Eyespot peek-a-boo: Leaf rolls enhance the antipredator effect of insect eyespots

Animal color patterns are often accompanied by specific, synergistic behaviors to most effectively defend against visual predators. Given the inherent context-dependence of color perception, understanding how these color-behavior synergies function in a species’ natural environment is crucial.

For example, refuge-building species create a unique visual environment where most (or all) of the body is obscured unless closely inspected. How these built environments affect the perception of defensive color patterns by predators is not well understood.

Using artificial caterpillars that resemble a refuge-building species with conspicuous markings (Papilio troilus; Lepidoptera: Papilionidae), I tested the hypothesis that leaf rolls amplify the antipredator effect of this species’ eyespots. I compared wild avian predation rates on 659 artificial swallowtail-like caterpillars from four treatment groups: eyespotted and non-eyespotted, and presented in leaf rolls or on open leaves of live host plants.

In support of my hypothesis, eyespots only reduced predation for larvae in leaf rolls. On open leaves, eyespots had no antipredator effect. I also found that leaf rolls reduced predation in general for both eyespotted and non-eyespotted prey.

These results highlight the importance of considering relevant behaviors in studies of animal coloration whenever possible, including behaviors that influence color perception indirectly (e.g. through habitat use or modification).

Methods
This project includes 3 datasets:

LRpred.csv: data from an artificial prey field experiment using hand-painted clay caterpillars (2021).

Beyond treatment (color and roll vs no roll), this dataset also includes a considerable number of plant- and habitat-related variables.

LRspectra.csv: spectral measurements for live and artificial swallowtails and host plant (Sassafras) leaves.

Spectral data were collected with an Ocean Optics Flame Miniature (FLAME-S-UV-VIS-ES) spectrometer with Ocean Optics PX-2 Pulsed Xenon light source, calibrated with a 99% Labsphere reflectance standard at the University of Michigan Museum of Zoology.

LRsurvey.csv: data from surveys of naturally-occurring leaf rolls along transects at the same site as the field experiment (2022).

All data were originally collected in google spreadsheets and downloaded as CSVs. I then cleaned, organized, and analyzed the data in R. All corresponding R scripts are available in the repository.

The repository also contains supplemental materials associated with the manuscript (JAE_2024_00285_supp_materials.docx), including 3 supplementary tables of observational data, 3 supplemental figures generated from LRpred.csv, and 1 supplemental figure generated from LRsurvey.csv.