Why you shouldn’t be scared of flying-foxes

Some politicians have been calling for the eviction of flying-foxes from urban areas (including by lethal force) on the ground that they are deadly threats to humans (see here and here for examples).

But are these politicians really concerned for our health? Does the risk from flying-foxes justify their alarmist statements? Will we be safer if flying-foxes are evicted or killed?

To provide some perspective on these questions, we have compiled the stats about what does kill Australians and ranked various causes of death (see Table 1 below). They show that flying-foxes are less deadly than horses, cattle, bees, hay bales, windmills, air conditioners, car jacks and more than a dozen better known killers. If those politicians really cared about your health, they’d be trying to evict fast food outlets and fast cars, not the fast flappers. 

Those who oppose the eviction of flying-foxes do not take the threat of disease lightly. Many are wildlife carers, researchers or conservationists who have very close contact with flying-foxes. If anyone is at risk, they are. But they know that the risk of catching disease from bats is extremely low, that measures can be taken to keep safe and that there are many other things much worthier of worry. After all, just one Australian is known to have become ill and died due to an encounter with a flying-fox (in 1998, from Australian bat lyssavirus) – one of more than 2.5 million Australian deaths since 1990.

Flying-foxes are safer than virtually everything else you encounter in an urban environment (just don’t touch them)! See here, here and here for more information. 

If you find a flying-fox down low in a tree or on the ground, call your local wildlife rescue group (see here for contacts).

Table 1: What kills Australians: various causes of death ranked from most to least deadly
 

Cause of death	Average deaths per year
Cardiovascular diseases	>10,000
Cancer
Diabetes	1,001 – 10,000
Suicide
Vehicle crashes
Infectious diseases
Accidental poisoning	101-1,000
Firearms
Homicide
Drowning
Being a pedestrian
Boat accident	11-100
Choking on food
Horses
Car jacks	1-10
Tree felling
Snakes
Cattle
Bees & wasps
Lightning
Dogs
Sharks
Windmills
Crocodiles	<1
Hay bales
Air conditioners
Spa baths
Flying-foxes

For statistics and sources, see the endnotes.

Endnotes:

Statistics for various causes of death in Australia (since 1990) and references.

Data could not be obtained, or was not obtained, for all years from 1990-2009 for most causes of death. However, sufficient was obtained to calculate an approximate average number of deaths/year and the rankings for Table 1 (the years for which data were obtained are listed). In a few instances where there was lack of recent data, statistics from 1980-1990 have been used. 

Major sources of data (for which endnotes below are abbreviated) are:

(1) Australian Bureau of Statistics, Causes of Death, Australia (annual data available for the period 1990-2009 on the ABS website);

(2) Australian Bureau of Statistics, Year Book Australia, (annual data available for 1990-2009 on the ABS website). See http://www.abs.gov.au/

(3) National Coroners Information Service report into Deaths Involving Animals, May 2006. See www.ncis.org.au/web_pages/Broadsheet2_Animal%20related.pdf.

(4) National Coroners Information System. 2007. A sample of consumer product related deaths. Deaths reported from 01/07/2000–30/06/2007. See www.ncis.org.au/Product%20related%20fatalities%20national%20version.pdf.

(5) Pollock K, Fragar L, Morton C. 2007. Traumatic deaths in Australian agriculture – The facts. Rural Industries Research and Development Corporation and Australian Centre for Agricultural Health and Safety

(6) Franklin R, Mitchell R, Driscoll T, Fragar L. 2000. Farm-related fatalities in Australia, 1989-1992. Moree: ACAHS, NOHSC & RIRDC

Cardiovascular diseases

Approx. average deaths/year: 47,000

Time period: 1990-1992, 1996, 2000-2008

Information source/s: 
- ABS. Causes of Death, Australia, various years.
- ABS. Year Book Australia, various years.

Cancer

Approx. average deaths/year: 36,000

Time period: 1990-1993, 1998-2005, 2007-2008

Information source/s:

- ABS. Causes of Death, Australia, various years.

- ABS. Year Book Australia, various years.

Diabetes

Approx. average deaths/year: 3000

Time period: 1990-1993, 1998-2003, 2007-2008

Information source/s:

- ABS. Causes of Death, Australia, various years-

- ABS. Year Book Australia, various years.

Suicide

Approx. average deaths/year: 2260

Time period: 1990-93, 1997-2008

Information source/s:

- ABS. Causes of Death, Australia, various years

- Harrison JE, Pointer S, Elnour AA. 2009. A review of suicide statistics in Australia. Injury research and statistics series no. 49. Adelaide: AIHW

Vehicle crashes

Approx. average deaths/year: 1890

Time period: 1990-2001, 2007-2008

Information source/s:

- ABS. Year Book Australia, various years.

