Australia’s bats are turning up in increasing numbers in city suburbs. But as they search for food, they’re bringing for some a newfound paranoia thanks to a global pandemic that likely sprang from one of their overseas relatives.
At Yarra Bend park in Melbourne, the state MP for Kew, Tim Smith, said last month some of his constituents have a fear of tens of thousands of grey-headed flying foxes.
He wants a solution “whether that’s drastic action like a cull, or simply moving them on.”
Dr Pia Lentini, one of Smith’s constituents and a bat expert, says: “Every context is different but the concerns are always the same – they’re noisy, the smell is overwhelming, ‘my car is covered in shit’, ‘I can’t dry my clothes outside’, or ‘I’m worried about diseases’.”
As our human settlements get bigger, we’re encroaching further into bushland where bats live. At the same time, bats have been hit by droughts, habitat clearing and bushfires that put pressure on their food supplies.
But bats can fly hundreds of kilometres a night to find food – whether that food is in the middle of a city or out in a national park.
Lentini is studying conflict between bats and human populations and she says the incidence of bats turning up in large numbers in towns is on the rise.
“There’s been conflict with flying foxes for decades – it started with fruit growers who had bats ‘raiding’ their fruit, and the economic cost of that.
“Now we have flying foxes becoming increasingly urban because they’re losing habitat. There’s now also a great diversity of trees in our cities. They are becoming more urban and the camps are becoming more prominent.
“They are in our cities because they are starving.”
Lentini lives near the Yarra Bend grey-headed flying foxes. The bat camp was established as part of a major relocation project from the Royal Botanic Gardens in 2003, when the bats were deliberately disturbed by noises at dawn and dusk.
Lentini says this demonstrates a problem with dispersing colonies of flying foxes. “If we keep trying to move them on – which is difficult anyway – then you also move the conflict.”
Associate Prof Justin Welbergen, an animal ecologist at Western Sydney University’s Hawkesbury Institute for the Environment, says: “Dispersals risk making a situation that’s already bad, worse. It becomes a game of musical chairs.”
Welbergen, the president of the Australasian Bat Society, says there’s another problem with dispersal of bat camps.
While it might not be obvious to a casual observer, Welbergen says each day there’s about a 10% turnover of the bats in a camp, as some leave and others arrive.
“It’s like a hostel,” he says. “The roost is the hostel and the bats are the clientele. Flying foxes rarely stay in the same place for very long.”
“Dispersals are predicated on the idea that you can teach flying foxes that another place is better. You might teach some individuals, but not others.”
In a single year, Welbergen says one individual bat might fly across the entire range of its species – from southern Victoria to south-east Queensland – multiple times.
As bats move, they perform a vital ecological function by spreading thousands of seeds through spit and poop, as well as pollinating flowering trees. Welbergen says lower numbers of bats likely means slower recovery of forest areas from the 2019-20 bushfires.
Australia has 81 species of bats, ranging from microbats weighing a few grams to the four large mainland flying foxes that can weigh up to 1kg.
It’s these larger flying foxes that experts say are causing conflict in towns and cities.
On Australia’s national threatened species list, grey-headed flying foxes are considered vulnerable and the spectacled flying fox was uplisted in 2019 from vulnerable to endangered.
Lentini is in the middle of a major research project to better understand people’s concerns. She has 32 hours of interview material from more than 60 residents living close to nine flying-fox camps in Victoria, New South Wales and Queensland. She is also analysing responses to 1,600 surveys returned from people living within 300 metres of 31 camps across the east of the country.
“There’s a lot of anger and frustration out there,” she says. “You do hear the loudest voices but it’s unclear if those people really do represent the broader views of the community.”
Lentini says “there’s no real quick fix” for helping people live close to flying foxes, but as with many things, she says “it will come down to compromise for those who are suffering with the sound and the smell. It’s going to be modifications like double-glazing and shade cloth.”
While bats might be a temporary annoyance for some (large influxes generally dissipate once the food has gone), the species itself is struggling.
Dr David Westcott of the CSIRO is an ecologist who has studied bats for more than 20 years and says 2019 was “a bad year for bats.”
“We had extreme heat and droughts and bushfires and all kinds of misery for flying foxes.”
Westcott helps coordinate a national monitoring program for flying foxes that covers more than 700 camps.
The most recent count in February, after the bushfires, suggests grey-headed flying-fox numbers are down by about a third based on an average count for that time of year, but he says they “may have moved to places we don’t know about”.
Numbers had been stable for several years before then, but the species is one of 119 animals assessed as “requiring urgent management intervention” after the 2019-20 bushfires.
A 2015 report on flying-fox numbers found the spectacled flying fox – found mainly in the wet tropics – had crashed from 214,750 in 2005 to just 92,880 in November of 2014.
Westcott says the last two years of drought and extreme heat – that can cause bats to die in their thousands – has left only about 70,000 spectacled flying foxes.
Australia’s bats – like all bats – can carry a wide range of viruses. The Sars-Covid-2 virus that led to the pandemic probably originated in bats, with the likeliest scenario being a “zoonotic” transfer to another animal, and then to humans.
“We shouldn’t pretend that flying foxes are not vectors for some nasty diseases,” says Westcott. But getting a virus from a bat “generally requires us to have intimate contact with an animal” and, with flying foxes, “we don’t do that”.
Public health authorities warn people not to handle dead or alive flying foxes because a small percentage carry Australian Bat Lyssavirus – a rabies-like virus that can be fatal if not treated. Bat carers are vaccinated against the virus. NSW Health says there have only been three cases of humans getting the virus in Australia.
A spokesperson for the federal environment minister, Sussan Ley, said bats and flying foxes “play important roles in our ecosystem, pollinating trees and dispersing seeds across wide areas.”
“While the department will continue to closely monitor the international science around zoonotic diseases in bats, there is no evidence of Sars-CoV2 (the virus which causes Covid-19) in any Australian bat species.”
Dr Michelle Baker, an expert in bit viruses at the CSIRO, says the risk of getting infections from bats is very low.
At the same time, there’s much we still need to learn about bats. For example, Baker says their life expectancy as a mammal relative to their size is “off the scale”.
“There’s a four-gram microbat that can live for 40 years, but compare that to a mouse that probably only lives for a couple of years. There’s also some evidence that bats don’t get tumours and, for a long-lived species, that is quite curious. People don’t understand how amazing these creatures are.”
Despite their talents, Welbergen says bats have “long had an image problem in western societies.”
“Just think Dracula or Halloween. They have a dark reputation,” he says.
In April, even a tweet from the Pope compared people “in a state of sin” to human bats.
“In times like this people are looking for things to blame,” says Welbergen. “Flying foxes and bats make a very easy scapegoat, especially because of the reporting that the virus that caused Covid-19 originated in bats.”