This year's mating season for New Forest ponies has seen more than just a little horseplay and led to some unexpected results.

Instead of having the usual offspring, two mares have delivered-mules. The two foals-one born at the beginning of May, near Fritham and the other at East Boldre, two weeks ago, are the result of jack donkeys, of which there are half-a-dozen in the Forest, mating with the ponies, normally the stallions' preserve.

The mule foals' arrival has prompted a discussion among Foresters about whether new methods being tried with the ponies during the breeding season should be allowed to continue.

Jonathan Gerrelli, one of the New Forest's five agisters, who are responsible for animals in the open forest, pointed out that the births were not unique. "It's just one of those things that happens occasionally, but I can't remember two being born. It's not exactly a problem, though."

Mr Gerrelli explained that, in the past, around 100 stallions regularly roamed among the 3,000 or so mares throughout the year. But three years ago, the number of stallions was reduced to around 35 and only the best were let out only for eight weeks, between May and July each year, to improve the quality of foals and reduce their numbers after their prices dropped dramatically at auction, with some animals fetching as little as £5.

"Now they're not covering all the mares available," he said. "Certain mares aren't coming into season, or come into season when the stallions aren't there. The donkeys are doing the business instead."

Despite that, the progeny had improved. "The numbers have been reduced and the quality has got better, so it has had the desired effect."

Mr Gerrelli said the mule foals, though unexpected, were welcomed, not least because of their rarity value. He added that discussions were continuing as to whether the breeding practices in the forest would continue.