Infectious diseases

Approx. average deaths/year: 1700

Time period: 1998-2001, 2006-2008

Information source/s:

- ABS. Causes of Death, Australia, various years.

- ABS. Year Book Australia, various years.

Accidental poisoning

Approx. average deaths/year: 740

Time period: 2000, 2002-2004, 2007-2008

Information source/s:

- ABS. Year Book Australia, various years.

Firearms (deliberate & accidental)

Approx. average deaths/year: 460

Time period: 1990-2002

Information source/s:

- Kreisfeld R. 2005. Firearm deaths and hospitalisations in Australia. See http://www.nisu.flinders.edu.au/briefs/firearm_deaths_2005.php

Homicide

Approx. average deaths/year: 310

Time period: 1990-2006

Information source/s:

- Australian Institute of Criminology, National Homicide Monitoring Program 1989-90 to 2005-06. See http://www.abcdiamond.com/australia/murder-crime-in-australia/

Drowning

Approx. average deaths/year: 280

Time period: 1992, 1998-2007

Information source/s:

- ABS. Year Book Australia, various years.

- Franklin R, Scarr J, Pearn H. 2010. Reducing drowning deaths: the continued challenge of immersion fatalities in Australia. Medical Journal of Australia 192(3): 123-26

Pedestrians struck by vehicles

Approx. average deaths/year: 300

Time period: 1997-2002, 2004-05, 2007-08

Information source/s:

- ABS. Year Book Australia, various years.

Boat accidents

Approx. average deaths/year: 40

Time period: 1999-2004

Information source/s:

- O’Connor P. 2008. National Assessment of Boating Fatalities in Australia 1999-2004. National Marine Safety Committee Inc

Choking on food

Approx. average deaths/year: 37

Time period: 1999, 2002-2005, 2007

Information source/s:

- ABS. Causes of Death, Australia, various years.

- Henley G, Harrison JE. 2009. Injury deaths, Australia 2004–05. Injury research and statistics series no 51. Adelaide: AIHW

- Henley G, Kreisfeld K, Harrison JE. 2007. Injury deaths, Australia 2003–04. Injury research and statistics series no. 31. Adelaide: AIHW

- Kreisfeld R, Newson R, Harrison J. 2004. Injury deaths, Australia 2002. Injury Research and Statistics Series Number 23. Adelaide: AIHW

- Kreisfeld R, Harrison J. 2005. Injury deaths, Australia, 1999. Injury Research and Statistics Series Number 24. Adelaide: AIHW

Horses

Approx. average deaths/year: 15

Time period: 1979-1998, 2000-2006

Information source/s:

- NCIS. 2006. Report into deaths involving animals

- Cripps RA. 2000. Horse-related injury in Australia. Adelaide: AIHW. See http://www.nisu.flinders.edu.au/pubs/bulletin24/bulletin24.html

Car jacks

Approx. average deaths/year: 4.1

Time period: 2000-2007

Information source/s:

- NCIS. 2007. A sample of consumer product related deaths.

Tree felling

Approx. average deaths/year: 3.4

Time period: 1989-1992, 2001-2004

Information source/s:

- Pollock et al. 2007. Traumatic deaths in Australian agriculture.

- Franklin et al. 2000. Farm-related fatalities in Australia, 1989-1992.

Snakes

Approx. average deaths/year: 3

Time period: 1979-2006

Information source/s:

- NCIS. 2006. Report into deaths involving animals

- McGain F, Rofe G, Sutherland S, Harrison J, Hawdon G, Winkel K. 2003. Snakebite Mortality in Australia. University of Melbourne. See www.nchirt.qut.edu.au/consultancy/amdig/workshops/documents/2003WinkelSlides.pdf

Cattle

Approx. average deaths/year: 2.2

Time period: 1989-1992, 2000-2006

Information source/s:

- NCIS. 2006. Report into deaths involving animals

- Pollock K, Fragar L, Morton C. 2007. Traumatic deaths in Australian agriculture – The facts. Rural Industries Research and Development Corporation and Australian Centre for Agricultural Health and Safety

Bees & wasps

Approx. average deaths/year: 1.9

Time period: 1979-1998, 2000-2006

Information source/s:

- NCIS. 2006. Report into deaths involving animals

- McGain F, Winkel K. 2000. Bee and wasp sting related fatalities in Australia. International Society on Toxinology 13th World Congress on Animal Plant and Microbial Toxins. See http://www.avru.org/files/imported/compendium/gallery/DR0000052.pdf

Lightning

Approx. average deaths/year: 1.7

Time period: 1980-1990, 2001-2004

Information source/s:

- Pointer S, Harrison J. 2007. Electrical injury and death. National Injury Surveillance Unit. See www.nisu.flinders.edu.au/pubs/reports/2007/injcat99.pdf

Dogs

Approx. average deaths/year: 1.6

Time period: 1990-2006

Information source/s:

- NCIS. 2006. Report into deaths involving animals.

