DOI: 10.5061/dryad.bzkh189k7
title: Data from: Detectability of a poison frog and its Batesian mimic depends on body posture and viewing angle

description: Aposematic signals warn predators that prey should be avoided due to
 dangerous secondary defences. However, as warning signals do not always
 produce avoidance, warning colours may evolve as a trade-off balancing
 detectability against signal saliency. For Batesian mimics, which display
 salient signals but lack secondary defences, the costs of predator
 encounters are greater, potentially increasing the benefit of crypsis.
 This raises the question of whether imperfect mimicry may reduce
 detectability while retaining mimetic efficacy. We tested this hypothesis
 with the poisonous frog Ameerega bilinguis and undefended Batesian mimic
 Allobates zaparo, using computational visual modelling and screen-based
 detection trials with human participants. We found that both species
 incorporate camouflage into their warning colours, but to different
 degrees depending on viewing angle and behaviour. Contrary to expectation,
 we found differences in detectability between model and mimic that do not
 adhere to the hypothesized cryptic mimetic phenotype. To aerial observers,
 we found the mimic to be more detectable than the model. To terrestrial
 observers, likely owing to the model’s bright ventral colour, we found the
 model more detectable in viewing angles that highlight the ventral
 colouration, while the mimic was more detectable in viewing angles that
 highlight the dorsal colouration. Consequently, we suggest that in
 addition to being the result of perceptual or developmental constraints,
 imperfect mimicry may also evolve as an adaptive strategy which balances
 camouflage with different signalling functions. Our findings complement
 the emerging view that aposematic signals may evolve in response to a
 multitude of selection pressures beyond aversion alone.
description: # Data from: Detectability of a poison frog and its Batesian mimic depends
 on body posture and viewing angle
 [https://doi.org/10.5061/dryad.bzkh189k7](https://doi.org/10.5061/dryad.bzkh189k7) ## Description of the data and file structure This experiment sought to quantify imperfect batesian mimicry, i.e. quantify differences in chromatic and achromatic salience in warning signals of a toxic frog 'model' species and its non-toxic 'mimic' species.  We collected live specimens from their natural habitat and photographed them. We then analysed those photographs in ImageJ and conducted human-participant observer detection experiments on a computer screen to quantify phenotypic mismatch and differences in detectability between model and mimic. ### Files and variables #### File: DRYAD\_data.zip **Description:** Contains all files required to replicate findings.  Data used in: McEwen, et al. Detectability of a poison frog and its Batesian mimic depends on body posture and viewing angle Brendan L. McEwen, Justin Yeager, Isaac Kinley, Hannah M. Anderson, & James B. Barnett For further information contact: Brendan L. McEwen Email: [mceweb1@mcmaster.ca](mailto:mceweb1@mcmaster.ca) James B. Barnett Email: [barnettdata@gmail.com](mailto:barnettdata@gmail.com) \## ==== IMAGE DATA - INTERNAL CONTRAST ==== ## Data files: 01_McEwen-etal_IntCont_BluetitLMS.txt internal chromatic & achromatic contrast from the bird visual model S1_McEwen-etal_IntCont_CoachwhipLS.txt Supp. Mat. internal chromatic & achromatic contrast from the snake visual model S1_McEwen-etal_IntCont_PoisonFrogLMS.txt Supp. Mat. internal chromatic & achromatic contrast from the poison frog visual model S1_McEwen-etal_IntCont_HumanLMS.txt Supp. Mat. internal chromatic & achromatic contrast from the human visual model RMarkdown file: McEwen_etal_2023-InternalContrast.Rmd | McEwen_etal_2023-InternalContrast.pdf Format: tab-delimited