Snakes on the plains will seek shelter in back yards and homes as the flood waters from the eastern states surge down the system into South Australia.
The state’s flood plains and relatively flat topography will slow the advance of the water from New South Wales and Victoria, before it is channelled into the River Murray.
South Australians are bracing for the river’s rise, putting flood protection in place, and facing the prospect of wildlife fleeing the wet, or drowning in it.
Karl Hillyard, the state department for environment and water’s principal ecologist, said people should give snakes a “wide berth”, especially as they become more active in the warmer weather.
“If there are snakes where the water’s rising, they’ll go somewhere it’s not wet,” he said.
“I don’t think we’re expecting anything biblical, but it’s natural to expect they’ll swim.
“If they’re in your house, contact a professional snake catcher. Don’t stick your hands where you can’t see. Clean up your yard. And if you have a rat or mice infestation, get on top of it – or the snakes will.”
Prof Richard Kingsford, a river ecologist and conservation biologist from the University of New South Wales, said water would flush out animals who have “set up homes in the cracks and burrows”.
“They’re in escape mode,” he said.
“They’ll climb up trees, they’ll go wherever they can. A lot will die. Some will go out to the margins.”
There are 46 snake species in the Murray-Darling Basin. Kingsford said aquatic types such as the red-bellied black snake would be all right in the water, while others, such as deadly brown snakes, would try to get out.
“They’ll wait. As the water dries back, there’ll be lots of food there,” he said.
Water flowing down the system from NSW and Victoria in the wake of their devastating floods is already flowing into SA, and is expected to peak next week. A larger second peak is predicted to hit the state around Christmas.
The peaks will take about a month to travel the length of the state to the ocean.
The flood levels in SA are not expected to surpass the famous 1956 event, during which the Advertiser reported that a dairy farmer killed 1,032 tiger snakes driven from their swamp habitat on to his property by the water.
Thousands of homes in SA (most of them not primary residences) are at risk of inundation, and businesses including tourism are already severely affected.
But experts say the water is also flushing out the system and removing the salinity that has been at harmful levels since the millennium drought, so many birds and fish are thriving.
The impact on turtles will be a mixed bag, Hillyard and Kingsford said.
Hillyard said turtles are often nesting at this time of year, and their nests could be in danger, while fast-moving water could wash young ones away.
On the other hand, they’re scavengers that will be able to feed on the detritus washing down the river.
Kingsford said the water could help turtles dodge foxes.
“If they nest in the wrong place, not expecting such a big flood, the eggs will drown,” he said.
“The turtles, though, will have another go and they’ll probably do pretty well because it’s such a vast area and foxes won’t know exactly where they’re nesting.”
All the water, meanwhile, is an “extravaganza” for the frogs that live in the river system.
Kingsford said black water – when oxygen is stripped from water by the bacteria consuming rotting animals and plants – would be harmful on the floodplains upstream, but once the tributaries flow into the River Murray, it could dissipate.
“If the water’s moving, it tends to disrupt it – the turbulence puts oxygen in,” he said.
While the floods have been so damaging for humans, Hillyard said the effects on the environment were complex and interwoven, and different when the water is rising to when it is receding.
“The black water … it’s not great for fish in the water,” he said.
“But at the same time, the flip side is we’ll see great flushes of vegetation, of habitats for frogs and birds.
“It’s swings and roundabouts.”