Heritage coast provides a home for rare butterfly population

Cabbage whites and red admirals aside, I’m not much of a butterfly aficionado… but just like the high brown fritillary I am quite partial to the Alun Valley.

For those not from that part of the world and those, like myself, unfamiliar with the name, the Alun Valley sits in the western section of the Vale of Glamorgan, near the villages of St Brides Major and Ewenny, which I know better for their pubs and a cracking little pottery that I visited frequently with my parents many moons ago.

But other than Ewenny ware and Brains SA I didn’t know much about the area until I spoke to members from Butterfly Conservation, who proudly informed me that it was in fact the last place in Wales to offer a home to the high brown fritillary (Argynnis adippe), the country’s most endangered butterfly.

Until 2003 there was also a small population in Montgomeryshire and others towards the southern end of the South Wales valleys, but the butterfly is now restricted to the western side of the Alun Valley, south of Bridgend, which also supports two other species of fritillary… the dark green and the small pearl-bordered.

A large orange butterfly with intricate black markings, the high brown fritillary is found in woodland clearings and on moorland slopes... where they thrive in dense bracken and grassy patches, or on outcrops of limestone rock where woodland or scrub has recently been cleared.

They’re also a bit fussy about their surroundings, with violets a necessity for their caterpillars to feed on. The common dog-violet is a staple but in limestone areas they also dine on hairy violets, although heath and pale dog-violets will also do in a pinch.

Adult butterflies emerge throughout June and are often seen flitting over the tops of bracken and other low vegetation. They have a fast, powerful flight that makes them hard to distinguish from the similar dark green fritillary, but they're much easier to identify when they rest to take nectar from the flowers of brambles, thistles or knapweeds.

Female high brown fritillaries lay their eggs on leaf litter, often dead bracken leaves, although they also use moss in limestone outcrops. The eggs remain in this state during the winter, before hatching in early spring for the caterpillars to feed on the violet leaves.

The spiny brown caterpillars blend in with dead bracken fronds on the ground, which they often use as sunbathing spots that can be 15-20°C warmer than the surrounding area. Then, after a couple of months, they pupate close to the ground, hanging from a pad of silk stuck to the underside of a leaf or stem.

They were once found throughout England and Wales, but have declined dramatically in abundance and in the number of areas they inhabit. Although a significant amount of targeted conservation work is helping them survive in their remaining strongholds, with some positive signs that populations may be stabilising, although they remain Britain’s most threatened butterfly having declined by 85 per cent since the 1970s.

The Morecambe Bay Limestones and Wetlands Nature Improvement Area and to a lesser extent, the South Cumbria Low Fells to the north, provide a home for two-thirds of the remaining populations.

Efforts to conserve the butterfly began as long ago as the mid-1980s and have continued under the auspices of the High Brown Fritillary Action Group, which comprises 11 partner organisations.

Despite the measures being taken, monitoring has shown a 40 per cent decline between 1990 and 2007, although populations on actively managed sites have stabilised in comparison to unmanaged sites where the decline is as much as 74 per cent.

In 1999 the high brown fritillary population in the Alun Valley had declined to a dangerous low but, with the help of the Glamorgan Heritage Coast Project and a dedicated team of volunteers, scrub clearance and coppicing has taken place every winter since 2003 to try to restore breeding habitats.

The Glamorgan Heritage Coast stretches for 14 miles from Aberthaw to Porthcawl and is characterised by plunging cliffs, secluded coves and breathtaking views that are popular with walkers and cyclists.

The tidal range in this part of the world is the second highest on the planet, surpassed only by Canada’s Bay of Fundy, and the dramatic cliffs create stunning seascapes to rival any coastline in Britain.

The coastline is fringed with picturesque towns, small villages and miles of footpaths and country lanes, which are best explored on foot, with the Glamorgan Heritage Coast Centre situated at Dunraven Park, Southerndown, bursting with information about the local area.

Unfortunately the centre is open to groups by appointment only but offers interactive stations with extensive information about the coastline, its geology, the history of Dunraven Park and the flora and fauna unique to the heritage coast.

Dunraven Bay – referred to locally as Southerndown beach – attracts thousands of visitors every year and is a great place to hunt for fossils. People have been living in the area from as far back as the iron age, with the clifftop locations thought to have been used as a trading post.

Much later, the Romans built a fort there, which was later replaced by a manor house in the 1700s, and finally a residence known as Dunraven Castle that was later transformed into a convalescence hospital during the two world wars.

The castle was demolished in the 1960s, but the walled gardens and the Dunraven Castle ruins still exist and provide a great place to explore when the tide comes in and hides the glorious beach at Southerndown.

The bay offers a great place to begin to explore the Glamorgan Heritage Coast which is perhaps one of Wales’ best kept secrets. With stunning beaches overlooked by dramatic clifftops the coastline provides the perfect backdrop to an area rich in geology and wonderful views.