DOI: 10.5061/dryad.390t3
title: Data from: What makes eyespots intimidating? - the importance of pairedness

description: Background: Many butterflies possess striking structures called eyespots
 on their wings, and several studies have sought to understand the
 selective forces that have shaped their evolution. Work over the last
 decade has shown that a major function of eyespots is their ability to
 reduce predation by being intimidating to attacking predators. Two
 competing hypotheses seek to explain the cause of intimidation, one
 suggesting ‘eye-mimicry’ and the other their ‘conspicuousness’ as the
 reason. There is an on-going debate about which of these better explains
 the effectiveness of eyespots against predation. We undertook a series of
 indoor experiments to understand the relative importance of
 conspicuousness and eye-mimicry, and therefore how predator perception may
 have influenced the evolution of eyespots. We conducted choice tests where
 artificial paper models mimicking Junonia almana butterflies were
 presented to chickens and their preference of attack recorded. Results: We
 first established that birds avoided models with a pair of eyespots.
 However, contrary to previous, outdoor experiments, we found that the
 total area of eyespots did not affect their effectiveness. Non-eye-like,
 fan shaped patterns derived from eyespots were found to be just as
 effective as eye-like circular patterns. Furthermore, we did not find a
 significant effect of symmetry of patterns, again in discordance with
 previous work. However, across all experiments, models with a pair of
 patterns, symmetric or asymmetric, eyelike or non-eye-like, suffered from
 fewer attacks compared with other models. Conclusions: The study
 highlights the importance of pairedness of eyespots, and supports the
 hypothesis that two is a biologically significant number that is important
 in prey–predator signalling. We discuss the implications of our results
 for the understanding of eyespot evolution.
description: Data Set providing the
 recordings of time (in seconds) of birds attacking either models in
 two-choice based experimentsThe excel sheet contains
 raw data from 5 two-choice experiments as described in the article. The
 data has been collected from field observations and have been entered
 manually in the excel sheet. Each trial/test of an experiment describes
 the time (in seconds) taken by a bird to attack both models. A trial was
 terminated either after the bird had attacked both models or after the
 completion of 5 minutes, so the time does not exceed 300s in any trial.
 The column headings have been described in accordance with the article.
 Experiment 1: i. 0 vs 1 ii. 1 vs 5 & iii. 0 vs 5 eyespots per
 hindwing; Experiment 2: Natural-sized eyespots (Area) vs eyespots with
 reduced area (Area/2); Experiment 3: A pair of natural eyespots (Eyespot)
 vs a pair of non-eyelike patterns with the same total area (Fan);
 Experiment 4: A pair of symmetric eyespots (Sym = OO) vs a pair of
 asymmetric patterns consisting of an eyespot and a fan (Asym = OF/FO);
 Experiment 5: A pair of natural eyespots (Paired) vs a single eyespot with
 twice the area (Unpaired)Raw
 Data.xlsx