The caves at Naracoorte provide a very important habitat for the
Bent-wing Bat (Miniopterus schreibersii bassanii). One cave in
particular provides the largest of just two known breeding sites for the
Southern Bentwing Bat, the other being in Western Victoria.
Each year in early spring (around September), thousands of pregnant
females return from their wintering caves across south-eastern Australia
to the ‘Bat Cave’. In early summer, the female gives birth to a single
offspring called a pup, although there are records of twins being born.
The pups are born without fur clinging to their mother for the first few
hours before being placed in an aven (domes in the cave roof) that
serves as a nursery.
With temperatures of over 30°C, the ‘maternity’
chamber provides the perfect environment for the nursery. The heat is
generated mostly by composting bat guano and the bats’ own body heat.
The pups are able to fly at about five weeks old, practising their
flying inside the cave for several weeks before flying outside to feed
the season change and it becomes cool, the bats fly back to their
wintering caves where they spend most of the time in torpor. Although other
species of bats have been recorded in the area and in the caves, most are
Bat Cave Teleview Centre
• At Naracoorte Caves there is an innovative viewing centre from where
it is possible to view the bats’ daily activities via television
monitors. Currently there are five infra-red cameras installed in the
Bat Cave, relaying images back to the Bat Cave Teleview Centre, allowing researchers and park
visitors to see just what goes on inside the cave. This world-first
technology has allowed visitors to witness bats giving birth, feeding
their young and the tiny pups develop from a tiny furless ‘jellybean’ to
a adult-size flying bat.
• The Bat Cave has a diverse ecosystem of invertebrates living on and in
the huge deposits of guano. Over forty species have been identified
including several that are endemic to Naracoorte. One of these species
is the Pseudoscorpion Pseudochelifer naracoortensis, a minute
predator of other cave dwelling invertebrates.
Around many of the cave
entrances, Cave Crickets (or wetas) Novatettix naracoortensis can
be seen. These small insects hide in the twilight zone of a cave and
only leave at night to feed on rotting vegetation.
Naracoorte Caves NP © N Birks
Cave crickets © Naracoorte Caves NP
Naracoorte Caves NP © K Sanderson
Bent Wing Bats (Miniopterus schreibersii bassanii)
- Insect eating bats and can eat up to ½
their body weight per night.
- Bent-wing bats weigh 12-15g, therefore could eat 7-8g per night.
- Some bats give birth to twins, but bent-wing bats only have one
baby per year, although there have been recorded instances of
bent-wing bats with twins. They are usually born in late
- Bent-wing bats have developed a very clever strategy of breeding
to ensure the baby bats are strong enough to survive their first
winter. The bats mate in May, before they go into torpor. There is a
delayed implantation of the embryo. The embryo is then dormant for
several weeks. It only stats to develop when the bats begin feeding
from September onwards. By doing this it allows the baby bat maximum
time to grow and store enough body fat to survive the first winter.
- The bat cave temperature rises to above 30°C
at the roof. The cave is heated mainly through the guano piles
composting. Minor temperature fluctuations maybe due to the bats body
heat and the very thin roof of the cave which may allow some solar
heating but also a means for heat to escape.
- The caves bats use for seeing out the winter are cold as this
helps the bats slow down their metabolism and lapse into torpor. The
bats generally congregate in torpor in the twilight zone of the cave.
This is generally the coolest part of the cave and also it is possible
that they use this
part of the cave so they can see the weather outside. If it were
raining outside the bat would not have to warm its body up to flying
temperature hence wasting energy to go out and have a look.
Waking up out of torpor involves a large expenditure of energy.
The bat actually burns its fat reserves to warm up its body. This is
visible as while this is happening the bat shakes and this gives the
appearance of being nervous. The bats can’t fly without warming their
body up and if
disturbed can drop from the roof.
- Blanche cave can go down to as low as 9°C
- Albino bat recorded in the cave in 1999
- The dates that the pups have been first seen in the four years the
cameras have been in:
- 1995 Dec 12
- 1996 Dec13
- 1997 Dec 14
- 1998 Dec 3
For the first few days of life the baby bats cling to their
mother, even while she is flying around the cave. After a few days the
pups are placed in the nursery, which then allows the mother to leave
the cave to feed.
- Pups born with large feet which allow them to hang on.
- Bent-wing bats are fast fliers – not as manoeuvrable as some. Eg.
Small forest bats are “gleaners” and feed in and around trees, while
bent-wing bats generally feed over open water or across the top of the
- Their feet have locking tendons which is why they don’t fall from
the roof when they are asleep and even after they die hanging on to
- Bent-wing bats can fly 50 km+ per hour.
- They can fly up to 50 km away from the cave at night – at
Naracoorte there is plenty of food close by eg. Bool Lagoon so they
may not venture such large distances.
- They can travel up to 200 km to wintering caves.
Dangers for the bats:
- Summer - Owls, Disturbance by humans
- Winter - Disturbance (Woken out of torpor), Winter caves (Fill in,
Gated – can’t get in, Used for dairy effluent)
- Benefits – eat insects that are pests to agriculture.
- Insect eating bats find their way around using echolocation. This
is a series or high pitched sounds emitted by the bat which ‘bounce’
off objects. The bat hears the sound back as an echo. They collect
echo via elaborate ears and they distinguish whether the object is
food, a wall or a potential predator.
- Bent-wing bats have been reported at greater that 30 years old
through a banding program.
- Commonly have ectoparasites (Bat flies which are conspicuous by
their orange colour).
- Egg for fertilisation always from the left ovum.
- Reach sexual maturity in 2nd year of life.
Other bat species in the region are: