Cease grazing on grassland to allow early succession
Overall effectiveness category Awaiting assessment
Number of studies: 22
Background information and definitions
Some grassland butterfly and moth species, which require generally open habitats, are also dependent on host plant species which are sensitive to disturbance (Eichel & Fartmann 2008), or may themselves suffer decreased juvenile survival from grazing (Dover et al. 2011). The cessation of grazing on grassland, also known as abandoning or fallowing, may enable host plant species to establish (Eichel & Fartmann 2008) or lead to an increase in the survival of eggs, caterpillars or pupae of butterflies and moths (Dover et al. 2011). It may also allow larger, woody plants to establish through succession, which increases habitat complexity, and may enable a more diverse, or different, community of butterflies and moths to establish, at least in the short-term (Bubová et al. 2015).
This action contains studies which compare abandoned grassland to grazed pasture. Note that the effect of grazing cessation may vary depending on the intensity of grazing before abandonment. See also “Cease mowing on grassland to allow early succession”.
For other studies on reducing grassland management, see “Reduce grazing intensity on grassland by reducing stocking density”, “Reduce grazing intensity on grassland by seasonal removal of livestock” and “Reduce management intensity on permanent grasslands (several interventions at once)”. For studies on reversing the process of abandonment, see “Restore or create species-rich, semi-natural grassland”.
Eichel S. & Fartmann T. (2008) Management of calcareous grasslands for Nickerl's fritillary (Melitaea aurelia) has to consider habitat requirements of the immature stages, isolation, and patch area. Journal of Insect Conservation, 12, 677–688.
Dover J.W., Spencer S., Collins S., Hadjigeorgiou I. & Rescia A. (2011) Grassland butterflies and low intensity farming in Europe. Journal of Insect Conservation, 15, 129–137.
Bubová T., Vrabec V., Kulma M. & Nowicki P. (2015) Land management impacts on European butterflies of conservation concern: a review. Journal of Insect Conservation, 19, 805–821.
Supporting evidence from individual studies
A replicated, paired, site comparison study in 1990–1991 in 21 calcareous grasslands in Northern Bavaria, Germany (Völkl et al. 1993) reported that abandoned grasslands had a similar density of meadow neb moth Metzneria metzneriella caterpillars, and a similar occurrence of hoary bell moth Eucosma cana caterpillars, to grazed grasslands. Results were not tested for statistical significance. In abandoned grasslands, 2.2–2.5% of greater knapweed Centaurea scabiosa flowerheads contained meadow neb caterpillars, compared to 2.9–3.3% of flowerheads in grazed grasslands. The occurrence of hoary bell was similar in abandoned and grazed grasslands (data not presented). Twenty-one grasslands (0.5–2 ha) were either abandoned for at least five years (14 sites, vegetation >25 cm with shrubs) or managed by light sheep grazing in early autumn (7 sites, vegetation <10 cm). In September–October 1990 and 1991, samples of 100–350 greater knapweed flowerheads/site were collected from seven pairs of grazed-abandoned grasslands, and seven (1990) and four (1991) unpaired, abandoned grasslands. Flowerheads were dissected in the laboratory to identify caterpillars.Study and other actions tested
A replicated, site comparison study in 1994 in 19 traditional hay meadows in Bavaria, Germany (Dolek & Geyer 1997) reported that the abundance and species richness of all butterflies, and of threatened species only, was lower in abandoned meadows than in meadows managed by grazing or mowing. Abandoned meadows had fewer butterflies of all species, and of threatened species alone, than grazed or mown meadows (data not presented). Two out of three abandoned meadows also had lower species richness than grazed or mown meadows (data not presented). Nineteen meadows, which had been managed in the same way for at least 5–20 years, were compared. Three meadows were not managed (abandoned), nine meadows were extensively grazed with sheep, cattle or horses for a few weeks each summer, one meadow was grazed by sheep throughout the summer, and six traditionally managed hay meadows were mown once/year in July or early August. From June–August 1994, butterflies were surveyed along a fixed transect five times in each meadow.Study and other actions tested
