Effects of large-scale cattle grazing on populations of Coenonympha glycerion and Lasiommata megera (Lepidoptera: Satyridae)

The effects of large-scale cattle grazing by herdsmen (Allmende) on the populations of two butterfly species, Coenonympha glycerion and Lasiommata megera, were analysed on a study plot in the foothills of the Eastern Carpathians, Republic of Ukraine, in the summer and autumn of 1995. In all, 280 individuals of C. glycerion (115 females) and 230 individuals of L. megera (61 females) were individually marked. At recapture rates of 35 to 39%, maximum population size was calculated at 410 and 434 individuals. C. glycerion reacted to high densities by shifting to smaller neighbouring habitats. An increased emigration rate was recorded for L. megera when the population maximum was reached. Both species essentially require habitats formed by the activity of cattle. C. glycerion significantly preferred south facing woodland margins, close to moderately and infrequently grazed grassland. Heavily grazed areas were avoided. L. megera mainly occupied well-trod cattle paths or landslips with rather sparse vegetation, induced by cattle. Preferred habitats are characterized by linear structures for patrolling, steep slope areas and a wide range of nectar resources. Smaller, sporadically used cattle paths did not show these features and were occupied mainly by males at times of high population densities. Both species depend on patchy habitat mosaics which will be lost by intensification as well as by a complete cessation of grazing. The low-intensity, large-scale system utilized in the Eastern Carpathians is therefore favourable to both species.