DOI: 10.5061/dryad.c866t1gfn
title: Bobbing behavior duration in aggregtions of Neotropical Opiliones

description: Animals perform antipredator behaviors when grouped, like bee shimmering.
 Individual phenotypic variations can affect the quality and success of
 defensive behavior. We tested three observational and experimental
 hypotheses regarding the bobbing behavior in one species of the arachnid
 group of Opiliones. We first tested if bobbing times varied with group
 size by recording the bobbing in field and lab groups. We found that the
 mean bobbing time increased with group size. Second, we tested if bobbing
 time differed between the types of stimuli eliciting it. We found that
 bobbing time lasted longer after a tactile stimulus (gentle stick
 touching) than a chemical stimulus (gentle blow). Third, we tested if
 bobbing time differs based on variation in the leg condition of these
 opiliones. We found no difference in the bobbing time between autotomized
 and intact individuals. Our findings on Neotropical Opiliones provide
 insights into the drivers of decision-making processes of movement
 defensive behavior by animals of variable body condition and how the
 between-individual phenotypic variation affects their engagement in
 defensive behavior. This work expands our knowledge of the sources of
 selection on collective behavior.
description: We video-recorded aggregations of Opiliones of the genus
 <em>Prionostemma</em> in the tropical rainforest of La Selva
 Research Station, Sarapiquí, Costa Rica. In the field, we recorded and
 subsequently quantified the bobbing time of individuals in the groups. We
 used a GoPro Hero 8 camera, with 120 fps and a narrow field of view (FOV)
 setting (to avoid fisheye lens’ distortion). At the beginning of each
 video, we presented a tactile stimulus (stick) or a chemical stimulus
 (gently blowing on them). Each group was recorded twice: once with tactile
 stimulus and once with chemical stimulus. We randomized the order of
 presenting the stimuli. We stopped each recording when all opiliones in
 the FOV stopped bobbing. We analyzed all videos in the QuickTime software
 by visually following ten randomly chosen opiliones for each stimulus type
 (chemical and tactile). We noted the frame that marked the start of each
 individual's bobbing and the last frame in which we could observe the
 animal bobbing. With these measures, we calculated each individual's
 bobbing duration in seconds. Then, to represent the group bobbing
 duration, we averaged the time of all the bobbing individuals per group
 (33 ± 18 opiliones/group). We then performed a lab
 experiment to test if the bobbing time differed as a function of group
 size, the stimuli presented, and if Opiliones missing legs bobbed for
 longer than intact individuals. We collected individuals in the forest at
 night. Then, we placed them in plastic shoe boxes (33 × 20 × 12 cm). We
 placed a wooden surface or bark fragment (20 × 10 cm) in the bottom of
 each box to serve as a substrate. The following morning (8:00 - 10:00 h),
 we repeated the field procedures described above (presented two stimuli).
 Then, we quantified the bobbing duration of ten randomly selected
 individuals. Lastly, we compared the bobbing duration of opiliones given
 their leg condition. When setting up the lab groups at night, we counted
 the number of legs of each individual and sorted them into two classes:
 autotomized (5 - 7 legs) or intact (8 legs).
