Quantifying visual acuity in Heliconius butterflies

• Published in: Biology letters (2005) Vol. 19; no. 12; p. 20230476
• Main Authors: Wright, Daniel Shane, Manel, Anupama Nayak, Guachamin-Rosero, Michelle, Chamba-Vaca, Pamela, Bacquet, Caroline Nicole, Merrill, Richard M
• Format: Journal Article
• Language: English
• Published: England The Royal Society 13.12.2023
• Subjects: Animal Behaviour; sensory perception; colour pattern; aposematism
• ISSN: 1744-957X; 1744-9561; 1744-957X
• DOI: 10.1098/rsbl.2023.0476

butterflies are well-known for their colourful wing patterns, which advertise distastefulness to potential predators and are used during mate choice. However, the relative importance of different aspects of these signals will depend on the visual abilities of and their predators. Previous studies have investigated colour sensitivity and neural anatomy, but visual acuity (the ability to perceive detail) has not been studied in these butterflies. Here, we provide the first estimate of visual acuity in : from a behavioural optomotor assay, we found that mean visual acuity = 0.49 cycles-per-degree (cpd), with higher acuity in males than females. We also examined eye morphology and report more ommatidia in male eyes. Finally, we estimated how visual acuity affects visual perception compared to a potential avian predator. Whereas the bird predator maintained high resolving power, lost the ability to resolve detail at greater distances, though colours may remain salient. These results will inform future studies of wing pattern evolution, as well as other aspects in these highly visual butterflies, which have emerged as an important system in studies of adaptation and speciation.