Heliconiini butterflies can learn time-dependent reward associations

For many pollinators, flowers provide predictable temporal schedules of resource availability, meaning an ability to learn time-dependent information could be widely beneficial. However, this ability has only been demonstrated in a handful of species. Observational studies of Heliconius butterflies suggest that they may have an ability to form time-dependent foraging preferences. Heliconius are unique among butterflies in actively collecting and digesting pollen, a dietary behaviour linked to spatiotemporally faithful trap-line foraging. Time-dependency of foraging preferences is hypothesised to allow Heliconius to exploit temporal predictability in alternative pollen resources, as well as contributing to optimal use of learnt foraging routes. Here, we provide the first experimental evidence in support of this hypothesis, demonstrating that Heliconius hecale can learn opposing colour preferences in two time periods. This shift in preference is robust to the order of presentation, suggesting that preference is tied to the time of day and not due to ordinal learning. However, we also show that this ability is not limited to Heliconius, as previously hypothesised, but is also present in a related genus of non-pollen feeding butterflies. This demonstrates that time learning pre-dates the origin of pollen-feeding and may be prevalent across butterflies with less specialized foraging behaviours.