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About Fruit & Nectar Bats - Why Conserve Fruit & Nectar Bats? | Fruit & Nectar Bat Biology | Global Conservation & Distribution Status | Global Conservation Threats | Regional Conservation Issues | Literature on Fruit & Nectar Bats
Jump to: Australia, Papa New Guinea, Solomon Islands
Thirty nine of Australia's 85 native species of bats are classified as threatened by the IUCN (Kunz & Racey, 1998). Bats account for a third of the continent's native mammal species. Eight species belong to the genus Pteropus, although the exact classification of some of them is a problem (those species identified by* in the table below)(Duncan et al., 1999). They occupy a broad margin that starts around Melbourne and stretches north up the eastern coastal region of the continent, around the northern coast and down along the west coast. Pteropus bats have become the most prominent conservation problem in Australia. They are considered a pest by fruit growers (Hall & Richards, 1987) but their vital seed dispersal role for tropical forests, cultivated fruit and the rejuvenation of timber trees has only recently started to be appreciated (Richards, 1990b; Eby, 1991). Many large scale surveys have identified forest fruit bats as valuable indicator species for forest condition that require special consideration in conservation planning (Lunney et al., 1985, 1988; Richards, 1990a, 1992a).
Australia has the worst conservation record in the world, and approximately half of the world's mammalian extinctions have occurred there since it was settled by europeans 200 years ago (Short & Smith, 1994). Most of the environmental problems stem from habitat destruction and alteration, environmental contamination, and, especially for bats, roost disturbance (Kunz & Racey, 1998). Australia is clearing its native vegetation faster than any other developed country in the world. Habitat clearance, resulting from human activities such as agriculture and industrial development, is the major threat to the threatened and lower risk species of bats in Australia. An estimated 20% of Australia has been thinned or cleared since European settlement (Graetz et al., 1995), and broadscale clearing has increased in the last 50 years (Duncan et al., 1999). Logging has had a major effect too, with 40 % of the forest having been cut down and another 40 % altered since European settlement. This deprives bats of roosts and food sources, which may affect foraging patterns and increase the risk of predation (Law, 1996) and forces the bats to forage in commercial fruit orchards. Almost 5000 km2 of native vegetation were cleared between 1991 and 1995 to accommodate urban expansion, tourism development, sugar production and other forms of agriculture such as cattle grazing and cotton and cereal growing (Krockenberger, 1998). Introduced species also pose a problem; cats eat bats, and an exotic species of parasitic tick has become a major new cause of death for Pteropus conspicillatus (Kunz & Racey, 1998).
Controls on habitat destruction have been introduced in many states but under enforcement and legal loopholes make it possible for it to continue virtually unabated. The Australian government's aim of re-vegitating 25,000 ha. of land per year is far outstripped by the present rate of habitat destruction (Morris, 1998).
Fruit bats have long been regarded as major pests of Australia’s commercial fruit growers, and hold 'noxious' pest status in Queensland. The damage they cause has been estimated at a total (Australian) $20 million to the industry (Tidemann et al., 1997). Pteropus poliocephalus and P. conspicillatus are the main culprits and as a result have been the subject of culling and electrocution with devices such as the ‘Fire Fox’, which uses networks of electrified wires placed above the orchard (Duncan et al., 1999). Electrocution of lactating mother bats causes starvation of their dependent young, who are left behind at the roost (Kunz & Racey, 1998). In the past it has even been attempted to introduce typhoid into the bat population to control their numbers (Churchill, 1998). Poisoning with strychnine in baited fruit is also used to control fruit bats, and other control measures include flame throwers targeted at camps, and strobe lights, although all of these methods appear to have been of little use in reducing damage to crops. Total exclusion from the orchards with nets seams to be the only viable long-term solution to controlling fruit bat damage (Wahl, 1994). Other more benign methods of crop protection include exclusion netting and disturbance of roosts. Investigation into less destructive alternatives like olfactory deterrents, more effective exclusion techniques and use of non-lethal electrical currents, and incentives offered for their use is encouraged (Duncan et al., 1999).
