Everything You Wanted to Know About Foxes That Fly
Love them or loathe them?
- Nicola Markus
- Jul 01, 2001
WHENEVER I am asked how I got involved with flying foxes, I vividly remember that first encounter: Grade Eight, fourth period (biology), just before lunch.
Unexpectedly, our teacher had interrupted the class's usual routine and asked us all to come forward to meet a visitor. An odd-looking woman had walked into the room. She appeared slightly disabled by a dark, furry growth that was attached to her left shoulder. It dangled almost down to her waist. Before any of us were able to distinguish the exact nature of this appendage, the woman reached up to detach it from her shoulder. To our amazement, it had a doglike face with a shiny nose, twitching ears and large brown eyes - attached to a furry, leathery body.
The reactions of my classmates ranged from fascination to terror, but the woman assured us that we were quite safe. I was already utterly mesmerized when she asked me to hold out my arm. Before I could consider the consequences, the furry object relaxed its foothold, opened its black-velvet wings and launched itself into the air. Amid the screaming, laughing and diving for cover that promptly took place around me, a flying fox connected with my arm.
My fascination with these intelligent, lively and very appealing fruit bats has continued to this day. After completing a degree in zoology and psychology, I set out to explore the nature of flying foxes firsthand, eventually pursuing a Ph.D. to study their ecology and behavior in an urban section of Australia.
For all their appeal to people like me, however, flying foxes have a poor public image and are still met with the same range of reactions as those exhibited by my grade-school classmates. The following tidbits, gleaned from my study of these bats in Australia and the people who react to them, provide some sense of the awe, fear, reverence and disrespect afforded to these amazing creatures.
1. Is It a Bird?
Flying foxes are nocturnal, arboreal forest dwellers that roost during the day by hanging upside down from high branches. They are highly social, winged mammals and generally live in colonies ranging in size from a few hundred to a few hundred thousand individuals.
2. Sorting Out Species
Bats can be divided into two main groups: the microbats (generally small, insect eaters that navigate and forage by echolocation) and the megabats (larger, fruit and nectar feeders that navigate by vision). Flying foxes belong to the megabats.
There are about 60 species of flying foxes worldwide. These occur in the warm tropical and subtropical climates of countries such as Madagascar, India, New Guinea, Malaysia and Australia.
All flying foxes are fruit bats, but not all fruit bats are flying foxes. Fruit bats comprise all bat species that consume fruit in their diet, including some microbats. The term "flying fox" refers to members of the group of large fruit bats belonging to the genus Pteropus.
3. Aussie Flying Foxes
Australia is home to four species of flying fox on the mainland and a further three on the surrounding islands of Boigu, Moa and Christmas. The mainland species are the spectacled, the little red, the gray-headed and the black. The distribution of each species depends on its specific dietary preferences. The predominantly fruit-eating spectacled flying foxes have the smallest distribution along the coast of Australia's northern tip, while the nectar- and pollen-preferring little red flying foxes migrate throughout the northern and eastern parts of the country. In general, flying foxes have a largely coastal distribution that overlaps the areas of highest rainfall and thus the most reliable sources of fruit and nectar from native eucalypts and rain forests.
4. Survival Under Threat
Flying foxes face serious challenges to their survival due to the rapid demise of their forest habitats. With native foods in short supply, the bats search for alternative foods in fruit orchards and suburbs, thus increasing their encounters with people. Overhunting, culling and starvation are among the biggest threats worldwide. Shooting, electrocution and poisoning at orchards are also problems. The burning of entire flying fox camps, as the animals' roosting aggregations are called, was once a popular management practice. In Australia, two of the four main species (gray-headed and spectacled) are in such dire straits that active protection is of serious concern to conservationists. Evening skies that once turned dark for more than 30 minutes due to the graceful exodus of flying foxes from their roosting trees is now a memory of the past.
5. No Place Like Home
In selecting roosting sites, flying foxes look for places with tall vegetation, proximity to freshwater streams and protection from temperature extremes. Once established, these camps may be used over many decades. In Australia, some current camps were recorded as far back as the late 1800s. When a camp is cleared for agriculture or development, the bats disperse into smaller camps in the local area. More often than not, these new locations are considerably less convenient and more disruptive to local human residents than the previous site.
6. Social Niceties
To an untrained onlooker, a noisy flying fox camp might appear to be composed of an assortment of motley misfits. The reality is that each colony is a well-ordered establishment marked by relationships among individual bats. Each bat occupies a space on a branch to which it returns daily. Neighbors recognize each other by scent; unfamiliar visitors are greeted with a harsh snarl and a hooking thumb claw.
