A Shetland pony on a UK farm has surprised its owners by giving birth to a half-zebra foal. The hybrid animal, now a week old, appears healthy and is bouncing around its paddock at the Eden Ostrich World, at Langwathby Hall Farm, near Penrith, Cumbria. The owners of the pony, called Tilly, had no idea she was pregnant when they bought her from a wildlife park, where she had been kept in a field with a male zebra.

"She was fairly fat when we received her and we thought that she was just getting fatter," Karen Pete said. "It really was a bit of a shock when we got up one morning and we saw the foal that was there. We realized then what had happened."

Genetic difference
A cross between a horse and a zebra is rare but by no means unheard of. Colchester Zoo in Essex has had three zedonks - crosses between a Chapman's Zebra and a black ass - since 1983. The Cumbrian foal would probably be called a zorse, although some have suggested it might better be termed a zetland. Hybrids are an interesting curiosity. The mule is perhaps the most famous cross - a combination between a horse and a donkey - and an animal of economic importance because it is a hard worker.

Hybrids are not easy to create, however. The mating pair's different number of chromosomes - the "packets" of DNA in each cell - makes a pregnancy hard to achieve. A horse has 64 chromosomes; the zebra has 44. The zorse that results from cross breeding will have a number of chromosomes that is somewhere in between.

The zorse can only result where the sire is the zebra. "The smaller number of chromosomes has to be on the male side,"Lesley Barwise-Munro, a veterinary surgeon in Alnwick, Northumberland, and spokeswoman for the British Equine Veterinary Association, told BBC News Online. "If it had been the other way around there would have been no pregnancy. It's how nature works." And hybrids are invariably sterile, she added.

Tourist attraction
Visitors will be able to see the foal when the centre reopens its gift shop and tea room on Monday. The attraction has been closed since March because of the foot-and-mouth crisis.

Good future
At first, Karen and her husband Jim were reluctant to publicize the new arrival because they were unsure whether it would live or not. "We didn't really want anybody to know about it because with the genetic mixture we've got with the two different species, we thought it might not survive," he told the BBC. "Now...there's a good chance. She's got her feet, she's drinking well and she's really lively."

Lesley Barwise-Munro agrees. "It appears perfectly healthy and I can see no reason why this animal should not go on and live a long life - barring any major health problems which could affect any animal."

(This Page last updated: February 15, 2002)