Exmoor ponies and Hebridean sheep have been moved to a new part of Chailey Common to maintain the nature reserve.
The animals help prevent invasive plants and trees from taking over the habitat, which is one of the largest heathland areas in Sussex and a Site of Special Scientific Interest.
They began grazing the Memorial, Pound and Romney Ridge on Tuesday March 31, having been moved from Lane End and Red House Commons. They will soon be joined by longhorn cattle.
The animals were introduced to the common in 2012 to protect the rare habitat.
Senior ranger for East Sussex County Council Jo Heading said: “Grazing is a long-term project. The livestock help to maintain the valuable heathland habitat by keeping scrub under control and trampling bracken.
“This is the best way of sensitively managing the site for wildlife and to keep more of the common open for walkers and horse riders.
“The livestock will remain on the combined commons until late autumn and, during this time, we would ask motorists using Beggar’s Wood Road and North Common Road to drive with extra caution, give plenty of space to animals on the road verges and be aware that animals could be crossing these roads at any time.”
Dog owners are asked to keep pets on a lead after a number of sheep were killed previously, or use commons where sheep are not grazing.