The Selfish Herd Revisited: Do Simple Movement Rules Reduce Relative Predation Risk?

Morton, Thomas L.; Haefner, James W.; Nugala, Vasudevarao; DeCino, Robert; Mendes, Lloyd

doi:10.1006/jtbi.1994.1051

Cited by 57 publications

(63 citation statements)

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“…a potential strike location) nearest neighbour (NN) [11] individuals moves towards closest neighbour in space 2 nearest neighbours (2NN) [12] individuals moves towards the average location of 2 nearest neighbours group centre (GC) [13,21] individuals move towards the area in the centre of all individuals within the group local crowded horizon (LCH) [14] individuals moves towards the area with the densest concentration of conspecifics; closer individuals have a stronger influence on direction, whereas distant individuals exert a weaker force; the perception function used is f(x) ¼ 1/ (1 þ kx), where x is the distance from the focal individual, and k ¼ 0.375 [14] rspb.royalsocietypublishing.org Proc. R. Soc.…”

Section: Results (A) Movement Rulementioning

confidence: 99%

“…Simple rules can, however, result in more rapid initial reduction in DOD area [17], which might be particularly important when animals have little time to respond following detection of a predatory threat [16]. Simple rules have been criticized for their inability to produce the dense groups seen in nature [12,14], whereas more complex rules may be cognitively too complex for animals to follow [20,21].…”

Section: Introductionmentioning

confidence: 99%

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‘Selfish herds’ of guppies follow complex movement rules, but not when information is limited

Kimbell¹,

Morrell²

2015

Proc. R. Soc. B.

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Under the threat of predation, animals can decrease their level of risk by moving towards other individuals to form compact groups. A significant body of theoretical work has proposed multiple movement rules, varying in complexity, which might underlie this process of aggregation. However, if and how animals use these rules to form compact groups is still not well understood, and how environmental factors affect the use of these rules even less so. Here, we evaluate the success of different movement rules, by comparing their predictions with the movement seen when shoals of guppies (Poecilia reticulata) form under the threat of predation. We repeated the experiment in a turbid environment to assess how the use of the movement rules changed when visual information is reduced. During a simulated predator attack, guppies in clear water used complex rules that took multiple neighbours into account, forming compact groups. In turbid water, the difference between all rule predictions and fish movement paths increased, particularly for complex rules, and the resulting shoals were more fragmented than in clear water. We conclude that guppies are able to use complex rules to form dense aggregations, but that environmental factors can limit their ability to do so.

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Section: Results (A) Movement Rulementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

‘Selfish herds’ of guppies follow complex movement rules, but not when information is limited

Kimbell¹,

Morrell²

2015

Proc. R. Soc. B.

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“…The elegance of the selfish herd has endeared it as a framework within which to interpret the behaviour of prey in response to predators, and more than 600 studies on a diverse array of taxa (Morton et al 1994) have provided support for it. While these studies have successfully quantified increased cohesiveness of groups when exposed to predators (Viscido 2003), shown that individuals prefer central to peripheral positions within a group (e.g.…”

Section: Introductionmentioning

confidence: 99%

Sharks shape the geometry of a selfish seal herd: experimental evidence from seal decoys

Vos

O’Riain

2009

Biol. Lett.

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Many animals respond to predation risk by forming groups. Evolutionary explanations for group formation in previously ungrouped, but loosely associated prey have typically evoked the selfish herd hypothesis. However, despite over 600 studies across a diverse array of taxa, the critical assumptions of this hypothesis have remained collectively untested, owing to several confounding problems in real predator-prey systems. To solve this, we manipulated the domains of danger of Cape fur seal (Arctocephalus pusillus pusillus) decoys to provide evidence that a selfish reduction in a seals' domain of danger results in a proportional reduction in its predation risk from ambush shark attacks. This behaviour confers a survival advantage to individual seals within a group and explains the evolution of selfish herds in a prey species. These findings empirically elevate Hamilton's selfish herd hypothesis to more than a 'theoretical curiosity'.

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“…Presumably, a fast NN animal could easily invade a population using slow NN, leading to the evolution of faster escape responses. The speed of decision-making may also be important: complex movement rules have been criticized [12,13] on the basis that they may be cognitively too demanding for animals to follow. Incorporating a 'thinking time' into each movement step could account for the complexity of the calculations.…”

Section: Discussionmentioning

confidence: 99%

“…-Multiple nearest neighbour (nNN). Individuals move towards the average location of several (n) nearest neighbours [12]. For simplicity, we consider only n ¼ 3 here.…”

Section: Methodsmentioning

confidence: 99%

The temporal selfish herd: predation risk while aggregations form

2010

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The hypothesis of the selfish herd has been highly influential to our understanding of animal aggregation. Various movement strategies have been proposed by which individuals might aggregate to form a selfish herd as a defence against predation, but although the spatial benefits of these strategies have been extensively studied, little attention has been paid to the importance of predator attacks that occur while the aggregation is forming. We investigate the success of mutant aggregation strategies invading populations of individuals using alternative strategies and find that the invasion dynamics depend critically on the time scale of movement. If predation occurs early in the movement sequence, simpler strategies are likely to prevail. If predators attack later, more complex strategies invade. If there is variation in the timing of predator attacks (through variation within or between individual predators), we hypothesize that groups will consist of a mixture of strategies, dependent upon the distribution of predator attack times. Thus, behavioural diversity can evolve and be maintained in populations of animals experiencing a diverse range of predators differing solely in their attack behaviour. This has implications for our understanding of predator -prey dynamics, as the timing of predator attacks will exert selection pressure on prey behavioural responses, to which predators must respond.

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The Selfish Herd Revisited: Do Simple Movement Rules Reduce Relative Predation Risk?

Cited by 57 publications

References 0 publications

‘Selfish herds’ of guppies follow complex movement rules, but not when information is limited

‘Selfish herds’ of guppies follow complex movement rules, but not when information is limited

Sharks shape the geometry of a selfish seal herd: experimental evidence from seal decoys

The temporal selfish herd: predation risk while aggregations form

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