We scan the ground, on the lookout for fine, tiny, white-coloured webs. For hours we weave our way through the field, anticipation rising to find just one. A few months prior, ecologist Peter, with whom I am on this marsh fritillary (Euphydryas aurinia, Rottemburg 1775) larval web hunt, had found 100 of the webs. But so far, no such luck. After two and a half hours of searching, we remain empty-handed

It is the start of September and usually the webs should be found in numbers, but not here, today, in this field. The marsh fritillary is a rare and threatened butterfly species, whose population distribution on the British Isles has decreased by around 79% since the 1970s and who are now mostly found only in the west – in Ireland, Wales and parts of western England [1]. They can be considered both a flagship (charismatic or beautiful species) and an umbrella species (species whose conservation indirectly benefits or protects other species), meaning they are particularly important for conservation. They are considered of national and international importance and are included in Annex II of the EEC/EU Habitat and Species Directive [2]. 

Eyes down, walking the field in lines, heads swaying as we scan our walking strips from side to side, Peter suddenly gives a cry “I’ve found one!” In over three hours of searching, this would be our only find, making it even more exciting.

The lifecycle of a marsh fritillary begins in May, when the eggs are laid. After several instar cycles, they begin to hatch and by September many larval webs can be found nested between tussocky grasses and devil’s bit scabious (Succisa pratensis L.), a purple-flowering grassland species on which marsh fritillary caterpillar feed. After a long overwintering, by the following May, marsh fritillary can be spotted on the wing again, perhaps nectaring on a grassland flower [3]. Marsh fritillary favour Rhôs pasture, a distinctive, Welsh marshy grassland with an uneven sward structure (mix of short and tall vegetation) rich in flowering plants, and home to devil’s bit scabious and purple moor grass (Molinia caerulea (L.) Moench) [3]. Habitat loss, degradation, and fragmentation mean Rhôs pasture has been assigned “high conservation priority” and “vulnerable” statuses [4]. Close to our site, a major road development project is threatening the habitat of the marsh fritillary and therefore its very existence.

Fig. 1: Galloway cattle wearing the NoFence tags (Robert Parry. Mid-Wales, 2023).

Successful management of Rhôs pasture helps promote devil’s bit scabious and involves the gradual opening of the vegetation through managed extensive grazing by cattle or ponies, occasional cutting and scrub management [5]. As we walk through the fields Peter tells me about the cows that are side-eyeing us from further downfield. He explains that they have spent too much time here, and need to move on to the next field as they are starting to overgraze. Unfortunately, they haven’t been moved yet as the construction of a fence in the opposite field is still pending. One interesting alternative to fencing involves the use of NoFence technology – a collar with GPS is attached to each individual (Galloway and Welsh Black Cattle are great grazing breeds – often used in projects like this one in Wales) and provide a small electric shock when the cow passes beyond the boundaries of the invisible fence [6]. Whilst research on this technology is still being undertaken, some countries, like Wales, have already implemented it on small scales.

Further on from our site, in the Upper Ely landscape of South Wales, the Llantrisant Commons Site for Special Scientific Interests are undergoing a landscape and population restoration project to support Rhôs pasture habitat and locally reintroduce marsh fritillary. The Commons cover an area of over 113 ha of contiguous Rhôs pasture, and the team at Initiative for Nature Conservation Cymru, an independent nature conservation organisation in Wales, took 80 marsh fritillary caterpillars from another South Wales site to rear in captivity [7]. After a round of reproduction, the second-generation caterpillars were brought to the commons to reinforce populations. The following year, in 2022, 195 marsh fritillary larval webs were counted during surveys in August and September – a real success for the project and marsh fritillary populations in South Wales!

As we walk home from the day in the field, Peter and I discuss some current issues in nature conservation. How can we engage decision makers, such that species of international importance as the marsh fritillary are protected against development projects? How can we manage in a way that is truly effective – such that the implementation measures suggested by ecologists are valued and followed, and farmers feel understood and considered? With an eye to the Llantrisant Commons site, we pause to let ourselves be inspired by the success of engaging the local community and schools in the project [8] and decide to envelop ourselves for a moment in the wonder of nature and the beauty of the marsh fritillary.  

References

Related articles:

Cover- and preview image: A marsh fritillary rests on a flower. Galičica NP, Macedonia, 07/06/2017. Free-source photo by Charlie Jackson on Flickr