Tools for estimating and comparing behavioral variation
Résumé
The field of “animal personality” has provided important insights into how behavioral variation is structured and has shown that consistent individual differences in behavior are common in nature. While early developments have focused on finding evidence for personality differences - measured as repeatability or the intra-class correlation coefficient - the field is now increasingly focusing on when and how behavioral variation should be generated. This has led researcher to ask increasingly sophisticated questions. An emerging challenge is now to predict haw behavioral variation will vary among population, species, sexes or experimental treatments rather than describing how much behavioral variation is present. These new questions require an expanded quantitative toolbox shifting the focus on repeatability onto the comparison of variance components. In this presentation, I will show why inference based solely on repeatability as a metric can be limited (Dochtermann and Royauté 2019) and why additional metrics such as differences in variance or coefficients of variation are better alternatives for comparing variation among groups (Royauté et al. 2015; Nakagawa et al. 2015). In simulations based on a 125,000 randomly generated datasets, I show that the power to estimate these differences at the among-individual level is very limited at low sample sizes (< 100 individuals per group) regardless of the number of repeated observations. Finally, I will introduce a new R package, delta_Variation, that provides hands-on tools to estimate differences in behavioral variation among group using Hierarchical Linear Models.
Dochtermann, N. A., and R. Royauté. 2019. The mean matters: going beyond repeatability to interpret behavioural variation. Animal Behaviour 153:147–150.
Nakagawa, S., R. Poulin, K. Mengersen, K. Reinhold, L. Engqvist, M. Lagisz, and A. M. Senior. 2015. Meta-analysis of variation: ecological and evolutionary applications and beyond. Methods in Ecology and Evolution 6:143–152.
Royauté, R., C. M. Buddle, and C. Vincent. 2015. Under the influence: sublethal exposure to an insecticide affects personality expression in a jumping spider. Functional Ecology 29:962–970.
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