Translocate to re-establish populations in known or believed former range

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages



  • Abundance (13 studies): Eight studies in the UK, Finland, the USA, Australia, the Netherlands and Belgium and the Netherlands reported that translocated populations of adult butterflies and Fisher’s estuarine moth eggs persisted for 2–12 years and increased in abundance (sometimes in areas where coppicing, selective felling, planting, fencing, host plant translocation, invasive plant removal, sheep grazing, scrub clearance or unspecified habitat restoration were conducted before or after release). Three studies (including two replicated studies) in the UK and Finland reported that some translocated populations of silver-studded blue and clouded Apollo adults, and belted beauty moth eggs and caterpillars, persisted for 1–49 years (in one case where vegetation had been removed before release), increased in abundance and colonized new sites, but other populations died out within 0–7 years. One of two reviews across the UK and Ireland found that 25% of translocated and released captive-bred butterfly populations survived for at least three years, but 38% died out in that time, and only 8% were known to have survived for more than 10 years. The other review reported that translocated populations of large copper adults and/or caterpillars (sometimes to areas planted with great water dock or where bushes had been cleared, or alongside the release of captive-bred individuals) survived for up to 38 years, but ultimately died out or had to be supplemented by further releases.
  • Survival (2 studies): Two site comparison studies (including one replicated, paired study) in the UK found that the survival of large blue caterpillars was higher when translocated into Myrmica sabuleti nests without queen ants present than with queens present, and the survival of translocated large copper caterpillars was higher than the survival of released, captive-bred caterpillars.
  • Condition (1 study): One site comparison in the UK and Sweden found that 19 years after translocation, large blue butterflies in the UK had similar genetic diversity to their Swedish source population.


About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A review from 1909–1964 in fens in Cambridgeshire and Norfolk, UK, and Tipperary, Ireland (Duffey 1968) reported that five translocated populations of large copper Lycaena dispar survived for up to 38 years, but ultimately died out or required additional releases to survive. Three populations of Lycaena dispar rutilus released as adults and/or caterpillars survived for zero, 23 and two years. One population of Lycaena dispar batavus survived for 38 years, but was supplemented by additional releases of captive-bred individuals, and ‘wild’ caterpillars were regularly reared in cages. Another L. d. batavus population died out 13 years after release. In 1909, L. d. rutilus caterpillars (number not given) were released at Wicken Fen, Cambridgeshire. In May 1913, following planting of great water dock Rumex hydrolapathum on a bog in Greenfields, Tipperary, 120 L. d. rutilus caterpillars from Germany were released. The following year, 400 adults raised from 700 caterpillars collected in Germany were released at the same site. In 1926, a total of 550 pupae from Tipperary were placed in cages in Woodbastwick Marshes, Norfolk, and the adults released as they emerged. In 1926, an 8.8-ha area of Woodwalton Fen, Cambridgeshire, was cleared of bushes and great water dock was planted. In 1927, thirteen female and 25 male L. d. batavus from the Netherlands were released at the site. This population was supplemented with captive-bred caterpillars or adults when numbers were low, and from the 1930s, ‘wild’ caterpillars were routinely reared in muslin cages to protect them from predation. In 1942, L. d. batavus (number not given) from Woodwalton were released in Tipperary.

    Study and other actions tested
  2. A site comparison study (years not given) in two grasslands in Devon and Dorset, UK (Thomas & Wardlaw 1990) found that translocated large blue Maculinea arion caterpillars were more likely to survive in Myrmica sabuleti nests without queen ants than in nests with queens present. The survival of caterpillars in nests without queen ants (8 out of 12 caterpillars) was higher than in nests with queen ants present (5 out of 20 caterpillars). In August, one locally caught caterpillar was placed near each of 21 ant nests in Devon, and one caterpillar collected in Dordogne, France, was placed near each of 11 ant nests in Dorset. Adoption of each caterpillar into the nests was observed. Two weeks later, nests in Dorset were excavated to measure survival. In Devon, adults were caught in emergence traps the following year and, after emergence, nests were excavated and the number of queen ants present in each nest was counted.

    Study and other actions tested
  3. A study in 1987–1989 in a woodland in Essex, UK (Warren 1991) reported that translocated heath fritillary Mellicta athalia released into a coppiced woodland survived and the population increased. Results were not tested for statistical significance. Two years after the release of 38 adult heath fritillaries, the population was around 200 adults. In 1987, a total of 38 adult heath fritillaries (20 females, 18 males) were translocated from a nearby population (which had been established from captive-bred butterflies in 1984), and released into a 30-ha wood with 0.5 ha of coppicing. In 1988–1989, butterflies were surveyed annually on timed counts along a zig-zag route covering the known flight area. The total yearly population was estimated by multiplying the peak population count by three.

