Story & photo Mary Gardner
I pause on the bridge over the Tallow. My senses are full of the changes with the recent equinox. The signs are all around. The cooler wind wrestles with the last of the wet season heatwave. From day to day, the temperature of the sea is now warmer than the air. The nights are getting longer. After the recent rains, the land is deeply watered. Wetlands are brimming. The season of mullet begins.
According to the Nyangbul Clan of the lower Richmond, these signs mark a seasonal shift in the cultural calendar. The people have certain expectations of the next few months in their Ngunya Jargoon, their wetlands. Byron Bay’s Cumbebin-Belongil complex, the Tallow wetlands and other coastal wetlands around Brunswick also share in these ecological patterns. Likely there are parallels down to the Clarence and up to the Tweed.
More rain and flooding can be expected but usually to a lesser degree. That’s because the tropical cyclones are easing as weather power shifts to become east-coast lows. Broadleaf paperbarks are flowering, soon to be followed by swamp mahogany. The blossoms of the blackbean trees become pods. Flocks of birds and bats will be at each of these trees in turn.
Lower down in the coastal swamps the lifecycles of butterflies turn with wetland plants. Under the grasses and rushes such as the Lomandra species, the arrowhead violet Viola betonicifolia is pollinated by common yellow grass butterflies Eurema hecabe. Sometimes, for reasons still unknown, these pale butterflies collect together on mysterious migratory journeys.
Also linked to arrowhead violets are the Australian Laced Wing Fritillary Argynnis hyperbius, who lay their eggs on the leaves. After the caterpillars feed and become butterflies, they will dine on blossoms within about a kilometre of their home plant. They are a pretty sight: their wings are fringed with black and coloured orange-brown with black spots. Being homebodies who depend on swamps, they are critically endangered outside of our region.
The Fritillary often carries a bacterial parasite Wolbachia. This infects the eggs, transforming males into infertile females. Sometimes infected females successfully reproduce without males.
The Wolbachia bacteria, which is found throughout the insect world, can also transfer some of its genes directly to the little animals. This process is called horizontal gene transfer. It’s a powerful example of how genes are shared outside of the usual egg-sperm interchange during reproduction.
Scientists take advantage of Wolbachia and, in an effort to limit the breeding success of mosquitoes, they infect females and release them. The Wolbachia interferes with reproduction but it offers some benefits too. During harsh conditions, it helps the stressed insects manage better. It also makes the insects more resistant to pesticides.
Meanwhile, the Southern Large Darter Telicota anisodesma is a rare butterfly of the lowlands. It may be near wetlands and also in sites such as Mount Warning National Park. They are skippers, darting from flower to flower. The tips of their antennae have a bend in them like a crochet hook. The caterpillars eat supple-jack Flagellaria indica (also known as bush cane).
Looking out for caterpillars has its uses. When ‘hairy grubs’ (also called Processionary Caterpillars) go marching lined up one after another, they are hunting for a new tree for their nest. Don’t touch them – these larvae of the Bag Moth Ochrogaster lunifer are extremely poisonous. But tradition has it that the march is also a seasonal sign about boomers.
Boomers – mullet – will soon be on the run. In the coastal freshwater, the water temperature falls and the westerly winds increase. These are signals to adults who swarm together and head to the sea. They travel in great shoals north and offshore to spawning grounds somewhere.
A few years ago, biologists Ashley Fowler and colleagues tested mullet otoliths (ear-bones) and found that in any year, only 15 per cent of the freshwater residents actually migrated to the sea. Most simply travelled up and down the waterway. A select few go to sea where their paths will criss-cross with the great humpback whales also migrating north.
Where to learn the signs?
In 2018, how do people get to know these deeper meanings to the signs of the season? Where do children and teens learn the details of such ecology? How about at a low-key community-based ecology centre! The location could be Byron Council land that was the old sewage treatment plant near the Tallow waterway. Birds and frogs already there might not object to such a gentle use of the site. They have messages of their own to share about the seasons.
Byron Council seeks Expressions of Interest for projects and partnerships for the Tallow site by 27 April 2018. If you support the idea or can help with developing a proposal for a community-based Ecology Centre please urgently contact Dr M Gardner [email protected]