LAUSR

Scarce Heath Coenonympha hero is considered to be one of the most seriously threatened European butterflies, especially declining in western and central Europe. It usually occurs in small, discrete colonies forming metapopulation systems, but the exchange of individuals between habitat patches is considered limited. Therefore the persistence of the species in fragmented systems is likely to depend largely on the demography of local populations. We investigated a highly isolated population of the species in Poland with mark-release-recapture (MRR). The seasonal population size was assessed at 168 adults, with a well balanced sex ratio. The slightly higher capture probability of females that we recorded is quite atypical for butterflies and may be related to the vegetation structure at the site. The flight period was relatively short (22 days), and the adult life span was estimated at 6.59 days, i.e., twice as long when compared with adult longevity in two other threatened Coenonympha species. Consequently, the temporal fragmentation index (i.e., the ratio of flight period length to adult life span) was calculated at 3.3, which is the lowest value recorded among all congeneric species, suggesting that temporal fragmentation is not a major problem in the investigated population. Nevertheless, the population may be at risk of extinction due to its small size and isolation. Moreover, the area of C. hero habitat has decreased considerably over the last decade due to afforestation. Our findings indicate the need for immediate conservation actions, in particular for the removal of tree seedlings that encroach on the butterfly habitat.