Assisted colonization in a changing climate: A test-study using two U.K. butterflies

Published source details Willis S.G., Hill J.K., Thomas C.D., Roy D.B., Fox R., Blakeley D.S. & Huntley B. (2009) Assisted colonization in a changing climate: A test-study using two U.K. butterflies. Conservation Letters, 2, 46-52.
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This study is summarised as evidence for the following.

	Action	Category
	Translocate to establish populations outside of known range Action Link

Translocate to establish populations outside of known range

A study in 1999–2008 in two limestone grasslands in Durham and Northumbria, UK (Willis et al. 2009) reported that translocated populations of small skipper Thymelicus sylvestris and marbled white Melanargia galathea survived and spread for eight years after release into climatically suitable areas north of their current range. Six years after release, the distribution of small skipper was 3.64 ha, compared to 0.17 ha in the first year, and the distribution of marbled white was 17.8 ha, compared to 7.2 ha in the first year. Six years after release, the abundance of marbled white was 14 butterflies/km, compared to 6 butterflies/km one year after release. However, most individuals of both species remained within 1 km of their release site. Eight years after release, both populations were still present. In July–August 1999, about 400 adult small skipper were collected from sites in North Yorkshire, and released in a quarry in Northumberland the following day, ~35 km north of the natural range. In July 2000, a further 200 small skipper were translocated to the same site, and ~500 adult marbled white were caught in North Yorkshire and released in a quarry in Durham, ~65 km north of their natural range. Roughly equal numbers of males and females were released. From 2001–2006, extensive searches of each release site and all suitable habitat within 3–4 km were conducted regularly to record adults during their flight period. In 2007–2008, more limited surveys were conducted. Marbled white were also recorded along a 1,550-m transect through their release site every 3–4 days during the flight period (years not given).

(Summarised by: Andrew Bladon)