Inferring collective behaviour from a fossilized fish shoal

Abstract

Collective motion by animal groups can emerge from simple rules that govern each individual's interactions with its neighbours. Studies of extant species have shown how such rules yield coordinated group behaviour, but little is known of their evolutionary origins or whether extinct group-living organisms used similar rules. Here, we report evidence consistent with coordinated collective motion in a fossilized group of the extinct fish Erismatopterus levatus , and we infer possible behavioural rules that underlie it. We found traces of two rules for social interaction similar to those used by extant fishes: repulsion from close individuals and attraction towards neighbours at a distance. Moreover, the fossilized fish showed group-level structures in the form of oblong shape and high polarization, both of which we successfully reproduced in simulations incorporating the inferred behavioural rules. Although it remains unclear how the fish shoal's structure was preserved in the fossil, these findings suggest that fishes have been forming shoals by combining sets of simple behavioural rules since at least the Eocene. Our study highlights the possibility of exploring the social communication of extinct animals, which has been thought to leave no fossil record.

Predator-informed looming stimulus experiments reveal how large filter feeding whales capture highly maneuverable forage fish

“…There is fossil evidence from freshwater deposits that schooling has existed as a fish behavior since, at least, 30-40 Ma earlier than when extreme gigantism arose in rorqual whales (18,19). The transition to the age of giants was coincident with changes in oceanographic processes that encouraged upwelling and the formation of dense swarms of zooplankton (19).…”

A statistical method for identifying different rules of interaction between individuals in moving animal groups

“…Tunstrøm et al [18] performed a systematic analysis of the emergent states of shoaling fish via order parameters at fine temporal scale; the decoupling of social and boundary interactions, and bursting and coasting movements, were addressed in [19,20]; and Heras et al [21] used artificial neural networks to infer interaction rules, including work to understand which independent variables are most important in the determination of such rules. The ambition of recent work has even extended to inference of repulsion and attraction behaviour in ancient, and extinct, species through the structure of fossilized fish shoals [22]. A number of studies over the last decade have also sought to construct collective motion models informed by, or derived directly as part of, the process of estimating rules of interaction [19,20,[23][24][25].…”

Crypsis in the pelagic realm: evidence from exceptionally preserved fossil fish larvae from the Eocene Stolleklint Clay of Denmark

“…2009; Mizumoto et al . 2019; Carnevale & Bannikov 2020), detailed records of specific larval characters, such as pigmentation patterns, are rare. In fact, we are only aware of a single publication describing fossil larval pigmentations (Marramà & Carnevale 2015, fig.…”