MUNTJAC deer - one of the most destructive introduced species in the countryside - are continuing their relentless spread across the North-East.

Established for many years in North Yorkshire, the tiny deer have arrived in Cleveland, and there have been several sightings in County Durham.

They are also known to be living in north Northumberland, where several have been killed on roads.

The deer were introduced into Britain from China as ornamental species to live in deer parks, but soon escaped and have been spreading through the countryside for about 100 years. In the South, they even live in urban areas.

Often mistaken for hares or foxes, they will eat almost any vegetation, which they crop close to the ground. They can clear areas completely and are often cited as threatening bluebell woods.

Terry Coult, conservation officer for Durham Wildlife Trust, said he had seen the muntjac's distinctive footprints by the River Leven, upstream from its confluence with the River Tees, and had also heard reports from Kirklevington, at Yarm, and Chopwell woods on Tyneside.

He said: "There have certainly been reports in Cleveland and there are records throughout Durham, but I talk regularly to people who shoot deer and they say they don't see any. It could be that they are not looking for certain species, but there is certainly nothing quantitative."

It is the muntjac's ability to live in small areas, and exploit habitat which the native roe deer would not inhabit, which makes them so successful.

One characteristic of the secretive muntjac is that it can live in an area for several years before numbers rise to a level where it is noticed.