Use rotational mowing
Overall effectiveness category Awaiting assessment
Number of studies: 10
Background information and definitions
Mowing large areas of grassland at once creates a uniform habitat structure, and removes all floral resources simultaneously (Morris 2000). It can also kill or injure butterfly and moth eggs or caterpillars living among the grass. Rotational mowing resembles many traditional meadow management practices, and involves cutting different areas at different times, such that some patches remain uncut (Bubova et al. 2015). This creates a more heterogeneous sward height, and may provide a refuge habitat for butterflies and moths (Morris 2000). Studies are included here if they look at rotational mowing both within and between growing seasons.
For other changes to mowing techniques or timing in productive grasslands, see “Reduce cutting frequency on grassland”, “Delay cutting or first grazing date on grasslands to create variation in sward height”, “Raise cutting height on grasslands” and “Use motor bar mowers rather than rotary mowers”. For studies on using mowing to manage wild or semi-natural grasslands, see “Habitat restoration and creation – Change mowing regime on grassland”.
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.
Morris M.G. (2000) The effects of structure and its dynamics on the ecology and conservation of arthropods in British grasslands. Biological Conservation, 95, 129–142.
Supporting evidence from individual studies
A replicated, site comparison study in 1980–1989 on eight grasslands in Cornwall, UK (Warren 1991) reported that grasslands managed by rotational mowing supported populations of heath fritillary Mellicta athalia while populations on unmanaged grasslands went extinct. Results were not tested for statistical significance. Two grasslands managed by rotational mowing maintained heath fritillary populations of 1,300–2,700 adults/year (5-ha site) and 200–600 adults/year (0.25-ha site), compared to six unmanaged grasslands where the heath fritillary populations went extinct (data not presented). From 1981–1989, the flatter areas of a 5-ha grassland were mown annually in autumn using a tractor-drawn ‘bush-hog’ cutter, while the steeper areas were cut every two or four years using hand-held brush cutters. A second 0.25-ha grassland was managed by cutting half of the site each year. Six other grasslands were unmanaged throughout this period. From 1980–1989, butterflies were surveyed annually on timed counts along a zig-zag route covering the known flight areas at each site. The total yearly population at a site was estimated by multiplying the peak population count by three.Study and other actions tested
A replicated, site comparison study in 1992–1993 in 42 tall-grass prairies in Missouri, USA (Swengel 1996) found that butterflies were more abundant in the first year after haying than in the second year after haying. In the first year following haying, the abundance of prairie specialist butterflies (81 individuals/hour) was higher than two years after haying (68 individuals/hour). The abundance of grassland species (11 individuals/hour), generalists (17 individuals/hour) and migrants (19 individuals/hour) in the year following haying was also higher than two years after haying (grassland: 9; generalist: 10; migrant: 5 individuals/hour). See paper for individual species results. Of 42 sites (6–571 ha), some were primarily managed by summer haying on a 1–2 year rotation with occasional cattle grazing (number not given). In June 1992–1993, butterflies were surveyed at least once/year at most sites, either along a transect (35 sites) or from a single point (7 sites, recording only regal fritillary Speyeria idalia). Transects were sub-divided by the most recent management. Sixteen species observed >49 times and at >5 sites were included, and divided into “prairie specialists” (only found on prairies), “grassland species” (found in prairies and other grasslands), “generalists” (found in grasslands and other habitats) and “migrants” (only present in the study area during the growing season).Study and other actions tested
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 (hayed, grazed 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), 27 were managed by haying, mostly on a two-year rotation, 77 areas were managed by rotational burning (every 2–5 years) in the cool-season (of which 24 were also hayed or mown), and seven areas within the Sheyenne National Grassland, North Dakota, were managed by rotational grazing (0.3–0.6 animal use months/ha/year). 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, paired, controlled study in 2006–2008 in 10 meadows in Hessen, Germany (Handke et al. 2011) found that after three years, rotationally mown grassland had a greater abundance and species richness of butterflies than annually mown grassland. Three years after rotational mowing began, the abundance and species richness of butterflies was higher on the rotational strips (abundance: 120 individuals/strip; richness: 7 species/strip) than on strips cut annually (abundance: 10 individuals/strip; richness: 5 species/strip) after mowing, but there was no significant difference between strips before mowing in any year (rotational: 10–70 individuals/strip, 4–7 species/strip; annual: 10–120 individuals/strip, 4–8 species/strip). However, in the first year, species richness on the rotational strips (7 species/strip) was lower than on the annual strips (12 species/strip) after the latter had been mown, but the abundance was similar (rotational: 60 individuals/strip; annual: 50 individuals/strip). From 2006–2008, in each of 10 meadows, two 500-m2 strips (usually 5 × 100 m) were managed in one of two ways: mown every two years (i.e. not mown in 2006 and 2008) or mown annually after 10 June. In 2007, most mowing took place in August due to wet weather. From May–August 2006–2008, butterflies were surveyed 4–6 times/year with 100 sweeps/strip of a 32-cm diameter net, and recording of other individuals at the same time (two meadows not surveyed in 2008).Study and other actions tested
