In just about anyone’s visual language the Ghost Bat Macroderma gigas is ugly as sin. But the world is a place full of weird people–like me–who reckon that M. gigas is as beautiful a creature as you’d like to meet on any dark night in the tropical north.
I’ve only run into them once–literally–in the flesh, though I’ve heard their distinctive twitter and cricket-like chirp plenty of times when out in the Top End bush at night and have seen them hawking after food at dusk–they are our only carnivorous bat and despatch their prey, according to one report–by holding it with their thumb claws and killing it with a single swift bite to the neck. Ghost Bats will prey on birds, mice, micro-bats, lizards, geckos, snakes and insects.
Red in tooth and claw indeed.
I first ran into a small colony of Ghost Bats living in a couple of ruined houses at the all-but-abandoned ranger station at Murganella, in western Arnhem Land sometime around 2000. I was checking the buildings out for work and walked into an old termite-riddled house, careful not to tread on rotting floorboards or disturb any snakes that might be around. As I slowly pushed open a door to enter one of the rooms, again more careful for snakes than anything else, a flurry of large greyish bats brushed past me to escape the room, chattering in a blind panic of shock and surprise that matched mine.
I knew these weren’t the much larger Black Flying Foxes Pteropus alecto and it soon became clear to me that these were no fruit-eating bats either, because on checking the bat-shit that lay in a thick circle under the ceiling fans–a convenient roost if ever there was one–the vertebrate remains therein–bone, feathers etc–told me that I was dealing with a large carnivore. Later the caretaker blithely told me that yes, if I’d bothered to ask him, he would’ve alerted me to the Ghost Bats that roosted by day in the ruined houses.
The other report I have of Ghost Bats is a sad tale in Sue Churchill’s book, Australian Bats, an excellent field guide (and more) on the subject. My first edition–now about twenty years old–has a chapter entitled “Beliefs about bats” and in part relates the story of a field trip to the south-west of the Northern Territory in the early 1980s where she was researching the distribution of Ghost Bats, which had been found there at the turn of the 20th century but with only isolated records dating back to the late 1950s and early 1960s since that time.
We approached the traditional Aboriginal custodians of this land to arrange a meeting … As it happened there was a meeting of traditional owners and tribal elders at Uluru. We were invited to discuss our study and were received with courtesy. Knowing that many of the older people would not speak English, I had prepared a study skin of a Ghost Bat to pass around. I was sure that if it was in the area they would recognise such a distinctive animal. When the moment came to show them the bat there was a collective gasp of shock. Women present at the meeting hurriedly covered their faces . The men looked stunned.It was a terrible moment. In my ignorance I had offended the very people whose help I needed.It turned out that this animal hasd great spiritual significance to these people and that it had to do with men’s business. As a female I had committed a serious faux pas.
Later, forgiving my blunder, the elders told us that they would like the project to go ahead. It was important to them to know where the bats were living. There was a problem however, as the caves were sacred sites connected with men’s business.
Further negotiation followed, and eventually senior men agreed to take Sue Churchill and the other researchers to the caves to see if they could find any extant Ghost Bat colonies. Over a period of some days they traversed the sand dunes and rocky out-crops of the south-west but each cave was “barren of Ghost Bats, although there was ample evidence of previous occupation.”
Even the caves of Uluru are a metre deep in dried and mummified Ghost Bat droppings. But the Ghost Bats had left. With each disappointment our Aboriginal mentors became more distressed and more anxious to check the next site. As we ran out of caves a great sadness overtook the men, and some of these dignified old gentlemen were in tears. It was a humbling experience and we wished there was something we could do.
Now we know that the Ghost Bat’s range has retreated even further from the vastness of the central deserts to a few, relatively small ranges in the tropical north of the country.