A replicated, site comparison study in 1993 in 34 fen meadows in Glamorgan, UK (Lewis & Hurford 1997) found that abandoning grassland did not affect marsh fritillary Eurodryas aurinia population size compared to grazing grassland. There was no significant difference in the proportion of unmanaged (4/8), cattle-grazed (3/9), horse-grazed (2/6), sheep-grazed (0/2), burned (5/8 sites) and mown (0/1) sites that had >20 caterpillar webs recorded. However, the three largest populations (>200 caterpillar webs) were on sites burned in early spring. Caterpillar webs were present on 28/34 sites where adults had been recorded in May/June. In 1993, eight grasslands were unmanaged, nine were cattle-grazed, six were horse-grazed, two were sheep-grazed, eight were burned and one was mown. Sites were separated by >1 km of unoccupied grassland, or >0.5 km of unsuitable habitat. From late August–mid-October 1993, caterpillar webs were surveyed on 34 fen grasslands. On sites <2 ha, all devil’s bit scabious Succisa pratensis were searched in 2-m-wide parallel strips until the whole area had been searched. On larger sites, 2-m-wide strips at 10-m intervals were searched, and areas around caterpillar webs were then searched comprehensively.Study and other actions tested
A replicated, site comparison study in 1988–1996 in 17 upland prairies in Missouri, Minnesota, North Dakota and Wisconsin, USA (Swengel & Swengel 1997, same experimental set-up as 6 and 8) found that abandoned prairies had a higher abundance of four specialist butterfly species, but a lower abundance of three species than prairies managed by grazing, haying or burning. Of seven prairie specialist butterfly species, four (gray copper Lycaena dione, regal fritillary Speyeria idalia, arogos skipper Atrytone arogos, Poweshiek skipperling Oarisma poweshiek) were more abundant in abandoned, unmanaged areas than in prairies managed by grazing, hayed or burning in at least one of three regions. However, three species were less abundant in abandoned prairies than in grazed (Gorgone checkerspot Chlosyne gorgone) or hayed (Pawnee skipper Hesperia leonardus pawnee, Dakota skipper Hesperia dacotae) prairies. See paper for individual species data. Across 17 prairies (16 to >120 ha), two areas were unmanaged for a long time (abandoned), while two areas were managed by grazing, six by haying (often in rotation), eight by burning on rotation, and three by burning and haying. From 1988–1996, butterflies were surveyed on transects through different management areas at each site. Sites were not surveyed in every year.Study and other actions tested
A replicated, paired, site comparison study in 1989–1993 in three upland grasslands in Scotland, UK (Dennis et al 1998) found that in two of three sites ungrazed grassland had a higher abundance of small invertebrates (including caterpillars) than sites with low or high grazing intensity. In two out of three grasslands, the abundance of invertebrates was higher in plots which had been ungrazed for 1 and 25 years (70–250 individuals) than in plots with low (6–125 individuals) or high (4–70 individuals) grazing intensity. At the third site, there was no significant difference between a plot which had been ungrazed for four years (35–78 individuals) and sites grazed at low (17–78 individuals) or high intensity (17–55 individuals). From 1989–1991, at three sites, experimental grazing plots were established where the number of sheep was adjusted weekly in order to maintain different sward heights from May–October each year. At two sites, two 0.3-ha plots had sward kept at each of 3.0, 4.5 (high intensity) or 6.0 cm (low intensity). At the third site, four 1–3 ha plots had sward kept at each of 4.5 and 6.5 cm, but from June–August six cattle were grazed on half of the plots. Separate plots which had been ungrazed for one, four or 25 years were also monitored at each site. In August 1993, invertebrates (insects and arachnids) were sampled from both tussocks and low sward at each of six randomly selected points/plot using a d-vac suction sampler.Study and other actions tested
A replicated, site comparison study in 1987–1995 in 16 tallgrass prairies in the upper Midwest, USA (Swengel 1998, same experimental set-up as 4 and 8) found that abandoned prairies had a higher abundance of five of 16 specialist butterfly species, but a lower abundance of four specialist species, than prairies managed by grazing. Of 16 prairie specialist butterfly species, five were more abundant in abandoned, unmanaged prairies than in grazed prairies, but four were less abundant in abandoned prairies than in grazed prairies. Two species were more abundant in abandoned prairies in one region, but less abundant in abandoned prairies in a second region. Five species had similar abundance in abandoned and grazed prairies. See paper for individual species data. Six prairies (including one previously grazed site in Wisconsin, locations and sizes not given) had not been managed for many years (abandoned). Nine prairies (259–2,024 ha) in Sheyenne National Grassland, North Dakota, and one prairie in Wisconsin, were managed by grazing. From April–September 1987–1995, butterflies were surveyed on transects at each site. Most sites were surveyed more than once/year, and in >1 year.Study and other actions tested
