Sampling strategies for millipedes (Diplopoda), centipedes (Chilopoda) and scorpions (Scorpionida) in savanna habitats

At present considerable effort is being made to document and describe invertebrate diversity as part of numerous biodiversity conservation research projects. In order to determine diversity, rapid and effective sampling and estimation procedures are required and these need to be standardized for a particular group of organisms to allow for comparisons between studies and habitat types. The savanna biome is one of the largest and most important in Africa; however, it is also one of the most poorly studied, especially in terms of invertebrates. This study was undertaken in the Greater Makalali Conservancy, Limpopo Province, South Africa. The effectiveness of six sampling methods (pitfall traps, active searching one 25 m² nested quadrat, active searching ten 2.25 m² random quadrats, cryptozoan traps, wet cloths and drive transects) was tested to determine which method, or combination of methods, was the best for sampling millipedes, centipedes and scorpions in the savanna environment. Active searching in a 9 m ² area was the most effective way to sample millipede species, while the drive transect method was important for sampling larger millipede species. Both the active searching of the nested quadrats and the random quadrats proved to be the most effective methods to sample centipedes. Scorpions were most effectively sampled using pitfall traps. Efficiency for all methods was calculated as the number of species collected per hour. The most effective method was not always the most efficient one, and this needs to be considered when designing a sampling strategy. Sampling more than one period in the summer is important for determining species richness. The number of random quadrats required to sample the fauna is likely to vary in different habitats, and there is a large amount of variation in the number of species collected between samples, which is probably related to high levels of habitat heterogeneity on a small scale. These points, as well as the size, mobility and other biological features of taxa need to be considered in designing a sampling strategy for invertebrates.