Flying-foxes - frequently asked questions
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The following general information about bats is provided by the Ku-ring-gai Bat Conservation Society Inc. in New South Wales
Genreal questions
Microbats
Megabats
General questions
What is a bat?
A bat is flying mammal – the only flying mammal. It is not a bird.
How many different types of bats are there?
There are about 930 species of bats in the world belonging to the Order Chiroptera (which means ‘hand winged’). These can be divided into 2 suborders:
- The Megabats (Megachiroptera) of which there are about 170 species. These larger bats feed on nectar, pollen and fruit.
- Microbats (Microchiroptera) of which there are about 760 species. These smaller bats are usually insect-eating, carnivorous bats.
Do bats have a pouch?
No, bats do not have a pouch. Only marsupial mammals have a pouch. Bats are eutherian (placental) mammals; their babies are born fully developed and are nourished on their mother’s milk – just like humans.
What is special about a bat’s wing?
The wings of bats are made of two thin layers of almost hairless, soft, strong, elastic skin which stretches between very elongated finger bones and joins the side of the body from the arm to the ankle. In microbats the membrane extends between the legs and includes the tail. These wings contain blood vessels and nerves. They stretch easily for flight yet contract when not in use. Different bat species have different wing shapes depending on where and how they catch their food.
How long have bats existed?
The oldest fossil bats known in the world are microbat fossils. Fossil teeth found at Murgon, Queensland, Australia, dated to 55 million years Hall L and Richards G (2000) Flying Foxes, Fruit and Blossom Bats of Australia, University of New South Wales Press.
Some bat fossils are so well preserved that remains of insects and other small animals that they had eaten can be seen inside the body. The rich Australian fossil beds at Riversleigh in north-west Queensland contain many microbat fossils up to 25 million years old.
Megabat fossils have been found in Thailand, Italy, Africa and New Guinea, but have not yet been found in Australia.
Why do bats feed at night?
By 100 million years ago, a great diversity of flowering plants became the most common vegetation on earth (according to studies of fossil plants and their pollen). Insects became abundant. By the time the first bats evolved there were already large numbers of birds feeding on fruit, nectar and insects during the day. Scientists think that bats evolved from small, nocturnal mammals to feed on night flying insects - therefore avoiding competition with birds that are active during the day. Megabats may have evolved from different ancestors to feed on night-flowering, nectar-producing plants.
How big are bats?
Bats vary in weight from a few grams for the smallest bats to the largest flying-foxes which weigh over one kilogram. The smallest bat species have a wingspan of about 20 millimetres while the largest reach almost 2 metres.
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Why do bats hang upside-down?
Bats hang by their feet with their head down because it is energy efficient. No energy is required to hang compared with defying gravity and standing upright. In order to reduce as much weight as possible for flight, the bones and muscles of the legs are very light weight compared with those of a non-flying mammal of comparable size. The biggest bones and muscles are those used for flying.
Can bats swim?
Yes, they row themselves with their wings. Bats do not go swimming by choice.
Are bats blind?
No. All bats have eyes and can see.
Do bats spread disease?
Like all other animals including humans, bats can be hosts to viruses and parasites.
Australian Bat Lyssavirus (ABL): This is a rabies-like virus that has been identified in flying-foxes and micro-bats. Infection of humans is extremely rare (only two cases ever documented in Australia). Research so far indicates that less than 1 % of wild flying-foxes carry the virus. This virus is transmitted by a bite or scratch from an infected bat. If bitten or scratched by a bat, wash the wound with water and contact your nearest Health Authority.
Health authorities state that people living near flying-foxes are not at risk provided they do not handle bats. People such as vets, researchers, educators or carers who handle bats should be vaccinated against ABL.
Hendra Virus: Some species of flying-fox can be infected with Hendra Virus (previously Equine Morbilli Virus). This disease has only ever been transmitted to people from infected horses. There is no evidence to show that bats can transmit this virus to humans.
Histoplasmosis: a respiratory illness, may be contracted by breathing in the fungal spores found in some bird and bat cave roosts, where there is high humidity and these organisms breed in the guano (droppings). Avoid breathing dust in caves where micro-bats or swifts roost.
Microbats (sub-order Microchiroptera)
Bats from this group are found on all continents across the world except Antarctica. In Australia there are many species of microbats ranging from the carnivorous ghost bat, the largest, weighing up to 150 grams, to tiny forest bats weighing 3 grams.
Why are microbats important?
Microbats are important because they eat vast numbers of insects thus contributing to the control of insect populations in the natural environment. This is important to modern society because they also control many insect pests of crops and insects that spread disease such as malaria.
What do microbats eat?