- Kreisfeld R, Bordeaux S. 1998. Injury resulting from dog bites. See http://www.nisu.flinders.edu.au/pubs/shortreps/canines.html#dyear%20

- Kreisfeld R, Harrison J. 2005. Dog-related injuries. See http://www.nisu.flinders.edu.au/pubs/reports/2005/injcat75.php 

Sharks

Approx. average deaths/year: 1.2

Time period: 1990-2010

Information source/s:

- Australian Shark Attack File. See http://www.taronga.org.au/animals-conservation/conservation-science/australian-shark-attack-file/australian-shark-attack-file 

- Stevens, J. D. and Paxton, J. R. (1992). Shark attack: but who's the victim? Australian Natural History, 24(3): 46-53

Windmills

Approx. average deaths/year: 1

Time period: 1989-1992, 2001-2004

Information source/s:

- Pollock et al. 2007. Traumatic deaths in Australian agriculture.

- Franklin et al. 2000. Farm-related fatalities in Australia, 1989-1992.

Crocodiles

Approx. average deaths/year: 0.9

Time period: 1980-1990, 2000-2009

Information source/s:

- NCIS. 2006. Report into deaths involving animals

- Sydney Morning Herald 2009. See http://www.smh.com.au/national/recent-crocodile-deaths-in-australia-20090411-a3b2.html 

Hay bales

Approx. average deaths/year: 0.9

Time period: 1989-1992, 2001-2004

Information source/s:

- Pollock et al. 2007. Traumatic deaths in Australian agriculture.

- Franklin et al. 2000. Farm-related fatalities in Australia, 1989-1992.

Air conditioners

Approx. average deaths/year: 0.4

Time period: 2000-2007

Information source/s:

- NCIS. 2007. A sample of consumer product related deaths.

Spa baths

Approx. average deaths/year: 0.3

Time period: 2000-2007

Information source/s:

- NCIS. 2007. A sample of consumer product related deaths.

Flying-foxes

Approx. average deaths/year: 0.05

Time period: 1990-2009 (1 death in 1998)

Information source/s:

- Hanna J, Carney I, Smith G, et al. 2000. Australian bat lyssavirus infection: a second human case, with a long incubation period. Medical Journal of Australia 172:597-9.  See http://www.mja.com.au/public/issues/172_12_190600/hanna/hanna.html#refbody11. The only other case was due to an encounter with a microbat

Australian bat lyssavirus. See http://www.csiro.au/science/Australian-bat-lyssavirus.html

Concocted bat maladies promoted by The Townsville Bulletin

How many ways can those fearsome flying-foxes inflict illness, injury or death on their hapless, helpless Homo sapien victims in Charters Towers? At least three viral diseases, a fungal disease, various blood-sucking insects, faecal contamination and getting in the way of the emergency helicopter is the tally to date based on stories published in the Townsville Bulletin.

Their list of bat maladies and health risks has been growing rapidly, with four new ones added in the past month: (A) histoplasmosis, (B) blood-sucking mites, (C) Melaka virus and (D) lyssavirus spread by the water supply. But there is no evidence to support the existence of any one of these alleged problems in Charters Towers and they are all based solely on the assertions of the town mayor, a federal MP and those claiming to be affected by these mystery ailments. No health experts are cited or quoted to substantiate the allegations, which contradict expert advice and medical information.

(A) Histoplasmosis [1]: Headlined ‘Disease strikes bat-ridden town’, this story was based on a man’s reported belief that his undiagnosed illness of three years was due to the bats: “Charters Towers man Ronald Jenkins believes an epidemic of bat disease, or histoplasmosis, is behind his major health problems and the ill health of many other town residents.” Despite no doctor having made a diagnosis, “Mr Jenkins swears the problem lies squarely with the colony of an estimated 20,000 bats that has infested the town for years.”

There are no records in the medical literature of histoplasmosis caused by flying-fox faeces, and it is most commonly caught from the accumulated droppings, known as guano, from insectivorous, cave-dwelling bats [2], which are very different to the flying-foxes that roost in Charters Towers.

(B) Bood-sucking mites [3]: The Townsville Bulletin has published two stories and an editorial on alleged tick-like mites, with the first claiming that “Charters Towers residents under siege from a colony of bats are also faced with a plague of blood-sucking mites” and the second that a resident had been wounded on an arm by one of the insects: “[Mr Burnham] showed the Townsville Bulletin a scar on his left arm that Mr Burnham said was caused by an insect that latched on to his skin and fed on his blood.”

