In some areas as many as 40% of deer are of mixed breed
Scotland's wild red deer may be lost if they continue breeding with a foreign species, scientists have warned.
Edinburgh University researchers found Japanese sika deer, brought to the country in the 19th Century, have bred extensively with native deer.
In some areas as many as 40% of deer are of mixed breed. Such cross-breeding can alter wild deer on Scotland's mainland permanently.
The study was conducted in Kintyre and is in the journal Molecular Ecology.
It found continued breeding could permanently change the appearance and behaviour of the native deer over generations.
Although it was already known that sika cross-breed with red deer, it was thought the overall impact on the native species was low.
Helen Senn, of the university's school of biological sciences, said: "The extent of cross-breeding we uncovered is worrying, and suggests that similar populations of red-sika hybrids could exist undetected elsewhere in the UK.
"This cross-breeding represents a serious threat to wild red deer on mainland Scotland.
"Thankfully legislation already exists to protect the red deer on many of the Scottish islands from cross-breeding with sika deer but the mainland red deer remain at risk."
The research was funded by the Natural Environment Research Council and the Macaulay Institute.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.