    Study and other actions tested
  4. A replicated study in 1983–1990 in four heathlands and three limestone grasslands in North Wales, UK (Thomas & Harrison 1992) reported that three of seven translocated populations of silver-studded blue Plebejus argus successfully established new colonies. One population of silver-studded blue released onto heathland, and two released onto limestone grassland, survived for at least 8–49 years. By 41–48 years after release, the oldest population had spread 2.5 km along a valley, colonizing 17/20 patches of suitable habitat (0.04–2.2 ha in size). Seven years after release, the newest population had colonized one new patch, 100 m from the release site, but 14 patches 210–2,000 m away remaining unoccupied. Two populations released on heathland persisted for 2–7 years before disappearing. The other two populations did not survive the first year after release. The authors reported that this was because butterflies were released into a different habitat type from that in which they were captured. In 1942, ninety female silver-studded blues were released on a limestone grassland site. From 1978–1983, groups of 5–30 female silver-studded blues (in one instance including some males) were released on two further grasslands and four heathlands. In 1983 and 1990, all suitable habitat patches at each site were surveyed for >20 minutes/patch to record silver-studded blue presence.

    Study and other actions tested
  5. A review from pre-1900–1988 across the UK and Ireland (Pullin 1996) found that at least a quarter of reintroduced butterfly populations survived for over three years, but only 8% were known to survive for more than 10 years after release. Of 274 documented reintroductions of native butterflies, 68 populations (25%) were known to have survived for more than three years, and 21 (8%) were known to survive for more than 10 years. However, 103 populations (38%) died out within three years of release. The remaining reintroductions were either poorly documented (73 releases) or occurred too recently to determine success (30 releases). Twenty-five releases which aimed to reinforce existing populations were not included. Records of all documented releases of butterflies in the UK and Ireland were compiled by Oates & Warren (1990), and their success up to 10 years after release was updated by this study. At least 29% of releases were of captive-bred butterflies. No further details were provided.

    Oates M.R. & Warren M.S. (1990) A review of butterfly reintroductions in Britain and Ireland. Joint Committee for the Conservation of British Insects/World Wildlife Fund, Godalming, United Kingdom.

    Study and other actions tested
  6. A study in 1992–1996 in a forest in Ruokolahti, Finland (Marttila et al. 1997) reported that a translocated population of baton blue Pseudophilotes baton schiffermuelleri butterflies (released into a site where areas of Scots pine Pinus sylvestris had also been selectively felled two years earlier) increased in size and survived for at least two years. One year after a population of 10 baton blue females were released, 24 butterflies were captured, and two years after release, 46 butterflies were captured. The 230 x 70-m Scots pine-covered site in Ruokolahti was divided into 10-m2 study plots. In 1992, pines were selectively logged, and in 1996 some additional saplings were removed. In Säkylänharju, in June 1994, ten female baton blues were captured and marked before being translocated 315 km east to Ruokolahti where they were released into different 10-m2 plots. In June 1995 and June and July 1996, surveys were conducted twice/day along the longitudinal boundaries of all plots, during which butterflies were captured, marked and released, and egg-laying and mating sightings were recorded.

    Study and other actions tested
  7. A replicated, paired, site comparison study in 1997–1998 in a fen in Norfolk, UK (Nicholls & Pullin 2000) found that translocated large copper Lycaena dispar batavus caterpillars had higher overwinter survival rates than released captive-bred caterpillars. The overwinter survival of translocated caterpillars (8 of 95 caterpillars found) was higher than the overwinter survival of released captive-bred caterpillars (1 of 95 caterpillars found). In September 1997, wild-laid eggs were collected from a 3,500-ha lowland bog in the Netherlands, and captive-laid eggs were obtained from a 25-year-old glasshouse-reared colony at Woodwalton Fen. Eggs from both sources were reared to overwintering in the laboratory. A total of 95 wild and 95 captive-bred caterpillars were placed on 19 pairs of great water dock Rumex hydrolapathum (5 caterpillars/plant) in an open fen in Norfolk. In May 1998, after late flooding, surviving caterpillars were counted on each plant.

    Study and other actions tested
  8. A study in 2002–2003 in a coastal sand dune in Merseyside, UK (Howe et al. 2004) reported that one of two disturbed plots where belted beauty moth Lycia zonaria britannica eggs and caterpillars were released had a small adult population the following year. Two years after two grassland plots were cleared, and one year after eggs and caterpillars were released, eight adult moths (7 females, 1 male) were present in a plot which had been stripped of turf and soil, but no adults were present in a plot which had been strimmed and raked. In the summer of the release, caterpillars had been observed feeding in both plots. In winter 2000–2001, vegetation was removed from two 15 × 10 m plots within a 6.5-ha dune grassland. One plot was completely stripped of turf and soil to expose the bare sand, and the other was heavily strimmed to ground level, with cuttings and leaf litter raked off. Both plots were allowed to re-vegetate naturally. In early April 2002, three egg batches and 33 caterpillars were introduced to each plot, and in late April a further 10 caterpillars were added to the stripped plot (source population not specified). Caterpillars were observed in summer 2002, and adults were recorded in April 2003.

