Drag Reduction by Formation Movement in Spiny Lobsters

Bill, Robert G.; Herrnkind, William F.

doi:10.1126/science.193.4258.1146

Cited by 85 publications

(70 citation statements)

References 5 publications

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“…A player's payoff is proportional to the fraction of other members of the group that choose the same option, with the constant of proportionality equal to 1 if the player chooses its own preferred option, and to 1 -k (where 0 < k < 1) otherwise. There is thus a common incentive for the group to agree on a joint decision, because an individual benefits from acting together with more companions [e.g., through enhanced foraging success (30,31), reduced predation risk (32,33), or improved locomotory efficiency (34,35)]. At the same time, there is conflict among group members over what this joint decision should be.…”

Section: Modelmentioning

confidence: 99%

Evolution of personality differences in leadership

Johnstone

Manica

2011

Proc. Natl. Acad. Sci. U.S.A.

137

121

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When members of a group differ in their preferred course of action, coordination poses a challenge. Leadership offers one way to resolve this difficulty, but the evolution of leaders and followers is itself poorly understood. Existing discussions have frequently attributed leadership to differences in information or need among individuals. Here, however, we show that in an n-player, repeated coordination game, selection leads to evolutionary branching and diversification in intrinsic leadership among the members of a population even in the absence of any variation in state. When individuals interact in pairs, repeated branching is possible; when individuals interact in larger groups, the typical outcome is a single branching event leading to a dimorphism featuring extreme intrinsic leaders and followers. These personality types emerge and are maintained by frequency-dependent selection, because leaders gain by imposing their preferences on followers, but fail to coordinate effectively when interacting with other leaders. The fraction of intrinsic leaders in the population increases with the degree of conflict among group members, with both types common only at intermediate levels of conflict; when conflict is weak, most individuals are intrinsic followers, and groups achieve high levels of coordination by randomly converging on one individual's preferred option, whereas when conflict is strong, most individuals are intrinsic leaders, and coordination breaks down because members of a group are rarely willing to follow another.boldness | collective decision

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Section: Modelmentioning

confidence: 99%

Evolution of personality differences in leadership

Johnstone

Manica

2011

Proc. Natl. Acad. Sci. U.S.A.

137

121

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“…Consequently, there should be a strong selection pressure-especially on young birds during their first migration-to minimize energy expenditure during migratory flights and increase the chance of survival. Traveling in close, structured groups has been proposed as an energy-saving strategy, with savings being accrued through positive aero-or hydrodynamic interactions between members of the group (7)(8)(9)(10). Flight in V-shaped or echelon formation by birds is perhaps the most prominent example of this.…”

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confidence: 99%

Matching times of leading and following suggest cooperation through direct reciprocity during V-formation flight in ibis

Voelkl

Portugal

Unsöld

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

109

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One conspicuous feature of several larger bird species is their annual migration in V-shaped or echelon formation. When birds are flying in these formations, energy savings can be achieved by using the aerodynamic up-wash produced by the preceding bird. As the leading bird in a formation cannot profit from this up-wash, a social dilemma arises around the question of who is going to fly in front? To investigate how this dilemma is solved, we studied the flight behavior of a flock of juvenile Northern bald ibis (Geronticus eremita) during a human-guided autumn migration. We could show that the amount of time a bird is leading a formation is strongly correlated with the time it can itself profit from flying in the wake of another bird. On the dyadic level, birds match the time they spend in the wake of each other by frequent pairwise switches of the leading position. Taken together, these results suggest that bald ibis cooperate by directly taking turns in leading a formation. On the proximate level, we propose that it is mainly the high number of iterations and the immediacy of reciprocation opportunities that favor direct reciprocation. Finally, we found evidence that the animals' propensity to reciprocate in leading has a substantial influence on the size and cohesion of the flight formations.formation flight | cooperation | social dilemma | reciprocity A considerable portion of the worldwide bird population performs biannual long-distance migrations (1, 2). These journeys impose large energetic costs on the animals, and as a consequence, mortality is considerably higher during migration than at any other time of the year (3). Reasons for this increased mortality during migration include suppressed immune response, starvation, and dehydration, among others (4, 5). In greater snow geese (Chen caerulescens), for example, mortality during the autumn migration was estimated at 5% for adult birds and up to 35% for juvenile birds (6). At least a part of this increased mortality can be directly or indirectly linked to the physical exertion during migration flights. Consequently, there should be a strong selection pressure-especially on young birds during their first migration-to minimize energy expenditure during migratory flights and increase the chance of survival. Traveling in close, structured groups has been proposed as an energy-saving strategy, with savings being accrued through positive aero-or hydrodynamic interactions between members of the group (7-10). Flight in V-shaped or echelon formation by birds is perhaps the most prominent example of this. The precise aerodynamic interactions in a flock have been the subject of detailed theoretical and, more recently, empirical studies (2,7,(11)(12)(13)(14). During flight, high-pressure air under the wings flows around the tips to a region of low air pressure above the wings. This flow forms two vortices in the bird's wake, produced by regions of upwash outboard of the wings, and a central region of downwash immediately behind the bird (7, 13). This up-wash can provi...

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“…This species has been shown to form long linear queues when migrating, with those containing five or more lobsters being effective in significantly reducing the average hydrodynamic drag of an individual and leading to substantial metabolic savings over long migratory journeys (Bill and Herrnkind 1976). The Leeuwin Current also affects the distribution of undersize lobster in deep water indirectly via its influence on the latitude of puerulus settlement 3 and 4 years previously.…”

Section: Discussionmentioning

confidence: 98%