Confusion of predators does not rely on specialist coordinated behavior

Ruxton, Graeme D.; Jackson, Andrew L.; Tosh, Colin R.

doi:10.1093/beheco/arm009

Cited by 68 publications

(53 citation statements)

References 28 publications

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“…Using the visual angle subtended by the group on the retina of the predator as a mechanism of visual detection, we provide the first theoretical and experimental evidence for this prediction. This mechanism of avoiding risk via group living does not require information transfer or coordination between individuals, which is needed for group vigilance and group defence mechanisms [1], nor even the movement of individuals to induce a confusion effect [32]. For these reasons, the reduced rate of finding prey through aggregation may be very general and widespread across taxa.…”

Section: Discussionmentioning

confidence: 99%

Unified effects of aggregation reveal larger prey groups take longer to find

et al. 2011

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Previous work has suggested that larger groups of prey are more conspicuous to predators. However, this ignores that prey populations are finite. As groups get larger they become fewer, hence the encounter rate between predator and prey decreases with prey aggregation. Here, we present a two-dimensional model based on visual angle to unify these encounter and conspicuousness effects of aggregation. With experimental support using three-spined sticklebacks (Gasterosteus aculeatus L.), searching for chironomid larvae, we demonstrate that the increase in visual angle with increasing group size is outweighed by its corresponding decrease as the groups become fewer and thus further away from the searching predator. The net effect is that prey are found with more difficulty when they aggregate, giving an additional anti-predatory benefit to group living rather than a cost.

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Section: Discussionmentioning

confidence: 99%

Unified effects of aggregation reveal larger prey groups take longer to find

et al. 2011

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“…Studies have focused on the costs and benefits of group size and position within the group (2-4), but how predation risk varies with the response of individuals to their neighbors is not well understood because of difficulties in its measurement (5,6) and manipulation (7). One such behavioral response that is common in nature is the tendency for individuals to align their direction of travel with that of near neighbors, forming coordinated "polarized" groups.…”

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confidence: 99%

“…One such behavioral response that is common in nature is the tendency for individuals to align their direction of travel with that of near neighbors, forming coordinated "polarized" groups. It is often assumed that coordination between prey makes them harder to catch by enhancing information transfer between individuals (5, 6) or by increasing the confusion effect, although little experimental work supports this idea (7,8).…”

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confidence: 99%

“…Consistent with a confusion effect (26), this decision time increased with the prey target's group size (GLM: LRT 1,67 = 11.32, P = 0.00077). Although this accounts for the targeting of prey in smaller groups, there was no evidence that a prey's tortuosity, either alone or as part of an interaction with group size, had any additional effect [LRT 1,67 = 0.029, P = 0.86; and LRT 1,66 = 0.22, P = 0.64, respectively; see also (7,8)]. …”

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confidence: 99%

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Predatory Fish Select for Coordinated Collective Motion in Virtual Prey

Ioannou

Guttal

Couzin

2012

Science

306

266

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Movement in animal groups is highly varied and ranges from seemingly disordered motion in swarms to coordinated aligned motion in flocks and schools. These social interactions are often thought to reduce risk from predators, despite a lack of direct evidence. We investigated risk-related selection for collective motion by allowing real predators (bluegill sunfish) to hunt mobile virtual prey. By fusing simulated and real animal behavior, we isolated predator effects while controlling for confounding factors. Prey with a tendency to be attracted toward, and to align direction of travel with, near neighbors tended to form mobile coordinated groups and were rarely attacked. These results demonstrate that collective motion could evolve as a response to predation, without prey being able to detect and respond to predators.

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“…Although cleaners often feed on ectoparasites instead of the more preferred mucus, if given the choice under natural conditions, they would usually approach the more attractive client (Bshary 2001). In contrast, predators such as sea lions, may Wnd it particularly easy to approach the smaller reward in such a test situation as the hunting success of many predators relies on their ability to isolate a single prey from its group in order to avoid confusion eVects (Landeau and Terborgh 1986;Ruxton et al 2008). The hunting technique of chasing after isolated prey provides a straightforward ecological explanation for the sea lions' ability to solve the reverse reward task (Genty and Roeder 2006).…”

Section: Methodological Considerationsmentioning

confidence: 99%

Do cleaner fish learn to feed against their preference in a reverse reward contingency task?

2009

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The ability to control impulsive behaviour has been studied in animals with a standard test in which subjects need to choose the smaller of two food items in order to receive the larger one (reverse reward contingency). As a variety of mammals that have been tested so far (mostly primates) have great diYculties to solve the task, it has been proposed that it is generally cognitively demanding. However, according to an ecological approach to cognition, a species' ability to solve the task should not depend on its general cognitive abilities but on whether its ecology causes selective pressure on the ability to restrain foraging behaviour. We tested this hypothesis using the cleaner wrasse (Labroides dimidiatus), a Wsh species that feeds against its preference in nature when engaging in cleaning interactions with so called 'client Wsh'. None of the eight tested individuals learned to choose a non-preferred item after 200 trials. In a subsequent test, one subject learned to respond correctly in a large or none contingency task (only the choice of the small food was rewarded). After a short re-experience treatment, this individual learned to solve the reverse reward task after 30 trials. In conclusion, we did not Wnd support for the general idea that interactions with clients prepared cleaners to quickly solve a reverse reward test. However, the results suggest that the potential to solve a reverse reward contingency may not be restricted to mammals but could be present also in a Wsh species in which the problem of choosing a non-preferred food over a preferred one is an ever present challenge in nature.

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Confusion of predators does not rely on specialist coordinated behavior

Cited by 68 publications

References 28 publications

Unified effects of aggregation reveal larger prey groups take longer to find

Unified effects of aggregation reveal larger prey groups take longer to find

Predatory Fish Select for Coordinated Collective Motion in Virtual Prey

Do cleaner fish learn to feed against their preference in a reverse reward contingency task?

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