Again, no health experts or biologists were cited to support the existence of these alleged mites. Flying-foxes are known to host a few species of mite as well as parasitic wingless flies (Nycteribiidae), but there is no record in the medical literature of insects transferring from flying-foxes and taking blood meals from humans. Wildlife carers who have close contact with flying-foxes have not reported problems with blood-sucking insect attacks [4].

Most mites and the Nycteribiid flies are specific to one or several related hosts and cannot parasitise other species [5]. For these insects to transfer from a host to another animal would normally require close contact with the host animal, which should not be occurring in Charters Towers. Mites do not survive long off their hosts [6]. Occasionally, humans catch scabies from animals (more than 40 species are known to host these mites), but the infestation is usually self-limiting and requires contact with the animal (and the scabies mite is not a blood sucker) [7].

(C) Melaka virus [8]: Mentioned as a threat along with lyssavirus and Hendra virus in a quote from the town mayor, this virus is not known to exist in Australia. It has caused a flu-like illness in one Malaysian family [9]. This virus was also falsely promoted as a risk for Charters Towers on an ABC TV news item on 28 November, see our blog post here.

Confusion about the presence of Melaka in Australia may have originated from this article on the ABC website that quotes Australian scientists and is not wholly clear that the infection had occurred just in Malaysia, not in Australia.

(D) Lyssavirus via the water supply [10]: The Townsville Bulletin quoted Federal MP Bob Katter saying about lyssavirus “Now remember I'm not saying it's as simple as it stepping out of a bat and into a human, but the water supply is one way."

Health experts say spread by the water supply is not possible, Queensland Health stating on its website “A bat bite, scratch or mucous membrane exposure to bat saliva is necessary to transmit the virus” [11].

Promoting fear and hypochondria amongst people who live near bats seems to be The Townsville Bulletin’s contribution to the campaign by Charters Towers politicians to get rid of bats from the town (and to get re-elected; the local state MP Shane Knuth has promised residents that within one month of his party coming to power the bats will be gone [12]).

Contrary to the alarmist statements published by The Townsville Bulletin, health authorities advise that living near a bat camp is not a health risk. A brochure published by Queensland Health states, “Flying foxes are not a health risk to you unless you are bitten or scratched” [13]. Of the only virus known, in Australia, to be transmitted by flying-foxes to humans, Australian bat lyssavirus, they say: “There is no known risk of contracting ABL from bats flying overhead, contact with bat urine or faeces or from fruit they may have eaten.  Living, playing or walking near bat roosting areas does not pose a risk of exposure to the virus.” [14]

Queensland Health has sought to reassure Charters Towers’ residents they are not at risk from flying-foxes. In a story carried by Charters Towers’ local paper (the Northern Miner) [15], but not the Townsville Bulletin, Townsville's public health medical officer Dr Steven Donohue was reported as saying that there is “absolutely no evidence” to suggest bats in Charters Towers are carrying human diseases and there had been “no reports of any local residents getting sick from bats”. “Specifically, Townsville Public Health Unit has no record of any cases of histoplasmosis, Hendra virus, Mokola [sic] virus, lyssavirus, mites, lice or any other parasites arising from bats in Charters Towers,” Dr Donohue said.


References:

[1] See http://www.townsvillebulletin.com.au/article/2010/12/01/188675_news.html

[2] O’Sullivan M, Whitby M, Chahoud C, Miller S. 2004. Histoplasmosis in Australia: A report of a case with a review of the literature.  Australian Dental Journal 49(2): 94-97.

[3] See http://www.townsvillebulletin.com.au/article/2010/11/23/186675_hpphoto.html; http://www.townsvillebulletin.com.au/article/2010/11/23/186775_opinion.html; http://www.townsvillebulletin.com.au/article/2010/11/29/188141_news.html

[4] Pinson D. 2007. The Flying Fox Manual. StickeeBatz Publishing.

[5] Walton SF, Currie BJ. 2007. Scabies: diagnostic problems for a global disease in human and animal populations. Clinical Microbiology Reviews 20:268-279.

Bruyndonckx N, Dubey S, Ruedi M, Christie P. 2009. Molecular cophylogenetic relationships between European bats and their ectoparasitic mites (Acari, Spinturnicidae). Molecular Phylogenetics and Evolution 51(2): 227-37.

Hall L, Richards G. 2000. Flying Foxes: Fruit and Blossom Bats of Australia. UNSW Press: University of New South Wales

[6] Mattsson JG, Ljunggren EL, Bergstrom K. 2001. Paramyosin from the parasitic mite Sarcoptes scabiei: cDNA cloning and heterologous expression. Parasitology 122: 555–562.

Bruyndonckx et al. 2009; Walton & Currie 2007. See Note [5].

[7] Mattsson et al. 2001. See Note [6].

