The flying foxes of Adelaide: South Australia adapts to the emergence and expansion of megabat colonies.
Each evening, a group of pine trees by the Adelaide zoo becomes a spectacle as thousands of megabats fly into the sky. The large, scalloped wings of these grey-headed flying foxes create a silhouette against the sky, resembling the emblem of a well-known superhero.
Flying foxes first appeared in numbers in Adelaide around 2010 after climate change-related food shortages drove them further south. Drought conditions and habitat loss forced them out of New South Wales and Victoria, and once they found a good spot they settled in – and bred.
Currently, they congregate in one large colony at Botanic Park, consisting of approximately 46,000 individuals, before embarking on their nightly search for food, creating disturbance along their route.
Jason van Weenen, the leader of Green Adelaide’s urban biodiversity team, states that the numbers for the urban camp are significantly high and are comparable to some of the highest numbers seen in South Australia.
In 2010, we saw the arrival of our first colony, which coincided with the species facing significant challenges in their primary habitat in the east.
“The challenging circumstances led them to discover Adelaide, which they have now integrated into their foraging practices.”
The Pteropus poliocephalus, commonly known as the grey-headed flying-fox, is a species of bat found in Australia. It is one of the largest bats in the world and is often called a fruit bat. These bats can weigh up to 700g and do not rely on echolocation like microbats, which can weigh as little as three or four grams.
A recently formed, compact SA settlement has been created close to the local Millicent town, and it is predicted that additional camps will be formed. However, temperatures reaching 38C pose a serious threat to the megabats, particularly the young ones – a significant concern in recent times.
In Adelaide, a sprinkler has been elevated to the height of trees in an effort to lower their temperature. They can sometimes be spotted sipping or even swimming in nearby rivers.
The mild summer and plentiful resources this year have resulted in a significant increase in the colony’s population, thanks to successful breeding and no major heat-related issues.
During the day, these animals gather in trees, resembling crinkling trash bags with their fluffy, fox-like faces visible. At night, they forage for nectar from eucalyptus trees and also consume fruits such as figs, apples, and pears.
However, during their search, they can create harm. The juveniles become fatigued more quickly and seek places to rest on power lines, resulting in power disruptions.
According to Paul Roberts, the head of corporate affairs at SA Power Networks, the months of February and early March are particularly problematic for power outages caused by bats as the young bats begin to venture out from their nests.
The speaker explains that customers may face long periods without electricity if an animal becomes trapped on powerlines, or brief interruptions when power is restored after the animal is no longer in contact with the lines.
“Many of these power failures happen during the early morning hours when young animals become fatigued from searching for food and attempt to perch on the top of electricity poles for a break.”
In the year 2023, there were numerous brief interruptions in addition to 55 longer-lasting interruptions, resulting in a loss of power to 72,000 customers. Roberts predicts that there will be more outages this year, but fortunately, they will mostly occur during the early hours.
SA Power Networks is working on fixes. Animal guards – Frisbee-like plastic devices – are being attached where powerlines are the most affected, but the bats’ flight paths are random, making it hard to be systematic. So crews put the guards on as they’re working on other issues, or if they have spare time.
According to Roberts, we are committed to reducing the effects as much as possible. However, because the number of colonies is increasing and we have a large number of poles, there is a significant amount of work that needs to be done in the next ten years. This includes installing animal guards and covering more powerlines, which will greatly decrease the occurrence of bat-related power outages that often happen in unpredictable locations.
While bats have the potential to transmit lyssavirus, instances of human infection are uncommon. Additionally, they can carry Hendra virus which can spread to horses and then to humans, but the risk has been reduced due to horse vaccinations.
Van Weenen explains that it has been a significant learning process, as the population is both safeguarded and presents difficulties for infrastructure and industry.
Each species has unique traits and qualities, and the flying foxes in South Australia stand out from other species due to their distinct differences.
“If you experience a scratch or bite, it is important to seek a rabies shot,” Van Weenen advises. “As the colony is relatively new in South Africa, we want to remind people not to touch the bats. Trained individuals are vaccinated and able to handle the bats safely and provide proper care for them.”
In back yards all over metropolitan Adelaide, grey-headed flying foxes can now be heard squawking and squabbling over the choicest food – they’re fond of river red gum and blue gum nectar, and go bananas for lemon-scented or spotted gums.
At sunrise, the group returns to its urban encampment where they will spend another day gripping onto trees with their feet, their furry heads peeking out from under their fluttering, dark wings.