How much space is needed for spider conservation? Home range and movement patterns of wolf spiders (Aranea, Lycosidae) at Baltic Sea beaches

Abstract

Beaches are often intensively used by tourists that compete with the area demands of specialised species. In order to estimate the area demand of beach spiders, home range, distribution and population dynamics of three species of Lycosidae (Arctosa cinerea, Arctosa perita and Pardosa agricola) were observed by mark-recapture experiments at two closed nature conservation beach areas at the Baltic Sea. Results revealed that the home range size of A. cinerea varied between beaches. The size of minimal complex polygons of males at a narrow sandy beach was 143.18 ± 22.62 m2 (females: 164.70 ± 13.48 m2) and was so significantly smaller than those found at a broader beach (males: 182.60 ± 13.46 m2; females: 179.36 ± 47.89 m2) with about 12 % stone coverage. General distribution of all spiders showed an increased frequency on the upper beach area. Estimates on the population size of the three species during summer revealed the highest population size in May and the least at the end of July. In addition, movement behaviour of A. cinerea was observed at a nature conservation area and at an accessible beach. Direct observations of movement patterns indicated that disturbed spiders take more detours and focus their movements seaward where they will be confronted with non-suitable conditions. This study underlines the sensitivity of predatory arthropods of beach habitats to human disturbance. This is particularly critical for the upper beach area. Based on these results, means of achieving viable arthropod populations through adjusted beach management are derived.