A West Australian man has captured on camera what may be one of the first documented cases of a redback spider capturing a mouse.

Key points: An arachnologist says a redback killing a mouse has not been officially documented

An arachnologist says a redback killing a mouse has not been officially documented Redbacks 'vomit' digestive juices onto their prey to dissolve it and then "suck up the slurry"

Redbacks 'vomit' digestive juices onto their prey to dissolve it and then "suck up the slurry" A mouse would need to be encased in a web to prevent it escaping

Ruben Boddington, who lives in Denmark on WA's south coast, stumbled upon the scene last week as he was about to go on a bike ride.

The pictures show the mouse wrapped in spider web.

"I was about to jump on my push bike when I saw something moving near the pedals," Mr Boddington said.

Redbacks vomit up digestive fluid to dissolve their prey. ( Supplied: Ruben Boddington )

"I had a close look and saw it was a redback wrapping up this mouse, which was still alive."

Mr Boddington said he had never found a redback on his property before but believed it might have been transported to his shed in a kayak, which had just been returned from his brother who lives in Fremantle, near Perth.

Mouse a massive meal

Arachnologist Robert Whyte, author of the Field Guide to Spiders in Australia, said redbacks used a neurotoxin to prevent their prey from moving, but a mouse would need to be encased in a web to prevent it escaping.

"A mouse would need a little bit more than a bite to render it unconscious," he said.

"It actually needs to be wrapped up so the redback can consume it."

The only other documented instance of a redback catching a mouse was an image taken in New South Wales in 2016 showing a small field mouse caught in a web.

Spider arachnologist Robert Whyte says redback spiders are among Australia's most-effective hunters. ( ABC News: Lucy Murray )

'Vomit up juices' to digest prey

Mr Whyte said the mouse would have been a generous meal for the redback and said spiders digested their food outside their stomachs.

"They vomit up digestive juices onto their prey, dissolve it, and then suck up the resulting slurry," he said.

"They are dissolving the muscles, gut, and brain — anything that is more or less flesh."

Mr Whyte said the redback, which has its origins near the border of Western Australia and South Australia, was an incredibly successful spider, spreading across Australia and the world.

Redback spiders have been found across the world ( Supplied: CSIRO )

"From there it has spread amazingly well because it's such an adaptive creature," he said.

"It can survive in ice and snow.

"It has now spread all over the world, in Japan, England, Belgium, the UAE; it's one of our most successful exports."

A redback bite can cause death, especially in children, but the spider often bites without introducing venom.

"Their bite is incredibly painful but only 25 per cent of people bitten experience pain. It's often a dry bite," Mr Whyte said.