Micro bats: The insect terminators
Bats are the only group of mammals that are specifically adapted for flight. There are two types of bats: the micro bats and the mega bats. The micro bats (also known as insectivorous bats), are small to medium-sized bats, weighing from 3g to 150g, and with wingspans of around 25cm. The mega bats (also known as fruit bats) weigh up to a kilogram and some have wingspans over one metre. These two groups of mammals are thought to have evolved separately and are regarded as two distinct groups. The micro bats mostly eat insects, while one Australian species (the ghost bat) is also known to eat frogs, birds, lizards and other mammals—even other small bats.
How do they see in the dark?
Micro bats are nocturnal, and rely on echolocation and, to a lesser extent, eyesight, to find their way and locate insects at night.
Echolocation is a technique used by bats to ‘see’ their environment through sound. The bats create a pulse of high-pitched sounds, which are normally at frequencies beyond the range of human hearing. The sound waves are created in the bat's voice box, and are emitted from the mouth or the nostrils. The echo that comes back to the bat can tell it how far away the object is, as well as it's size and texture, and if it's moving! In this way they are able to sense their environment, avoid flying into objects, and find their prey. Using an 'ultrasonic bat detector' can help to identify the bat as well as tell us whether the bat is navigating or feeding.
Micro bats do make some sounds that humans can hear, but these are usually social chatter, alarm calls and communications between mothers and their young at the roost. There are a couple of species that have echolocation calls that people with sharp ears can hear; these are the yellow-bellied sheathtail bat and the white-striped freetail bat. Their calls are a regular a metallic-sounding tick….tick….tick….tick….
Micro bats rely on echolocation to find insects while flying quickly through the air. They do this with startling efficiency. Under controlled conditions a Myotis bat (a small insectivorous bat that lives near waterways) has been recorded capturing 1200 tiny fruit flies in one hour, one every three seconds, while navigating in the air.
Where do bats sleep?
Micro bats use an array of roost sites for sleeping during the day. The majority of micro bats roost in tree hollows or caves, although some sleep under bark or under dead fronds of tree ferns, or even in the discarded nests of some birds!
Some species will sleep in human structures such as in mines, tunnels, buildings, under bridges and in rooftops, especially if their natural roosts are in short supply in the area.
How fast do bats fly?
The speed a bat flies is determined by the shape of their wings, what they eat, and where they find their prey. The common bentwing-bat flies at a speed of up to 50km/h, similar to the speed of a car driving in city streets. Other bats have a slow, fluttery flight, and can almost hover. "Fast" bats usually feed high above the canopy where there's not much to bump into, whilst slower, more manoeuvrable species are found in cluttered environments, such as in rainforest.
How far do bats travel for food?
Species, such as Gould's wattled bat have been found to forage up to 15km away from their roost site, and the diadem leafnosed-bat will spend 1½-7½ hours foraging each night.
Most insectivorous bats concentrate on catching and eating their prey in the air, while flying. They may remain airborne for hours at a time. To catch insects that are not flying, some bats will use a special technique called 'gleaning' to pluck insects off leaves, branches or the ground. To ‘glean’ insects, the bats fly slowly, using echolocation to identify insects on leaves, branches or the ground. Some may even perch on branches or on the ground and listen (without echolocating) for the sounds of moving insects before attacking. The golden-tipped bat can even pluck spiders straight from their webs!
On some nights you may see micro bats flying around streetlights in order to catch the insects that are attracted to the light.
Why do bats hang upside down?
The body modifications that enable bats to fly mean that bats can no longer stand on their hind legs. They have a small pelvis, and their legs as well as arms are altered to form wings. However, bats also have special tendons in their feet that cling to objects, allowing them to hang upside down without any effort. This is the reason why you sometimes see bats hanging on ceilings or wires long after they have died. Some things, however, just need to be done right way up, and bats solve this problem by hanging from their thumbs when they give birth or go to the toilet.
Why are they declining in numbers?
Habitat loss and the disturbance of roost sites are the biggest reason for declining numbers in micro bats. Habitat loss, through the clearing of vegetation, inappropriate fire regimes and the invasion of weeds destroys feeding and roosting habitats. Some bats form large colonies, and disturbances at roost sites caused by the effects of tourism, mining activities, recreational caving and land clearing can have disastrous impacts on these colonies. This problem is more pronounced in bat species that have specialised requirements for maternity colonies (where females gather to give birth). Other bat populations have been affected when mines have been closed or collapsed, blocking access to the bats.
What species are threatened?
There are approximately 70 species of bats in Australia, with 43 species identified as being locally or nationally threatened. Thirty-five of these threatened species are micro bats.
The following is a distribution list of some of the species of micro bats found in Queensland.