description: # Bobbing behavior duration in aggregtions of Neotropical Opiliones
 [https://doi.org/10.5061/dryad.c866t1gfn](https://doi.org/10.5061/dryad.c866t1gfn) ## Description of the data and file structure "FILE ""field_bobbing_data.csv""" OVERALL DESCRIPTION: "This file contains the data of the bobbing duration video recordings of Prionostemma sp.2 opiliones field groups. Each group was presented with two stimuli: chemical (blow) and tactile (touch). We recorded until the bobbing stopped. Afterwards we analyzed the bobbing duration of ten focal individuals per group-stimulus pseudoreplicate." COLUMN EXPLANATION group_ID: "A unique identification code for each individual recording, made of the date it was recorded and the stimuli used (blow = chemical; touch = tactile)" simplified_group_ID: "same as above, but only with the date the group was recorded" date: "date of the recording" location: "code for the field trail site in which animals were collected, in La Selva, Sarapiquí, Costa Rica" stimulus: "chemical (blow) or tactile (touch)" stimulus_order: "if the above stimulus was performed first (1) or second (2)" group_size: "number of opiliones in each group" individual_ID: "the identification number of each focal individual" fotogram_start: "the first fotogram of the video recording in which the focal individual is bobbing" fotogram_end: "the last fotogram of the video recording in which the focal individual is bobbing" bobbing_duration: "(fotogram_end - fotogram_start) / 120. We diveded by 120 because we recorded videos at 120 frames per second" fled_FOV: "if the focal individual fled the field of view (yes / no)" notes: "additional comments" NOTE: "NA" (non-applicable) is included in various columns to reflect instances in which we were unable to record the respective information for that variable. "FILE ""lab_bobbing_data.csv""" OVERALL DESCRIPTION: "This file contains the data of the bobbing duration video recordings of Prionostemma sp.2 opiliones lab groups. Each group was presented with two stimuli: chemical (blow) and tactile (touch). We recorded until the bobbing stopped. Afterwards we analyzed the bobbing duration all individuals of each group." COLUMN EXPLANATION group_ID: "A unique identification code for each individual recording, made of the date it was recorded and the stimuli used (blow = chemical; touch = tactile)" simplified_group_ID: "same as above, but only with the date the group was recorded" date: "date of the recording" location: "code for the field trail site in which animals were collected, in La Selva, Sarapiquí, Costa Rica" stimulus: "chemical (blow) or tactile (touch)" stimulus_order: "if the above stimulus was performed first (1) or second (2)" group_size: "number of opiliones in each group" individual_ID: "the identification number of each focal individual" number_legs: "the number of legs of the analyzed opilion2 center_periphery: "the position within the aggregation of each opilion (center / periphery)" fotogram_start: "the first fotogram of the video recording in which the focal individual is bobbing" fotogram_end: "the last fotogram of the video recording in which the focal individual is bobbing" bobbing_duration: "(fotogram_end - fotogram_start) / 120. We diveded by 120 because we recorded videos at 120 frames per second" fled_FOV: "if the focal individual fled the field of view (yes / no)" brace: "if the focal analyzed opilion did not moved during the stimulus (yes / no)" prio_sp2: "if the observation belonged to an Opilion of Prionostemma sp.2 (yes) or to any other species (no)" notes: "additional comments" NOTE: "NA" (non-applicable) is included in various columns to reflect instances in which we were unable to record the respective information for that variable. "FILE ""lab_field_number_legs.csv""" OVERALL DESCRIPTION: "This file contains the data of the bobbing duration video recordings of Prionostemma sp.2 opiliones for every individual whose number of legs was counted (n=964), for lab (n=882) and field (n=82) conditions. Each individual was sorted into the categories intact (8 legs) or autotomized (&lt;8 legs). This data was used to analyze the bobbing duration given the location (lab vs field) and the leg condition (intact vs autotomized)." location: "location were the opilion was filmed: either in the lab or in the field" number_legs: "the number of legs of each opilion" leg_condition: "either intact (opilion with 8 legs) or autotmized (&lt;8 legs)" bobbing_duration_s: "duration in seconds of the bobbing behaviour, is the same variable as in the files field_bobbing_data.csv and lab_bobbing_data.csv" prio_sp2: "if the opilion belonged to Prionostemma sp.2 (yes) or to another species (no), all the opiliones belonging to another species were excluded from the analysis". "FILE ""opiliones_bobbing_script.R""" OVERALL DESCRIPTION: "This file contains the R script to run all the analyses performed. The script is fully annotated, for easier reproducibility." "FILE ""video_S1.mp4""" "Sample video of the bobbing behavior of Prionostemma sp.2 opiliones at La Selva Research Station, Sarapiquí, Heredia, Costa Rica. The video depicts four trials; one of each of the two stimuli (chemical and tactile) presented in field conditions, and one of chemical and one of tactile stimulus in laboratory conditions."