The flying-foxes

Stand under a flying-fox camp at dusk and you will watch the coast’s largest daily migration leave home. The bats stir, bicker, drop from the branches and beat out over the river in a loose, wheeling stream that seems to have no end, thousands of them, off to work the night. By dawn some will have flown forty kilometres out to feed and forty back (Eby 1991; DAWE 2021). Almost nothing else on this coast moves like that, or does the work they do while they are gone.

The residents here are two: the grey-headed flying-fox (Pteropus poliocephalus) and the black (P. alecto), joined when the eucalypts flower heavily by the nomadic little red (P. scapulatus), which arrives on the blossom and moves on with it. All are big fruit- and nectar-eating bats, and all, by common consent, a nuisance. They are noisy. They smell. They roost in great, conspicuous camps in the riverside paperbarks right where the towns want to spread, and they carry a couple of serious viruses. So they have earned a thoroughly bad press. It is one of the great misjudgements of the coast, in the same family as our old contempt for the mangrove and the swamp, and it gets the animal exactly backwards.

Take the viruses first, since they do most of the frightening. The bat lyssavirus passes only by a bite or a scratch, or a bat’s saliva in an eye or mouth; Hendra has reached people only through an infected horse, never by casual proximity, never from a camp overhead or a bat crossing the yard. The risk is real for anyone who handles an injured animal, and vanishingly small for everyone else. It is not a reason to want the bats gone. It is a reason not to pick one up.

The flying-fox is a keystone, one of the most prolific long-distance pollinators and seed-dispersers in eastern Australia. As it works the blossom of the eucalypts and paperbarks it carries pollen from tree to distant tree, across gaps a bee would never bridge. And when it swallows the fruit of a rainforest tree in one patch of forest, it voids the living seed, hours and kilometres later, in another. Across a hundred and more tree species it runs a delivery service measured in tens of kilometres a night. That long-range freight is what the rainforest cannot regenerate without. A forest is only as mobile as its couriers. Strip out the ones that carry the big seeds and it slowly loses the power to move, and the cleared paddock next door stays a paddock because the seed never arrives.

Here the usual account turns over. Most animals you read forwards, by what they cannot do without. The flying-fox you read backwards, by what cannot do without it. In a landscape chopped into isolated fragments, it is often the only thing still physically joining them, gene by gene and seed by seed, a linchpin invisible right up until it is pulled out. Remove the flying-foxes and the forests they quietly service begin, over years, to wink out, and scarcely anyone would connect the loss to the maligned bats they drove away.

The cruel turn is that the courier is now in trouble itself. It loses feeding habitat as the forests shrink. It meets conflict wherever a camp butts up against an expanding town. And, more and more, it is killed outright by heat. A flying-fox has no good way to shed a large heat load, and on a searing afternoon, when the air climbs past the low forties, a whole camp can tip over into mass mortality: the bats simply cannot cool themselves, and they fall from the branches in their thousands. A single catastrophic heat event in south-east Queensland on 4 January 2014 is thought to have killed at least 45,500 flying-foxes in a day (Welbergen et al. 2014). Days like it are forecast to come more often as the century warms.

So the animal streaming out over the river at dusk, the one the town would happily be rid of, is the thread holding the fragmented forests together. Hated for all the wrong reasons, and among the coast’s animals most exposed to a heating world besides. We would miss the flying-foxes far more than we imagine, though few of us would ever know to blame their absence.