text Column identification: Visual_Model: visual model used in analysis (Bluetit_LMS (bird), Coachwhip_LS (snake), PoisonFrog_LMS (frog), or HumanLMS (human)) Species: frog species (Am_bilinguis = Ameerega bilinguis, Al_zaparo = Allobates zaparo) Frog_ID: unique code for each frog (n = 10 / species) Photo_ID: unique code for the original image from which data were extracted Viewpoint: body region that was the basis for the pairwise comparisons (Dorsum_vs) dS_Venter: chromatic contrast (ΔS = hue) between the Viewpoint (dorsum) and the venter dL_Venter: achromatic contrast (ΔL = luminance) between the Viewpoint (dorsum) and the venter dS_FSpot: chromatic contrast (ΔS = hue) between the Viewpoint (dorsum) and the front spots dL_FSpot: achromatic contrast (ΔL = luminance) between the Viewpoint (dorsum) and the front spots dS_RSpot: chromatic contrast (ΔS = hue) between the Viewpoint (dorsum) and the rear spots dL_RSpot: achromatic contrast (ΔL = luminance) between the Viewpoint (dorsum) and the rear spots dS_AvSpot: chromatic contrast (ΔS = hue) between the Viewpoint (dorsum) and the mean of the front and rear spots dL_AvSpot: achromatic contrast (ΔL = luminance) between the Viewpoint (dorsum) and the mean of the front and rear spots \## ==== IMAGE DATA - EXTERNAL CONTRAST ==== ## Data files: 02_McEwen-etal_ExtCont_BluetitLMS.txt external chromatic & achromatic contrast from the bird visual model S2_McEwen-etal_ExtCont_CoachwhipLS.txt Supp. Mat. external chromatic & achromatic contrast from the snake visual model S2_McEwen-etal_ExtCont_PoisonFrogLMS.txt Supp. Mat. external chromatic & achromatic contrast from the poison frog visual model S2_McEwen-etal_ExtCont_HumanLMS.txt Supp. Mat. external chromatic & achromatic contrast from the human visual model RMarkdown file: McEwen_etal_2023-ExternalContrast.Rmd | McEwen_etal_2023-ExternalContrast.pdf Format: tab-delimited text Column identification: Visual_Model: visual model used in analysis (Bluetit_LMS (bird), Coachwhip_LS (snake), PoisonFrog_LMS (frog), or HumanLMS (human)) Species: frog species (Ad_hylaedactyla = Adenomera hylaedactyla, Am_bilinguis = Ameerega bilinguis, Al_zaparo = Allobates zaparo) Frog_ID: unique code for each frog (n = 10 / species) FrogPhoto: unique code for the original frog image from which data were extracted Leaf_ID: unique code for each leaf litter background sample (n = 60) LeafPhoto: unique code for the original background image from which data were extracted FrogRegion: body region that was the basis for the pairwise comparisons to the leaf litter (Dorsum, Fspot (Front spot), Rspot (Rear spot), or Venter) dS: chromatic contrast (ΔS = hue) between the FrogRegion and the leaf litter background dL: achromatic contrast (ΔL = luminance) between the FrogRegion and the leaf litter background \## ==== ALTERNATE VISUAL MODELING CONTRASTS ==== ## A series of alternate visual contrasts were computed for each region of each frog, using a smaller (25 x 25mm) background ROI as opposed to the larger leaf litter scene Data files: Bluetit_Alternate_Background_Contrasts.csv alternate chromatic & achromatic contrast from the bird visual model Coachwhip_Alternate_Background_Contrasts.csv alternate Supp. Mat. external chromatic & achromatic contrast from the snake visual model Pumilio_Alternate_Background_Contrasts.csv alternate Supp. Mat. external chromatic & achromatic contrast from the poison frog visual model Human_Alternate_Background_Contrasts.csv alternate Supp. Mat. external chromatic & achromatic contrast from the human visual model Format: comma-separated values RMarkdown file: ReAnalysis_Markdown.rmd | ReAnalysis_Markdown.pdf Column identification: FrogPhoto: Unique code for the original frog image from which data were extracted LeafPhoto: Unique code for the original leaf image from which data were extracted FrogRegion: body