Breeding groups of wild horses have been re-introduced to a nature reserve in Cambs after a 4,000 year absence.
Konik ponies are a primitive Polish breed of horse
The last herds roamed the area of Wicken Fen thousands of years ago, wardens said on Tuesday.
A herd of konik ponies - a primitive Polish breed - was brought to the fen to help manage it in a sustainable way.
The fen has been home to the breed since 2001, but the first breeding herd came in 2003. After two years, they have produced their first offspring.
Four male foals have been born this spring, increasing the herd to 29.
Wicken Fen is one of Britain's oldest nature reserves and has been managed by the National Trust since 1899.
Martin Lester, the reserve's head warden, said the koniks originated in eastern Europe and were the closest living relative of the last breed of western European wild horse, the tarpan, which is now extinct.
He said the tarpan would have roamed the fen about 4,000 years ago.
"They don't like to be handled, but they are usually quiet, placid animals, and are not really any different to native breeds like Exmoor and Dartmoor ponies," he said.
"They are ideally suited to wetland conditions and through grazing at Wicken Fen, they are helping to control scrub encroachment and conserve the valuable wetland and fen habitats."
Carol Laidlaw, reserve warden, said the ponies had formed a matriarchal society, with the dominant mare deciding where to graze and disciplining the other members of the herd.
She said that staff at the reserve were cultivating a bachelor group of stallions who will spend the next two years together learning the social skills required to challenge the dominant male and form their own harems.