7. Rank and Height
Social groupings in camps are indicated by roosting associations in the trees. Small groups roosting together may consist of male-female pairs, males with several females (harems) or single individuals - often younger, sexually immature animals. Outside of the mating season, some sections of the camp contain mostly males. Others consist predominantly of females, with or without young. While there is no single dominant animal in a colony, rank is indicated by height: Higher-ranking individuals within a social group roost higher in the branches than those of lower rank.
8. Sharing Their Space
Where distributions overlap, a camp site may be shared by two or three flying fox species at a time. Each has a designated area within the camp. Gray-headed flying foxes often occupy the central section while blacks prefer taller trees along the edges. However, both species disperse temporarily following the arrival of little red flying foxes, several hundred thousand of which may swoop into camp overnight to feed on locally flowering blossoms.
9. Foraging Habits
Using their excellent eyesight in low light for navigation, flying foxes forage at night. Individual animals regularly return to the same trees and bushes to feed over subsequent nights and even weeks until all fruit or nectar has been consumed. Many revisit old foraging sites over numerous seasons. In between feeding bouts, some flying foxes like to roost in other potential food trees nearby that are not currently in season. In this way, they are able to monitor the flowering and fruiting status of a number of trees and shrubs in a given area and can move smoothly from an expiring food source to an emerging one.
10. Winging It
With a wingspan of three feet or more, flying foxes are the largest mammals capable of sustained flight. Remarkably, though, bat wings have the same bone structure as human hands. Central to the outstretched wing is the wrist from which long and delicate bones provide the frame that supports the flexible membrane. Only the thumb is free of the membrane and is mainly used for grooming and climbing. In addition, simultaneous use of both thumbs to grasp a branch allows the inversion of the bat from its usual upside-down position to a head-up, feet-down position to toilet.
11. Foresters in Flight
Australia's native forests rely on flying foxes to aid in the dispersal of seeds and in the pollination of many types of trees. Although birds, insects and mammals - such as possums and gliders - fulfill a similar role on a smaller scale, the combination of two characteristics is unique to the bats: They forage at night and their size enables them to disperse larger fruit and more pollen over greater distances. The combination of these abilities is vital in supporting the genetic health of fragmented forest patches.
12. Holes in the Wings
The delicate membrane of the wing is easily injured. To aid in healing, flying fox wings have an excellent blood supply throughout their leathery skin. Small holes caused by rough landings, occasional territorial altercations or bullets heal quickly and leave only a small scar. Injuries along the edge of the membrane, however, are often permanent and may impair the bat's ability to fly.
13. Tongues and Diet
As fruit and nectar feeders, flying foxes survive on a seasonal diet of nectar, pollen and fruits, which are occasionally supplemented by leaves and insects. While some species utilize all of the above, others are specialists. The degree and type of dietary specialization is reflected in the structure of a flying fox's tongue. Species with a preference for nectar (little reds) have narrower tongues with brushlike tips to extract nectar from the flowers of native eucalypts, Grevilleas and bottlebrushes. Species that also consume native rain-forest fruits, such as lilly-pillies and figs, have wider, more muscular tongues to help pulp the fruit.
14. Time to Go Courting
The flying foxes' mating season marks their noisiest and most social time of year. For three Australian species, this period takes place in February and March; little reds mate six months later. Courtship is a loud and exhausting affair that happens at camp during the day. After establishing a territory by scent marking branches around one or more females, the males woo their chosen partners with screaming and extensive foreplay that consists of licking of the genital area. Matings commence pre-dawn and often occur in waves throughout the day as the mating screams of a few of the males trigger courtship among others.
15. Calcium and Survival
Flying foxes reproduce slowly. A female carries a single pup for six months. To ensure the healthy development of the fetus, the mother resorbs calcium from her already delicate bones into her blood and passes it on to her growing offspring via the placenta. Once the pup is born, she cares for and nurses it until its independence at about four months. After birth, the calcium supply is delivered via the mother's milk. A shortage of food for the female during gestation or while she is nursing may lead to the abortion of the young or to its early death due to malnutrition.
16. Trials of Birthing
From about two years of age, a female flying fox is sexually mature and gives birth once a year. Birthing takes place in the treetops of the camp or at a foraging site. During labor, the female takes great care not to accidentally drop her pup to the ground. Immediately after delivery, she cradles it with her wings and guides it to her teats, in the wing pits. Additional insurance is provided by delayed expulsion of the afterbirth, which allows the pup to remain secured to its mother by the umbilical cord for up to an hour after birth. If dropped to the ground, a pup cannot be recovered and faces certain death within hours from starvation, dehydration or predation.
