Do 3-D predators attack the margins of 2-D selfish herds?

Romey, William L.; Walston, A.R.; Watt, Penelope J.

doi:10.1093/beheco/arm105

Cited by 36 publications

(33 citation statements)

References 28 publications

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“…spiders, mussels, shoaling fish, beetles, tadpoles) are at greater risk (Okamura 1986;Rayor and Uetz 1990;Bumann et al 1997;Hirsh and Morrell 2011;Morrell et al 2010). For example, Romey et al (2008) used bass and goldfish predation on either whirligig beetles or tadpoles to empirically demonstrate that, even with predators moving in threedimensional space and prey in two dimensions, predators were significantly more likely to attack the periphery. Therefore, if herding behavior reflects solely an attempt to reduce predation risk, all individuals may be expected to maximize the number of conspecifics between themselves and the potential attackers by seeking a position in the center of the group (Hamilton 1971;Vine 1971;Morrell et al 2010).…”

mentioning

confidence: 99%

Individual movement rates are sufficient to determine and maintain dynamic spatial positioning within Uca pugilator herds

Knotts

Griffen

2016

Behav Ecol Sociobiol

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mentioning

confidence: 99%

Individual movement rates are sufficient to determine and maintain dynamic spatial positioning within Uca pugilator herds

Knotts

Griffen

2016

Behav Ecol Sociobiol

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“…Since the starter was knowledgeable about the existence of a predator, this could explain why it took up a position in the centre of the group in our study, after detecting the stimulus. Central positions have been found to be safer, even in two-dimensional groups like whirligigs (Romey, Walston, & Watt, 2008). It is unclear why the starter turned less than other group members in our empirical study.…”

Section: Pgmentioning

confidence: 66%

Flash expansion and the repulsive herd

2015

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The Selfish Herd hypothesis, as proposed by Hamilton in 1971, is a powerful hypothesis to explain emergent grouping behaviour by individuals acting in their own selfinterest. However, immediately after prey detect a predator, the prey group may undergo a rapid disassembly, called a flash expansion, which might be considered a "repulsive herd". Although flash expansion occurs in bird flocks, fish schools, and insect swarms, few empirical or simulation studies have directly examined it or tested if there are differences among its members. Additionally, flash expansion is typically thought of as a nearsimultaneous movement of individuals away from the group centre, little data has been collected to verify this. We performed an empirical study to test whether the overall movement of individuals within a flash expansion is away from the 1) first individual to startle; 2) geometric centre; or 3) point of highest density. Replicate swarms of marked whirligig beetles (Gyrinidae: Dineutes) were videotaped during flash expansion and their trajectories determined. Overall, individuals were found to move away from the geometric centre, more strongly than for the density maximum or the first to respond (starter). The geometric centre hypothesis was also supported by the lack of polarization of the group and that the bearing angle was away from the geometric centre. It was found that the starter was more likely to be a female at the edge of a group and that she moved more quickly than others and favoured the centre of the group. This is one of the first detailed examinations of flash expansion and the individual differences within it. Future empirical and simulation studies of the movement rules and emergent properties of flash expansion are needed to better understand the collective motion of other animals.

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“…Pickard‐Cambridge (Araneae: Araneidae), individuals located at the periphery are more susceptible to predation than those located in the center. Some experiments suggest that even peripheral individuals of two dimensionally distributed colonies should be more susceptible to predation by three‐dimensional roaming predators (Romey et al ., ). Currently there is no information available about the possible existence of selfish herd type mechanisms in larvae, pupae, or adult ladybeetles.…”

Section: Introductionmentioning

confidence: 97%

Gregarious pupation act as a defensive mechanism against cannibalism and intraguild predation

et al. 2015

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Coccinellid pupae use an array of defensive strategies against their natural enemies. This study aims to assess the efficiency of gregarious pupation as a defensive mechanism against intraguild predators and cannibals in coccinellid. The study was designed specifically (i) to determine the natural occurrence of gregarious pupation in the field for different coccinellid species, and (ii) to evaluate the adaptive value of gregarious pupation as a defensive mechanism against 2 types of predators (i.e., cannibals and intraguild predators). In the field, gregarious pupation consisted of a group of 2-5 pupae. The proportion of gregarious pupation observed varied according to species, the highest rate being observed with Harmonia axyridis Pallas (Coccinellidae; 14.17%). Gregarious pupation had no impact on the probability that intraguild predators and cannibals locate pupae. Intraguild predation occurred more often in site with gregarious pupation, while cannibalism occurred as often in site with gregarious pupation as in site with isolated pupa. However, for a specific pupa, the mortality rate was higher for isolated pupae than for pupae located in a gregarious pupation site both in the presence of intraguild predators and in the presence of cannibals. The spatial location of pupae within the group had no impact on mortality rate. Since it reduces the risk of predation, it is proposed that gregarious pupation act as a defensive mechanism for H. axyridis pupae.

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Do 3-D predators attack the margins of 2-D selfish herds?

Cited by 36 publications

References 28 publications

Individual movement rates are sufficient to determine and maintain dynamic spatial positioning within Uca pugilator herds

Individual movement rates are sufficient to determine and maintain dynamic spatial positioning within Uca pugilator herds

Flash expansion and the repulsive herd

Gregarious pupation act as a defensive mechanism against cannibalism and intraguild predation

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