A walrus that has made very rare appearances in the waters of southern Finland is not doing well after lumbering 150 metres from a riverbank to a backyard in Kotka on Tuesday morning.

Plans were still underway to transfer the animal to Korkeasaari Zoo in Helsinki as of Tuesday evening, but it remained unclear on whether the animal could survive the ordeal involved in its treatment.

Nina Trontti, the zoo's director of animal care and protection, said on Tuesday evening that the facility was preparing to receive the large mammal.

"Right now we are measuring the door openings and figuring out how to get the animal safely out of a transport crate and into the treatment ward," Trontti said.

"At the moment it is an animal in poor condition," she noted.

The walrus' normally thick layer of fat is very thin and it is very unlikely the creature would survive in the wild in such a condition, according to the zoo.

The walrus was first seen on Friday on the bank of another river in the nearby seaside town of Hamina, then was caught in a fisherman's trap days later.