Note: Species status as listed under the Nature Conservation Act 1992.
|Found from Cape York to Cooktown, sightings have also been noted as far south as Maryborough|
|The large form of this species has been recorded from the Broken River limestone north-west of Townsville to Iron Range on the eastern coast of Cape York Peninsula. The small form has been recorded from a restricted area from the McIlwraith Range to Iron Range on the east coast of Cape York Peninsula.|
Saccolaimus saccolaimus nudicluniatusEndangered
|Occurs in two distinct populations, one in coastal Queensland from around Townsville to near Coen, and another in the top end of the Northern Territory.|
Taphozous troughtoniLeast Concern
|Although it is listed as Least Concern this species is only known from three localaties near Mt Isa.|
|Occurs along a narrow coastal zone from Shoalwater Bay in Queensland up to the Torres Straight and on off-shore islands throughout this range.|
|Its national distribution extends into north-western Queensland, with colonies near Camooweal and at Lawn Hill Gorge. The distribution continues across the top of the Northern Territory to the Kimberley in Western Australia.|
|It is distributed throughout northern Australia, commonly above the tropic of Capricorn. Ghost Bats roots in caves, on overhangs, crevices and abandoned mines. Each population seems to have a maternity site.|
|Southern central Queensland, western New South Wales, and southern central South Australia.|
|This species occurs within the wet tropics, and from one site further north in the Iron Range, which may represent another species.|
|Distributed from the Coen region northwards to the tip of Cape York. Distribution extends to South-east Asia and Melanesia.|
|The only records in Queensland are from Mt. Isa. It also occurs in the Northern Territory and in the Western Kimberley region.|
Large-eared pied bat
|Spreading from central south-eastern Queensland to the ACT, this species roosts in caves, mines and disused nests of fairy martins.|
Little pied bat
Chalinolobus picatusLeast Concern
|From south-eastern Queensland to northern regions (Maryborough area) and across south-western Queensland, western New South Wales and north-eastern South Australia. Occurs in dry, open woodland forests.|
Kerivoula papuensisNear threatened
|This species occurs in a narrow band along the east coast from Cape York Peninsula to Bega in southern NSW and it appears to be patchily distributed within its range.|
Gould's wattled bat
Chalinolobus gouldiiLeast concern
|Abundant over most of Australia, this species roosts in tree hollows, rock crevices and buildings.|
Chocolate wattled bat
Chalinolobus morioLeast concern
|Found throughout eastern and southern Australia.|
Living with micro bats
Often bats are portrayed in a bad light, through movies and the media. However, this depiction is misguided. Micro bats are very small animals; the largest species only grow to a body length of approximately 11cm. They will keep to themselves in their roosts, some will stay still if approached, while others will try to crawl or fly away from you. They will not try to fly into your hair! Any disturbance of their roosts should be avoided. These bats eat insects, and they will not suck your blood. Australia does not have any species of vampire bats.
Catching diseases from bats is extremely unlikely. Australian Bat Lyssavirus (ABL) can only be caught from untreated bites or scratches from infected bats. One person has died from lyssavirus from a micro bat (there has also been a lyssavirus death from a fruit bat). At least three species of insectivorous micro bat can carry ABL, and all four common species of fruit bats can carry it. Members of the public should not handle bats.
Sick, injured or orphaned bats - what to do
If you find a sick, injured or orphaned insectivorous bat, do not touch it. Contact your local wildlife care organisation or the RSPCA Qld. They will put you in contact with a licensed and fully vaccinated wildlife rescuer who is trained to handle and care for wildlife. In North Queensland you will need to contact the local office of the department or the Queensland Parks and Wildlife Service.
If it relates to C3 bats (a bat that has bitten or scratched a person, or the person has had exposure to the bat’s saliva or neural tissue through their mucous membranes, e.g. eye, skin), contact the department.
If the bat shows signs of paralysis, or has come into contact with a dog or a cat, contact the nearest Department of Employment, Economic Development and Innovation office as they may wish to inspect the bat. If the bat is dead, use a shovel and/or tongs to remove it and then burn or bury it. Do not touch the bat without wearing gloves. If burying it, ensure that the hole is deep enough so that a dog could not dig it up.
What do you do if bitten or scratched by a bat?
- Do not scrub the wound.
- Wash the wound gently but thoroughly for at least five minutes with soap and water. Apply an antiseptic (e.g. povidone iodine or another iodine preparation or ethanol alcohol) and cover the wound.
- Contact your doctor or hospital immediately - they will arrange for the vaccinations that are necessary to protect you against ABL. These vaccinations should start as soon as possible after being bitten or scratched.
- It is possible to have the bat tested for ABL. The department/QPWS and Queensland Health will assist with the collection of the bat. If bat saliva gets into your eyes, nose, or mouth or into an open wound, flush thoroughly with water and seek medical advice immediately.
- Prompt treatment following a bite or a scratch is vital.