Sunday, January 24, 2010

Grey-headed flying foxes

A colony of Grey-headed flying foxes moved into the Wolli Valley in the middle of 2007. It is thought they moved here when a plant they usually feed on in Queensland had failed to flower. Numbers grew gradually from the hundreds to a colony of over 5000 then suddenly, the next winter, they vanished when the temperatures dropped.

They returned for the next summer and this time the population grew rapidly. In no time the monthly count was regularly recording over 7000 bats. You'd think with so many around that they'd be easy to photograph, but no! The colony is situated in a triangle of land between Wolli Creek and the train line so you can't get very close.

The best time to see them is when they fly out at dusk, but that's not a very helpful time for photography. Unless you like silhouettes!

The trick is to attend the fly-out on a particularly hot day. The flying-foxes are keen for a cooling dip and a drink of water and tend to leave the colony before it gets dark.

It's still close to dark so the photos are quite grainy! After the flying-foxes dip in the water, they land in nearby trees to lick the water from their fur.

In the following profile shot you can see the wet fur along the belly of a freshly-dipped bat.

With thousands of bats needing a drink, the trees can become quite crowded.

Sometimes, an inexperienced bat will hit the water too hard and fall in! At least three bats fell in this night and the one below did right next to the kids and I. It then dogpaddled to the creek bank right next to us and scarpered up the tree to fly away.

The other two bats that fell in headed for the opposite side of the creek. It was tricky work getting through the weeds on the opposite bank and then there were no trees to climb. I'm guessing they need something of a high point to be able to resume flight. I saw them climb up some reeds and suppose they must have flown away from there.

Here's a video clip of the flying-foxes dipping into Wolli Creek before flying off into the night:

Video by Gavin Gatenby.