Yorkshire's rarest butterfly is spreading across the moors thanks to efforts made by Butterfly Conservation and North York Moors National Park Authority. Pearl-bordered Fritillary butterflies spotted in the last month have given fresh hope to conservationists who feared the butterfly could become extinct in the county.
Pearl-bordered Fritillaries are nationally scarce and have lost more than half their population over the past 30 years. In Yorkshire the butterfly has survived on just two sites for the past decade. The butterfly disappeared from a third site in 2002 and since then, work has been underway to prevent further losses.
On the North York Moors the caterpillar of this species feeds on violets growing in Bracken-dominated grasslands on limestone soils. When foliage becomes overgrown, not enough light reaches the ground, preventing the wildflowers from growing.
Butterfly Conservation has been working with the North York Moors National Park Authority to create the right conditions for the butterfly to spread its wings and re-colonise the third site.
A team of volunteers regularly attend the site to clear dense areas of bracken and scrub, restoring the habitat to suit the butterfly's needs. Their hard work was rewarded this month when five butterflies were seen enjoying the spring sunshine, in an area where they had previously been unrecorded.
Dr Dave Wainwright, Butterfly Conservation Officer, who discovered the butterflies said:
"All three sites lie within a kilometre of each other so we were hopeful that this natural colonisation would eventually occur.
"The Pearl has really taken advantage of the good spring weather in the last two years, building up large enough populations on the existing sites to enable it disperse and locate the new habitat created by all the hard work of the previous decade. It is thanks to the National Park Authority and the efforts of our dedicated volunteer team that this butterfly is doing so well."
Sally Weightman from the North York Moors National Park Authority said:
"We're very pleased to hear that such a rare butterfly is doing so well on the Moors. The Authority contributed towards the cost of gorse cutting and burning on this site in March 2006, which has helped to open up new violet areas on the site for the Pearl-bordered Fritillary to feed on.
"We had hoped that the scrub control work would result in providing favourable habitat conditions encouraging the butterfly back to the site and so we are very glad that the butterfly has been spotted here at last."