A replicated, site comparison study in 1997 in 14 alpine calcareous grassland sites in the Jura Mountains, Switzerland (Balmer & Erhardt 2000) found that old fallow pastures which had not been grazed for 10 years had a higher species richness, but not abundance, of butterflies and day-flying moths than extensively grazed pastures, young fallow pastures or young forest. Old fallow pastures had a higher species richness (37–50 species), species diversity and more Swiss Red List species (9 species) than extensively grazed pastures (27–44 species, 4–9 Red List species), young fallow pastures (27–38 species, 4–7 Red List species) or young forest (2–5 species, 0–1 Red List species). However, total abundance was not significantly different between pasture types (old fallow: 282–560; extensive pasture: 387–823; young fallow: 420–1,103 individuals). Fourteen 1,000-m2 sites with a southerly aspect were selected, including three old fallow pastures had not been grazed for around 10 years, five extensively grazed pastures were still cultivated, three young fallow pastures had not been grazed for 2–3 years, and three dense young forests (up to 4 m) had not been grazed for 20–30 years. The old pastures contained scattered blackthorn Prunus spinosa, 50–60 cm in height. From June–September 1997, butterflies and day-flying moths were surveyed once/week on each site.Study and other actions tested
A replicated, site comparison study in 1990–1997 in 106 tallgrass prairies in Illinois, Iowa, Minnesota, Missouri, North Dakota and Wisconsin, USA (Swengel & Swengel 2001, same experimental set-up as 4 and 6) found that in some states, abandoned, unmanaged prairies had a lower abundance and species richness of specialist and grassland butterflies than prairies managed by grazing, but a higher abundance and species richness than prairies managed by burning. In Illinois, Wisconsin and eastern Iowa, the abundance and species richness of specialist and grassland butterflies was lower in unmanaged prairies than in grazed prairies, but higher than in rotationally burned prairies. However, there were no differences in western Iowa, Minnesota, North Dakota or Missouri. All data were presented as models results. Across all prairies, specialist and grassland butterfly abundance and richness tended to be higher at rotationally managed sites (grazed, hayed or burned) longer after they were last managed. Of 106 prairies (1.2–2,024 ha), nine contained areas which had been unmanaged for many years (abandoned), eight were managed by grazing, 27 were managed by haying (mostly on a two-year rotation), and 77 areas were managed by rotational burning (every 2–5 years) in the cool-season (of which 24 were also hayed or mown). From May–September 1990–1997, butterflies were surveyed on parallel transects (5–10 m apart) at each site. Most sites were surveyed more than once/year, and in >1 year. Species were classified as “specialists” (of native plants), “grassland” (occurring widely in open habitat) and “generalist” (occurring in a range of habitats).Study and other actions tested
A replicated, site comparison study in 1999–2000 in southwest Finland (Poyry et al. 2004, same experimental set-up as 10) found that abandoned grasslands had a higher abundance of butterflies and day-flying moths than grazed pastures, but a similar species richness. The abundance of butterflies and moths was higher in abandoned pastures (306 individuals) than in both continuously grazed (126 individuals) and restored (126 individuals) pastures. The number of species was not significantly higher in abandoned pastures (33 species) than in continuously grazed pastures (26 species), but was higher than in restored pastures (22 species). Butterflies and moths were monitored in 1999 or 2000 on 12 abandoned pastures which had not been grazed for at least 10 years, 11 continuously grazed pastures, and 10 restored pastures where, after at least 10 years of abandonment, grazing had re-started 3–8 years before the study. All restored and most continuously grazed pastures received support under the Finnish agri-environment scheme. All grazing was by cattle. Butterflies and day-flying moths were counted along transects four (1999) or seven (2000) times from May–August. Either searching time (1999) or transect length (2000) were standardized across sites.Study and other actions tested
