Virtual biologists observe virtual grasshoppers: an assessment of different mobility parameters for the analysis of movement patterns

An individual-based model was developed to investigate the accuracy of three mobility indices commonly used in field studies: mean daily movement, maximal distance and mean activity radius. Although the model is based on a field study of the mobility of the grasshopper Oedipoda germanica (Saltatoria: Acrididae) in Thuringia (Germany), the results are valid more generally. We show that the observational interval is the key factor influencing the accuracy of all three indices. Moreover, there is an optimal observational interval that minimises the absolute error. The influence of individual mobility, recapture probability, accurate registration of the capture and recapture points and the effect of the observer on the movement of the animals, are also considered. (C) 1999 Elsevier Science B.V. All rights reserved.