A peripatetic walrus who became a local celebrity as he toured the north-east coast of Scotland has now been spotted in Norway, bringing to an end his Celtic sojourn.

The young male was christened Magnus after he after first hauled his estimated 2.5-metre frame out of the sea on to Stronsay pier in Orkney on 16 April.

Although walruses usually prefer to rest on sea ice, Magnus has since then been found snoozing on piers and pontoons along the Moray coast after swimming 200 miles south to the Scottish mainland.

Police asked the public to report sightings of a wandering walrus, and his appearances drew hundreds of spectators as he swam from Lossiemouth to Macduff, Fraserburgh, Findochty and then Hopeman, entertaining crowds with his vigorous itching and – in a move surely conceived for Instagram – accidentally rolling off a harbour wall.

Walruses are rare visitors to Scottish shores, although sightings have increased in recent years, prompting concerns that the effects of climate change on their Arctic ice habitat may be causing these southbound excursions.

While walruses are known to be highly social animals, by 21 April police took the step of erecting a cordon at Lossiemouth marina to contain his admirers.

Further along the coast in the fishing village of Findochty, Katie Wilson spotted Magnus on April as she was dropping her three-year-old daughter at nursery near the harbour. “The kids could not believe it,” said Wilson at the time. “They were in shock. It’s not every day you see a walrus here.”

Wilson said that Magnus appearing to be sunbathing on a pontoon after swimming a lap around the harbour. “He seems quite happy. He is just chilling,” she told a local reporter.

On 30 April, the tusked traveller was again spotted swimming alongside a group of pupils from Gordonstoun, King Charles’s alma mater, who were taking a sailing lesson in Hopeman harbour. Magnus was later seen sunbathing on a nearby rock and rolling off a pontoon while napping.

A fortnight later, a local birdwatcher from an archipelago south of Stavanger, in Norway, has raised the alert that Magnus had crossed the North Sea.

Åge Jakobsen told BBC Scotland: “We went out to Buerholmen at Hidra to look for and photograph the walrus Magnus who is staying there. It was a little different to take pictures of one of the birds I usually do – didn’t seem like it would fly away.”

He said that the walrus appeared “really tired” after the 400-mile journey across the North Sea but was having a “great time in the sun on the floating dock”.

The team from British Divers Marine Life Rescue had been monitoring Magnus as he made his way around Scotland, noting that adolescent walruses do experience wanderlust.

The Orkney Marine Mammal Research Initiative said it this was “a genuinely rare event” and only the third time a walrus has been sighted in Orkney in the last decade.

“Walruses are Arctic animals, native to the sea ice and subarctic waters of the northern hemisphere. The individuals that turn up on our shores are typically young roving animals – adolescents striking out beyond their usual range, possibly following food, possibly just exploring, likely due to climate change to some extent.”