The reindeer that call Scotland's Cairngorms home

Since the 1950s, a herd of reindeer have roamed the Cairngorms.

Today, 150 of them live in the hills.

Tilly Smith and her family have cared for the herd for more than 40 years.

They roam 6000 acres, and return to the Cairngorm Reindeer Centre to be fed. The Smith family take tourists out to visit them in the hills.

The deer were re-introduced to Scotland in 1952 by Mikel Utsi, a reindeer herder from Lapland.

Tilly said reindeer probably lived in the area before the Ice Age.

When they disappeared is unclear. She said: "The Vikings were thought to have hunted them in Caithness and Sutherland - that's only 800 or so years ago."

Little is known about the effect the reintroduction of the reindeer has had on the environment.

Academics from the University of the Highlands and Islands are assessing their impact. They want to determine how sustainable reindeer tourism is.

The researchers are looking at the ecological role reindeer play in the Cairngorms. It will study their movements, behaviour and diet.

All images are copyright of Cairngorm Reindeer Centre.