A foreign breed of deer which threatens wild flowers has arrived in the North East, say conservationists.
Muntjac are secretive and tend to frequent dense woodland
Durham Wildlife Trust said recent sightings of muntjac, a small Oriental deer, near Darlington and Sedgefield were "very worrying".
The species, introduced into southern England in the early 1900s, is known to devour endangered bluebell woodlands.
The trust has now launched a survey in a bid to establish the strength of the population in the area.
Muntjac sightings have also been reported near the A1's Washington services, at a farm in Houghton-le-Spring and in the Tow Law area of Weardale.
Jim Cokill, Director of Durham Wildlife Trust, said: "The problem with the muntjac is that it is an alien species, which was brought over to this country because people thought it made an attractive addition to the English landscape.
"But as often happens with such species, they escape or are released and damage the ecological balance of the countryside.
"It happened with the likes of mink, which have devastated the water vole population, and grey squirrels, which are out-competing the now endangered red squirrel, and there are very real fears that it will happen again with muntjac."
Muntjac are small, stocky, russet brown in summer and grey brown in winter, with short antlers and a ginger forehead.
Any sightings should be reported to the trust.