CAPRICORN CAVES BATS
Bat Facts
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One quarter of all mammal species are bats. There are 930 species of bats in the world
belonging to the order chiroptera (meaning hand winged).
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There are two sub orders megabats of which there are 170 species and microbats of which
there are 760 species. In Australia there are 58 species of bats of which 12 are megabats.
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The oldest fossilised bat known in the world is a microbat dated at 55 million years ago. This
was found at Murgon, Queensland .
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Bats are the only mammals capable of sustained flight.
Distribution and hibernation
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Bats evolved in hot humid areas. Bats are small and their heat and water loss through their
wings is significant.
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Tropical non hibernating bats are limited to north of the Tropic of Capricorn .
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In cooler regions bats switching off their internal thermostat and allowing their body
temperature to drop to that of their surroundings. This is known as torpor and enables the
bats’ rate of energy consumption to be reduced and less heat lost to the environment. Cave
bats will assume a temporary state of torpor on a wet or cold night.
Why is a megabat not a micro bat?
Size
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Black flying fox weighs 500-700 gms whereas the little bent wing bat only weighs 7 gms
Diet
Micro bats are insectivorous with the ability to fly at high speed to catch flying insects. They
are considered to be natural pest controllers and beneficial to the environment.
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Mega bats are fruit and nectar eating. Long tongues enable them to access the nectar and assist with cross pollination of the flowers. They are also seed disperses due to their ability to eat
fruit and expel the seeds whilst flying. The native rain forests depend on seed dispersal from
flying foxes but their fruit diet also means they are unpopular with
orchard growers!
Vision
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Micro bats have small eyes but their sense of echolocation enables them to navigate at high
speeds through darkness. Echolocation is a high frequency sound pulse made in the voice box
that echoes back to the ear to determine relative distance, position and
character of objects.
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Mega bats have excellent nocturnal vision due to their large eyes. They do not have
echolocation.
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Habitat
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Microbats require 24 hours of darkness so caves provide the perfect habitat during daylight
hours. They have inbuilt time clocks and emerge from the darkness of the caves on sunset
and return on sunrise.
Megabats roost in camps in trees during the day time – sunlight is not a problem . But like
their smaller cousins they are nocturnal feeders.
Is a flying fox a bat?
All bats have evolved with the same bone structure in the wings. This can be
compared to that of the human hand – hence the term chiroptera meaning hand winged.
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All bats are mammals. They give birth to live babies, usually only one per season and feed the
babies milk from teats located under the wing.
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Bats are the only mammals that can fly. No bat can initiate flight from the ground. All bats
hang “upside down” and require elevation to launch into flight – fruit bats from the tree branch
and cave bats from the roof of the cavern.
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All bats feed at night .
Bat species at Capricorn Caves
Ghost bat
Horseshoe
Sheathtail
Little bent wing
Bats are beneficial
Microbats eat vast quantities of insects every night. These insects are considered pests
by the farmer . In Central Queensland 300,000 little bent wing bats eat half their body
weight each night. Some insects may also carry disease such as malaria.
Mega bats feed on nectar and pollen from flowering native trees such as eucalypts. This
spreads the pollen from tree to tree over long distances as bats fly at least 50k. They
also eat the native fruits from rainforest plants such as figs and lillypilly. They chew the
fruit, digest the juice and spit out the seed. This is all done in flight mode so they are
also significant seed distributors in native forests.
CAPRICORN CAVE MICROCHIROPTERA BAT SPECIES
Little bent-wing bats – Miniopterus australis Abundant
Distribution East coast of Qld and northern NSW
Weight 7-8 gms
Diet: Small insects beneath the canopy of well timbered habitats.
Bat Cleft Mt Etna is the largest maternity site with its high dome trapping heat to 37c
necessary for the survival of the naked pups left at night when their mothers forage for food .
Over 110,000 bats use this maternity site from December to February.
Common bent wing bats – Miniopterus shreibersii abundant
Similar characteristics to the little bent wing bats but larger weighing in at 13-17 gms.
Distribution extends further south along the Victorian coast so these bats hibernate in winter.
The bats have the capacity to delay implantation of the fertilised egg during winter
But the embryo develops at normal rate with the onset of warmer weather and an increase
in food supply.
Sheathtail-bat - Taphozous georgianus
Common
Distribution Northern Australia dependent on caves and mines with dim light
Weight 17-27 gms
Diet Insects caught in flight at intermediate heights above a variety of vegetation
Eastern horseshoe-bat – Rhinolophus megaphyllus Common
Distribution East coast of Australia in warm humid caves.
Weight 9-14 gm
Characteristic nose leaf shaped like a horseshoe directs the echolocation
pulses to detect prey on the ground or in the foliage. Flight is slow and
fluttery and low to the ground, enabling it to catch large slow insects.
The prey is caught in the mouth and taken to night roosts to be dismembered.
Ghost bat – Macroderma gigas Vulnerable
Distribution tropical regions of Australia and coast from Rockhampton to Cape York
Weight 74-144 gms Wing span 64-72 cms
The Ghost bat uses its nose leaf and large eyes to scan the area for prey.
Diet insects eg cockroaches, beetles, small birds, frogs, lizards, bats.
They return to a roost site to eat their prey. Australia’s only carnivorous bat.
Roost in colonies or individually and prefer a 27c temperatures.