The owners of Tilly the Shetland pony received a double shock when she gave birth. They didn't know she was pregnant - and they certainly weren't expecting a zebra.

Tilly's owners at Eden Ostrich World, a modest visitor attraction on a farm near Penrith in northwestern England, had been unaware of the pony's exotic past life at a wildlife park, where she shared a field with a male zebra.

"She was fairly fat when we received her and we thought that she was getting fatter," Ostrich World manager Karen Peet said.

"It really was a bit of a shock when we got up one morning and we saw the foal that was there."

The striped half-Shetland, half-zebra foal - dubbed a "zetland" or a "shebra" but as yet unnamed - has flourished since her birth a week ago, and Peet said visitors would be able to view her beginning Monday.

The farm plans to hold a competition to name the creature, which has black-and-tan stripes and a zebra's distinctive large head.

Veterinarians say such a foal is rare, but not unknown. British zoos have reported the birth of several "zeedonks" - offspring of a zebra and a donkey - over the years.

"Ponies and zebras very rarely share the same environment even in the wild. A meeting between the two is very rare in the natural environment," said Lesley Barwise-Munro, spokeswoman for the British Equine Veterinary Association.

"If the zebra is the father and the horse is the mother there is no reason why a normal fertilization and a pregnancy should not take place," she added. "But the offspring is unlikely to be fertile."

(Agencies)