    Study and other actions tested
  9. A study in 2000–2003 in a coastal grassland in Essex, UK (Ringwood et al. 2004) reported that a translocated population of Fisher’s estuarine moth Gortyna borelii lunata survived for at least three years. One–three years after the translocation of 300 eggs, 50–54% of 24 established hog’s fennel Peucedanum officinale plants had signs of caterpillar feeding. The proportion of plants with signs of caterpillars feeding in the roots was 29% after one year, 38% after two years, and 42% after three years. In February 2000, twenty-five mature hog’s fennel plants were translocated to a 125-m2 unimproved coastal grassland, and one was planted every 4 m2. A rabbit-proof fence was erected around the site. In October 2000, around 300 moth eggs were placed in two clusters at the site. In July 2001–2003, the number of plants with signs of caterpillars feeding was recorded.

    Study and other actions tested
  10. A study in 2000–2004 on a restored prairie in Iowa, USA (Shepherd & Debinski 2005) reported that translocated regal fritillary Speyeria idalia survived and bred for three years.  In 2001, the first year after translocation, no butterflies were seen at the release site, but in 2002, one year after a second release, 84 adults were recorded. In the following two years, 11–12 fritillaries were observed in planted violet plots and other areas on 1–2 days/year. On 15 days in 2004, between 1–23 fritillaries were seen/day. In 1998 and 1999, prairie violets Viola pedatifida were planted at four sites in a 2,083-ha reserve of restored and remnant tallgrass prairie. At each site, five plots of 99 violets were planted in a grid (9 × 11 m), 1 m apart. In July 2000 and August–September 2001, seven female fritillaries were caught in two prairies (118–500 ha), placed in a cooler, and transported to the restored prairie within two hours. Fritillaries were placed in mesh cages (0.6 × 0.6 m or 1.8 × 1.8 m) directly over violet plants, and provided with nectar from cut flowers and moved to new violet plants each day. Translocated females survived for 3–20 days. In June–August 2001–2004, butterflies were surveyed or opportunistically recorded across the site.

    Study and other actions tested
  11. A study in 2004–2007 in one shrubland in New South Wales, Australia (Mjadwesch & Nally 2008) reported that, three years after translocation, along with habitat management and host plant translocation, a population of purple copper butterfly Paralucia spinifera caterpillars had persisted and increased in number. A site designated for development and adjacent retained and compensatory habitat initially had an estimated purple copper population of 2,000 caterpillars. After the development, and habitat management of and translocation of butterflies into the retained and compensatory habitat, the estimated caterpillar population size reduced to 1,600 in the following year but increased to an estimated 1,995 two years and 2,780 three years after translocation. Of the caterpillars found in the third year, 61% were in the area of retained original habitat and 39% were in the compensatory habitat. In 2004–2005, two thirds of an area of purple copper butterfly habitat was cleared for road-building and an area adjacent to the retained third was designated as compensatory habitat. Invasive plants were cleared from the compensatory habitat and caterpillars and their host plant blackthorn Bursaria spinosa var. lasiophylla were moved from the land about to the cleared to the retained and compensatory habitat. Over 12 nights in December 2004–January 2005, one thousand two hundred and sixty caterpillars were moved. In 2005–2007 blackthorn plants in the retained and compensatory habitats were surveyed for caterpillars, signs of their feeding, and their mutualistic ants Anonychomyrma itinerans. Estimated caterpillar population sizes were calculated by multiplying the number of caterpillars found by five.

    Study and other actions tested
  12. A study in 1990–2000 in a wet grassland reserve in Noord-Brabant, the Netherlands (van Langevelde & Wynhoff 2009) reported that translocated scarce large blue Maculinea teleius and dusky large blue Maculinea nausithous populations increased in size and survived for 10 years. Results were not tested for statistical significance. Five to seven years after the release of 86 scarce large blue, the population consisted of ≥126–296 individuals/year. Five to six years after the release of 70 dusky large blue, the population consisted of ≥592–751 individuals/year. Ten years after reintroduction, the scarce large blue was only found at the release site, despite having occupied another site shortly after reintroduction. The dusky large blue had colonized two other sites (a railway embankment and a road verge), but was no longer present at the release site. In July 1990, seventy dusky large blue (22 males, 48 females) and 86 scarce large blue (33 males, 53 females) were caught in the Wisla Valley, Poland. Butterflies were placed in groups of three in paper boxes in a car-refrigerator, driven to Moerputten in two days, and released into a 116-ha reserve on a warm evening. Details of the translocation taken from Wynhoff (1998). In most years from 1990–1997, butterflies were captured and marked to estimate population size. From 1991–2000, occupied sites were visited at least once/week during each species’ flight period, and after the peak period all road verges and ditch sides were searched for butterflies.