Each species eats different sized food including mice, frogs, other bats, small birds, fish, large grasshoppers, moths, caterpillars, beetles, bugs, spiders, scorpions, cockroaches, flies, ants, mosquitoes, termites and gnats.
On the American continents there are microbat species which also feed on fruit, flowers and blood.
What sounds do microbats make?
Microbats are able to find their way in the dark and catch their food using echolocation. High frequency sound pulses made in the larynx (voicebox) are emitted either through the nose or mouth. Echoes of these sounds reflected back to the bat’s ears allow it to know the position, relative distance and character of objects in its environment. The echo-location sounds are nearly all above the hearing range of people. Microbats use other sounds for communication particularly in the roost.
Where do microbats go in the daytime?
Some microbat species live in caves in large colonies. Other species roost in hollows in trees, under bark, in small holes in logs or fence posts, in birds nests, under bridges, in the roofs or walls of buildings. Radio-tracking of individual microbats has shown that they use a number of different roosts in an areas. Microbats rarely move about in daylight.
Where do microbats go during the night?
They go hunting for food. Most catch prey in flight but a few species hunt on all fours for ground living invertebrates.
What do microbats do in the winter?
In winter there are few insects about so microbats, in cold climates (e.g. southern Australia), save energy by hibernating. They roost in a cold sheltered place, and are able to drop their body temperature close to that of their surroundings and slow their heart rate. Disturbance of hibernating bats can cause them to return to operating temperature. This uses up fat reserves, which they need to survive until there are enough insects to feed on. Disturbance of hibernating bats can cause them to die. Microbats can also use torpor which is similar to hibernation, but used only for a few hours or days to conserve energy when food is scarce.
When and where do microbats have their babies?
Microbat babies are born in the Spring/Summer when days are warm and food is plentiful. Most species give birth to one young per year. Newborn microbats are not furred and their eyes are closed at first. By 6-8 weeks, they are fully developed and able to fly and feed with adults.
Some species give birth in maternity caves where the shape of the cave roof traps the body heat of the adults so that the unfurred young are able to survive when the mothers leave them to feed at night. Some maternity caves are known to contain hundreds of thousands of bats. Other species form maternity colonies in the hollows of big old trees or in buildings. Mother microbats, which roost in tree hollows, carry their babies from one hollow to another. This behaviour may be to avoid predators or it might be to avoid a build up of parasites, or both.
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Megabats (sub-order Megachiroptera)
Megabats are large bats that navigate by sight and smell and feed on plant products. They can be found in Africa, the Middle East, Southern Asia, Australia and many islands.
In Australia there are 12 megabat species. These include flying-foxes, tube-nosed fruit bats and blossom bats. Of the 8 species of flying-fox there are four widespread species occurring on the mainland of Australia. These are the Black, the Spectacled, the Grey-headed and the Little Red Flying-foxes.
The first three of these have similar habits and lifestyle but are found in different parts of Australia, their ranges overlapping in part. The Little Red Flying-fox is smaller and gives birth at a different time to the others and tends to follow the flowering of the eucalypts inland, moving to the coast irregularly.
Is a flying-fox a bat?
Yes. Flying-foxes are sometimes called fruit bats but many of them eat parts of plants other than fruit, especially pollen and nectar.
What do flying-foxes do at night?
Flying-foxes leave their camp soon after sunset to feed during the night, even in rainy weather. They return to camp before sunrise.
What do flying-foxes eat?
Their main source of food is nectar and pollen from the flowers of native trees, such as the many species of eucalyptus, as well as turpentines, paperbarks, banksias.
They also eat fruit from many rainforest plants, such as figs and lilly pilly. They chew the fruit to extract the juice and spit out the fibre and drop the big seeds. They swallow the juice and some small seeds up to 4 mm in diameter. They also chew leaves of plants such as mangroves and figs. At times they feed on fruit and flowers of plants brought into Australia from other parts of the world.
Why are flying-foxes important?
They move pollen and seeds over vast areas of forest.
The pollen is carried on their fur between flowering trees which can be many kilometres apart. Many Australian trees, especially eucalypts, need pollen from another tree of the same species to make fertile seed. Rainforest seeds are carried away from parent trees which gives them a chance to germinate and grow.
Flying-foxes are essential in maintaining many ecosystems because they are able to move pollen and seeds over long distances and across cleared ground, thus linking patches of native vegetation.
Birds and insects don’t fly the long distances needed. The clearing of native vegetation in the last two centuries has removed much of it and has left the remainder scattered in isolated patches.
How long do Grey-headed flying-foxes take to digest their food? Why is this important?
