Fluttering in a Changing World: Effects of Urbanization and Nectar Plants on Butterfly Movement Patterns

We aimed to answer the general question of whether urbanization and nectar plant abundance affect butterfly movement patterns and more specifically, (1) whether the mobility of the investigated small white (Pieris rapae) and the small heath butterfly (Coenonympha pamphilus) is affected differently, and (2) whether these butterflies show altered tortuosity patterns along a rural-urban gradient. The study sites were situated along a rural-urban gradient in the Berlin-Brandenburg metropolitan region (Germany). We recorded GPS movement trajectories of two common butterfly species differing in territoriality, agility, and habitat requirements, following them afoot with a DGPS backpack. Movement trajectories were analyzed in terms of mobility (flight speed and time investment in stopping, nectaring, and resting), tortuosity, and the effects of urbanization and nectar plant coverage on the derived variables were investigated using generalized linear mixed-effect models. Nectar plant coverage negatively affected flight speed but increased flight path tortuosity for both species. P. rapae displayed a slightly increasing and C. pamphilus a slightly decreasing flight speed with increasing urbanization. With increasing urbanization, flight path tortuosity decreased for P. rapae. The results possibly reflect differences in the species' life history strategy, which might induce different adaptive responses in their movement behavior.