Natur Cymru

A full version of this article appears in the magazine.

Fritillary butterflies remain a focus of much conservation effort in Wales. For some, like the Marsh Fritillary, it is because Wales has a significant proportion of NW European populations. For others, it is because they are endangered in these islands, on the north western edge of their European range. One such is the High Brown Fritillary Argynnis adippe.

The High Brown Fritillary has suffered a massive decline in Wales. Back in 2003 (Natur Cymru 7, p22) we talked about the last two Welsh sites: seven years on, efforts on the last Powys site, at Allt Dolanog, were too late to save the butterfly there. However, work focussing in the Vale of Glamorgan has been hugely successful. So, for once, let us celebrate a success and see what lessons we can learn.

The last site in Wales is centred on the Alun Valley in the western Vale. The butterfly occupies just five 1km squares, with the next nearest population across the Bristol Channel on Exmoor. The total landscape is about 254 hectares of unimproved habitat. However, only 15ha were thought to be suitable breeding habitat for the High Brown Fritillary. We realised had to do more, and quickly, to save the butterfly. Baseline data and transect results helped all the partners agree to a shared vision of what needed to be done.

The work focussed on knocking back the scrub, bramble and dense bracken on the valley slopes. By 2007, an additional 48ha had been restored and up to a further 2ha are now cut each year on a rolling cycle. However, it was clear that manual cutting would not sustain the site on its own. Three further grants from the Countryside Council for Wales and PONT have seen 17ha of the private land fenced and in 2010 a livestock corral was erected. This will allow rough grazing by ponies, and possibly cattle, to be reintroduced, enabling volunteer effort to focus on the unfenced areas and clearing the scrub regrowth that the livestock leave.

Over 90 people have attended walks and workshops to see the butterflies and work that had been done. The project put out press releases and a newsletter, but having the Heritage Coast as a partner has helped disseminate the message to schools and visitors, as part of their programme of talks and events, reaching a far bigger audience than the project on its own could achieve.

Further afield

The partners felt we needed to look at restoring former sites, where the butterfly had been present in the late 1990s. We visited 11 sites and recommended work on eight of these. However, to put it in to context, only 8.82ha of suitable or potentially suitable habitat was found compared with the 69ha in the Alun Valley landscape, so a key recommendation was to expand the Alun Valley work as already described.

Butterfly Conservation used Species Challenge funding to start work on the eight other sites. Even though it was a relatively small pot of money, it went a long way to helping build relations on two other local commons.

At Y Graig above Llantrisant, three years’ work cutting back dense bracken and opening paths has allowed the commoners to re-introduce grazing. This prominent site was regularly subject to large scale arson but, thanks to the work, the scale of burns has been reduced and suitable habitat is being created. At Mynydd Ruthin, where grazing restoration is much more difficult, the work mainly involved clearing scattered thorn bushes and arson has remained a potential problem.

How do we know it is working?

Adult numbers declined up to the trial coppicing in 1999, but since the scale of this work was extended from 2003, numbers have dramatically increased. Annual numbers are fluctuating, possibly due to the weather, but even the low points have still been above the best pre-1999 high in 1995.

In 2006 the abundance of violets, the larval foodplant, had increased by 112% and the sward height more than halved compared to the 2002 baseline figures. These are both positive signs that the management is working. This work was repeated in 2010. Violet abundance has fallen back but is still well above 2002 figures; sward height has remained static; and grass/moss and bramble have declined further.

Searching for larvae

The larvae are very well camouflaged and it takes a great deal of patience to spot them. The figures suggest that the larvae tend to feed on the open bracken slopes rather than the hazel scrub edge. As 80% of larvae found since 2006 were found on the recently managed sub sites, it suggests the females are preferentially selecting managed bracken stands for egg laying. However, we have not yet corrected this for survey effort.

The future

The future conservation focus for this butterfly has to be on its existing locality where most of the habitat is. However, we will continue to look for opportunities to work with commoners on other sites. The High Brown Fritillary is a target species for the targeted element of Glastir but it is difficult to see at the moment how this will help, as the scheme’s focus is on soil carbon and water quality.

There is potentially more habitat to be created in the Alun Valley by getting the secondary hazel scrub in to a coppice cycle. But perhaps most important is introducing grazing by cattle or ponies on to both the private and common land to create the niches needed by violets and the High Brown Fritillary.

Russel Hobson is Head of Conservation and Richard Smith is High Brown Fritillary Project Officer, Butterfly Conservation Wales.

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