Flying-foxes have a very short intestine and absorb their mostly liquid diet very rapidly. Average time from mouth to anus (doing a poo) is about 20 minutes although some material takes up to an hour. This is important for seed dispersal because the small seeds contained in the faeces (poo) fall and germinate in new areas leading to new trees and vines.
How fast do flying-foxes fly?
Grey-headed Flying-foxes fly about 25 -30 km per hour. Some were observed in a wind tunnel where their average flight speed for distance travelling was recorded as 7m per second (25 km/hr). In the wind tunnel test a grey-headed flying-fox maintained a speed of 26 km/hr for 4 hours. Carpenter R E (1985) Flight physiology of flying foxes, Pteropus poliocephalus Journal of Experimental Biology, 114 pp 619 - 47.
Flying-foxes also use the wind to travel long distances and have been recorded at speeds of 50 km per hour. Nelson J and Tidemann C Satellite tracking of flying-foxes, Monash University website
How far do flying-foxes fly in one night?
The majority of flying-foxes feed during the night within a radius of 30 km from their camp, however, when feeding on blossom may travel up to 100 km during the night. Some feed in the same place on successive nights. This information was obtained by radio-tracking individual flying-foxes. Eby P (1995) The biology and management of flying foxes in NSW Species management report No 18, NSW National Parks and Wildlife Service
How well do flying-foxes see?
Flying-foxes see very well during the day and much better than humans at night. They have relatively large eyes in the front of their skull. Their acute eye-sight enables them to navigate accurately and to find food at night. Many of their food plants have white blossom making them easy to see when flying above the trees at night. In daylight they are also able to fly and land on branches within the camp and use sight during social interactions in bright sunlight.
How important is smell to a flying-fox?
Flying-foxes use their excellent sense of smell to locate nectar and ripe fruit.
What do flying-foxes do in the daytime?
Flying-foxes are social animals. They roost together in the tops of trees. During the day they spend some time sleeping, often hanging by one foot, with their wings wrapped around their body. They also spend many hours grooming themselves, squabbling noisily and fanning themselves when hot. Females care for their young.
The area they occupy is called a camp or a colony. A camp may contain a few hundred to tens of thousands of flying-foxes. Sometimes the camp is empty if food is not available nearby. Most of these camps have been in use for more than 100 years.
What predators do flying-foxes have?
Predators known to eat flying-foxes include carpet pythons, goannas, sea-eagles and the Powerful Owl. Currawongs and ravens are known to attack flying-foxes found on their own in the daytime.
These predators do not significantly reduce the overall flying-fox population. The most likely victims are the young, the sick or old. The numbers taken are small relative to the flying-fox population. Predators contribute to the health of a population by removing the least fit individuals.
Humans and their technology are responsible for more flying-fox deaths than natural predators – removing habitat by clearing native vegetation, shooting, electrocutions on power lines.
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What sounds do flying-foxes make?
Flying-foxes are social animals and make a wide range of calls. These include contact calls, chirps and squabbles, searching calls by mother flying-foxes seeking their young when returning to the colony, and a range of mating and warning calls.
At night feeding flying-foxes are often heard in flowering or fruiting trees as they compete for food.
Australian flying-foxes do not echo-locate; that is, they do not use sound to locate or navigate.
What do flying-foxes hear?
Flying-foxes have a simple external ear, unlike the complex ears of micro-bats. The part of the brain which controls hearing is small in flying-foxes compared to that in micro-bats. This suggests that hearing is of minor importance to flying-foxes compared with other senses.
How do flying-foxes recognise each other?
They recognise each other by sight and smell.
Flying-foxes have scent glands on their shoulders. This scent is spread over their body while grooming. They sniff each other during social interactions. Males rub their scent glands onto tree branches in the colony to mark a territory. Mothers recognise their young by their calls and by their smell.
How far do flying-foxes move during the year?
Flying-fox numbers in a camp increase and decrease throughout the year, depending on the availability of food. The flowering of many species occurs irregularly in different areas and different times of the year, governed mainly by variations in weather.
Radio-tracking of Grey-headed flying-foxes found that in 1990 one moved from Grafton to feed on the flowers of spotted gum near Narooma - about 800 km south and another flew from Lismore to Bundaberg in Queensland, about 400 km to feed on lemon-scented gum. Hand-reared juvenile flying-foxes were tracked between Gordon, Sydney Botanic Gardens and Cabramatta Creek and some found 310 km north and 279 km south in April and May. Augee M and Ford D (1999) Radio-tracking Studies of Grey-headed Flying-foxes, Pteropus poliocephalus, from the Gordon Colony, Sydney.
