Study

Benefit of permanent non-fire refugia for Lepidoptera conservation in fire-managed sites

  • Published source details Swengel A.B. & Swengel S.R. (2007) Benefit of permanent non-fire refugia for Lepidoptera conservation in fire-managed sites. Journal of Insect Conservation, 11, 263-279.

Summary

Remnants of tallgrass prairies in North America are often burned to prevent scrub growth, but the effect of this management on butterflies is unclear. This study monitored butterfly communities at three prairie sites in Wisconsin, USA with patches kept permanently unburned, as recommended for sites with threatened or endangered butterflies.

At three sites - Crex Meadows, Bauer-Brockway and Muralt Bluff - one or two areas between 3 and 15 ha in size were unburned between 1990 and 2005. These ‘fire refugia’ were managed by hand-cutting, mowing and occasional herbicide use. Comparison areas burned regularly at these sites were selected, along with eleven other remnant prairie sites, also managed with fire. The longest interval between burns for these comparison sites was eight years.

All adult butterflies were counted on standard transect counts between 07:00 h and 18:30 h on dry warm days on dates selected to match the flight periods of the frosted elfin Callophrys irus, the Karner blue Lycaeides melissa samuelis and the regal fritillary Speyeria idalia. The phlox moth Schinia indiana was surveyed by searching its larval food plant, downy phlox Phlox pilosa for caterpillars. Each site was surveyed annually between 1990 and 2005.

At two sites (Crex Meadow and Bauer-Brockway), higher proportions of specialist species than expected were found in the fire refugia than in the burned comparison sites in the second half of the study 2002-2005. When numbers of specialist species (Karner blue, Gorgone checkerspot Chlosyne gorgone, Mottled duskywing Erynnis martialis, Olympia marble Euchloe olympia, Persius duskywing Erynnis persius, dusted skipper Atrytonopsis hianna and phlox moth) were changing, they were always increasing in the fire refuge sites.

At Muralt Bluff, regal fritillaries were more abundant in the fire refugium than in burned areas of the same site, but the Ottoe skipper Hesperia ottoe did not benefit from the fire refugium, disappearing from the site after 1998.
 
To avoid the effects of annual variation in numbers, results are presented as analyses of population trends rather than actual numbers of butterflies.
 
The authors recommend leaving areas of managed prairie permanently unburned, but stress that the areas must be carefully selected to include important habitat elements for species of concern.
 
 
Note: If using or referring to this published study, please read and quote the original paper, the abstract of which can be viewed at: http://www.springerlink.com/content/1366-638X
 

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