Summer frog-song and the wet

The wallum swamps and floodplain hollows spend most of the year holding their level in silence, waiting. Then the wet arrives, the warm storm-fed months from about December, and on the first hot night of real rain the whole low country finds its voice at once. Stand near a paperbark swamp or a wallum hollow after dark in a summer downpour and the noise astonishes. The pobblebonk lays down a deep banjo bonk, plucked and answered from across the water. The striped marsh frog cracks out a sharp tok, like a finger flicked against a taut drum. A green tree frog growls low from the reeds. Over the lot comes the ringing scream of the bleating tree frog, far too big a sound for the small animal making it. It is the loudest thing the coast does all year. It lasts only as long as the warm rain keeps coming.

Most of these are ordinary frogs having a very good night. A floodplain swamp fills fast and empties faster, and everything that can seize the window does. Water to breed in, cover to hide in, a sudden glut of insects to eat, the lot arriving together and gone in weeks.

But under the general uproar, down in the sour blackwater of the wallum swales, are the callers worth crossing the region to hear. The acid frogs, the wallum froglet chief among them, breed in water too sour for almost anything else to spawn in. How they pull that off belongs to the chemistry of the blackwater, not to the chorus. Their season is this one and no other. For anyone who knows the note to listen for, the thin call threaded through the din comes from an animal that breeds on these few wet nights and nowhere else on Earth.

While the frogs sing, the same rain does a second job you cannot hear. Every summer storm that soaks into the sand sinks more or less straight down and gathers as a great freshwater lens inside the dune mass, so large and so slow that water entering at the surface may wander underground for years before it sees daylight again. That hidden store keeps the swamps wet, the blackwater flowing and the acid-frog nurseries alive through the coming dry, long after the storms have gone. Recent mapping of the Cooloola sand mass shows how far its wetlands, lakes and streams lean on a water table nobody can see, and how easily that support draws down, with nothing to show at the surface until the loss is already done. Here is the quiet bargain of the wet season on the sand coast: the noise you can hear on a summer night is paid for by the water you cannot, soaking away beneath your feet to be spent out over the coming twelve months.

By the turn of the year the wet heath hangs out its own marker of the season. The Christmas bells come up on slender stalks, big waxy trumpets of red and gold standing clear of the low scrub, and the birds that probe them for nectar pollinate them as they feed. They flower toward Christmas, which is how they came by the name, and they put on their best show in the year or two after a fire. High summer on the sand coast runs as one connected event. The bells come up, the frogs roar, and beneath the din the country takes in, without a sound, the water it will live on until the next wet.