[8] See http://www.townsvillebulletin.com.au/article/2010/11/29/188141_news.html

[9] Chua KB, Crameri G, Hyatt A,  et al. 2007. A previously unknown reovirus of bat origin is associated with an acute respiratory disease in humans. Proceedings of the National Academy of Sciences of the United States of America 104(27): 11424-11429.

[10] See http://www.townsvillebulletin.com.au/article/2010/11/29/188141_news.html

[11] See http://www.health.qld.gov.au/goodhealthintnq/topics/abl.asp

[12] See http://www.townsvillebulletin.com.au/article/2009/03/20/45761_news.html

[13] See www.health.qld.gov.au/ph/documents/cdb/livingwithflyingfoxes.pdf

[14] http://www.health.qld.gov.au/goodhealthintnq/topics/abl.asp

[15] Jenkins C. Bats 'no health risk'. Northern Miner. 7 December 2010, page 1.

Even the ABC propagates nonsense about bats

As the public broadcaster, the ABC is required to abide by standards of accuracy, impartiality and balance in its reporting (see the ABC code of practice). But these standards have slipped in some reports filed on flying-foxes, particularly when journalists have yielded to the temptation of sensationalising disease risks.

Flying-foxes carry viruses that can affect humans BUT only one person is recorded as having caught a disease from Australian flying-foxes: a woman died in 1998 from Australian bat lyssavirus after being bitten [1]. Her death could have been prevented by vaccination.

Health departments and health experts advise that mere proximity to bats is not a disease risk (eg. see here) [2]. People just need to take care not to touch bats, and to consult their doctor if they are bitten or scratched (because “bats rarely initiate contact with humans,” this mostly occurs when people try to rescue [3] or harm bats).

But some media reports would have you believe that living near a bat camp is a potential death sentence, including a recent ABC TV news report about a protest in Charters Towers, Queensland, against a bat camp in town (broadcast 28 November, it can be viewed here).

Bat-borne diseases were reported to be the main reason Charters Towers’ residents want the town’s flying-foxes gone, with the newsreader stating that locals say the government is putting their lives at risk by refusing to permit “more proactive measures” to get rid of the bats. Federal MP Bob Katter was shown telling the protesters that “they’ll [the bats? the government?] just laugh at us as we go out there and quite literally die.” The reporter Megan Woodward then referred to three viruses – lyssavirus, Hendra and Melaka – implying that they were all a risk for Charters Towers residents due to the presence of bats: “While links with Hendra and lyssavirus are well-known, the Council says there’s another virus, Melaka, that can be transmitted to humans by bat faeces.”

Not only did the reporter neglect to note that humans don’t catch Hendra virus from bats, and that lyssavirus can’t be transmitted through mere proximity to bats, she concocted a new disease risk that doesn’t even exist in Australia (Melaka virus caused a flu-like illness in a Malaysian family), on the basis of advice from the local government (not normally regarded as health experts). No health expert was interviewed.

The ABC’s failure to research this story properly and the propagation of false information about health risks, with the potential to cause unnecessary alarm in listeners, is irresponsible.

Even an ABC environmental blog managed to inflate disease risks (see here), with reporter Sara Phillips defending Bob Katter’s views on bats and disease: “But Bob Katter isn't mad, you just need to know what he's going on about. Flying foxes do kill people.” [4]

Ms Phillips claimed that flying-foxes have killed six Australians: two from lyssavirus and four from Hendra. But just one death from lyssavirus is attributed to a flying-fox (the one other from a microbat), and flying-foxes do not infect humans with Hendra virus; horses do (but there are no calls for horse culls!) [5].

Flying-foxes are a natural host for Hendra virus. Ironically, people who disperse or kill flying-foxes and destroy their habitat could cause stress-induced spillover events that lead to occasional infections of horses. A scientific review of Hendra and other viruses by Andrew Breed and colleagues [6] warned that the processes driving spillover of infection are those that cause flying-fox decline, including “hunting, roost disturbance and habitat loss or alteration”.

This highlights the importance of reporters properly investigating stories about health threats and consulting experts, to avoid inadvertently supporting the messages of those advocating the very actions likely to increase disease risks.

The ABC news item on the Charters Towers protest was flawed in other ways as well. It implied that the only reason the State Government had refused a permit for helicopter dispersal of the bats was a small risk that bats could be harmed. In fact, human safety was also an issue as flying low over residential areas is considered a hazard by aviation authorities and requires special authorisation, which had not been obtained. Helicopter “mustering” is also likely to fail and result instead in bats moving into residents’ backyards, as has occurred with previous dispersal attempts. Bats are nothing like cattle, and helicopter dispersal didn’t work when it was tried in the Northern Territory.

