Experience Improves Spatial Foraging Performance in a Complex Environment in Heliconius Butterflies

Heliconius butterflies rely on spatial memory to maintain trapline foraging routes, repeatedly visiting pollen resources along memorized paths. Increased foraging performance resulting from learning the spatial distribution of resources is thought to have driven the evolution of this specialized behavior. Here, we experimentally test whether prior experience in a spatially complex environment influences relative foraging performance in the pollen-feeding butterfly Heliconius erato, a species with well-documented behavioral, ecological and neuroanatomical specializations for spatial learning. We reared freshly eclosed adults in either an open cage or a cage that was matched for resource distribution but structurally divided to increase the spatial complexity experienced by the butterflies. We then tested them individually in a controlled foraging assay under familiar and unfamiliar environments. Butterflies reared in the spatially complex environment efficiently reached the feeder regardless of familiarity with the environment, whereas butterflies reared in the open environment showed strong context dependence, performing well only in the open cage. These results indicate that prior experience of a spatially complex environment supports greater foraging efficiency in Heliconius butterflies, highlighting environmental structure as a likely determinant of the ecological value of spatial learning in this group, with potential consequences for foraging behavior in natural environments.