17. Conquering the Skies
The relatively large size of a flying fox requires it to develop strong flight muscles before it can take to the air. From the first week of life, pups practice wild flapping - also known as static flight - while firmly clinging to a branch with their feet. They are able to cover short distances between branches at about 10 weeks. At 14 weeks or so, they are strong enough to accompany Mum on her nightly foraging trips.
18. Hanging On
One explanation for why flying foxes hang by their feet: As an adaptation to minimize overall weight for flight, they've evolved reduced leg muscles. Hanging is also made easier by strongly curved foot claws and ratchet tendons that naturally lock the feet in a hooked position until they are released by the horizontal body positioning that leads up to flight. This explains why flying foxes continue to hang even after they die: To let go of a branch, a flying fox has to actively release its grip by straightening its body and unhooking its feet.
19. Coping With Heat
Despite roosting in direct sunlight, flying foxes are not immune to heat stress. In Australia, temperatures in excess of 104 degrees F trigger a number of active coping strategies. These include moving into the lower branches of trees for shelter, licking of the wings, flying to pass cool breezes over the blood vessels of the wings and open-mouthed panting. Little red flying foxes, the smallest and at around 17.5 ounces the lightest of the Australian species, even immerse themselves briefly in streams of fresh water before flying to a nearby tree to lick their bodies dry. Black flying foxes are most prone to heat stress; sudden heat waves can result in the death of many hundreds in one colony in just one or two days.
20. Soaking Up Rays
For an animal living in humid, tropical conditions, sunlight and copious bouts of grooming are necessary to stay dry and to prevent bacterial accumulations on the skin and between the joints. Flying foxes often roost with their wings wide open to soak up the early-morning sun. A lack of sunlight on the wing membranes can cause a slimy fungal infection that may lead to permanent lesions in the skin.
21. Scent Marking
Male flying foxes have scent glands located above their shoulder blades. Musk produced by these glands is rubbed along branches and leaves to mark out individual territories during the mating season. In addition, males will "bathe" in strongly musk-scented urine throughout the year to assert their identity. Scent recognition of familiar individuals - such as neighbors and relatives - reduces aggression in the colony.
22. Wild Enemies
In addition to human foes, Australian flying foxes must contend with a number of natural predators, including pythons, wedge-tailed eagles and powerful owls. These predators target their prey either at the roost or while the bats are in flight. In northern Australia, the flying foxes' habit of cruising low and open-mouthed over a river or stream to drink exposes them to another lurking hazard: crocodiles. Unlucky flying foxes are nabbed in mid-flight, providing fast food for the crocs.
23. Ratlike Flying Pests?
In the minds of many Australians, the word "bat" still conjures up images of bloodthirsty, cave-dwelling vampires that emerge at night to spread terror and disease. This idea is based on the incorrect interpretations of early naturalists who attributed perceived behaviors of vampire bats in South America to that of bats in other countries. Even today, many Australians combine a natural apprehension of the unfamiliar with their dislike of any animal that threatens fruit crops. They also vastly exaggerate the fear of bat-carried diseases. Such traditional prejudices are difficult to change, and, like sharks and crocodiles, flying foxes suffer as a result of them.
24. False Folklore
A famous old wives' tale (still heard today) insists that flying foxes have no anus and excrete waste through their mouths. This unsavory and incorrect idea has its origins in observations of the fruit-eating habits of the bats. After thoroughly chewing a piece of fruit such as a fig and extracting all of its juices, a flying fox tilts its head to the side and ejects - or spits out - the remaining pulp as a tightly compacted pellet. Flying foxes use only the high-energy, liquid parts of their diet and are unable to digest the fibrous skins and seeds of all but the smallest of figs.
25. Disease Carriers?
Since 1996, three diseases have been discovered in populations of flying foxes: Hendra virus, Menangle virus and Australian Bat Lyssavirus (ABL). They may affect horses, pigs and humans, respectively, and Hendra may also be transmitted to people via contact with infected horses. ABL, a virus similar to rabies, can be transmitted directly from bats to people via a scratch or bite. The administration of the standard rabies vaccine, either as a prevention or following a scratch or a bite but prior to the development of disease symptoms, safely prevents the development of the disease. The only human death caused by a flying-fox-transmitted disease (ABL) occurred in an unvaccinated woman who was bitten by a wild flying fox in 1996.
