Long-term spatial memory, across large spatial scales, in Heliconius butterflies

Locating food in heterogeneous environments is a core survival challenge for many animals. The distribution of resources shapes foraging strategies, imposing demands on perception, learning and memory, and associated brain structures. Indeed, selection for foraging efficiency is linked to brain expansion in diverse taxa, from primates1 to Hymenoptera2. Among butterflies, Heliconius have a unique dietary adaptation, actively collecting and feeding on pollen. This provides a source of essential amino acids as adults, negating reproductive senescence and facilitating a greatly extended longevity3. Several lines of evidence suggest that Heliconius learn the spatial location of reliable pollen resources within an individual’s home range4, and it is hypothesized that spatial learning ability will be more pronounced, or only present, at these large spatial scales. However, experimental evidence of spatial learning in Heliconius, or any other butterfly, is so far absent. We therefore tested the ability of Heliconius to learn the spatial location of food rewards at three ecologically relevant spatial scales, representing multiple flowers on a single plant, multiple plants within a single locality, and multiple localities. Heliconius are able to learn spatial information at all three scales, consistent with this ability being an important component of their natural foraging behaviour