A pygmy possum has hitched a ride around southern Yorke Peninsula in South Australia in the bottom of a mail bag.

The mail sorter at Minlaton post office, Jack May, said he thought at first there was a mouse in the bag from Foul Bay, but then noticed large eyes and a curled tail.

"It was hard to know who got the biggest surprise — me or the possum," he said.

Post office staff called on the team from Natural Resources Yorke and North to arrange a return of the tiny possum to its home, about 90 kilometres from Minlaton.

Deborah Furbank from Natural Resources said many rural properties used empty drums as their mailboxes and these proved to be popular napping spots for native animals.

"The possum was fine, it was very frisky and very curious when we looked in the bag," she said.

"We gave it flowers with nectar so it had food to eat."

Possum returned to original habitat

Ms Furbank said it was important to release the possum back to where it had travelled from.

"They are territorial so it was really good that the post office kept the details of which bag it had arrived in so we knew where to let it go," she said.

"It travelled over 200 kilometres by the time we got it back to its original destination.

"It must have got picked up in the morning and was replaced the following morning, so it must have been about 24 hours.

"It was a big day for a little possum."

Another member of the Natural Resources team, Cath Cameron, was due to travel from Minlaton to Foul Bay so got the extra job of chauffeuring the pygmy possum home.

"It was a classic case of return-to-sender," she said.

"When I dropped it back near the mailbox it hopped off my hand and scampered into nearby bush without even a wave."