Making sense of a prairie butterfly paradox: The effects of grazing, time since fire, and sampling period on regal fritillary abundance

Published source details Moranz R.A., Fuhlendorf S.D. & Engle D.M. (2014) Making sense of a prairie butterfly paradox: The effects of grazing, time since fire, and sampling period on regal fritillary abundance. Biological Conservation, 173, 32-41.
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This study is summarised as evidence for the following.

	Action	Category
	Increase grazing intensity or cutting frequency on grassland Action Link
	Use rotational burning Action Link

Increase grazing intensity or cutting frequency on grassland

A replicated, randomized, paired, controlled study in 2005–2007 in four tallgrass prairies in Missouri, USA (Moranz et al. 2014) found that increasing cattle grazing reduced the abundance of regal fritillary Speyeria idalia, particularly after recent burning. The number of regal fritillaries in grazed prairie (0–14 individuals/ha) was lower than in ungrazed prairie (1–25 individuals/ha) throughout the summer. However, the difference was greatest in prairies which had been burned earlier the same year (grazed: 0–2 individuals/ha; ungrazed: 3–22 individuals/ha). From 2000–2004, four remnant prairies were burned on rotation and occasionally hayed or lightly grazed. In 2005, half of each prairie was randomly assigned to one of two treatments: grazing and rotational burning, or rotational burning only. Each half was sub-divided into three plots (20–34 ha), which were randomly assigned to be burned in either March 2005, 2006 or 2007. The grazed sites were stocked with cattle (2.2 ha/animal unit) annually from April–August. From June–July 2006–2007, butterflies were surveyed three times/year on a transect through each plot.

(Summarised by: Andrew Bladon)
Use rotational burning

A replicated, randomized, paired, controlled study in 2005–2007 in four tallgrass prairies in Missouri, USA (Moranz et al. 2014) found that spring burning reduced regal fritillary Speyeria idalia abundance in mid-summer, but increased abundance later in the summer. In late June, the number of regal fritillaries in plots burned that spring (3–12 individuals/ha) was lower than in plots burned one (12–22 individuals/ha) or two (7–25 individuals/ha) years earlier. However, by late July, the number was higher in recently burned plots (14–22 individuals/ha) than in plots burned one or two years earlier (1–9 individuals/ha). In early June, fritillary abundance was not significantly different in recently burned plots (5–22 individuals/ha) and those burned in previous years (7–9 individuals/ha). From 2000–2004, four remnant prairies were burned on rotation and occasionally hayed or lightly grazed. In 2005, half of each prairie was randomly assigned to one of two treatments: grazing and rotational burning, or rotational burning only. Each half was sub-divided into three plots (20–34 ha), which were randomly assigned to be burned in either March 2005, 2006 or 2007. The grazed sites were stocked with cattle (2.2 ha/animal unit) annually from April–August. From June–July 2006–2007, butterflies were surveyed three times/year on a transect through each plot.

(Summarised by: Andrew Bladon)