In New South Wales the issue of permits to orchard owners for the culling of fruit bats is done without concern for their life cycle or population dynamics, or whether the population can withstand such losses. Fruit bats are particularly vulnerable to high levels of mortality due to their low reproductive rate; it takes two years before maturity is reached and females typically have only one infant per year (Kunz & Racey, 1998). It has been calculated that a cull of 10 % of the population per year will halve it in five years and reduce it to approximately one fifth its size in 20 years (Pierson & Rainey, 1992). Using the model of Pierson and Rainey (1992), Kunz and Racey (1998) predict that if an average of 10 % of fruit bats are culled in the coastal region between Sydney and the Queensland border per year, then the present population of 2 million fruit bats will be reduced to fewer than 800,000 individuals in 10 years and fewer than 100,000 in 30 years. Between 1986 and 1992 it is calculated that at least 250,000 fruit bats were culled in that area alone (Wahl, 1994).
In Australia the level of protection afforded to fruit bats varies between individual states. In Queensland, where they cause severe crop damage, Pteropus bats are considered to be 'non-protected fauna' under the Queensland Protection Act (1989) and are heavily persecuted (Wahl, 1994). In other states, however, legislation affords them protected status, resulting in the restriction of most control measures, besides shooting. In New South Wales fruit bats are 'protected fauna' so fruit growers wanting to cull problematic populations must obtain a permit before doing so. The permit sets a maximum number that may be killed, normally around 50-100, and is normally valid for no more than three months. The only Pteropus species to occur in South Australia (Pteropus scapulatus) is fully protected and does not cause damage to crops (Wahl, 1994).
A study by the University of Queensland has revealed that Australia’s fruit bat populations living in urban areas are succumbing to the toxic affects of lead poisoning (Hariono et al., 1993). The symptoms of lead poisoning include inability to fly, loss of appetite, weakness, emaciation, uncoordinated movement and muscle tremors. Studies on the lead concentration in the organs and tissues of dead bats either hit by cars or found dead or in a distressed condition in the urban area of Brisbane, Queensland, were found to be consistent with toxicity. High levels of lead were also found on the teeth, bones and fur, indicating long term exposure, and its presence in the kidneys (up to 0.025 g per g of tissue) and liver (up to 0.1 g per g of tissue) indicate recent and continuing exposure. In contrast, bats captured in non-urban areas were found to have relatively low concentrations (Hariono et al., 1993). The source of the lead is unknown but industrial and automobile emissions seem the most likely candidates. Bats may ingest the lead particles from their fur when grooming and inhale airborne lead particles into the lungs, from where it would be quickly distributed to the tissues via the bloodstream. Concentration levels in the bodies of many of the bats would be considered toxic if they were detected in domestic animals and the authors suggest that a similar survey performed on domestic and other wild animals species might yield similar results (Hariono et al., 1993).
Concern verging on the point of panic followed reports that fruit bats are harbouring a new and deadly virus that can be transmitted to humans and horses. So far the occurrence of this new form of Paramyxoviridae virus, related to those that cause canine distemper and measles, has infected a total of 23 horses. In humans it has been limited to only three separate incidents in Queensland, two of which were fatal. This news provoked a spate of indiscriminate shootings of fruit bats (Anderson, 1998).
In September, 1994, 49 year old horse trainer Vic Rail from Brisbane fell sick with a sore throat, head and muscle ache. A number of horses at the stables where he worked had also become ill and died. By the 27th of that month Vic had died of numerous complications including respiratory failure after seven days in intensive care. It is thought that he contracted the virus when the frothy nasal and oral discharges of the sick horses got into cuts on his hands (Paterson et al., 1998). Both the man and the horses were found to contain a novel member if the Paramyxoviridae family of viruses, which virologists want to assign to a new genus called megamyxovirus (Anderson, 1998). At the same time, also in Brisbane, a 40 year old stable hand became sick with similar symptoms to Vic Rail, but soon made a full recovery. Tests revealed that he too had been infected by the new virus (Paterson et al., 1998). The second and only other fatality from the virus was Mark Preston, 39, from Mackay, a town ~1000km north of Brisbane. He is thought to have contracted the virus from contact with two infected horses that consequently died. Again, the infection seems to have entered his body from the horses body fluids through cuts in his arms. He died of meningitis 25 days after admission to hospital (Paterson et al., 1998).
