Movement, translocation and MRR data for Heliconius butterflies

Site fidelity plays an important role in increasing foraging efficiency, particularly when food resources are reliable. In insects, site fidelity has largely been studied in Hymenopteran species, which consistently return to their nest site after foraging bouts. In butterflies, evidence of foraging site fidelity are limited but may be present in species with specific foraging specialisations, such as Heliconius, which have a derived foraging behaviour centred around active pollen feeding. Unlike many Hymenoptera, Heliconius are neither eusocial nor nesting species, positioning them as a peculiar case where foraging site fidelity may occur in the absence of any central nest-like structure. However, to date, existing studies do not consider low dispersal as an alternative to site fidelity. In this study, we use a mark-release-recapture experiment to test whether individuals of two Heliconius species exhibit true site fidelity. We further test this fidelity by measuring flight orientation during a translocation experiment, and by recapturing translocated butterflies to identify whether individuals return to their site of origin. We found that non-translocated butterflies display extreme stability in site choice, and translocated butterflies consistently return to their site of origin, rapidly orientating towards their home site upon release. This suggests site fidelity in Heliconius is not solely explained by low dispersal, but is a response to the distribution and stability in ecological resources. We further note that the ability to return to home sites when artificially dispersed suggests a sophisticated ability to navigate to specific spatial goals. Our study provides insights into the ecological drivers of site fidelity, a novel example distinct from nest building or group living, and opens an avenue of new research on navigational mechanisms in insects.