region that was the basis for the pairwise comparisons to the leaf litter (Dorsum, Fspot(front spot), Bspot (rearspot), or Venter) LeafRegion: leaf region used for the pairwise comparisons ColJND: Unit of chromatic contrast between the pairwise FrogRegion-LeafRegion comparison LumJND: Unit of achromatic contrast between the pairwise FrogRegion-LeafRegion comparison Species: Species of the frog used for pairwise comparison \## ==== DETECTION DATA - AERIAL DETECTION ==== ## Data file: 03_McEwen-etal_Detection-01.txt detection data from detection experiment 01 - aerial observers RMarkdown file: Det1_MD.Rmd | Det1_MD.pdf Format: tab-delimited text Column identification: file: unique human participant identification number bg_n: unique code for each background image fg_n: unique code for each frog trial_idx: trial sequence order for each participant rt_ms: reaction time in milliseconds (time taken to click on the frog) is_hit: TRUE = target found, FALSE = target missed spcs: frog species forming base of treatment AHY = Adenomera hylaedactyla, ABI = Ameerega bilinguis, AZA = Allobates zaparo tmnt: frog spot treatment ABS = Ameerega bilinguis spots, AZS = Allobates zaparo spots, NOS = no spots cond: experimental treatment - combination of spcs & tmnt \## ==== DETECTION DATA - TERRESTRIAL DETECTION ==== ## Data file: 04_Det2Data.csv detection data from detection experiment 02 - terrestrial observers RMarkdown file: Det2_MD.Rmd | Det2_MD.pdf Format: comma-separated values Column identification: id: unique human participant identification number bg_src: unique code for each background image fg_n: unique code for each frog trial_count: trial sequence order for each participant rt_ms: reaction time in milliseconds (time taken to click on the frog) is_hit: TRUE = target found, FALSE = target missed spcs: frog species ABI = Ameerega bilinguis, AZA = Allbates zaparo tmnt: frog orientation treatment B = Posterior (back), F = Anterior (front), H = Crouched (huddle), L = Left Lateral, R = Right Lateral cond: experimental treatment - combination of spcs & tmnt \## ==== SPECTROPHOTOMETRY DATA - SUPPLEMENTARY MATERIAL ==== ## Data files: S3_McEwen-etal_SpectroData.zip spectrophotometry reflectance data Subfolders: Dorsal reflectance data from the dorsum (60 files) Ventral reflectance data from the venter (60 files) FSpot reflectance data from the front spots (80 files) RSpot reflectance data from the rear spots (80 files) RMarkdown file: McEwen_etal_2023-SpectroAnalysis.Rmd | McEwen_etal_2023-SpectroAnalysis.pdf Format: compressed (.zip) folders containing multiple tab-delimited text (.txt) files export format generated automatically by Ocean Optics Flame S-XR1-ES spectrophotometer (Ocean Optics Inc. USA) (appropriate for use with R package pavo 2 (Maia et al. 2019. Methods Ecol. Evol. 10:1097-1107, doi = {10.1111/2041-210X.13174})) File identification: Prefix (3 characters): frog species (ABI = Ameerega bilinguis, AZA = Allobates zaparo) Prefix (2 numbers): unique code for each frog Middle 1 (multiple characters): body region: Dorsal = dorsum, VBlue = venter FLY = front left yellow spot, FRY = front right yellow spot BLY = back (rear) left yellow spot, BRY = back (rear) right yellow spot Middle 2 (multiple characters): 'Reflection' measurement type Suffix (3 numbers): measurement number (1-3 for Dorsal & VBlue, 1-2 for FLY, FRY, BLY, & BRY) (e.g., "ABI-01_FRY_Reflection_002.txt" = Ameerega bilinguis, frog number 1, front right yellow spot, reflectance measurement number 2) \## ==== Thank you for your interest in our work ==== ## \## ====================== END ====================== ## ## Code/software Analyses were performed in R, using the packages lme4, multcomp, and performance. All analyses present have Rmarkdown documents detailing their execution, which also points to packages being used for each set of models.