A replicated, site comparison study in 1999–2000 in southwest Finland (Poyry et al. 2005, same experimental set-up as 9) found that 14 of 32 butterfly and day-flying moth species were more abundant in abandoned grassland than in grazed, semi-natural pasture. Fourteen out of 32 species of butterfly and day-flying moth were more abundant in abandoned grassland than in either continuously grazed or restored pasture, but three species were less abundant in abandoned grassland than in continuously grazed pasture. A further two species were more abundant in both abandoned grassland and continuously grazed pasture than in restored grassland. The remaining 13 species had similar abundance in all three grassland types (see paper for data on individual species). Butterflies and day-flying moths were monitored in 1999 or 2000 on 12 abandoned pastures which had not been grazed for at least 10 years, 11 continuously grazed pastures, and 10 restored pastures where, after at least 10 years of abandonment, grazing had re-started 3–8 years before the study. All restored and most continuously grazed pastures received support under the Finnish agri-environment scheme. All grazing was by cattle. Butterflies and day-flying moths were counted along transects four (1999) or seven (2000) times from May–August. Either searching time (1999) or transect length (2000) were standardized across sites.Study and other actions tested
A replicated, paired, site comparison study in 2003–2004 in 36 semi-natural grasslands near Lund, Sweden (Öckinger et al. 2006) found that the species richness and abundance of butterflies and burnet moths was similar in abandoned and grazed semi-natural grasslands. On abandoned grassland, the species richness (11 species) and abundance (216 individuals) of butterflies and burnet moths was similar to the richness and abundance on both continuously grazed (richness: 13 species; abundance: 225 individuals) and recently restored grassland (richness: 9 species; abundance: 101 individuals). However, sites with no grazing had more species (12) than sites currently grazed by sheep (7 species). Butterflies and burnet moths were surveyed using transects (150 m/ha) six or seven times in May–August 2003 or June–August 2004 on 12 grasslands which had been abandoned for 5–15 years, 12 continuously grazed semi-natural grasslands, and 12 previously abandoned grasslands which had been restored from 1999–2003 by clearing trees and shrubs, erecting fences, and re-introducing grazing animals. Under current management, 12 sites were cattle grazed, six were horse grazed, eight were sheep grazed and 10 had no grazing.Study and other actions tested
A replicated, randomized, controlled study in 2003–2005 on an upland grassland in Perthshire, UK (Dennis et al. 2008, same experimental set-up as 13) found that in ungrazed plots the abundance of moth caterpillars was higher than in grazed plots, but only after >2 years. After 18 months of grazing, there was no significant difference in the number of caterpillars on ungrazed (2.8 individuals/plot), lightly grazed (1.9–2.4 individuals/plot) or commercially grazed plots (2.3 individuals/plot). However, after 30 months, there were more caterpillars in the ungrazed plots (4.9 individuals/plot) than in the lightly grazed (1.9–2.4 individuals/plot) or commercially grazed plots (0.5 individuals/plot). From January 2003, four management regimes (no grazing; light grazing: sheep at 0.9 ewes/ha or sheep and cattle equivalent to 0.9 ewes/ha; commercial grazing: sheep at 2.7 ewes/ha) were replicated six times each in twenty-four 3.3-ha plots (in three pairs of adjacent blocks). Caterpillars were sampled by sweep net in 2003–2005.Study and other actions tested
A replicated, randomized, controlled study in 2003–2007 on an upland estate in Scotland, UK (Littlewood 2008, same experimental set-up as 12) found that ungrazed plots had a higher abundance and species richness of moths than plots grazed by sheep at a commercial stocking rate, or sheep and cattle at low density, but were similar to low density sheep-grazed plots. After four years, ungrazed plots had a higher abundance (48 individuals/night) and species richness (13.2 species/night) of moths than plots grazed by sheep at commercial densities (abundance: 34 individuals/night; richness: 10.6 species/night), or plots grazed by sheep and cattle at low density (abundance: 42 individuals/night; richness: 11.3 species/night), but were similar to low density sheep-grazed plots (abundance: 52 individuals/night; richness: 12.3 species/night). In January 2003, one of four management regimes was established on each of 24 plots (3.3 ha each) on a grazed acid grassland upland estate. The treatments were: no grazing; commercial high density sheep grazing (9 sheep/plot); low density mixed grazing (2 sheep/plot plus two cows and calves for 4 weeks in autumn); and low density sheep grazing (3 sheep/plot). Moths were sampled between June and October 2007 using four 15 W light traps placed randomly within plots of each treatment, for six or seven sample nights/plot.Study and other actions tested
