Grouping promotes risk-taking in unfamiliar settings

Abstract

Acting collectively in a group provides risk-reducing benefits. Yet individuals differ in how they take risks, with some being more willing than others to approach dangerous or unfamiliar settings. Therefore, individuals may need to adjust their behaviour when in groups, either as a result of perceiving greater safety or to coordinate collective responses, the latter of which may rely on within-group dynamics biased by group composition. In zebrafish we explored how these aspects of grouping affect risk-taking behaviour by comparing solitary to group conditions and testing the ability of group-member solitary responses to predict collective responses. We focused on approach-latency towards a novel object and an unusual food to test this, for shoals of five fish. There was no indication that collective latencies are predicted by how each fish responded when alone in terms of the extremes, the variance or the mean of group-member latency towards the unusual food and the novel-object. However, fish were overall faster and less variable in their approach when shoaling. This indicates lower risk aversion by individuals in groups, presumably as a result of group safety. An interesting consequence of the overall low risk-aversion in shoals is that more risk-aversive fish adjust their behaviour more than less risk averse fish.

The effect of group size on the speed of decision making depends on compromise and predation risk across populations in the guppy Poecilia reticulata

“…Firstly, individuals may make faster decisions when they are in groups due to a reduced perception of risk and/or greater perception of competition (Magurran & Pitcher, 1983;Grand & Dill, 1999), an effect which does not rely on information transfer between individuals. Such an effect is consistent with individuals in groups being bolder (i.e., less risk averse) and more active than solitary individuals (McDonald et al, 2016;Kareklas et al, 2018). Larger groups are also statistically more likely to contain individuals that make decisions more rapidly, for example because these individuals are less risk averse (i.e., are bolder (Ioannou & Dall, 2016)), hungrier (Balaban-Feld et al, 2019), or better informed (Ioannou et al, 2015).…”

“…Our experiment shows that the speed of decision making is affected by group size in fish from low predation habitats more than in fish from high predation habitats, at least in small groups from 2 to 8 individuals. The time taken to reach the decision zone followed the expected direction that larger groups were quicker to leave the start area, and hence were bolder and more exploratory than smaller groups (McDonald et al, 2016;Kareklas et al, 2018).…”

Zebrafish models for personalized psychiatry: Insights from individual, strain and sex differences, and modeling gene x environment interactions

“…Environmental factors have also been studied in zebrafish by modifying environmental conditions (e.g., by stressing the fish before testing or treating them developmentally with alcohol or nicotine). Several recent studies have addressed the impact of environmental enrichment or impoverish on zebrafish, involving complex cognitive (Collymore, Tolwani, & Rasmussen, ; DePasquale, Neuberger, Hirrlinger, & Braithwaite, ; Manuel et al, ; Spence, Magurran, & Smith, ) and/or social (Kareklas, Elwood, & Holland, ; Seguret, Collignon, & Halloy, ; Wafer et al, ) contexts. For instance, environmental enrichment exerts beneficial effects on brain and behavior in both wild‐type and genetically modified zebrafish (Collymore et al, ; Manuel et al, ; Wafer et al, ).…”

Enrichment for Laboratory Zebrafish—A Review of the Evidence and the Challenges

“…For example, the behaviour of zebrafish housed in groups has been shown to return to normal levels after handling more quickly than in paired or isolated fish [ 54 ], suggesting that the presence of a group promoted faster recovery from stress. In another study, group-housed fish were bolder than isolated fish in a novel object test, which may suggest that the presence of other individuals led to greater feelings of safety, which in turn could indicate a better welfare state [ 62 ]. However, some studies have shown that isolated fish mount a smaller response to a stressor than group-housed fish [ 60 , 63 ], while another found that isolated fish had smaller cortisol responses than group-housed fish to being chased with a net, but bigger responses to predation stress [ 59 ].…”