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THE MOUNTAIN RINGLET IN CUMBRIA

If you are walking in the Lake District in June or early July please look carefully and report any sightings via "Contact Details" above. Please include a grid reference and number seen if possible.

The Mountain Ringlet Erebia epiphron is a speciality of the Lake District, this being the only place in England and Wales where it occurs. It is an enigmatic species, living on the high fells but only flying in sunshine! Its larval foodplant, Mat Grass, is everywhere, but the butterfly is found only in specific areas, apparently linked to the geology, soil type and possibly aspect.

Don't believe everything you read in butterfly books about this species; this webpage is based on local knowledge and the efforts of members of Butterfly Conservation's Cumbria branch, who monitor the fells. One esteemed text, recently re-issued, quotes "evidence" that, because of global warming, a third of colonies have become extinct and on average other colonies have moved 140 metres higher up the fells. Apart from the fact that this would mean that most colonies were now on the very summits, which are usually avoided, there is actually no evidence, based on observation, that the species is in anyway declining in Cumbria. In fact, survey results from 2010 onwards are very healthy, but that may only mean that a lot of effort was expended searching for this difficult species and the weather was reasonably favourable.

The research quoted above was apparently based on surveys of sites in the last three weeks of July, as that is when the books say the species usually flies. In Scotland perhaps, but in Cumbria you will only find the tail-end stragglers by then (see below). Furthermore, the weather is crucial when conducting surveys. Two visits in 2010 to the same site, two days apart, yielded counts of 200+ and 5, the former when it was sunny the latter when largely cloudy! On one day you might conclude from casual surveys that the species was thriving, on the other that it was in difficulty!

There is no doubt that the species does spread out during the flight period in good or even most years, which is why records of ones and two's are of little value in monitoring its distribution. But we are now fairly sure that breeding sites do move and absolutely certain that it breeds as low as 200 metres (650 feet).

Breeding sites show a marked preference for the west and south-west of the region, especially around Wasdale, the Langdales and Honister where numbers have traditionally been highest and are holding up well. Colonies to the east, around Helvellyn, Haweswater and Kirkstone, are fewer in number and more isolated, although some are very strong. The Red Screes site, where the species was first discovered in Britain in the early 1800's, now appears to be weak, but new breeding sites have been found close by, one as recently as 2010. The species does appear to move about (sometimes downhill!), for reasons we don't yet understand. This is another reason why it is difficult to assess population changes; one site may become extinct but there may be two new ones nearby in some less accessible place that we don't know about!

Mountain Ringlets may be found in the Lakes between the beginning of June and mid-July, but at one low level site emergence sometimes occurs before the end of May! However, numbers peak for most colonies around the last two weeks of June, followed by a fairly long tail when only small numbers tend to be found. Analysis of breeding records (i.e. sites where significant numbers have been recorded) over the last ten years gives a distribution:


Week beginning
5th June
12th June
19th June
26th June
3rd July
10th July
17th July
23rd July
No. of Records
2
1
18
26
9
10
3
0

This is a frustrating species for the casual observer to plan to see and why records over the years are relatively sparse, despite the increasing popularity of fell-walking! If you want to see the species, I'd suggest you pick the day in the last fortnight of June that has the best weather forecast promising long periods of sunshine with temperatures above 15 C at 500 metres!!! However, be warned, a cold spring, as in 2015, can delay emergence by two or more weeks. Try Hartsop Dodd, Kidsty Pike, Raise, Cold Pike/Little Stand, Brandreth or the Irton Fell/Illgill Head ridge rather than sites suggested in the books.

Breeding sites are normally found between 550 metres and 700 metres (to set that in context, the very highest peaks in Cumbria are just over 900 metres). However, we know they can thrive at 200m just as well as at 650m if the conditions are right – we just don’t know what those conditions are yet!

Altitude (m)
250
400+
450+
500+
550+
600+
650-700
No. of Colonies
1
1
1
2
7
10
10

In spite of its preference for altitude the species does avoid the summit tops, as it is nearly always found in sheltered spots or flushes at the base of crags. Mat Grass, its larval food plant, occurs in every 2 km square of the Lakes. BUT there have been no records ever from some fells (although well walked) such as Great Gable, Bowfell and the Band, The Fairfield Horseshoe, and Skiddaw, despite the abundance of Mat Grass throughout. The species is very strong just to the north of the Wrynose Pass, but curiously has never crossed the road to the Coniston range!

