The microbats are the least known of our mammals.  Along with the Flying Foxes they make up the 'flying mammals'.  There is a lot of diversity in this group and you will see some of them at night flying across the landscape.  The flying foxes are large and slow moving as they head out from their roosting sites to feed.  The microbats are smaller and usually faster and much less easy to see.  If you are near a roosting site, including many of the drains in a place like Darwin you will often see the microbats heading out to feed as darkness falls.