Use rotational grazing
Overall effectiveness category Evidence not assessed
Number of studies: 6
Background information and definitions
Many butterfly species rely on transitional grassland habitats, where continuous management (often by grazing) results in a grass sward which is too short, or prevents the growth of their host plant, but complete abandonment leads to the sward becoming too long or the host plant being outcompeted (e.g. Eichel & Fartmann 2008). Rotational grazing, where livestock are moved between different areas of a site throughout the year, is one option for creating this kind of intermediate habitat, as well as generating a mosaic of more or less recently grazed areas on a larger scale. For other rotational management options, see “Use rotational mowing”, “Reduce grazing intensity on grassland by seasonal removal of livestock” and “Natural system modifications – Use rotational burning”.
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.
Supporting evidence from individual studies
A replicated, site comparison study in 1990–1997 in 105 tallgrass prairies in Illinois, Iowa, Minnesota, Missouri, North Dakota and Wisconsin, USA (Swengel & Swengel 2001) found that rotationally managed prairies (grazed, hayed or burned) which were last managed longer ago had a higher abundance and species richness of specialist and grassland butterflies than more recently managed prairies. All data were presented as models results. Of 105 prairies (1.2–2,024 ha), seven areas within the Sheyenne National Grassland, North Dakota, were managed by rotational grazing (0.3–0.6 animal use months/ha/year), 77 prairies were managed by rotational burning (every 2–5 years) in the cool-season (of which 24 were also hayed or mown), and 27 were managed by haying, mostly on a two-year rotation. 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, randomized, controlled study in 2005–2008 in six pastures in Auvergne-Rhône-Alpes, France (Farruggia et al, 2012) found that, at high, but not low, stocking density, pastures cattle-grazed in rotation with one area left ungrazed for two months had higher butterfly species richness and abundance than constantly stocked areas. At high cattle stocking density, rotational pastures had higher butterfly species richness (7) and abundance (22) than constantly stocked pastures (richness: 4; abundance: 8), but at low stocking density there was no difference between rotational (richness: 6; abundance: 17) or constant pastures (richness: 5; abundance: 13). Within rotationally grazed pastures, at both high and low stocking the ungrazed sub-plot had higher butterfly species richness (4–5) and abundance (10–13) than three grazed sub-plots (richness: 2–4; abundance: 3–5). Within an 80-ha mountain pasture, two grazing treatments (each replicated three times) were compared: cows grazing on rotation around four sub-plots, with one plot being left ungrazed early June–early August, and constant grazing across the whole plot. Plots were grazed at a high stocking rate (1.6 livestock units/ha) from late May–late September 2005–2006 and at a low rate (1.2 livestock units/ha) from late May–mid- or late October 2007–2008. Butterflies and burnet moths were counted twice annually along 50-m walking transects in July and/or August. There was one transect/rotational sub-plot and three transects overall/constant grazing plot.Study and other actions tested
A replicated, controlled study in 2009–2010 in two semi-natural grasslands in central France (Scohier et al. 2013) found that rotationally grazed plots had a similar abundance and species richness of butterflies and burnet moths to continuously grazed plots. In rotationally grazed plots, the abundance (15 individuals/plot) and species richness (7 species/plot) of butterflies and burnet moths was not significantly different from in continuously grazed plots (abundance: 15 individuals/plot; richness: 8 species/plot). Two grasslands were studied: one which had been extensively managed for 40 years, and one which had been fertilized and grazed at a higher stocking density. From 15 May–30 September 2009–2010, four 5,500-m2 plots/grassland were grazed by five (extensive management history) or seven (intensive management history) 3-year-old ewes/plot. Two plots/grassland were divided into four and sheep were grazed on rotation, spending seven days/sub-plot before moving on. One sub-plot was excluded from the rotation from 26 May–14 July during peak flowering. The other two plots/grassland were grazed continuously. From June–July 2009–2010, butterflies and burnet moths were surveyed four times on one 30-m transect/sub-plot in the rotationally grazed plots, and three 30-m transects in each continuously grazed plot.Study and other actions tested
A replicated, paired, controlled study in 2010–2012 in six permanent pasture fields in Devon, UK (RSPB 2016) found that rotationally grazed grassland initially had a higher abundance of invertebrates (including caterpillars) than continuously grazed grassland, but the effect disappeared over three years. In the first year, the number of “bird food invertebrates” was higher on rotational grassland (154 individuals/plot) than on continuously grazed grassland (112 individuals/plot). However, after two and three years, there was no significant difference between rotational (two years: 76; three years: 51 individuals/plot) and continuously grazed plots (two years: 78; three years: 42 individuals/plot). From April 2010–September 2012, six permanent pasture fields were divided into two 1-ha plots. One plot/pair was rotationally grazed by cattle, managed to keep sward height between 9–12 cm, and the other was continuously grazed, keeping the sward at 6–8 cm. None of the fields were fertilized during the trial. In July 2010–2012, invertebrates were sampled in 10 locations/plot using a Vortis suction sampler (ten 15-second samples over 0.19 m2) and sweep-netting (20 double sweeps with a 46-cm diameter net). Invertebrates <2 mm long were excluded from analysis.Study and other actions tested
Referenced paperRSPB . (2016) Utility of lenient grazing on agricultural grassland to promote in-field structural heterogeneity, invertebrates and bird foraging [BD5207: Extensive cattle grazing: what is the best approach to improve species-poor pastures for birds and invertebrates? (Phase 2)]. Natural England report, Project BD5206/BD5207 RSPB Final Report to DEFRA/Natural England (RP00196).
