boxes are relatively easy to make for someone with a little woodworking experience.
I share how we made our microbat box over on the Milkwood blog.
They can also be purchased. But a word of caution – some commercially available bat boxes are simply ornamental and are not suitable as microbat roosts. Typical faults include being too small, not being made of durable timber or hardware, and having entrances that are too large. I share links to a few suitable commercially available microbat boxes in the Milkwood article.
There are three things that can potentially undo all your good work encouraging microbats: pesticides, electric insect buzzers and cats.
Pesticides and electric insect buzzers don’t just kill annoying mosquitoes or garden pests – they also kill beneficial insects and leave microbats with little to eat.
Microbats are easy prey for household cats. They are stationary during the day and in winter they can go into torpor (like mini-hibernation). Even those cats that owners claim "could never catch a thing" can easily catch a microbat in torpor. Keeping your cat inside night and day, or in an outdoor cat run, will help protect microbats and other wildlife.
More information on microbats and building a microbat box.
Originally published in the Newcastle Herald Monday 26th October 2015.