A replicated, site comparsion study in 2004 in an agricultural region in central Sweden (Sjodin et al. 2008) found that abandoned grasslands did not have a greater abundance or species richness of butterflies and burnet moths than low intensity or intensively grazed pasture. On abandoned grassland, the abundance (29.5 individuals/visit) and species richness (10.4 species/visit) of butterflies and burnet moths was not significantly different from either low intensity pasture (abundance: 22.9 individuals/visit; richness: 9.1 species/visit) or intensively grazed pasture (abundance: 22.8 individuals/visit; richness: 9.4 species/visit). Three pastures, >2 km apart, were selected in each of eight sites (>10 km apart). Within a site, one abandoned pasture had been ungrazed for >10 years, one low intensity pasture was managed by horse or cattle grazing, and one high intensity pasture was managed by cattle grazing. From June–August 2004, flower-visiting insects were surveyed four times on four 5 × 5 m plots/pasture. Plots were observed for 10 minutes/visit.Study and other actions tested
A replicated, controlled, before-and-after study in 1997–2004 in six meadows in Catalonia, Spain (Stefanescu et al. 2009) found that in meadows where grazing and mowing were abandoned, grassland butterflies decreased while woodland and hedge butterflies increased, and the community became dominated by generalist species and species with fewer generations/year. Over seven years after abandonment, species which prefer grasslands declined in abundance, and species which prefer woodland and bramble hedges increased. The abundance of “generalist” butterfly species (which are able to persist in a wide range of habitats) and species with only one generation/year increased in abandoned meadows, while the abundance of “specialist” species (with specific habitat requirements) and species with multiple generations/year decreased. One grassland specialist, the silver-studded blue Plebejus argus, went extinct in some abandoned meadows. There was little change in the butterfly community in the continuously managed meadow. All data presented as model results. In 1997, six traditional hay meadows (0.55–3.71 ha) were managed normally: two were mown in June, and four were mown in June and August and grazed by cows in winter. From 1998–2004, five of the meadows were abandoned, but the sixth meadow continued to be mown in June and grazed by cattle and horses in winter. From March–September 1997–2004, butterflies were surveyed once/week along a fixed 1,122-m transect through the meadows (117–286 m/meadow), and the total number of each species recorded in each meadow each year was compared.Study and other actions tested
A replicated, site comparison study in 2003–2005 in 47 alpine meadows in Picos de Europa, Spain (Dover et al. 2011) found that abandoned or winter grazed meadows had a lower abundance or occurrence of seven out of 44 butterfly species than managed meadows, but one species occurred more frequently in abandoned meadows. In abandoned meadows, the abundance of five species (black-veined white Aporia crataegi, meadow brown Maniola jurtina, small skipper Thymelicus sylvestris, small white Pieris rapae, ringlet Aphantopus hyperantus) was lower than in meadows managed by grazing or mowing (data presented as model results). In addition, two species (grizzled skipper Pyrgus malvae and painted lady Vanessa cardui) occurred less frequently in abandoned meadows than in managed meadows, but one species (small pearl-bordered fritillary Boloria selene) occurred more frequently in abandoned meadows than in managed meadows (data presented as model results). The remaining 36 species did not differ in abundance or occurrence between abandoned and managed meadows. From summer 2003–2005, management was recorded on 47 meadows. Sixteen meadows were either abandoned or only grazed in the winter, seven meadows were grazed by livestock in summer and 24 meadows were cut for hay. The abandoned meadows had different amounts of scrub growing within them. From June–July 2004, butterflies were surveyed nine times on a transect around the edge of each meadow.Study and other actions tested
Referenced paperDover J.W., Rescia A., Fungarino S., Fairburn J., Carey P., Lunt P., Arnot C., Dennis R.L.H. & Dover C.J. (2011) Land-use, environment, and their impact on butterfly populations in a mountainous pastoral landscape: individual species distribution and abundance. Journal of Insect Conservation, 15, 207-220.
