Surviving the floods has been a test of our resilience in recent times, but how do the local wildlife manage the storms and the flooded creeks?
The answer is surprisingly well. Many species have very attuned senses and they are in many cases better forecasters than Bureau of Meteorology when it comes to detecting imminent storms. Most of our birds can easily detect drops in barometric pressure, wind changes, temperature drops, lightning and thunder miles away and either fly off to safer locations or take shelter in dense foliage or in nooks and crannies of tree trunks. Small birds are experts at positioning themselves close to the trunks on the leeward faces of the trees.
The biggest danger for birds is during nesting when eggs or young can get flooded. It pays to check out your area after a big storm. Several years ago I was out inspecting the damage from a particularly heavy rain period and I heard some tiny chirps at the base of an Iron bark tree and found a pair of small chicks with only pin feathers. I knew they were parrots but after feeding them for several days I was amazed to find they were Major Mitchell Cockatoos. I was aware of the parents who regularly visited us after they were expelled from a flock of 6 that lived up near the Gold Creek dam. After the chicks were fully grown they flew up into a Grey Ironbark and one re-joined the parents and the other cried for three days until I climbed about 12 metres up the tree to retrieve it. After another storm I found a Black Bittern, a seldom seen bird in Brisbane, resting after sheltering from a particularly bad storm.
Many of the larger birds just sit out in the rain and take advantage of the feast of worms flooded out to the surface. Generally, the birds manage the storms quite well.
A bedraggled but very satisfied Australian Magpie after feasting on worms brought to the surface by the flooding rain.
With the huge volumes of water flowing down Gold and Moggill Creeks during the recent flooding you might wonder if all the fish were washed down the Brisbane River into Moreton Bay. Fish are also adept at handling the conditions. The main defence of the Eel-tailed Catfish is to find deep spots in the creeks where the water flow is less strong. Other species move to the edges of the water where they find slower water behind obstructions such as clumps of refuse, large tree bases and side channels. It is well-known that the small mosquito fish, Gambusia, swims up the edges of the flow in floods and this is how they successfully populate farm dams where they were never intentionally introduced. Some natives such as Firetailed Gudgeons also use this method. Flooding can be a bountiful time for fish as fast water can dislodge aquatic insect larvae such as Dragonflies and Mayflies making them easy food for the waiting fish.
Fish are also highly streamlined and coated with mucus which reduces the friction and makes them highly capable of swimming against strong currents.
Frogs are very well adapted to flood periods, which actually stimulate their breeding as their calling during the recent rains will testify. The constant wet weather makes it easy for them to travel and some species make use of flooding conditions. The Great Barred and the Great Brown Brood-frogs lay eggs well away from creeks under stones or in clumps of grass and rely on flood water to wash their eggs into the waterways. Other species such as the Ornate Treefrogs and Ornate Burrowing Frogs lay their eggs in temporary ponds where there are fewer predators. These species develop very rapidly with the Ornate Treefrog taking only three weeks in the tadpole stage as they feed on the algae and micro-organisms that develop rapidly in the ephemeral ponds.
The Ornate Treefrog lays eggs in temporary water after heavy rain. They go through metamorphosis in 6 to 8 weeks.
For our two aquatic mammals, platypus and water rats, big floods can cause some problems. Both are highly intelligent animals and they also have some heightened senses and quickly adapt to changing conditions.
The Platypus have two types of dens. Breeding Den entrances usually are at normal water level and rise upwards and go back a metre or two. Fortunately the young were out by about the end on November so there would have been no losses of pugs during the recent flooding.
The Platypus have several other dens where they hole up during the daytime during the rest of the year. Along our part of Gold Creek there are lots of places where the banks are undercut from earlier floods and many go back a considerable distance and are well above normal water level. The Platypus use multiple dens along their range depending where they are feeding. During the recent flood most dens would have been underwater and the Platypus would have to move out. They are extremely strong swimmers and would have skirted around the edges of the flood and probably made temporary dens in the flotsam pushed up from the flood.
An undercut bank in Gold Creek which a Platypus has been using for several years. It goes back at least 1.5metres. The Platypus’ senses are so acute that it can detect movement at the lookout above.
The Water Rats are not as committed to needing an aquatic environment as the Platypus. They regularly raid our nursery buildings well away from the creek and steal goldfish and ornamental snails. They are very clever animals and would have had no difficulty in finding cover for their daytime sleeping quarters while the flood was raging. They would not have any problem keeping warm as they have one of the most dense waterproof furs of any animal.
A Grass Skipper butterfly sheltering from the rain
Butterflies are rather delicate creatures and small enough that a raindrop in comparison to their size would be like a 10-litre bucket of water hitting us. They have a number of defences, but foremost is simply perching on the undersides of a good strong leaf. Some shelter in nooks and crannies of trees and the common Evening Browns shelter under clumps of grass. Ladybirds also shelter on the undersides of leaves and some species congregate in large numbers under loose bark of Eucalyptus trees.
After the Flood.
Mostly our wildlife survive these periods quite well if they don’t coincide with their breeding season. But after the flooding there can be a period of where feed can be in short supply. Nectar and insect eating species can have problems, but unless it is just before winter it usually doesn’t take long before things get back to normal.
For seed eaters there can be a feast on the ground.
Fish in the creeks may have a shortage as the insect larvae live in the debris and mulm that will have been washed out. However, in a few weeks the build-up of mosquito and midge larvae will result in plenty. Without these periodical flooding events the creeks get overgrown and the water quality goes down so the cleanout and inflow of water from the land loaded with nutrients results in a bloom that starts a flush that benefits the environment and the animals living in our creeks. This recent event fortunately was during the warmer months so the recovery will be rapid.
Photos and words by Ed Frazer.