A replicated, randomized, controlled study in 2011–2013 in semi-natural mountain pastures in Massif Central, France (Ravetto Enri et al. 2017) found that rotationally grazed grassland plots had a higher abundance and species richness of butterflies and burnet moths than continuously grazed plots, and subplots which were not grazed in summer had the most butterflies and burnet moths. In rotationally grazed plots, both the abundance (36 individuals/plot) and species richness (8.4 species/plot) of butterflies and burnet moths was higher than in continuously grazed plots (abundance: 23 individuals/plot; richness: 7.1 species/plot). Within rotationally grazed plots, subplots which were not grazed in summer had a higher abundance (14 individuals/subplot) and species richness (5.3 species/subplot) of butterflies and moths than subplots grazed in summer (abundance: 5–9 individuals/subplot; richness: 2.7–3.8 species/subplot). From 1992–2011, pastures were grazed extensively by cattle without fertilization. From May–October 2011–2013, six 3.6-ha plots were each grazed by seven Charolais cattle (heifers), and six 0.6-ha plots were each grazed by seven female Limousine sheep (both 1.75 livestock units/ha). Three plots in each group were grazed continuously, and three were sub-divided into four subplots each grazed for 35 days/year. One subplot in each plot was not grazed for 63 days from early June–early August each year. From early July–early August 2011–2013, butterflies and burnet moths were surveyed twice/year on four 50-m fixed transects/plot (one in each rotational subplot).Study and other actions tested
A replicated, site comparison study in 2015–2016 in two grassland reserves in North Dakota, USA (Bendel et al. 2018) found that rotational grazing did not affect butterfly community composition, but did affect the species richness and abundance of individual species, compared to pastures managed by rotational grazing with mowing, season-long grazing, or patch-burn grazing. Rotational grazing did not affect butterfly community composition compared to other management (data presented as model results). Two out of nine species (meadow fritillary Boloria bellona and regal fritillary Speyeria idalia) were more abundant in rotationally grazed pastures, while two species (small pearl-bordered fritillary Boloria selene and purplish copper Lycaena helloides) were less abundant in rotationally grazed pastures than other management, and five species had a similar abundance between management types (see paper for details). Thirty butterfly species were recorded in rotationally grazed pastures, compared to 25 species in rotationally grazed pastures with mowing, 22 species in season-long grazed pastures and 26 species in patch-burned grazed pastures (statistical significance not assessed). Eight pastures (54–484 ha) managed under one of four management practices (rotational grazing, rotational grazing with lowland mowing, season-long grazing, patch-burn grazing) were selected. Rotational pastures were sub-divided into four paddocks, each grazed twice/season. In mown pastures, sedge-dominated patches were cut once/summer. On season-long pastures cattle were free to select grazing areas. One-third of each patch-burn grazed pasture was burned in the dormant season, but prior to April 2015 these sites were rotationally grazed. All other sites had the same management for at least a decade. Pastures were stocked with cattle (0.5–0.75 cow-calf pairs/ha) from May–October. From June–August 2015 and 2016, butterflies were surveyed three times/year along twelve 100-m transects/pasture.Study and other actions tested