As a result of this habitat loss, the Ghost Bat has now been listed as Vulnerable on both the IUCN Red List of Threatened Species and under the EPBC Act because it has a small population (less than 10,000 mature individuals), and the inferred decline in the last three generations has been greater than 10%, and there is the potential for the population to decline even faster within the next three generations.
Major threats include the Ghost Bat’s vulnerability to disturbance in its roost sites. Cave tourism has been identified as a problem, but the most serious threat is from quarrying and reworking of old mine areas. In some cases, the collapse of disused mines may also be a threat. Habitat modifications for livestock may be a problem in some areas, as may competition for prey with introduced foxes and feral cats (Hutson et al. 2001). Barbed wire fences on cattle stations and lantana cause some direct mortality (Armstrong and Anstee 2000). For the populations at the southern limits of the species’ range, the general paucity of suitable roost sites, the geographic distance between existing colonies, and the evident complete lack of gene flow indicates that these populations are totally isolated and will not be rescued by immigration or recolonised should local extinctions occur (J. Worthington-Wilmer pers. comm.). (from the IUCN Red List website).
So what to do?
Well, listening to what the Ghost Bats have to say to each other–and what they can tell us–is a very good start.
Nicola Hanrahan is a PhD student at the Hawkesbury Institute for the Environment at Western Sydney University and is working with experts in the forefront of this field: Dr. Justin Welbergen, Dr. Christopher Turbill from the Hawkesbury Institute for the Environment, Dr. Anastasia Dalziell from the Cornell Bioacoustics Research Program, and Dr. Kyle Armstrong from the University of Adelaide. This team is working in collaboration with Dr. Alexei Vyssotski at the Institute for Neuroinformatics at the University of Zurich, who is the inventor of the Neurologger 3.
What is the “Neurologger 3” and what does it have to do with Ghost Bats?
For that we need to look a little more closely at Nicola Hanrahan’s research.
This is from the Pozible Campaign Page for her research group:
Ghost bats communicate vocally with calls in the audible and ultrasonic range (listen here), but it is yet unknown what the specific purposes of the calls are. If their calls can be deciphered, we can unlock a wealth of information about ghost bats, including on their social structure and movements between roosts, which is important for informing successful management plans. It has historically been difficult to study bat social vocalisations, but fortunately, recent advances in acoustic technology and analytical techniques mean that we can now study such vocalisations in great detail.
That acoustic technology is the Neurologger 3:
A device called the Neurologger 3 (Evolocus LLC) lets us do exactly that! The Neurologger was originally developed for looking at brain activity in birds and rodents. Application of the device is expanding, for example Anisimov et al. 2014 (more here) used the Neurologger to investigate vocal interactions in zebra finches allowing vocalisations to be separated irrespective of the number of individuals calling simultaneously.
Bats fitted with the Neurologger 3 will be recorded while communicating naturally in a group. This allows us to determine if there are any age or sex biases within their call repertoire. Following this, we will record the behavioural response of the ghost bats to the playback of conspecific calls. The reaction of each of the bats to these stimuli will be recorded, allowing the function of the call to be worked out and subsequent playback experiments to be designed. Hetero-specific stimuli such as models and calls of predator and prey will also be used to provide further understanding of behavioural and vocal reactions to other species.
So what can you do to help this project? Check out the group’s Pozible Campaign Page, read up on their great work and–most importantly–throw a little dosh their way. There are some great rewards for pledging and you’ll be all the better for helping to decipher the whispers of our most iconic and mysterious flying mammal–the Ghost Bat.
The funding target is $12,000 and this will be used to purchase three Neurologger units and Neurologger accessories. Three Neurologger units are the minimum required to conduct our experiments and we would greatly appreciate your help in buying each item. If we exceed our funding target of $12,000, for every additional $3,000 raised, we will purchase an additional Neurologger unit. Each additional unit will increase the number of individuals we can record at once, giving a more complex view of group interactions.
You can learn more about Nicola Hanrahan’s work through her Twitter stream at: @nicci_hanrahan!