DNA fingerprinting has disproved a widely held theory that the biggest British newts are immigrants – and found they are almost certainly indigenous to the Highlands.

The great-crested newts which live in the inner Moray Firth and Inverness area, are separated by more than 50 miles of unfavourable habitat from the main areas where the newts live in Central Scotland. So most experts assumed that they were introduced into the Highlands.

But work by Scottish Natural Heritage (SNH) staff and local enthusiasts suggested that some of these groups might be native.

As a result, SNH commissioned internationally-recognised authority, Dr Robert Jehle of Salford University, to use DNA fingerprinting to find out more.

He and his team looked at eight populations from the Highlands and compared their DNA with two populations from the northern limits of their more continuous UK distribution.

The study showed that great crested newts are almost certainly native to the region. It also showed they are genetically distinct from those in central Scotland. This may be the result of the Highland newts being isolated from the rest of the British population about 3000 years ago

David O'Brien of SNH said: "It's important to know the newts' origins, as they're rare and protected nationally and internationally.

"This research gives even more reason to conserve the small, unique populations of great crested newts in the Highlands."