Feral deer numbers are exploding across the country and are costing farmers and motorists up to $200 million a year.
Farmers bearing the brunt of the cost, with up to $164m a year lost in agricultural output, a Centre for Invasive Species Solutions report found.
Alarmingly, deer are costing motorists up to $13.2m with an estimated 300 crashes a year across NSW, Tasmania, South Australia and Victoria.
Invasive Species Centre chief executive Andrew Cox said the true figure was probably much higher, but the true figure could be much higher, as the deer-specific crash data is not well collected.
Mr Cox said a close friend of his was lucky to be alive after a night-time collision with a deer on the highway between Canberra and Sydney.
"Deer are cute for the first few months, then they start raiding gardens and having close calls with cars," Mr Cox said.
There are six species of deer in Australia, including the Sambar deer which can weigh up to 300kg.
"The car hazard is a big one... they're massive animals," National Deer Management Coordinator Annelise Wiebkin said.
"I was working with one landholder who hit a deer on their way home, after a meeting about how to best manage deer in the region."
There are also about 30 train collisions with deer every year, which cost $2m due to the high call out cost, while governments spend up to $26.7m on deer management and research annually.
CISS chief executive Andreas Glanznig said the costs are predicted to rise to the billions over the next 20 years if nothing is done.
"Without concerted action to control feral deer numbers the report finds that their costs are set to jump over the next few decades, with Australian agriculture bearing the brunt," Mr Glanznig said.
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It's estimated that 500,000 cattle and two million sheep are stocked in areas where feral deer are a major problem, or around three per cent of the national beef herd and sheep flock. In NSW, deer are expanding their range by a million hectares, or an area roughly the size of Lebanon.
Mr Cox said deer were difficult to deal with because they were generalist feeds and drought resilience, with the ability to jump over six-foot fences. There are currently no baits for deer and their wily nature makes ground shooting ineffective.
"If you're not removing 40 per cent of deer in the area per year, they're numbers will keep going up - aerial culling is one of the few effective measures we have," Mr Cox said.
The National Feral Deer Action Plan, which will guide government policy to eradicate and manage the pest, is expected to be released in the coming weeks.
Dr Wiebkin said farmers struggling to manage feral deer had a simple message to other landholders; "if you see a few, act now before it's too late".
"Landholders see a few on hillside and like them around - they think they're nice to look at and they can fill the freezer for meat," Dr Wiebkin said.
"Then five years later they feel the impact. They didn't notice until all of sudden there were too many to deal with. It's a really common story."