A replicated, site comparison study in 2007 in a grassland and woodland reserve in the Czech Republic (Slamova et al. 2013) found that temporarily abandoned grasslands had a higher abundance of Scotch argus Erebia aethiops than grasslands managed by sheep and goat grazing. On temporarily abandoned grasslands, the abundance of Scotch argus males (19 individuals/ha) and females (13 individuals/ha) was higher than on grazed grasslands (males: 7; females: 4 individuals/ha). The abundance of Scotch argus was also lower on occasionally mown (males: 9; females: 5 individuals/ha) and intensively mown (males: 3; females: 2 individuals/ha) grasslands. Within a 55-ha reserve, 27 grasslands (128–6,072 m2) were either temporarily abandoned, or managed by sheep and goat grazing, occasional mowing or intensive mowing. On 33 days from July–August 2007, butterflies were caught, individually marked, and recaptured at each site.Study and other actions tested
A review in 2015 of 126 studies in Europe (Bubová et al. 2015) reported that abandoning grassland to allow early succession benefitted six out of 67 butterfly species of conservation concern. Results were not tested for statistical significance. The review reported that six studies found that abandoning grassland benefitted six butterfly species (blue argus Aricia anteros, large heath Coenonympha tullia, El Hierro grayling Hipparchia bacchus, Zullich's blue Plebejus zullichi, Lulworth skipper Thymelicus action and Turanana taygetica). Grazing was abandoned on meadows to allow taller vegetation and shrubs to develop, but the optimal length of time for abandonment is not given. The review focussed on 67 butterfly species of conservation concern. The available information was biased towards studies in Northern and Western Europe.Study and other actions tested
A replicated, site comparison study in 2006–2010 in 28 grassland sites in Bílé Karpaty Protected Landscape Area, Czech Republic (Bonari et al. 2017) found that abandoning semi-natural grassland did not affect the species richness or species composition of butterfly and moth communities. Both the species richness and species composition of butterflies and moths were similar in abandoned, unmanaged grasslands and in grasslands which were managed by grazing, mowing or a mix of management types (all data presented as model results). One of four different management practices (abandoned (no grazing or mowing); grazed by sheep, cattle or deer; mown once/year; or ‘mixed’ management) was applied to each of 34 sites (1.5–70.7 ha) for at least five consecutive years. ‘Mixed’ management included mowing different parts of the site at different times, often with patches left uncut for a year, or mowing followed by grazing. From 2007–2010, butterflies and moths were surveyed on >6 visits between April and October in each of two consecutive years to each of 28 sites.Study and other actions tested
Referenced paperBonari G., Fajmon K., Malenovský I., Zelený D., Holuša J., Jongepierova I., Ko?árek P., Konvi?ka O., U?i?á? J. & Chytrý M. (2017) Management of semi-natural grasslands benefiting both plant and insect diversity: The importance of heterogeneity and tradition. Agriculture, Ecosystems & Environment, 246, 243-252.
