Fear contagion in zebrafish: a behaviour affected by familiarity

Abstract

Emotional contagion has recently been described in fish but whether it is affected by familiarity is not known. We tested whether the sight of a distressed conspecific elicited fear in zebrafish, and whether this was modulated by familiarity. Groups of six zebrafish were housed together in the same tanks for 7 days to create familiar conditions. The behaviour of individual fish was then recorded in paired tanks within sight of either a familiar or an unfamiliar individual, before and after distilled water or an alarm substance was added to the demonstrator, but not to the observer. As expected, addition of distilled water did not elicit any behavioural change in either the demonstrator or the observer. However, addition of an alarm cue triggered anti-predatory behaviours in the demonstrator, which caused the expression of equivalent anti-predatory behaviours in the observer, suggesting the existence of fear contagion. Furthermore, the extent of fear contagion and behavioural matching was affected by familiarity, and observers matched the behaviour of the demonstrators more closely when they watched a distressed familiar neighbour than when they watched an unfamiliar fish. Our results have implications for fish welfare because they show that fish can become stressed by simply watching others become stressed. They also have implications for experimental design because fish housed in separate tanks cannot be assumed to be statistically independent if they can eavesdrop on their neighbours.

Emotional contagion in nonhuman animals: A review

“…Two studies have examined emotional contagion of fear in zebrafish ( Danio rerio ) (Fernandes da Silva et al, 2019 ; Oliveira et al, 2017 ). Both works registered the behavioral changes triggered in zebrafish when visually exposed to antipredator behaviors of other conspecifics.…”

Does the presence of a conspecific increase or decrease fear? Neophobia and habituation in zebra finches

“…A more plausible alternative explanation for our results is provided by the "contagion of fear" hypothesis, which proposes that individuals take longer to approach a novel object in a social context because their fear is influenced by the fear demonstrated by their conspecific (Boissy et al, 1998;Fernandes Silva et al, 2019;Stöwe, Bugnyar, Loretto, et al, 2006). This has been demonstrated by Boissy et al (1998) when they tested the latency for an Aubrac heifer (Bos taurus) to feed in a novel environment with a companion who had either received shocks or not in the environment.…”

Early Mistreatment Contributes to Social Behavior Disorders in Zebrafish

“…However, when considering the effects of early stress on zebrafish using the mirror test, a protocol that accesses fish motivation to approach and display aggressive signals toward its image, we observed differences in fish behavior: a decreased number of attacks against the image and increased distance kept from the interaction zone. These results could be interpreted as reduced motivation for social interaction, a behavioral feature that is characteristic of the zebrafish, a species considered highly social (Silva et al, 2019). The social avoidance response could be discussed in terms of the memory of the stressful situation experienced earlier, but there is no evidence supporting the idea that zebrafish retains memory for such a long time (Blank et al, 2009;Hieu et al, 2020).…”