The ABC news report was also politically biased. It featured three conservative politicians who are each opposed to both bats and the current Queensland Government. The Government was not given a voice in the story (there was one throwaway reference to the environment minister, Kate Jones, at the end of the piece) or the opportunity to respond to false allegations.

Both biased and inaccurate, the reporter stated “With the Bligh Government’s popularity proving to be slipping in polls released today, Charters Towers’ residents are asking Queensland voters to show some solidarity and back their cause and boot the government out.” The reporter had no basis for claiming that “Charters Towers residents” in general want to boot the government out. She could not even legitimately claim that all the protesters want the government booted out unless she had interviewed them all. There are undoubtedly ALP voters in Charters Towers and there are even residents who like having flying-foxes in their park. Unfortunately, bats are being treated as football number one in a nasty political battle, and the ABC seemed to be favouring one side.

The most positive thing that can be said about that ABC news item was that it wasn’t quite as bad as the reporting by the Townsville Bulletin, which has concocted a new blood-sucking creature that jumps from bats to humans in Charters Towers and has sent people to hospital (see here and here).

However, there is usually more to distinguish the ABC from the Townsville Bulletin, as it does regularly feature balanced and informative reporting on flying-foxes. It’s a pity the reporter for the Charters Towers story didn’t at least consult the ABC Online Scribbly Gum site about flying-foxes (see here), which conveys disease risks accurately and states that “just being near a roost will not put you at risk of being infected”.



References:

[1] Hanna J, Carney I, Smith G, et al. 2000. Australian bat lyssavirus infection: a second human case, with a long incubation period. Medical Journal of Australia 172:597-9. Note that the other case of lyssavirus (also fatal) was thought to be due to contact with a microbat. 

[2] For example, a brochure published by Queensland Health explicitly states: “Flying foxes are not a health risk to you unless you are bitten or scratched”. See www.health.qld.gov.au/ph/documents/cdb/livingwithflyingfoxes.pdf.

[3] McCall B, Epstein J, Neill A, et al. 2000. Potential human exposure to Australian bat lyssavirus: Brisbane South and South Coast, Queensland, 1996-1999. Emerging Infectious Diseases 6: 259-264.

[4] It seems strange that an environmental reporter would set out to defend Bob Katter’s views on flying-foxes. Mr Katter characterises flying-foxes in extreme terms as killers and advocates mass culling; contrary to all evidence, he claims they are in “plague” numbers: "There are no varieties that aren't 10 to 100 times the numbers they were at European settlement because back then they had nothing to eat” (see here)

[5] Contrast this with reporting on other diseases. Ross River virus and Barmah Forest virus have been spread to humans by mosquitoes which bit kangaroos and wallabies. The media reports these diseases as being transmitted by mosquitoes, not kangaroos and wallabies. When there is a sequence of hosts, there seems to be a tendency to focus ‘blame’ for the disease on the least popular of them.

[6] Breed A, Field H, Epstein J, Plowright RK, Daszak P. 2006. Emerging henipaviruses and flying foxes conservation and management perspectives. Biological Conservation 131: 211-220.

‘Scout bats’ are a myth

To justify killing flying-foxes, some fruit growers and politicians peddle the myth of ‘bat scouts’ (see below for more examples). Like honeybee scouts, bat scouts are said to search the landscape for new food sources and guide their fellow bats to them. So, they claim, if a fruit grower can shoot the alleged scouts, the orchard remains a secret to all other bats.

It’s a convenient myth for fruit growers because they can claim they only need to kill a few scouts to protect their orchards from vast numbers of flying-foxes. Queensland MP Rob Messenger asserted that “most farmers only needed to take a maximum of ten scouts in order to protect investments worth tens of thousands of dollars”.[1] Federal MP Bruce Scott told parliament that flying-foxes weren’t a problem for Queensland farmers when shooting was permitted as “the scout bat … [can] be terminated—quickly and humanely”.[2]

But the scout notion is biologically bogus [3] and it is fanciful to claim that fruit growers protect their crops by killing just a few flying-foxes when so many have been slaughtered in the past.

Peddling the myth: claims about ‘bat scouts’ Before damage mitigation permits were revoked by the city-centric Queensland Labor government, the flying foxes did not pose a problem because the DMPs allowed for the scout bat, which is the bat that looks for a new roosting place for the colony, to be terminated—quickly and humanely. Bruce Scott, Federal Member for Maranoa, 22 November 2010 [4] The fruit growers in the Granite Belt are asking the Queensland Government to temporarily reinstate damage mitigation permits. These permits would allow fruit growers to minimise the damage to their orchards by controlling the number of fruit bats who scout for food prior to an invasion by the main colonies. Senator Barnaby Joyce, 18 August 2009 [5] We're not talking about the wholesale shooting of bat colonies, but the selective deterrence of lead scout bats that will deter bat colonies from coming into an area. Mike Horan, Shadow Queensland Primary Industries Minister, 24 July 2008 [6] Like many other fruit growers, Ms Ferris advocates shooting the 'scout bat', the lead flying fox which apparently flies ahead of the flock, alerting others to the location of food.     The Government has repeatedly stated that the scout bat theory cannot be proved and has little basis in science.     But fellow district grower Ian Mungall is also a strong believer in the concept and told QCL earlier this year he had watched how scout bats called other flying foxes into his orchard. He could only watch helplessly as they devoured large swaths of his nectarine crop resulting in losses of $20,000. Queensland Country Life, 24 November 2009

