Assessing grasshopper communities in mountainous meadows – a comparison of a visual‐acoustic and a novel, purely acoustic soundscape method

Abstract

Grasshoppers (Orthoptera, suborders Ensifera and Caelifera) are often used as bioindicators to assess the effects of human-induced land-use changes. However, such assessment is largely depending on the methods that provide an accurate estimation. In the present study, we compared grasshopper species richness and assemblages on mountainous meadows in the Austrian Alps by applying a commonly used visual-acoustic method and a novel soundscape method. For the visual-acoustic method, we walked through the meadows for 1 h at a slow pace and recorded any visually and acoustically noticeable species. For the soundscape method, sound recorders combined with bat detectors were installed at fixed positions. Comparing both methods, there was no significant difference in species richness; however, we found significantly higher numbers of Caelifera species with the visual-acoustic method and marginally higher numbers of Ensifera species with the soundscape method. Grasshopper assemblages differed marginally significantly between the two methods. With the soundscape method significantly more species were found between 12:00 and 17:00 hours compared to the samples taken between 10:00 and 12:00 hours. The soundscape method represents a reliable and by the observer unbiased technique to investigate grasshoppers within their environment. The visual-acoustic method is especially preferable for the detection of non-stridulating species which cannot be assessed with the soundscape method. Thus, researchers might consider using a sampling plan that mixes different sampling methods in order to offset potential limitations in sampling grasshopper species.