26. Food for Thought
In countries around the world, flying foxes are culturally significant to many traditional human inhabitants, who sometimes eat them. In Australia, apart from enjoying the flavor, native Aboriginal inhabitants claim a medicinal benefit from eating flying foxes: the treatment of respiratory problems such as asthma. In some countries, cultural uses have come at a high cost: On the South Pacific island of Guam, populations of the local flying foxes have been eaten to near extinction. Similar hunting pressures also threaten flying foxes in many other countries, including Malaysia, Indonesia and Madagascar.
27. Political Pawns
People's fears, often fanned by anti-bat hysteria in the media about the danger of contracting bat-carried diseases, have made bats political pawns. The animals often come up on the short end, thanks to squabbles over property development, for instance. During one election campaign in rural New South Wales, the removal of a historical flying fox camp in a patch of rain forest adjacent to a school became a key election campaign issue. Health risks to school children were proclaimed the main concern. The site is now earmarked for development. The school later revealed its true motive: to extend its campus into the immediate vicinity of the bat colony.
28. Chasing Blossoms
Flying foxes that prefer nectar to fruit must migrate seasonally to follow the irregular flowering flushes of native eucalypt and paperbark trees. In Australia, migrating little red flying foxes may cover a couple of thousand miles per year and individual gray-headeds have been found to travel up to 435 miles in one direction. Losses from land-clearing of more than two-thirds of native forests in some parts of the country have significantly reduced the bats' food options and left large gaps in their seasonal menu. In the absence of native foods, many must compromise by seeking out commercial fruit orchards in the summer to avoid starvation.
29. Assaults on Orchards
During seasons of drought and shortages of native fruits and blossoms, damage to fruit orchards by desperate flying foxes can be substantial. Growers of stone fruit, bananas and lychees suffer most.
To protect their crops, orchardists employ a long list of bat-deterrent strategies. The more benign of these include strong odors such as kerosene (put in buckets), shots fired randomly into the air, bright lights reflected through the trees and a range of loud noises.
Although most fruit growers initially report some success after introducing new scaring techniques, the hoped-for outcomes rarely last longer than a few days. Once the bats realize the absence of any real threat, the deterrents can even backfire, becoming beacons that herald the presence of food to the hungry hordes.
One fruit grower told me that he had seen a bat hanging from a flashing strobe light, apparently waiting for the arrival of the rest of his colony. Only orchards protected with cover-all netting effectively exclude bats, as well as birds and hail.
30. Shrinking Camp Sites
An abundance of forest once meant that flying fox camps were able to shift slowly in a dunelike fashion within a given area, enabling trees to recover foliage damaged by the roosting bats. Today, the small size of remaining forest patches restricts or prevents the local movement of permanently roosting bat colonies. Result: Some trees may be irreparably damaged and die. This problem is particularly obvious in camps used by little red flying foxes, which roost in tight, heavy clusters and place considerable strain on leaves and branches.
31. City Slickers
Along Australia's east coast, flying fox camps are becoming increasingly common in cities and suburbs. In some areas, this is due to the expansion of human development into the bats' traditional roosting areas, while in others it is the bats' own choice. As natural forests decrease, shrubs and trees in irrigated suburban yards and green spaces provide more reliable food supplies than patchy forest remnants that are frequently subject to drought. Nevertheless, even in suburban Brisbane, more than 2,500 flying foxes were found dead or aborted during September of 2000 when no trees or shrubs flowered for several weeks due to drought conditions. This number is likely to be just a fraction of the actual deaths.
32. Nosy Scientists
Studying flying mammals is difficult - so a lot remains unknown about our winged cousins. Scientists have learned important ecological information through radio-tracking studies and have helped to determine foraging patterns - including flight distances, food types and fidelity to specific feeding sites - of each species. Details of the social behavior of flying foxes, however, are still poorly understood.
33. Learning to Love Em
Despite their fearsome image, flying foxes have a unique knack for converting "battophobes" (fearers of bats) to "battophiles" (lovers of bats) in a very short time. Often, all it takes is a controlled encounter with a live bat through a wildlife guide or zookeeper and the horror spell is permanently broken. Part of the reason for this easy transition is the universal appeal of any cute and furry brown-eyed critter. More important, though, is the surprise at finding reality so different from the myth. Once bats are revealed to be neither scary nor slimy, bat phobia can be ticked off the list, and new converts, who can take great pride in having mastered their fears, can add a new dimension to their appreciation of nature.
Zoologist Nicola Markus recently completed her Ph.D. thesis at the University of Queensland on the black flying fox in Australia. Wildlife photographer Theo Allofs lives in the Yukon but has extensively photographed the unique fauna and flora throughout wild Australia.