Recent research on Scottish Mountain Ringlets have shown the species prefers herb-rich Nardus grassland. The herbs on which the Mountain Ringlet nectars, such as Thyme, Tormentil and Meadow Buttercup, tend to be found at the base of crags and gullies, where mineral enrichment occurs (see photo above at Whin Rigg - photo courtesy of Steve Clarke). They are virtually absent on the summit tops, making this another reason why the species is unlikely to move higher in the Lakes. Perplexingly however, one site (High Raise) that regularly returns good counts, including 1600 in 2011, has virtually none of the above flower species and only tiny amounts of Heath Bedstraw. What was significant about this site is that the height of the vegetation was higher than that measured at all other sites surveyed.

There appears to be a very strong geological link to its habitat requirements (see map below). Known sites are found only on certain of the igneous Borrowdale Volcanic rocks - the Skiddaw and Silurian Slates to the north and south respectively have no colonies. It may be that the areas avoided, being more acidic, are mineral deficient (especially in calcium). Mat Grass is so lacking in mineral nutrition that even the sheep leave it alone (which is why it becomes dominant if the fells are over-grazed). It is known that small areas within the Volcanic rocks are base rich. David Clarke reports (2010 Carlisle Naturalist 18.2) finding the lichens Solorina saccata and Peltigera leucophobia and the spleenwort Asplenium viride in a gill-ravine near Thirlmere. These are all calcicoles; perhaps species of this type may be indicators of Mountain Ringlet habitat.

 

Known breeding sites for Mountain Ringlet grouped together by colonies within loose geographical boundaries determined by valleys and ridges. The western colonies could be regarded as one super-colony.
The light and dark pink backgrounds are areas of igneous rock. Of the areas not used by Mountain Ringlet, the lilac background is Skiddaw slate, red is granite and brown to the south Silurian slate.



I have grouped the known breeding sites into colonies that have some degree of geographical separation, as there is really no strong evidence that these breeding sites should be treated as separate colonies in the conventional sense i.e. are separated by intervening habitats that are unsuitable. Thus, a
ll the sites along the Irton Fell to Illgill Head ridge form a "Wasdale" colony, the High Raise and Kidsty Pike sites form a "Haweswater" colony etc.

Indeed, the colonies in the west of the Lake District could all be considered to be one super-colony as they are all inter-connected by the ridges that radiate out from the central dome of the Scafells. Any interchange that does occur here will enable genetic mixing and strengthen future generations. It may be the case that colonies in the east have a different genetic make up and, being more isolated, could decline through lack of genetic mixing. On the other hand it may be the case that this area is under-recorded and there may be more inter-linking sites than we know about at present!

Within a colony there are genetic differences of size, brightness and number of spots. English specimens differ slightly from those of Scotland, which differ again from European specimens.

There has been much speculation about the potential loss of an alpine species like the Mountain Ringlet as global warming occurs. It is just speculation, as so little is known about the habitat requirements and ecology of this species. The site that always features the earliest emergence (Irton Fell) is the one found at lowest altitude (200-250m) and is on the milder west coast, where it enjoys the benefits of warm Gulf Steam air and higher humidity - just the sort of conditions Global warming is supposed to bring. This colony has been observed for over 60 years, with little apparent change in strength, even in recent years.

On the other hand, despite global warming, we had two of the hardest winters for years in 2009-10 and 2010-11. Snow covered the fells continuously for five months and numbers of Mountain Ringlets recorded in 2010 and 2011 did seem to be good; 1600 were recorded on one day across four 10 km squares at High Raise in 2011. But this may only be the result of more determined monitoring. Flight times were not noticeably different in 2010 and 2011, perhaps because the early months enjoyed dry sunny weather just at the time larvae were developing and pupating. Could it be that the amount of snow cover is important? At low altitudes this protective cover is not present and appears not to be needed. At high altitude it may be beneficial, in which case the species may well benefit from moving to higher ground in Scotland, but this is not possible in the Lake District. It's such a complex picture. To throw another spanner in the works, many pupae are devoured by Field Voles, a species notorious for rapid fluctautions in numbers from year to year even without hard winters!

Any effects of global warming will manifest themselves in changes in the habitat, but we need to understand the precise habitat requirements of this species before we can assess what changes are taking place! Butterfly Conservation Cumbria branch is working hard to try to understand those requirements.

All in all, the Lake District Mountain Ringlets are a fascinating and unsolved enigma! If you have any comments on the above theories please get in touch.