A mysterious and rarely seen female octopus has washed up on a Port Fairy beach but scientists are unsure exactly why.
Parks Victoria says the blanket octopus was sighted in Port Fairy, along with another at Barwon Heads.
The female octopus can grow to two-metres long and weigh up to 40,000 times more than males, which are about the size of a jelly bean.
The octopus can distract predators by casting off tentacles. It can also carry the stolen tentacles of venomous jellyfish.
The tiny male detaches an arm containing sperm, passes it to the female, then dies. The female is then known for attaching all of her eggs to a rod that she holds within the protection of her arms.
Museums Victoria marine invertebrates senior curator Dr Julian Finn said there was still much to know about the octopuses.
"While we can study the individuals that unfortunately wash up on our beaches, much of their lives remain a mystery," Dr Finn said.
"The blanket octopus gets its name from the expanded webs, or 'blankets, that unite the female's dorsal arms.
"When swimming, she can unfurl and trail these giant webs, giving her an apparent total length of up to two metres."
But scientists aren't exactly sure why the octopus washed up on the beach at Port Fairy with recent storm activity a likely answer.
Storms or onshore winds push the creatures into coastal waters, which are too shallow to allow them to dive, and they can then get caught in wave action and wash up on the beach.
Parks Victoria chief conservation scientist Dr Mark Norman said those same weather conditions likely also washed up a handful of knobbed argonaut shells along the south-west coast.
Dr Norman said the argonaut, another open-ocean dwelling octopus, was among the "strangest and most beautiful creatures".
"They are free-swimming octopuses. The female builds an intricate delicate shell which is one of the most beautiful of all beach-washed shells," Dr Norman said. "Past strandings of argonauts in Victoria have involved tens of thousands of females washing ashore with their shells."
Beachcombers prize the shells, but Dr Norman said seabirds were also quick to swarm on the shells in search of the octopuses' eggs.
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