Validating two-dimensional leadership models on three-dimensionally structured fish schools

Abstract

Identifying leader–follower interactions is crucial for understanding how a group decides where or when to move, and how this information is transferred between members. Although many animal groups have a three-dimensional structure, previous studies investigating leader–follower interactions have often ignored vertical information. This raises the question of whether commonly used two-dimensional leader–follower analyses can be used justifiably on groups that interact in three dimensions. To address this, we quantified the individual movements of banded tetra fish (Astyanax mexicanus) within shoals by computing the three-dimensional trajectories of all individuals using a stereo-camera technique. We used these data firstly to identify and compare leader–follower interactions in two and three dimensions, and secondly to analyse leadership with respect to an individual's spatial position in three dimensions. We show that for 95% of all pairwise interactions leadership identified through two-dimensional analysis matches that identified through three-dimensional analysis, and we reveal that fish attend to the same shoalmates for vertical information as they do for horizontal information. Our results therefore highlight that three-dimensional analyses are not always required to identify leader–follower relationships in species that move freely in three dimensions. We discuss our results in terms of the importance of taking species' sensory capacities into account when studying interaction networks within groups.

Comparison between two- and three-dimensional scoring of zebrafish response to psychoactive drugs: identifying when three-dimensional analysis is needed

“…Conversely, experimental subjects treated with low and medium concentrations of citalopram exhibit reduced anxiety-related behaviors during the early stages of the task, which gradually rise to attain control values toward the end of the session. Similar to Watts et al (2017), we found that although 3D measures offer higher precision, the benefit of using 3D compared to a view from the top is limited regarding general behavioral pattern. The use of a front view remains necessary to capture specific behaviors linked to the position of the fish in the water column.…”

Peer Review #1 of "Comparison between two- and three-dimensional scoring of zebrafish response to psychoactive drugs: identifying when three-dimensional analysis is needed (v0.1)"

“…Manuscript to be reviewed behaviors during the early stages of the task, which gradually rise to attain control values towards the end of the session. Similar to (Watts et al 2017), we found that although 3D measures offer higher precision, the benefit of using 3D compared to a view from the top is limited regarding general behavioral pattern. The use of a front view remains necessary to capture specific behaviors linked to the position of the fish in the water column.…”

Quantifying the structure and dynamics of fish shoals under predation threat in three dimensions

“…Further, most models investigating so-called 'marginal predation' have only considered this from a two-dimensional approach (Hamilton 1971, Hirsch & Morrell 2011, Viscido et al 2001. For some systems, where prey form two-dimensional group structures, this approach is clearly warranted (De Vos & O'Riain 2010, Romey et al 2007, Watts et al 2017, but in systems where animals use both the vertical and horizontal planes to move, it is necessary to investigate whether the predictions, and assumptions of the models, hold true. Indeed, in Hamilton's original model, it was proposed that predators could attack from anywhere within the group, but this assumption that was later critiqued, with it being suggested that predators may only attack from the outside of groups (Vine 1971, Viscido et al 2001.…”