To re-introduce or not? that is the question. Attempting to re-introduce a species extinct in a country for over 40 years is a bold move. Have the reasons that caused the extinction in the first place been understood and consequently resolved? A recent publication1, in partnership with Belgian and Dutch colleagues, demonstrates the in-depth analysis undertaken before the re-introduction was attempted in 2018.
Butterfly Conservation was first involved in Chequered Skipper research as far back as the early 1990’s when Dr Martin Warren (BC’s first conservation officer at that time), visited the north of France and southern Belgium to assess their suitability as sources of stock2. He was accompanied by Dr Neil Ravenscroft, who had recently completed a PhD on the ecology of the Chequered Skipper in Scotland,3,4,5. At the same time, PhD student John Moore began studying the ecology of Chequered Skippers in northern France along with a trial release on potential receptor sites in Lincolnshire6. The general conclusion from this study was that the amount of suitable habitat in Lincolnshire was scarce compared to the large wooded landscapes of northern France and the attempt to re-introduce the butterfly was put on hold until a suitable landscape could be found.
Research continued in Scotland with species modelling being used to target surveys for new populations of this scarce and localised butterfly7. The modelling highlighted the importance of climatic factors, especially rain, along with altitude and woodland coverage; rough grass cover and southern aspect were slightly less significant. The model suggested the butterfly was as much as 80% under-recorded at the 1km resolution. Three years of field surveys then tested these predictions; 57 of the top 100 1km squares included in the prediction, subsequently recorded the presence of the species once they had been visited. This, along with other new squares found during the survey, has increased the known range of the butterfly by 42% in Scotland at a 1km resolution8.
In England interest in re-introducing the Chequered Skipper never really waned and by the mid 2000’s attention had shifted to the Rockingham Forest landscape which had seen some significant changes in management of the forest area. Was this area now similar to the extant populations in north west Europe? Would this landscape offer a suitable location for an experimental re-introduction of the Chequered Skipper to England?
Working with Belgian and Dutch colleagues, species distribution models using similar environmental variables to the modelling in Scotland were used to determine potential source regions in NW Europe for its reintroduction to England.
We gathered distribution data of the butterfly and the environmental variables (Corine Land Cover and climate data) from four regions in Belgium, two in the Netherlands and from Argyll, Scotland. The models were calibrated within these regions and then projected onto the Rockingham Forest landscape. The Fagne–Famenne–Calestienne and the Gaume–Lorraine model resulted in the highest average probability of sustaining a population in the long-term and under future climatic conditions. Based on additional expert knowledge on potential host plant abundance and the presence of large source populations, the Fagne–Famenne–Calestienne in Belgium was then selected as the source region for the reintroduction of the Chequered Skipper to England1.
The possible impact of climate change was also assessed, by comparing present-day climate data in NW Europe and modelling the probability of occurrence in the Rockingham Forest landscape by the year 2070. Encouragingly the species is predicted to increase under future climate conditions. The re-introduction began in 2018 led by Butterfly Conservation along with Forestry England, as part of a National Lottery-funded Back from the Brink project, ‘Roots of Rockingham’. In May 2019, Chequered Skippers emerged in England for the first time in 43 years.
Research is now focused on the newly established English population to determine what features within Rockingham Forest influence adult distribution and density and what impact the habitat management has on the target species and other taxa. A PhD student, Jamie Wildman from University of Northampton is focusing his research on these areas, studying the adult behaviour of the butterfly, vegetation quality and collecting information on other wildlife groups.
A second PhD student, Georgina Halford, is starting at University of Liverpool this academic year and will aim to understand the key habitat factors that promote Chequered Skipper population growth and persistence. This will build on the understanding gained by John Moore in the 1990's on the population structure and the spatial-scale of the landscape required. Determining the minimum area of habitat needed to support a population or several linked populations, and whether Rockingham currently provides this or if further habitat improvement is required.
Rigorous scientific research has produced the evidence to support the investment in a reintroduction programme and this will continue, to ensure the ecology and population dynamics of this species is sufficiently understood so that Chequered Skipper populations can thrive in England.
Dr Nigel Bourn
Director of Science
1. Maes, D., Ellis, S., Goffart, K.L., Cruickshanks, K.L., van Swaay, C.A.M., Cors, R., Herremans, M., Swinnen, K.R.R., Wils, C., Verhulst, S., De Bruyn, L., Matthysen, E., O’Riordan, S., Hoare, D.J. & Bourn, N.A.D. 2019. The potential of species distribution modelling for reintroduction projects: the case study of the Chequered Skipper in England. Journal of Insect Conservation 23, 419-431.
2. Warren, M.S. (1990) The chequered skipper Carterocephalus palaemon in northern Europe. The British Butterfly Conservation Socienty Ltd., Chequered Skipper Working Party, Dorchester, Dorset. Unpublished.
3. Ravenscroft, N.O.M. and Warren, M.S. (1992) Habitat selection by larvae of the chequered skipper butterfly, Carterocephalus palaemon (Pallas) (Lepidoptera: Hesperiidae) in Northern Europe. Entomologists Gazette, 43, 237-242.
4. Ravenscroft, N.O.M. (1994) The Ecology of the Chequered Skipper Butterfly Carterocephalus palaemon in Scotland. I. Microhabitat, Journal of Applied Ecology, Vol. 31, No. 4, pp. 613-622
5. Ravenscroft, N.O.M. (1994) The Ecology of the Chequered Skipper Butterfly Carterocephalus palaemon in Scotland. II. Foodplant Quality and Population Range Journal of Applied Ecology, Vol. 31, No. 4 pp. 623-630
6. Moore, J. L. (2004) The ecology and re-introduction of the Chequered Skipper butterfly Carterocephalus palaemon in England. PhD University of Birmingham.
7. Ball, S. (2012) Modelling the distribution of Pearl-bordered Fritillary, Boloria euphrosyne and Chequered Skipper, Carterocephalus palaemon. Unpublished report to Butterfly Conservation, Wareham.
8. Prescott, T. (2015) Chequered Skipper Survey – The Final Results. Unpublished report to Butterfly Conservation, Wareham.