Vic Rail's rapid decline and the apparent high rate of infectivity between horses sparked concern for the safety of the human population. It was suggested that the virus must have a natural host species capable of migrating large distances. Since this family of viruses are typically found in mammals the focus of attention fell on bats. A wide screening of wild animal species revealed that 20 out of the 224 Pteropus bats tested were seropositive for antibodies for the novel virus. Others have so far been found in Brisbane, Mackay, Darwin (Northern Territory), Melbourne (Victoria) and Madang in Papua New Guinea. Concern was raised for the safety of Australia’s many bat handlers and carers who take in injured and orphaned fruit bats, 70 % of whom admit to being bitten by bats. Two thousand horses were tested but none possessed antibodies for the virus. In addition, all 128 bat handlers tested (who had been in close contact with bats for years) were found not have been exposed to the virus either. Likewise those hospital personnel who had cared for the human victims of the disease and all people who had been in contact with the infected horses were also seronegative (Paterson et al., 1998). Vic Rail may have used the same syringe to inject the horses with vitamins, which would explain the rapid transmission from horse to horse. What is not clear is precisely how the virus got from bats to horses, but it has been suggested that horses might have inadvertently eaten bat droppings on grass, or birth fluid or placenta (the infections occurred during the season when the bats give birth) (Paterson et al., 1998).
The clear indication is that the new virus is not highly infectious and transmission is easily prevented by standard precautions. None of the cases involved transmission of the virus from bat to human and since 1995 no further human infections with this particular virus have been reported.
More bad press for Australia’s bats came when a Rockhampton (Queensland) woman who cared for sick and injured bats died from infection of Australian Bat Lyssavirus (ABL), which she most probably caught from a yellow-bellied sheathtail bat (Saccolaimus flaviventris) (Anderson, 1998). Lyssaviruses occur all round the world and can infect a wide range of mammalian hosts, and Pteropus poliocephalus and P. scapulatus have also been found to contain antibodies for the virus. There are six types that cause disease in humans, although only rabies (serotype 1) usually causes serious pathology. The others are referred to as rabies related diseases: serotype 2 - Lagos bat virus; serotype 3 - Mokola virus (West Africa); serotype 4 - Duvenhage virus (South Africa); serotypes 5 & 6 - European bat lyssavirus types I and II (Finland, Denmark and Russia); and serotype 7 - Australian bat lyssavirus (Churchill, 1998).
In the last few years Australian fruit bats have been found to harbour a number of novel viruses besides those already mentioned, though none with human fatalities. Among these are three new members of the Paramyxoviridae, one of which caused mild disease in two pig farm workers in New South Wales (Anderson, 1998). It should be remembered that these diseases are very rare and can easily be avoided by simple safety precautions when handling sick or injured animals. In fact, transmission seems to have occurred only when hygiene measures were flagrantly neglected.
Precautions for bat handlers should include:
There has been little financial support for studies into the ecology and conservation of Australian bats and a lack of knowledge about the taxonomy and distributions of bats has hampered their conservation up until now. Nevertheless, since the early 1970s there has been a steady accumulation of scientific knowledge of Australian bats and data is now available on the distributions, habitat preferences and morphological differences for practically all regions of the continent (Duncan et al., 1999). Increasing concern about Australia's environmental degradation and its impact upon bats, and problems between Pteropus and the fruit industry has led to the formation of an action plan for Australian bats. The Action Plan for Australian Bats, commissioned by the Biodiversity Group of Environment Australia, through the Endangered Species Programme (ESP), outlines its objectives in rank of priority, thus:
The action plan recommends that state forestry agencies be encouraged to carry out further research into the impact of logging on tree dwelling bats, particularly which species are affected, whether current management prescriptions are effective, the effect of forest fragmentation on bats at a landscape scale, and whether bats are useful indicators of forest health (Duncan et al., 1999).
The micro-continent of Papua New Guinea and its associated islands are home to a staggering diversity of old world fruit bats. These number somewhere in the region of 47 species and sub-species, of which at least 16 belong to the genus Pteropus, although there is a great need for further studies to confirm this data (Kula, 1992; Mickleburgh, 1992). Many of these species are in present danger from habitat loss due to rapid deforestation in the region (Mickleburgh et al., 1992; Kula, 1992)
Papa New Guinea includes the eastern half of New Guinea and the nearby islands of the Bismarck Archipelago, the D’entrescarteaux Islands, the Lousiade Archipelago and the North Solomon Islands. This covers a total of 462,842 km2 of land, 97 % of which is held under customary land tenure, making the allocation of protected areas difficult (Kula, 1992). Of this, only 2.3 % (10,656 km2) is classified as conservation areas, while wildlife management areas only cover 10,529 km2 and national parks 127 km2 (Asigau, 1989). The Pteropus species present include the vulnerable Pteropus gilliardi (endemic) and P. mahaganus, and several endemic subspecies, which are made particularly vulnerable due to highly restricted ranges (IUCN: Baillie & Groombridge, 1996). Although these bats are not specifically protected by law they do enjoy a degree of protection by the Department of the Environment and Conservation under existing legislation (Kula, 1992). This includes the Fauna (protection and control) Act, 1978, which designates areas where the suitably managed harvesting of certain animals can take place, and also gives protection to listed endangered species. Under this act the permission of the Conservator of Fauna is required to import, export or hold wild animals in captivity. Under the Conservation Areas Act of 1978, protection is ensured for areas designated as important to conservation or the national heritage. The Customs Regulations Act of 1979 bans the import or export of whole or parts of living or dead wild animals without the permission of the Conservator of Fauna. Papua New Guinea also upholds the CITES agreement, which controls the import and export of protected plants and animals (including Pteropus bats) between member countries (Kula, 1992).
