Flying-foxes and cicadas

Grey-headed Flying-foxes feast on seasonally abundant cicadas.

We add to a growing knowledge of how flying-foxes acquire protein from seasonally abundant cicadas. Understanding where and how these animals obtain nutrients is important at a time when habitat quantity and quality is in decline.

Flying-foxes are commonly known as fruit bats due to their mainly plant-based diet, but it has been known for some time that these large bats also eat insects – either as they come across them by accident or by catching them in flight. However, flying-foxes have not previously been recorded seeking out insects among foliage in a similar way to how they feed on pollen, nectar and fruit.

After observing an unexplained flurry of flying-fox activity at night in non-flowering or fruiting trees where cicadas were congregating, we found some unusual small ‘parcels’ on the ground the following morning. Upon closer inspection, the ‘parcels’ looked like little clumps of smashed up cicadas with their red eyes dotted through. Flying-foxes feed on fruit juices and pulp by pressing the fruit against the ridged roof of the their mouth, and spitting out the dry remains as ‘parcels’ called ejecta pellets. Were the cicada remains evidence that flying-foxes deliberately target cicadas using this feeding method?

We collected two of the pellets we found of the ground, froze them, and brought them to the Museum for further testing. With some detailed swabbing, we collected and sequenced the DNA from these pellets to confirm that each cicada-filled ‘parcel’ had indeed been processed by a flying-fox. In both cases we got a positive match – to be precise, to the Grey-headed Flying-fox, Pteropus poliocephalus.

We conclude that flying-foxes use an array of insect feeding strategies. Our observations suggest that these clever animals can adapt their hunting methods to different situations – catching cicadas on the wing when light levels are good and the insects are mobile, or among foliage when the insects are at rest. Seasonal congregations of larger insects such as cicadas may be an important way for flying-foxes to supplement the nitrogen in their otherwise protein-restricted diets. Understanding feeding behaviour and food resources is important for effective conservation of these mobile, vulnerable species when their habitat is declining in quantity and quality.

Helen M Smith, Technical Officer, Arachnology

Linda E Neaves, Wildlife Geneticist, Australian Museum & Royal Botanic Gardens, Edinburgh

Anja Divljan, Technical Officer, Mammalogy

More information:

• Smith, H.M., L.E. Neaves & A. Divljan (in press and preprint online). Predation on cicadas by an Australian Flying-fox Pteropus poliocephalus based on DNA evidence. Australian Zoologist.