A replicated, site comparison study in 2015 in 20 grasslands in Saxony, Germany (Ernst et al. 2017) found that abandoned grasslands had a higher abundance of woodland butterflies and burnet moths, but a lower abundance of farmland butterflies and burnet moths, than managed grasslands, but there was no difference in species richness or community composition. In abandoned grasslands, the abundance of 20 species of woodland butterflies and burnet moths (34–44 individuals) was higher than in managed grasslands (17–36 individuals). However, the abundance of 35 species of farmland butterflies and burnet moths was lower in abandoned grasslands (127 individuals) than managed grasslands (195–206 individuals). The species richness of both farmland and woodland species was similar in abandoned (farmland: 13–14; woodland: 5–6 species) and managed (farmland: 14; woodland: 5–6 species) grassland. The community composition was also similar in managed and abandoned grasslands (data presented as model results). Twenty calcareous grasslands (0.90–5.38 ha) were surveyed. Ten were abandoned (not grazed or mown), eight were managed by summer grazing (May–September, <1 animal/ha, with cattle, sheep, goats, horses or donkeys), one was managed by mowing, and one was mown and grazed. From May–August 2015, butterflies and burnet moths were surveyed three times along a 20-minute transect on a 0.8 ha patch at each site. Butterflies and burnet moths were classified as 35 farmland and 20 woodland species.Study and other actions tested
A replicated, site comparison study in 1984–2015 in 24 grasslands in Blekinge province, Sweden (Johansson et al. 2017) found that ungrazed grasslands had a lower abundance of clouded Apollo Parnassius mnemosyne than lightly grazed grasslands, but a higher abundance than heavily grazed grasslands. In ungrazed grasslands, the abundance of clouded Apollo (0–109 individuals/grassland/year) was lower than in lightly grazed grasslands (1–169 individuals/grassland/year), but higher than in heavily grazed grasslands (2–22 individuals/grassland/year). In addition, abundance was higher on larger grasslands, and grasslands which were close together were more likely to be colonized (data presented as model results). From 1984–2015, twenty-four open grasslands (>150 m apart) with >0.5 m2 cover of the host plant Corydalis spp. and the presence of a major nectar plant Lychnis viscaria were assigned annually to one of three management categories: no grazing; light grazing (grazing commenced after 15 June with 1–9 animals/hectare); heavy grazing (grazing commenced before 15 June or with ≥10 animals/hectare for ≥8 weeks). Grazing animals were cattle and sheep. In 1984–1987, 1991 and 2003–2015, butterflies were surveyed ≥6 times/year on each site, by marking and recapturing individuals along irregular routes through each grassland. In 1988–1989 and 1992–2002, grasslands were visited more irregularly and their presence recorded. Surveys were used to estimate the local population size on each grassland each year.Study and other actions tested
A replicated, paired, site comparison study and a replicated, paired, controlled, before-and-after study in 2014–2015 on a farm in Galilee, Israel (Berman et al. 2018) found that ungrazed paddocks had fewer spring webworm Ocnogyna loewii caterpillar nests and solitary caterpillars than grazed paddocks. After 10–20 years of abandonment, the number of caterpillar nests and older, solitary caterpillars in ungrazed paddocks (nests: 1; individuals: 6–14) and plots (nests: 1–6; individuals: 1–2) was lower than in grazed paddocks (nests: 3–10; individuals: 24–77) and plots (nests: 2–14; individuals: 3). In addition, after two weeks of grazing exclusion, there were fewer caterpillar nests in recently fenced areas (5–21 individuals) than in unfenced, grazed areas (13–31 individuals), despite having similar numbers before fencing was installed (fenced: 16–19; unfenced: 18–20 individuals). From 1994, a 1,450-ha farm was divided into paddocks managed permanently by moderate (0.55 cows/ha) or heavy (1.1 cows/ha) grazing, or left ungrazed. In January 2015 and March 2014–2015, caterpillar nests (January) and individuals (March) were counted once/year on three 20-m-long transects in each of four ungrazed paddocks (0.5–4 ha) and four grazed paddocks (~27 ha). Within each of the four grazed paddocks, cattle were excluded from five fenced, 10 × 10 m plots for >10 years. In January 2014–2015, all caterpillar nests were counted in each fenced, ungrazed plot and a paired, grazed plot 3 m away in the surrounding paddock. In March 2015, individual caterpillars were counted in three 30 × 30 cm sub-plots in each grazed and ungrazed plot. In January 2014 and 2015, seven and six fenced plots (6 × 6 m, 12 m apart) were constructed within a 50-ha, heavily grazed paddock to exclude cattle. From January 2014 and 2015, caterpillar nests were counted weekly in each ungrazed, fenced plot and a paired, grazed plot 3 m away.Study and other actions tested