North Ronaldsay, the most northerly of Scotland’s Orkney Islands, shares several properties in common with the country’s other remote northern isles. There’s the Neolithic-era standing stone, for example, and the lighthouse built by members of the famed Stevenson engineering clan. But look out to the shoreline and you’ll spot something altogether more particular to this island. Small sheep—wrapped in thick fleeces of brown, black, white, and gray—nimbly pick their way across sand and wet rocks. As waves break close behind them, they pass basking seals and munch on seaweed, thick pieces of brown kelp trailing from their mouths.

A primitive breed, part of the North European short-tailed sheep group, and smaller than most modern breeds, North Ronaldsay sheep have evolved in isolation since their arrival on the island, possibly as far back as the Iron Age. There are currently around 3,000 on North Ronaldsay, grazing all along the coastline and eating seaweed at low tide. Aside from the Galapagos marine iguana, they are thought to be the only land animals able to survive solely on seaweed. This is not just a quirk, but the result of necessary evolution.

Read the rest of my story about saving these seaweed-eating sheep at Atlas Obscura.