Setting up camp in Adelaide: Ecological Insights into the Range Expanding Grey-headed Flying Fox (Pteropus poliocephalus)

Abstract

Grey-headed flying foxes, Pteropus poliocephalus, classified as Vulnerable under the EPBC Act, 1999, historically ranged from Melbourne in Victoria to Ingham in Queensland. However, for the first time, a population set up camp close to the Adelaide city centre in 2011, expanding the range of the species. I wanted to investigate what had motivated them to move to Adelaide including whether there are ‘pull’ factors at work; environmental factors attracting flying foxes into the area. Specifically, I wanted to investigate how they were utilising the greater Adelaide landscape to forage and what they were eating. Furthermore, I wanted to measure the population’s exposure to viruses of zoonotic potential to investigate whether their arrival poses a risk to public health. Using GPS telemetry, I tracked individual flying foxes (n=5) to document their Spring foraging movements and activities. Despite being a highly mobile species, the mean core foraging range estimate was only 7.3 km2 and maximum foraging distance from the camp in the Botanic Park was 9.5 km with most foraging occurring within a 4 km radius which indicates they found sufficient foraging resources entirely within the residential area of Adelaide on streets, parks and residences. They foraged on introduced tree species either not native to South Australia or exotic to Australia. Movements of individuals also indicated persistent utilisation of same foraging sites over many days, regular use of water resources and the use of air space around Adelaide International airport. To further document the diet of Adelaide’s flying foxes on a larger scale, I used DNA metabarcoding on 161 faecal bat samples to confirm which plants they were eating. I found that their diet included 40 operational taxonomic units (OTU) across 15 orders, 15 families and 10 genera. Over 86% of all plant sequences belonged to just three orders: Rosales (54.35%; including the families Rosaceae and Moraceae, the latter incorporating the genus Ficus), Myrtales (21.63%; including the family Myrtaceae which includes the genera Eucalyptus, Angophora and Corymbia) and Malpighiales (10.26%; including the family Salicaceae which incorporates the genus Populus). The genus, Ficus, from the Moraceae family and Rosales order, which is not native to South Australia accounted for 22.10% of the sequences identified while the family, Myrtaceae which contains the genus Eucalyptus and is native to Australia accounted for 21.56% of all sequences. Overall, the majority (75%) of sequences were aligned to plant OTUs that could be considered either non-native to South Australia or exotic to Australia which indicates that Grey-headed flying foxes have been able to establish a camp in Adelaide as a result of the human-modified landscape. On the global scale, flying foxes are known to act as spill-over hosts for emerging infectious pathogens including viruses of zoonotic potential. I therefore sampled a total of 301 flying foxes in the camp, over six serosurveys and investigated, using a multiplex Luminex binding assay, the levels of exposure to known viruses of zoonotic significance. I found strong serological evidence of common exposure to Cedar (apparent seroprevalence; AP = 26.6%; 95%CI: 21.7%-31.9%), Ebola Zaire (AP = 18.9%; 95%CI:14.7%-23.8%), Hendra (AP = 43.2%; 95%CI: 37.5%-49%), Severe acute respiratory syndrome (AP = 31.6%; 95%CI: 26.4%-37.1%), and Tioman (AP = 95.7 %; 95%CI: 92.7%-97.7%) virus antigens. Temporal variation in antibody levels suggests that antibodies to Hendra virus and Tioman virus may wax and wane on a seasonal basis. For all viruses, exposure could have occurred anywhere along the flying fox species distribution range continuum. However, I found no serological evidence of exposure to Middle Eastern respiratory syndrome virus (AP = 0.7%; 95%CI: 0.01%-2.4%) or Australian bat lyssavirus (AP = 0.0%; 95%CI: 0.0%-1.22%), despite a case caused by the latter virus being diagnosed in a bat from the camp in 2012. In conclusion, I found the flying foxes have been attracted to Adelaide because of the abundance of foraging resources which has allowed them to thrive, and the population has been exposed to many viruses of zoonotic potential which may pose a biohazard risk to the human inhabitants of Adelaide.