Deforestation is the greatest threat to the Pteropus bats of Papua New Guinea. In addition, little is known of the size and distributions of many populations. Surveying is needed, especially of New Guinea, Bouganville, the islands north of Papua New Guinea, and the Bismarck Archipelago, and the IUCN Action Plan for Old World Fruit Bats (Mickleburgh et al., 1992) highlights the need for information about the endemic Pteropus temmincki basiliscus of Karkar and the Schoutan Islands. Long term monitoring of this subspecies is needed, and studies to determine its feeding habits, reproduction and threats, as well as the establishment of protected areas, and dissemination of information about the bats’ vulnerability and general environmental education of local people is also recommended (Mickleburgh et al., 1992). An initiative by the Papua New Guinea Department of the Environment and Conservation is currently underway to produce a database of all information regarding the distribution of animal and plant species of Papua New Guinea. This is being done with a view to aiding future conservation programmes in the establishment of protected areas and determination of the degree of danger to individual species (Kula, 1992).
The Solomon archipelago is located just off the eastern side of Papua New Guinea. This widely scattered group of islands stretches 1,600 km south-east towards the Vanuatu Archipelago and is notable for its exceptional biodiversity and high levels of endemism (Whewell, 1992). It is the only home to three out of the four species of Pterapolex fruit bats (monkey-faced flying foxes) in the world (Bowen-Jones, 1998). Eighteen species and subspecies of Pteropus fruit bats are represented on the islands, 15 of which are endemic to the area (Mickleburgh et al., 1992). These include the IUCN graded Vulnerable Pteropus mahaganus (Baillie & Groombridge, 1996), which is confined to just three islands, and Pteropus rayneri, which is the the most widespread and common fruit bat on the islands.
The Santa Cruz tube nosed bat Nyctimene sanctacrusis (Megachiroptera) is already extinct, and was known from a single specimen collected in 1892 (Bowen-Jones, 1998).
Human activitiessuch as heavy and unsustainable logging of the forests pose a major threat to the fruit bats of the Solomon Islands. In 1991 the IUCN predicted that all accessible forest will have been exploited in 15 years if the current trend continues (IUCN, 1993). The islands have a human population of about 300,000, which grows at around 3.6 % a year (Whewell, 1992). 80 % of the land tenure is held by individual tribes, according to tradition, which makes the appointment of protected areas difficult and at present only 2 % of the total land area is within protected areas (Whewell, 1992; Bowen-Jones, 1998). However, some biologically important areas are also of cultural importance and so the tribes are keen to see them protected, which presents an opportunity for the development of sustainable, community based conservation (Bowen-Jones, 1998).
Competition with and predation by introduced species are serious problems for many of the native species. Cane toads (Bufo marinus), cats (Felis catus) and black rats (Rattus rattus) are among the most problematic introductions and have already caused the extinctions of a number of native species. In addition, an introduced disease thought to have been carried in with exotic coconut palms has caused severe population declines of Pteropus rayneri (Bowen-Jones, 1998). At the moment hunting is not restricted by law (Whewell, 1992). There is some evidence of low level subsistence hunting of fruit bats, which Whewell (1992) warns could develop into an export industry in the near future, once their commercial value is realized. There is a pressing need for more research into the threats to fauna on the Solomon Islands and surveying of bat populations, particularly on the islands Choiseul, Fauro, Guadalcanal, Kolombangara, Malaita, Nggela Sule, Santa Isabel and Vella Lavella (Mickleburgh et al., 1992). Little is known about the degree of damage to crops caused by fruit bats, although it is said to be common, and the relationships between the bats and their environment and how this is affected by the rapid habitat changes (Whewell, 1992).
Information on this page was compiled and authored by Oliver Thatcher and is currently being updated.
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