Unravelling arthropod movement in natural landscapes: small-scale effects of body size and weather conditions

Abstract

Movement is a crucial life history component and holds direct significance to population dynamics, thereby influencing population viability. For arthropods in general, larger species achieve greater dispersal distances and large-scale movements are influenced by weather conditions. However, many aspects of arthropod movement behaviour remain relatively unexplored, especially on small spatial scales. Studies on this topic are scarce and often limited to a few specific species or laboratory conditions. Consequently, it remains uncertain whether the effects of body size and weather conditions can be generalized across a wide range of arthropod species in natural environments. To help address this knowledge gap, we conducted a field study in two nature reserves in Belgium, focusing on both flying and cursorial arthropods. Over 200 different arthropod species were captured and released within a circular setup, allowing quantification of movement speed and direction. By analysing the relationship between these movement variables and morphological (body size) as well as environmental factors (temperature and wind), we aimed to gain insights into the mechanisms driving small-scale arthropod movement under natural conditions. For flying species, movement speed is positively correlated with both body size and (tail)wind speed. In contrast, movement speed of cursorial individuals was solely positively related with temperature. Notably, movement direction was biased towards the vegetated areas where the arthropods were originally caught, suggesting an internal drive to move towards suitable habitat. This tendency was particularly strong in larger flying individuals, in smaller cursorial species and under tailwind conditions. Furthermore, both flying and cursorial taxa were hindered from moving towards the habitat by strong upwind. Body size can be used as a useful proxy for not only movement speed, but orientation capacity as well. This movement-size correlation is, at least at small temporal scales, conditional to the prevailing wind conditions.