1. Ecology
  2. Evolutionary Biology
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Signal categorization by foraging animals depends on ecological diversity

  1. David William Kikuchi  Is a corresponding author
  2. Anna Dornhaus
  3. Vandana Gopeechund
  4. Thomas N Sherratt
  1. University of Arizona, United States
  2. Carleton University, Canada
Research Article
Cite this article as: eLife 2019;8:e43965 doi: 10.7554/eLife.43965
3 figures and 2 additional files

Figures

Figure 1 with 2 supplements
Design and results of Experiments 1 - 5.

(A) Properties of the experimental prey communities used in this study, with examples. All communities had a 1:1 ratio of ‘good’ prey to ‘bad’ prey. A reliable trait allowed perfect discrimination. The richness and evenness of its values varied between experiments. An unreliable trait that did not vary between experiments yielded less accurate discrimination. The exact distribution of prey in each community is given below its richness and evenness statistics, with numbers to indicate the abundance of each prey. As drawn here, shape is the reliable trait (e.g. circle = good, star = bad), whereas color is the unreliable trait (blue = good 78% of the time, yellow = bad 78% of the time). Red boxes indicate the focal prey that were compared across experiments in panels B and C (their actual colors and shapes differed among treatments). (B) Total discrimination subjects exhibited towards focal prey, that is the summed influence of both reliable and unreliable traits. (C) Subjects’ relative use of the reliable trait compared with the unreliable trait for discrimination, that is the difference between the effect of reliable and unreliable traits. The y-axis indicates the difference in the ability of the reliable trait to predict behavior compared to the unreliable trait. In (B) and (C), estimates are grouped using the Bonferroni correction for multiple pairwise comparisons, and 95% confidence intervals are shown. See Methods for details on interpreting log-odds.

https://doi.org/10.7554/eLife.43965.002
Figure 1—source data 1

Data used to generate Figure 1 and its supplements.

Includes results from the test trials of Experiments 1–5. Please refer to Supplementary file 1 for full description and analysis.

https://doi.org/10.7554/eLife.43965.005
Figure 1—figure supplement 1
Tabulated attack rates for prey of different types.

Attack rates when all trait values were recoded, so that they were combined into just two per trait (‘good’ and ‘bad’). For the reliable trait, values are abbreviated B = ‘bad’, G = ‘good’.

https://doi.org/10.7554/eLife.43965.003
Figure 1—figure supplement 2
Tabulated attack rates for prey of different types.

Attack rates when trait values were coded with separate trait values within the ‘good’ and ‘bad’ types. The reliable trait values (colors in the legend) are labeled in descending order of relative abundance in experiments where there were in fact differences in abundance, that is G1 is more abundant than G2, and B1 is more abundant than B2.

https://doi.org/10.7554/eLife.43965.004
Figure 2 with 1 supplement
General experimental procedures.

Subjects were randomly assigned to one of four different treatments within each of five experiments. Between treatments, colors and shapes were shuffled with respect to ‘good’ and ‘bad’ prey to prevent subjects from generalizing across experiments.

https://doi.org/10.7554/eLife.43965.006
Figure 2—figure supplement 1
All experimental treatments used in this study.

For illustration, ‘good’ prey are shown on the top three rows of each grid, and ‘bad’ prey on the bottom three rows. In the actual experiment, their locations were randomized. In the top two treatments for each experiment, shape is the reliable trait; in the bottom two treatments, color is the reliable trait. Good and bad prey are reversed from left treatment to right treatment. The test trial is also shown. It did not vary regardless of the treatment that subjects experienced, except in randomized locations of prey.

https://doi.org/10.7554/eLife.43965.007
Graphical predictions of hypotheses described in the text.

(A) The relative use of the reliable trait will decrease if increased prey richness causes predators to prefer the unreliable trait. (B) If the relative validity effect is robust to changes in richness, predators will always use the reliable trait. (C) If predators cannot process all of the information available in diverse communities, they will guess randomly. (D) If the reduced effective richness of prey in uneven communities reduces the costs of information, then use of the reliable trait will increase.

https://doi.org/10.7554/eLife.43965.008

Additional files

Supplementary file 1

RMarkdown with full analysis, including code to reproduce all results.

The file includes a legend to the columns of the Figure 1—source data 1 with detailed explanation of the variable codings. It is preferable to use this file as a guide to the data.

https://doi.org/10.7554/eLife.43965.009
Transparent reporting form
https://doi.org/10.7554/eLife.43965.010

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