A minimum distance of 978 km was recorded when one was marked on the thumb by a numbered band and released in Lismore on 31/8/91 and was reported electrocuted at Bombala on 12/2/92. By tracking a few individual flying-foxes by satellite it has been found that individuals travel great distances, for example, one moved from Melbourne to Mallacoota then north along the coast, stopping at Ulladulla and Jamberoo, then to Sydney, where it moved between several more camps.
How long do flying-foxes live?
Little is known about what age the majority of flying-foxes reach in the wild. Records of banded flying-foxes indicate that some live for up-to 12 years in the wild. The oldest captive educational Grey-headed flying-fox, cared for by Ku-ring-gai Bat Conservation Society, was born in 1978 and died of old age in 2000 - aged 22. Several others have lived to a similar age in captivity.
Natural disasters such as the high temperatures, over 40C, and low humidity which occurred in Sydney in January 2002, killed thousands of flying-foxes of all ages.
How do flying-foxes keep clean?
Flying-foxes groom their fur frequently with their claws and lick their wings. They urinate on themselves to wash and in the summer they urinate on themselves, then fan their wings to cool down.
Do flying-foxes have parasites?
Like all mammals bats are hosts to tiny parasites that live much of their life cycle on the animal. Bat flies are wingless flies, only a few millimetres long, which are adapted to avoid being groomed out of the fur by the bat or blown off during flight. They feed on the bat’s blood. They are species specific and cannot live on other mammals such as humans.
Flying-foxes also have internal parasites which have adapted to live in the flying-fox population without causing undue illness in their hosts except during times of food shortage. One is a worm (Toxocara pteropodis), which is transferred with the milk from mother to young and from young to adult through faeces on branches. Again this organism cannot live in humans.
Occasionally flying-foxes are hosts to ticks and mites. In Queensland a number of Spectacled Flying-foxes die each year from tick poisoning.
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Do flying-foxes drink?
Yes. They swoop down to belly-dip in rivers and dams. They then land on trees and lick the water from their belly fur. They also lick dew from leaves.
Where do they get protein?
Pollen is the major source of protein, much of it licked from its fur while the flying-fox is grooming. Protein is used to build muscle tissue. Pollen grains break open in the gut so that the contents are absorbed. Some native fruits such as figs are also a source of valuable protein.
Where do flying-foxes get carbohydrate?
Nectar and fruit juice provide the carbohydrates – sugars. These provide energy. Some species of eucalypts, especially bloodwoods (Corymbia spp) are known to produce most of their nectar at night.
How many teeth does a flying-fox have?
34
Their dental formula:
When and where do flying-foxes give birth?
After becoming pregnant in Autumn (March-April), they give birth in Spring (mainly October-November). This is a gestation period of about 6 months. They give birth in the tree tops, usually in the colony.
How many babies do they have?
One baby is born to each female. The baby is born furred and with its eyes open. It weighs about 80 grams at birth although birth weight varies according to the availability of food for the mother during her pregnancy.
How do flying-fox mothers care for their young?
The female has two nipples, one on either side of her chest beneath the wingpit. As soon as the baby is born it begins to suckle. Its milk teeth curve backwards so that it can keep a firm hold. She protects her baby with her wings during the daytime. At night when she flies to search for food the baby holds onto its mother, with its mouth around the nipple and with its claws in her fur. The baby is not able to maintain its own body temperature until it is 15 - 17 days old so for about a month is carried by the mother while she feeds at night. The young are then left in the camp during the night and the mother returns to it before sunrise. Young flying-foxes gradually increase their flying skills until by 12 weeks of age they explore the local area around the camp, then increase the distance beyond until they are flying out with the adults to feed. Some are seen still suckling in the daytime in the mating season.
When do flying-foxes mate?
Mating occurs between March and May. Males mark a territory in a tree and defend it from other males during the summer and autumn. They are joined by females, many with young. Males guard several females in their harem. Harems are generally unstable groupings, with the females moving, at will, to other males.
Do they mate for life?
Observations indicate that flying-foxes do not form lifelong relationships. Eby P and Jones V (2002) A bloke in every port: group composition and gender bias in the migration patterns of grey-headed flying foxes Pteropus poliocephalus, Abstracts, 10th Australasian Bat Society Conference, 2002.
Is it true that flying-foxes are primates?
The theory that flying-foxes are related to lemurs, lorises, monkeys, apes and man (primates) was proposed by Dr Pettigrew at University of Queensland based on studies of the brain and nerves to the eye. The structure of the brain is more like the primates than the microbats. He has proposed that the megabats and microbats evolved from different ancestors and that the structure of the wings of these two groups of bats has evolved independently (known as convergent evolution).
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