    Wynhoff I. (1998) Lessons from the reintroduction of Maculinea teleius and M. nausithous in the Netherlands. Journal of Insect Conservation, 2, 47–57.

    Study and other actions tested
  13. A study in 1997–2009 in two calcareous grasslands in Belgium and the Netherlands (van Noordwijk et al. 2012) reported that two introduced populations of Glanville fritillary Melitaea cinxia survived for two and 12 years. At one site, 41 caterpillar nests were present 12 years after reintroduction, and at a second site 120 nests were present two years after the reintroduction of 14 nests (no further details provided). In 1997, Glanville fritillaries were reintroduced to a 4-ha grassland in Belgium, managed by low density rotational sheep grazing from April to October. In 2007, fourteen caterpillar nests from that site were reintroduced to a network of grasslands 10 km away in the Netherlands, managed by high density sheep grazing in spring and autumn, and lower density grazing over winter. In the first year after introduction, part of the grassland containing the most caterpillar nests was fenced off during autumn grazing. No further details were provided. In July–August 2009, both grasslands were searched three times for caterpillar nests.

    Study and other actions tested
  14. A site comparison study in 2010–2011 in 12 grasslands in Somerset, UK and Öland, Sweden (Andersen et al 2014) found that large blue butterflies Maculinea arion reintroduced to the UK in 1991 survived for at least 19 generations and had similar levels of genetic diversity to the Swedish source population. Nineteen generations after release, the translocated population had similar genetic diversity to the source population (data presented as standardised allelic richness and expected heterozygosity). Low levels of inbreeding were also found amongst the UK populations (data presented as inbreeding coefficients). In 1991, as part of a wider reintroduction, 281 large blue caterpillars were translocated from 11 sites in Sweden to a single site in the Polden Hills, UK. Following natural dispersal and three further translocations from the first release site, large blues spread to 25 sites in the Polden Hills. In 2010 and 2011 hindwing clippings were taken from 128 adult butterflies at seven sites in Sweden, and 59 whole caterpillars were taken from five sites in the Polden Hills, for genetic analysis.

    Study and other actions tested
  15. A replicated study in 2000–2013 in two semi-natural grasslands in Uusimaa district, Finland (Kuussaari et al. 2015) reported that one of two translocated populations of clouded Apollo Parnassius mnemosyne increased in abundance and colonized new habitat. Results were not tested for statistical significance. From 11–13 years after the release of 20 mated females, the population at one release site was estimated to be 250–650 butterflies, and all 11 suitable habitat patches within 2 km had been colonized and were estimated to have an additional 451 butterflies in 2013. At the other site, no clouded Apollos were seen in the first summer after translocation, or in later years. The authors suggested that the higher abundance of host plants and surrounding forest cover enclosing the successful site may have been important (see paper for details). In June 2000, forty mated female butterflies were caught from four areas in a large population, stored in a cool box, and translocated to two unoccupied sites 25 km apart, and 105 and 130 km from the nearest known populations. Half of the butterflies were translocated on each of two days, one week apart, during the peak flight season. From 2000–2001, both sites were visited several times to monitor survival. From 2001–2003, the successful site was monitored for 5–6 days/year. From 2004–2013, all 11 suitable habitat patches within 2 km of the release site were also monitored on 7–24 days/year.

    Study and other actions tested
  16. A study in 2007–2018 in a heathland in Suffolk, UK (Parker 2018) reported that a population of silver-studded blue Plebejus argus translocated into a site with ongoing habitat management, survived for at least 11 years, increased in number and expanded its range. The highest single day count increased from 60 butterflies released in 2007 to 160 in 2013. Along a fixed transect, the annual butterfly ‘population index’ was 41 a year after release and 662 ten years later. Authors reported that the area the butterflies were recorded in increased over time. In 2007, sixty butterflies were translocated to Blaxhall Common from two existing colonies in Suffolk. From 2007–2018, areas of bell heather Erica cinerea were forage harvested to create young patches, silver birch was controlled and areas of gorse Ulex spp. and other scrub were cleared. For 2007–2013 a daily peak count figure was provided from fixed point counts and for 2008–2018 a population index figure was calculated from recording butterflies along a fixed transect (number of counts and transects/year not given).

    Study and other actions tested
Please cite as:

Bladon A.J., Bladon, E. K., Smith R.K. & Sutherland W.J. (2023) Butterfly and Moth Conservation: Global Evidence for the Effects of Interventions for butterflies and moths. Conservation Evidence Series Synopsis. University of Cambridge, Cambridge, UK.

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