Our Bushland Diary

Tuesday, February 8, 2011

the mammal that everyone forgets

When most people think of wild mammals around Perth, I suspect that kangaroos are high on the list.  We have possums, surely, and quenda (bandicoots).  There are chuditch, if you're lucky, and even some native rodents.  But what about our flying mammals?  The ones we tend to forget about because we never see them?

I'm talking about bats.  

This year, 2011, is the International Year of the Bat

 There are basically two types of bat - large ones called flying foxes or fruit bats, and small ones called insect bats or microbats.  (If you like your Greek roots and scientific words, they are megachiroptera and microchiroptera, respectively)  That's a rough guide - some of the small fruit bats are smaller than the large microbats!  A better way to tell them apart is how they navigate in the dark.  Fruit bats are visual; they use their very large and sensitive eyes to see where they are flying.  Sometimes this doesn't work too efficiently, and they become a tragic mess in powerlines or fences.  (We don't have fruit bats in Ellenbrook; it's too cold for them in winter, and we don't have the kinds of trees that they need for pollen and nectar.)

Microbats use a complex system similar to our human invention "sonar" - they make noises and listen to how their surroundings bounce and distort the soundwaves, to form a 3D image in their heads.  Microbats therefore have large scoopy ears and weirdly shaped outgrowths on their faces, to catch the reflected soundwaves.  In contrast, flying foxes have heads like little dogs.

Around Ellenbrook, we have a few species of microbats, including White-striped Bats (Tadarida australis).  These bats sleep in hollows or under loose bark in trees during the day, and emerge at sunset or later to hunt their favourite food; insects.  You might sometimes see them skimming around sporting ovals, grabbing the insects attracted to the lights, or flying around above the road surfaces like swallows just on dusk.  For an excellent photo of one - here.

White-striped Bats have been chosen as an "indicator species" for scientific study - an indicator of ecosystem health and changing night-time temperatures.  The presence of bats in your neighbourhood means that there are probably healthy insects living on healthy trees and shrubs.  For the White-striped Bat, it also means that the nights are cool enough for the bats to come out.  Usually, the sounds that microbats make are too high-pitched for human ears to pick up, but the White-striped Bat is different.  It makes a metallic "chink...chink....chink" which is in our aural range, so it's easy for people to hear, and the call is quite distinctive so it's not likely to be mistaken for much else.  So this bat is readily noticed by people who know what they are listening for.  

Scientists working with Climate Watch have been collecting observations about the White-striped Bat.  Their website - link here - gives you more info about this interesting bat, plus a recording of the call (in case you want to improve your bat observation skills!)

You can read about other kinds of bats on Wikipedia - link here.

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