Flying-foxes don’t need a ‘bat scout’ to find food

With good vision and sense of smell, long-distance navigation skills, and an excellent memory for locations, each flying-fox has the ability to find its own food.[7] They undoubtedly gain information about local food sources by observing other bats but there is no evidence for a special category of bats that generously seek out food on behalf of others.

Flying-foxes are not sharers

Bats aren’t like ants or bees; they don’t live in organised cooperative societies with designated roles.[8] They are territorial about food and can spend much of the night defending their patch in a food tree from others (the reason for all the bat squabbling heard at night).[9] A flying-fox has much to gain if it can find a fruit tree all its own. It makes no sense to suggest that a designated few would search out food for the rest of the camp.

Orchards are easy to find

Orchards are much easier to find than natural food sources such as isolated fruiting or flowering trees in forests. They are very concentrated sources of food that stand out in the landscape as a regular array of trees, easy for a bat to spot from the air and easy to smell when fruit is ripe. Many orchards are close to flying-fox camps and couldn’t be missed.

Bats have a good memory for food sources

Flying-foxes have an excellent memory for locations.[10] Some return each year to the same branch in a bat camp after many months away. They are not likely to forget an orchard they have fed in previously, so there would be no need for a scout to find each orchard all over again at the beginning of each fruit season. Whether or not flying-foxes choose to feed in an orchard depends on what other food is available. When natural foods are in short supply, orchards are heavily targeted.[11]

Shooting is not a practical solution

There is no practical way for fruit growers to effectively protect their crops by shooting small numbers of flying-foxes.[12] They cannot spend all night every night guarding their orchard and be guaranteed of shooting every bat that enters. A NSW survey of 17 growers found that on average they shot for just 1.6 hours/night for 3 nights a week for 4.4 weeks, leaving their orchard unguarded for more than 90% of the time.[13] Shooting a few bats is particularly useless when natural bat foods are in short supply and orchards are heavily targeted. This is when the majority of fruit losses occur. Netting offers full-time protection and is the only method known to be effective, which is why it is the industry standard.

The scout bat theory hasn’t worked in the past

Fruit growers haven’t been able to protect their orchards in the past by killing a few alleged scout bats, which is why a large proportion of commercial fruit targeted by flying-foxes is now under netting.[14] It flies in the face of history for growers to contend that they need kill only a few flying-fox scouts to protect crops, when it was common past practice for a grower to kill hundreds or thousands a season.[15] Growers complained they couldn’t protect their crops when governments reduced the numbers of flying-foxes permitted to be killed (due to declining populations). Now that shooting bats has been banned in Queensland and could be in NSW (as recommended by a government-appointed independent panel),[16] it suits some growers and politicians to peddle the scout myth in an attempt to justify ongoing shooting.

Shooting is inhumane and anti-conservation

When bats are shot at in orchards at night, it is inevitable that some are wounded rather than die immediately, and because the ripening of most commercial fruit coincides with flying-fox births, shooting results in the starvation of babies when their mothers are shot.[17] There is no way of making shooting humane, which is why the Queensland Government has banned it.[18]

Shooting also puts pressure on declining flying-fox populations. Because flying-foxes don’t breed successfully until they are 2 or 3 years old and have only one baby a year, they have a low capacity for population growth.[19]  Two species killed in orchards – grey-headed and spectacled flying-foxes – are listed as nationally threatened.[20]

Shooting flying-foxes for crop protection is inhumane and anti-conservation. Killing mythical bat scouts won’t help growers protect their crops. The scout myth rather than mythical scouts should die.  



References:

[1] Messenger R. 2009. Government must change flying fox policy now to stop disaster. Media release 12 January.

[2] Scott B. 2010. Environment Protection and Biodiversity Conservation (Public Health and Safety) Amendment Bill 2010. Second Reading. House of Representatives Votes and Proceedings. Hansard 22 November 2010, page 33. 

[3] There is no published evidence for bat scouts – a search of scientific databases found no references – and it is inconsistent with knowledge of bat behaviour. 

