Exotic snakes, many poisonous, are slipping unseen into Australia by plane, ship and the mail, prompting a new plan to stop more coming before they threaten native flora and fauna.

"Snakes on a plane are a real phenomenon," said Michelle Christy, the facilitator of the Invasive Animals Co-operative Research Centre's incursions response. "In the last week, a snake from Brisbane hitchhiked to New Zealand, while another was accidentally left behind by a passenger on a flight to Alaska," she said.

Some snakes arrive in Australia accidentally in a suitcase or a packing container, but many more are being smuggled as part of the growing illegal trade in pets. Some can survive three months in a shipping container without water, Dr Christy said, and even tropical snakes can survive in the cold in a ship's hold.

"A range of exotic snakes are illegally kept in Australia and now and then they are found in the wild, often by a member of the public," she said.