Saturday, 14 May 2016

Duke of Burgundy: Gladiators of Heyshott Escarpment

Duke of Burgundy (Hamearis lucina), family Riodinidae (Metalmarks), originally named 'Mr Vernon's Small Fritillary'.

Ready for the fight: a territorial male Duke of Burgundy

Male Duke of Burgundy are one of the bad boys of British butterflies. Put them to music and, while Orange-tips might daintily flutter along in a trail of moondust to Clair de Lune, Dukes are zipping headlong along to a death metal anthem. The sole British representative of the metalmark family, they are one of the smaller butterfly species but they punch well above their weight (ask any passing Brimstone butterfly). Put simply, they are brutes. Heavy metal metalmarks. It is apt, therefore, that these gladiatorial insects are best represented in Sussex in a colossal amphitheatre above the small village of Heyshott: the Heyshott Escarpment. Today, I was one of a group of enthusiasts who, led and compèred by Neil Hulme of Butterfly Conservation, ascended the arena to spectate as the territorial Dukes challenged all-comers.

We have parked our vehicles in the few available spaces along the roadside at Hoyle Lane and followed the bostal southwards until we reach a fork. Here we take the left path and climb a circular route up towards the eastern gallery of the escarpment, which continues through a gate around to the west, where we pick up the route back downhill to the bostal. The distance is short, but the terrain is punishingly steep in places and, beneath a hot sun and clear sky, the going is tough.

Heyshott Down - undulating former mine workings on the east escarpment
The east-side undulations - the steep north-facing escarpment interrupted everywhere by omni-facing mine workings - has been hewn both by nature and, from the Neolithic and Bronze ages until the first half of the 20th Century, hewn also by men. This is a tough landscape inhabited by a tough little butterfly. The site is owned and managed by the Murray Downland Trust (MDT), which works with Butterfly Conservation to restore and protect a habitat which is suitable for Dukes. Numbers were close to extinction about ten years ago. This decline has occurred across most of its national range, mainly caused by the decline in woodland coppicing and subsequent encroachment by scrub as a result of the natural succession of vegetation. Neil explained to us how the site had been managed by the MDT following the cessation of quarrying activity in the 1930s, with scrub being removed to protect the Dukes' preferred habitat of a variable low scrubby mosaic (work continued even during the Second World War, when clandestine night-time operations were made beyond billeted Canadian troops). Numbers had dwindled so seriously by the first decade of this century that numbers were counted for some years on the fingers of a single hand. In 2006 Butterfly Conservation with the MDT began a significant programme of scrub removal to restore a mosaic of scrub interspersed with the Dukes' Primula foodplants. It worked. In 2015 the count was in three figures. The little gladiators had fought back from the brink of defeat.

Neil led our group up beyond a former village landfill, which has been cleared of scrub to encourage the Dukes and Pearl-bordered Fritillaries, and into the Dukes' arena, which is an area of cowslips interspersed with low scrubby growth with a fair amount of regenerating dogwood. Within minutes the first of the territorial male Dukes is strutting around making a show of itself. Moments later we watch as two males spar in an upward spiral: a dogfight above the dogwood. During our visit we will observe male Dukes see off not only their own kind, but also Dingy and Grizzled Skippers, Green Hairstreaks, Brimstones, Whites and even Red Admirals. The small tortrix moth, the Red-fringed Conch (Falseuncaria ruficiliana), which shares the Dukes' foodplants keeps a low profile and skulks through the scrub as though to evade attack.

If the males are typically male in their behaviour, the females - the Duchesses - are also cast in the quintessential female mould. They are demure and seek not the sunlight, preferring instead the umbrella of a shading leaf. The Duke males form leks; the females visit the leks and are unceremoniously grabbed by the quickest male and Neil describes how this can occur faster than the eye can follow. Seemingly, there are two types of Duke genes: the quick and the dead.

The bostal back to Heyshott village
Neil also explains how Dukes can be frustratingly lazy insects. They rise late at around 11am and retire early by around 4pm, resulting in a comparatively short window of activity. This behaviour could negatively affect their capacity for radiation and colonisation of new territory. To an extent, it seems that outward expansion occurs mainly by females, which are known to travel up to 5km from their source (Thomas & Lewington, 2010). In practise, entire colonies are on the move from year to year, following their preferred level of vegetational succession across scrubby mosaics on north-facing downland escarpments. The west escarpment and adjacent areas at Heyshott Down have been cleared to encourage their expansion, but this has not yet resulted in a permanent settlement by the established colony on the east side, although we are encouraged by the sight of two individuals as we walk through the area today. One might speculate about the reason why they did not go extinct at Heyshott and ponder whether they are just too tough or because they just couldn't be bothered. We all give thanks to the Murrays, to Neil Hulme and to Butterfly Conservation for intervening at Heyshott before this beautiful, pugnacious little butterfly did succumb. Long may it prosper here.

As we traverse the bostal leading back to Hoyle Lane we pass halcyon Orange-tips attending their pastoral flowers while a steady stream of Red Admirals bursts past us in a flurry of colour. Their route will take them across Heyshott Escarpment; they are in for a rough welcome when they arrive.

Butterfly royalty: the Duke of Burgundy

Reference

Thomas, J. and Lewington, R. 2010. The Butterflies of Britain & Ireland. British Wildlife Publishing: Gillingham, Dorset.

Species seen during the walk
Green Long-horn (Adela reaumurella)  1
Red-fringed Conch (Falseuncaria ruficiliana)  13
Purple Bar (Cosmorhoe ocellata)  1
Dingy Skipper (Erynnis tages)  7
Grizzled Skipper (Pyrgus malvae)  5
Orange-tip (Anthocharis cardamines)  6
Green-veined White (Pieris napi)  2
Brimstone (Gonepteryx rhamni)  29
Red Admiral (Vanessa atalanta)  23
Peacock (Aglais io)  1
Small Tortoiseshell (Aglais urticae)  3
Duke of Burgundy (Hamearis lucina)  46
Green Hairstreak (Callophrys rubi)  14





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