The Bat – Creepy Symbol of Halloween

One day, after our caves reopen, you may find yourself enjoying a fascinating cave tour, when out of the corner of your eye, you detect a flicker of movement, high up in the shadowy limestone formations. You as soon as you look, it’s gone.  Microbats flit so fast that by the time your brain registers the movement, the tiny creature has vanished. 

 

We don't often talk about our bats. They are not cute and cuddly-looking. People are often frightened them, and the  poor little things are so ugly, no wonder they are associated with Halloween.  But although they look creepy, bats help the environment.  

 

Believe it or not, this week, October 24 to 31, is International Bat Week, to highlight how important bats are to our planet.  Worldwide, there are more than 1,400 species of bats—that’s almost 20 percent of all mammal species. Bats live almost everywhere on Earth except the most extreme desert and polar regions. Bats are amazing animals that are vital to the health of our environment and economy. Although we may not always see them, bats are hard at work all around the world each night. A single bat can eat up to its body weight in insects each night. This helps protect our crops from insect pests. Also, bats provide vital services by pollinating plants and dispersing seeds.

 

The main type of bat that you might spot on a Jenolan cave tour is the Eastern Bent-wing, a species of microbat. Each microbat weighs only 13 to 17 grams. Their little bodies are around 10 cm long but their wingspan can be up to 30 to 31cm. They have chocolate to reddish-brown fur on their backs and lighter coloured on their bellies.  Their long third finger folds back, creating a distinctive bent wing appearance. They can fly up to 50km per hour. A Eastern bentwing bat can live up to 30 years. To catch small insects mid-air, they use sight. Also, they produce sound waves at frequencies above human hearing, called ultrasound. The sound waves emitted by bats bounce off objects in their environment. Then, the sounds return to the bats' ears, which are finely tuned to recognize their own unique calls. This is called echolocation.  Eastern Bent-wing Bats are found along the east coast of Australia, in colonies of up to 150,000. 

 

Each spring, the female Eastern Bent-wing bats return to the same breeding cave, called the ‘maternity cave’, where they give birth to a single young. When the female bats leave to hunt for insects at night, the infant bats are left together in ‘maternity camps’. When choosing maternity caves, the bats have very specific temperature and humidity requirements. There are very few maternity caves in the whole of NSW. 

 

Then the bats go elsewhere to roost. They might choose caves, mines, or even man-made structures.  Jenolan is an important roosting site. Thousands upon thousands of bats reside in the myriad of limestone caves and overhangs. Throughout the reserve, thousands of eastern bentwing-bats use the caves for shelter, and the contribution Jenolan makes to conserving this species is significant. While not ‘endangered’, the Eastern Bent-wing Bat is considered ‘vulnerable’. The disturbance of a single roost cave could mean the displacement of upward of 1000 bats.

 

In a survey by NSW National Parks and Wildlife in 2011, 16 species of bat were found in the Jenolan Karst Conservation Reserve.  Of those species, 5 are on the ‘threatened’ species list.  Most of those bat species were found in the area around the caves, while the Eastern Bent-wing Bat inhabits the caves themselves.

 

We do not really know if bat populations at Jenolan have declined since tourism started.  The caves system is so enormous, with hundreds of entrances, and the public enter only a few of the caves that have been discovered at Jenolan.  But we never disturb main bat roosting sites and we are careful to not block doorways to caves. We always use gates, rather than doors, so that bats can fly in and out easily and the natural air flow in the caves is not hindered.

 

Inside at least one of Jenolan’s most famous caves, there is evidence that a massive bat roost once existed, where bats lived in ancient times, for thousands, perhaps millions, of years. Ross Pogson, mineralogist from the Australian Museum has theorised that below this huge, ancient roost was a pool of water that gradually filled with dung and bones from the bats above it, to create what is now a huge mineral deposit, rich in phosphates, which you can see if you tour the Chifley Cave, when it reopens. 

 

Today, Jenolan’s microbats are a very important part of our cave fauna.  Their guano is vital for the cave ecosystem because microscopic lifeforms live in and feed on bat guano.