To bob or not to bob: Context-dependence of an antipredator response in neotropical harvestmen

Inducible defence strategies evolve in response to temporally and spatially variable predation risk. Selection should favour the expression of these strategies when risk crosses a threshold, but expression may also depend on how effective a strategy is across contexts. For neotropical harvestmen, aggregation behaviour is a group-level defence strategy, but can be supplemented by additional behaviour to enhance antipredator defence. A secondary behavioural strategy termed “bobbing”, in which individuals rapidly move their bodies up and down, has been proposed to confuse or deter predation as the group moves en masse. While this behaviour may be performed in isolation, we propose that its net pay-off may depend on the presence of conspecifics and group size. Therefore, due to the benefits of plasticity in a behaviour with such an apparent context-dependent pay-off, we hypothesize that the aggregation size of neotropical harvestmen affects the propensity of individuals to engage in the ant..., Lab-based experiments were conducted to determine whether the social context of harvestmen (i.e., isolation or aggregation) affects the propensity of individuals to perform antipredator bobbing following a predator simulation. As control experiments for potential confounding factors from the isolation versus aggregation experiment, subsequent trials were conducted to determine whether the behaviour was affected by sex and density within an enclosure. In addition to the lab-based experiments, field observations were carried out to assess the propensity of harvestmen to exhibit bobbing as affected by group size.
Analyses were performed in R v 4.3.2 (Team, 2020). Generalized linear and mixed effects models with the lme4 (Bates et al., 2015) and glmmTMB (Brooks et al., 2017) packages were used to analyse the bobbing behaviour during experimental trials. The propensity of individuals to exhibit bobbing in experiment 1 and experiment 2 was fitted using a generalized linear mixed effects model..., , # Data from: To bob or not to bob: Context-dependence of an antipredator response in neotropical harvestmen

[https://doi.org/10.5061/dryad.kh18932j5](https://doi.org/10.5061/dryad.kh18932j5)

## Description of the data and file structure

Lab-based experiments were conducted to determine whether the social context of harvestmen (i.e., isolation or aggregation) affects the propensity of individuals to perform antipredator bobbing following a predator simulation. As control experiments for potential confounding factors from the isolation versus aggregation experiment, subsequent trials were conducted to determine whether the behaviour was affected by sex and density within an enclosure. In addition to the lab-based experiments, field observations were carried out to assess the propensity of harvestmen to exhibit bobbing as affected by group size.

### Files and variables

#### File: ALL_Calhoun_et_al_Harvestmen_Bobbing_data_2024.xlsx

**Description:** Excel file containing three separate...,