Monitoring and conservation of Saga pedo (Orthoptera: Tettigoniidae) in an isolated nothwestern population

Abstract

The bush cricket Saga pedo is a critically endangered species in the EU and is included in Annex IV of Council Directive 92/43/EEC. This species is therefore subject to mandatory regular monitoring within all member countries where it occurs. Because its abundance is low and little information is available concerning its ecology, however, an effective monitoring method that would yield standardized results has yet to be devised. We found S. pedo passing through 6 instars during its development in Central European conditions. Our findings indicate that, after hatching, S. pedo moves constantly through terrain with optimal vegetation and thereby reduces its population density. Based on recaptures of marked individuals, adults moved usually between 0.5 and 2 m in 24 h, the largest distance moved during a day was recorded as 37.5 m. Combined with a high mortality rate, this continual movement leads to very low density late in the season. Based on extensive surveys conducted during 2006–2011 at 10 sites in the Pálava Protected Landscape Area (Czech Republic), we show that the optimal time for monitoring in order to achieve comparable results from different investigators in different locations is the period just after nymphs hatch (1–10 May in Central Europe). Because S. pedo populations in Europe are threatened by habitat destruction resulting from successional overgrowth of habitat by vegetation and afforestation, ensuring the survival of this species will require that successional changes in vegetation and afforestation be stopped by mowing and removal of woody plants and seedlings or by farming (extensive grazing). Management need not be performed every year but should occur when the S. pedo population is already adult and dispersed. The most suitable period for partial machine mowing (1/3–1/2 of a specific area) is September. Mowing with scythes and extensive rotational grazing are the best methods for managing sites where S. pedo is found.