ESPERANCE — Housemates in Esperance, Western Australia, found a live frog the size of a man's palm inside a sealed plastic bag of lettuces purchased from a supermarket. The pair of lettuces had been reduced for quick sale to $1.15.

Laura Jones and Billie Le Pine appeared on ABC News Breakfast to discuss finding the frog. Le Pine said they named the frog Greg, released him into a nearby dam and played the song "Crazy Frog" as part of the release.

A Woolworths spokesperson said the company apologized to the customer and provided a replacement item. "Our suppliers have rigorous processes to maintain product quality. For heads of lettuce this involves washing and a number of quality checks, which includes checking for foreign materials, before they are packaged and sent to our stores," the spokesperson said.

Dr Jodi Rowley, who was in the Blue Mountains on Monday afternoon, could not definitively identify the frog species from the television footage but narrowed down the possibilities. "But it's a bell frog for sure," Rowley said.

"If it came from WA, then it's a relatively common species of frog called the motorbike frog. If it is from the east coast, then it is either the green and golden bell frog, or the southern bell frog – and both of those species are threatened," she said.

Rowley has written that thousands of frogs accidentally hitchhike on shipments around Australia and end up packaged in produce. She said typically stowaway frogs are rehoused, quarantined and then become people's pets. Rowley encouraged anyone who finds a frog in their shopping to put it in a container and contact an expert for identification, to improve the frog's chances of survival and to prevent the spread of disease.