A replicated, controlled study in 2005–2006 in 11 hay meadows in Eastern Bohemia, Czech Republic (Cizek et al. 2012) found that rotationally mown meadows were preferred by most species of butterfly. Most butterfly species (29/32 species) preferred rotationally mown meadows to complete cut meadows. The three species which preferred complete cut meadows were all woodland species which would only be visiting the meadows temporarily. In 2005 and 2006, one of three mowing regimes was applied to 11 meadows: alternating cut and uncut 5–10-m strips in June and cutting the remaining strips in August; alternating cut and uncut 50-m blocks in June and cutting the remaining blocks in August; mowing the whole meadow in June and August. The latter represented standard agri-environment scheme meadow management in the Czech Republic, and all meadows were managed like this prior to the study. Management of some meadows changed between years. From May–September 2005–2006, butterflies were surveyed fortnightly along transects through 11 meadows.Study and other actions tested
A review in 2015 of 126 studies in Europe (Bubová et al. 2015) reported that rotational mowing of grassland benefitted 27 out of 67 butterfly species of conservation concern. Results were not tested for statistical significance. The review reported that 30 studies found that rotational mowing benefitted 27 butterfly species. See paper for information on individual species. Meadows were mown in rotation at low intensity, with different fragments cut at different times, and with a single fragment mown no more than once/year. Rotational mowing was often combined with extensive grazing. 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, randomized, paired, controlled study in 2010–2013 in 24 meadows in the Swiss Plateau, Switzerland (Bruppacher et al. 2016) found that leaving some areas uncut when mowing extensively managed meadows increased the abundance, but not species richness, of butterflies and burnet moths. Before first mowing, the abundance of butterflies and burnet moths in meadows with uncut refuges from previous years (1.0–2.9 individuals/100 m) was higher than in standard agri-environment scheme (AES) meadows without refuges (1.1–1.3 individuals/100 m). After 15 June, there was no difference in butterfly abundance between meadows with refuges (1.8–19.9 individuals/100 m) and standard meadows (2.3–17.9 individuals/100 m). The overall species richness of meadows with refuges (10 species) was similar to standard meadows (8 species). However, species richness of specialist butterflies was higher in meadows with refuges (1.7 species) than in standard meadows (1.1 species). In 2010, at 12 sites (>5 km apart), two meadows (0.3–1.7 ha) which had been in AES since at least 2004 were randomly allocated to two treatments: standard Swiss AES management (no cutting before 15 June) or refuge cutting (no cutting before 15 June and leaving 10–20% of the meadow uncut). The location of the uncut area had to vary between cuts. Meadows were cut on average twice/year. From late April–August 2013, butterflies were surveyed along a transect (65–215 m) through the middle of each meadow. Three surveys were conducted before 15 June, one between 15 June and 15 July, and two after 15 July.Study and other actions tested
A replicated, site comparison study in 2012–2013 in 12 semi-natural grasslands in Nagano Prefecture, Japan (Uchida et al. 2016) found that meadows managed by traditional rotational mowing and burning had a higher species richness and diversity of butterflies than annually mown, annually burned or abandoned meadows. In rotationally managed meadows, the diversity and species richness of threatened (6–7 species/meadow) and common (10–12 species/meadow) butterflies was higher than in annually mown (threatened: 3; common: 4 species/meadow), annually burned (threatened: 2–3; common: 6 species/meadow) or abandoned meadows (threatened: 1–2; common: 1–2 species/meadow) (diversity data presented as model results). Three meadows were managed traditionally: each year half of the meadow was burned in April and mown in September, while the other half was unmanaged, and management rotated each year. An additional three meadows had been mown annually in April or August for 8–9 years, three meadows had been burned annually for 7–13 years and three meadows had been abandoned (unmanaged) for 6–13 years. From May–September 2012–2013, butterflies were surveyed monthly on three 5 × 30 m plots/meadow.Study and other actions tested
A replicated, site comparison study in 2007–2010 in 28 grassland sites in Bílé Karpaty Protected Landscape Area, Czech Republic (Bonari et al. 2017) found that mixed grassland management, which included leaving some areas uncut each year, supported the highest species richness of butterflies, but an intermediate species richness of moths. The species richness of butterflies was higher in grasslands under mixed management than in mown, grazed or abandoned grasslands, but species composition was not affected by management. However, the species richness of moths was highest in mown grasslands, lowest in grazed grasslands, and intermediate in mixed management, and these sites had different species composition (all data presented as model results). One of four different management practices (mown once/year; grazed by sheep, cattle or deer; abandoned (no grazing or mowing); or ‘mixed’ management) was applied to each of 28 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 site.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 2009–2011 in 133 mixed farms in the Central Plateau, Switzerland (Stoeckli et al. 2017) found that farms with more in-field agri-environment scheme (AES) options, including staggered mowing, had a similar abundance and species richness of butterflies to farms with fewer (AES) options. Both the abundance and species richness of butterflies on farms with a larger area of in-field AES options were similar to farms with smaller areas of in-field AES options (data presented as model results). A total of 133 farms (17–34 ha, 13–91% arable crops) were managed with in-field AES options, including staggered mowing, use of bar mowers, no silage, undersown cereals, undrilled patches in crops, wide-spaced rows, cover crops and no chemical inputs. Fields without chemical inputs contributed about half of the area of AES options, on average. From May–September 2009–2011, butterflies were surveyed six times on 10–38 transects/farm, totalling 2,500 m/farm. Each transect ran diagonally through a single crop or habitat type, with all available crops and habitats represented. All visits to a farm were completed in a single year, and the species richness was summed across all visits. Total abundance of butterflies was calculated from the number recorded in each habitat, and the availability of each habitat across the farm.Study and other actions tested