[4] Scott, 2010. (See note 2)

[5] Joyce B. 2009. Flying foxes and fruit in Queensland’s granite belt do not mix. Website for Senator Barnarby Joyce.  http://www.barnabyjoyce.com.au/Issues/Thisweekinpolitics/tabid/56/articleType/ArticleView/articleId/941/categoryId/7/FLYING-FOXES-AND-FRUIT-IN-QLDS-GRANITE-BELT-DO-NOT-MIX.aspx

[6] Horan, M. 2008. Quoted in Hendra virus: Qld’s bat policy ‘out of touch’. Queensland Country Life 24 July 2008. 

[7] Eby P. 1995. The biology and management of flying foxes in NSW. NSW National Parks and Wildlife Service, Hurstville. Hutcheon JM, Kirsch JAQ, Garland T. 2002. A comparative analysis of brain size in relation to foraging ecology and phylogeny in the Chiroptera. Brain, Behavior and Evolution 60: 165-180. Safi K, Dechmann DKN. 2005. Adaptation of brain regions to habitat complexity: a comparative analysis in bats (Chiroptera). Proceedings of the Royal Society (Biological Sciences) 272: 179-186. 

[8] Bat camps or colonies do not constitute a discrete or fixed population of flying-foxes. Some bats may be resident in a camp, others are regular or sporadic occupants. There is considerable population flux in bat camps mostly related to the availability of food. Flying-foxes can travel thousands of kilometers a year between different camps. 

[9] Hall L, Richards G. 2000. Flying Foxes: Fruit and Blossom Bats of Australia. UNSW Press, University of NSW.

[10] Safi and Dechmann, 2005. (see note 7).

[11] NSW Flying-fox Licensing Review Panel. 2009. Report to Landscapes and Ecosystems Conservation Branch, NSW Department of Environment and Climate Change. 10 May 2009.

[12] A survey of 17 fruit growers in the Sydney Basin by Dang et al. (2009, see note 13) found that 88% of them did not believe that shooting ‘scouts’ (early arriving bats) was effective at deterring others and most believed that flying-foxes returned to the orchard after being scared off. 

[13] Dang H, Jarvis M, Fleming P, Malcolm P, Brook J, McClelland K. 2009. Grey-headed flying-foxes (Pteropus poliocephalus) in orchards: damage estimates, contributing factors and mitigation. Final report to Hawkesbury Nepean catchment Management Authority. NSW Department of Primary Industries and NSW Department of Environment and Climate Change. 

[14] According to the Queensland Department of Primary Industries (2005), about 90% of lychee, longan and rambutan growers in North Queensland had netted their orchards by 2005. According to Dang et al. (2009, see note 13), netting on the north coast of NSW covers 100% of stone fruit orchards (61 ha), 67% of lychee orchards (30 ha), 100% of blueberries (430 ha), 50% of custard apples (200 ha) but none of bananas (1728 ha) or mangoes (180 ha). In the Sydney Basin, 30% of surveyed orchard area was netted  (89 ha of 296 ha). The NSW Flying-fox Licensing Review Panel (2009, see note 11) reported that about 23% of stone fruit and apple orchards in the southern sector (450 ha total) are netted.

Queensland Department of Primary Industries. 2005. Nets save lychee industry from flying fox and bird attacks. Media release, 16 February 2005. 

[15] A federal court judgment [Booth v Bosworth] found that one fruit grower probably electrocuted 18,000 spectacled flying-foxes in one season. From 1986-1992 more than 240,000 grey-headed flying-foxes were shot in orchards under 616 licences in NSW; many more were shot illegally. Wahl (1994) reported that 69% of orchardists surveyed said they had shot without a licence or outside licence provisions. 

Wahl D. 1994. The management of flying foxes (Pteropus spp.) in New South Wales. M. App. Sci. Thesis. Applied Ecology Research Group. Canberra. 

[16] NSW Flying-fox Licensing Review Panel, 2009 (see note 11).

[17] Divljan A, Parry Jones K, Eby P. 2009. Report on deaths and injuries to grey-headed flying-foxes, Pteropus poliocephalus, shot in an orchard near Sydney, NSW. 

[18] AWAC. 2008. Animal Welfare Advisory Committee’s Recommendations. Advice to the Minister for Primary Industries and Fisheries The Honourable Tim Mulherin. 

[19] Martin L, McIlwee AP. 2001. On the intrinsic capacity for increase of Australian flying-foxes (Pteropus spp., Megachiroptera). Australian Zoologist 32: 76-100.  

[20] Grey-headed flying-foxes and spectacled flying-foxes are listed as vulnerable under the federal EPBC Act.  Currently, NSW still permits the shooting of flying-foxes (which includes grey-headed flying-foxes) but Queensland no longer permits the shooting of any flying-foxes (which includes both grey-headed and spectacled flying-foxes) for crop protection.