Landowners are being urged to be extra vigilant after two Muntjac deer were seen in Dumfries and Galloway.
The deer are not native to the area and are thought to cause severe damage to vegetation.
The deer originate in China and, if they establish themselves in Scotland the SNH estimate it would cost up to £2m due to damaged crops and vegetation.
Muntjac deer have spread rapidly across England and Wales over the past 40 years and caused extensive crop damage. The small deer are originally from China and are now moving north. So far, they have not become established in Scotland. If Scotland did have to manage a Munjtac population, SNH has estimated the costs would be up to £2m a year.
Scottish Natural Heritage Wildlife Operations Unit are investigating the incident.