Megabats
Megabats include tube-nosed bats, blossom bats, and flying-foxes:
Flying-foxes (commonly called fruit bats) have the largest body size of all bats, weighing from 300 up to 1000 gms, with an average wingspan of up to one metre.
Four species of flying-fox are found on the Australian mainland. Their ranges and distribution vary across coastal regions, tropical and sub-tropical forests, and woodlands. The Little Red Flying-fox ranges further inland and is highly nomadic, flying 5,000km per year on average.
Black Flying-fox
Pteropus alecto
Grey-headed Flying-fox
Pteropus poliocephalus
Spectacled Flying-fox
Pteropus conspicillatus
Little Red Flying-fox
Pteropus scapulatus
Eastern Tube-nosed Bats
Nyctimene Robinsoni
Eastern tube-nosed bats range from northern NSW through to Cape York Peninsula. They feed on native rainforest fruits, particularly figs, and also nectar from eucalypt blossoms. They have solitary roosting habits and the ability to hover and turn in midair.
Eastern Blossom Bat
Synconycteris australis
The diminutive eastern blossom bat (weighing up to 20 gms) has a similar range to tube-nosed bats. Their preferred habitats are rainforests, wet eucalypt forests, and paperbark swamps. They feed on nectar and pollen from banksia, callistemon, paperbark, and eucalypt blossoms.
Megabats
Diet
Flying-foxes are Australia’s original FIFO workers, capable of commuting 50km (or more) every night using their excellent vision and keen sense of smell to navigate and find food. They seek the protein-rich pollen and energy-rich nectar of native blossoms, and rainforest fruits.
Blossoms from the Myrtaceae family (particularly eucalyptus, corymbia, melaleuca, syncarpia and angophora) are a major flying-fox food source. Black and grey-headed flying-foxes extract the nectar with their long muscular tongue which has taste buds located on the tip. Fleshy fruits such as native figs and lillipillies are chewed and squeezed against their hard palate to extract the juice, and fibrous remains are expelled (called a ‘spat’). Their shorter intestine enables rapid digestion, often within half an hour. This is thought to be an adaptation to keep flying-foxes light for flight. Little red flying-foxes, which are primarily nectarivorous, have a narrower tongue with taste buds located at the base.
Native eucalypts depend on cross-pollination by flying-foxes for maximum fruit-set and seed viability.
Flying-foxes visit flowers that are strongly scented and visible at night. Flowers are usually white or light-coloured and located on the tips of branches where flying-foxes can more easily see and access them.
With vast quantities of pollen clinging to their fur and the ability to transport it great distances, flying-foxes are more efficient pollinators than birds, bees, and other insects. In addition, seeds that flying-foxes have consumed can be expelled less than one hour later, by which time they may have flown many kilometers away.
Pioneer tree species from seeds carried by flying-foxes are the first to regenerate land which has been cleared or destroyed by events such as fire.
Trees such as Brush Box and Plunkett Mallee produce nectar that specifically attracts flying-foxes. Spotted Gum, Blackbutt, and Moreton Bay Ash have flowers that can only be fertilized at night.
A wide range of rainforest trees, corymbias, eucalypts, and native vines rely heavily on the pollination services of flying-foxes. The seeds of many species of rainforest trees will not germinate unless moved some distance from the parent tree, a service provided by flying-foxes and tube-nosed bats.
After completing their nightshift of seed-dispersing and pollinating, flying-foxes return to their campsites before dawn to spend their days grooming, socialising and sleeping.
Corymbia (bloodwoods) time their peak nectar production for around midnight.
Megabats
Habitat
Flying-foxes usually prefer to camp in close proximity to water sources, choosing tall trees with a dense understorey in wet and dry eucalypt forests, or paperbark swamps, mangroves, and casuarinas. Some camps are permanently occupied all year round, while others may be occupied for only a few months or until local food sources are depleted.
A symbiotic relationship exists between mangroves and flying-foxes. Research has found that mangrove plants growing underneath flying-fox roosts grew at nearly six times the normal rate. This was attributed to the nitrogen and other nutrients contained in the bat poo. In return, the mangroves provide the flying-foxes with shelter, roosting sites, and salty leaves to nibble on. Mangroves provide essential shelter and breeding habitat for fish and crustaceans, prevent erosion and stabilize shorelines.
Megabats
Survival Challenges
Flying-fox numbers have decreased dramatically in the last 50 years to the point where the national listing of the grey-headed flying-fox is Vulnerable, and the spectacled flying-fox is Endangered. It is feared that both species could be functionally extinct by 2050.
While loss of habitat is the major challenge for all of Australia’s wildlife, destruction of prime foraging and roosting habitat can have a disproportionate effect on bats. In the past 200 years, almost 40% of Australia’s forests have been cleared for development and agriculture, leaving behind a fragmented landscape.
The large Myrtaceae family (which includes paperbarks, eucalypts, lillipillies and bottlebrushes) provides an important food source for flying-foxes.
An invasive myrtle rust fungus, which originated in South America, was first identified in Australia in 2010. It poses a serious risk to native trees. It is feared that reduced flowering due to myrtle rust would have a knock-on effect on not only flying-foxes, but the insects and birds which also rely upon these food sources.
Various eucalypt species have a naturally unreliable cycle, flowering only every three to five years. In addition, different species flower at separate times throughout the year, with variations in nectar and pollen production.
Consecutive days of summer temperatures exceeding 40°C are becoming a regular occurrence. Mass fatalities from heat stress can result. Other climate events such as floods and drought can disrupt normal flowering or fruiting cycles and consequently influence the movement of flying-foxes across their ranges. They are often forced to travel greater distances than ever to find sufficient sustenance.
Increasingly, flying-foxes seek alternative food and roosting habitat close to urban areas. Watered and fertilised gardens, parks, and roadsides offer a more reliable and plentiful variety of food. However, closer proximity inevitably increases the likelihood of interaction with humans, domestic pets and various man-made hazards.
Megabats
Hazards
In urban settings, hazards include dog attacks, collisions with cars, getting caught on barbed wire fencing and electrocution on overheard powerlines (particularly when flowering or fruiting trees are nearby).
Culling practices, attempts to relocate or destroy camps, and human harassment driven by fear or ignorance also impact flying-foxes. When there is abundant flowering within their range, the population of urban camps can swell temporarily. Conflict can arise with residents, who do not always appreciate the noise and odour issues associated with their unwelcome neighbours. Local councils are often pressured to disperse the camps.
Lethal methods of control such as shooting, poisoning and electrocution have been used in commercial orchards. Shooting bats is considered inhumane and ineffective. It is now illegal in all States, except Queensland. However, Queensland has officially committed to phase out licensed shooting of bats for crop protection purposes and will encourage the use of alternative non-lethal deterrents.
Australia’s pursuit of renewable energy solutions presents a new and emerging threat to all wildlife. The destruction of native bush to accommodate wind and solar infrastructure is particularly detrimental to flying-foxes. In addition to the loss of foraging habitat, there will also inevitably be collisions with wind turbines which are operating in the path of flying-foxes migrating between food sources.