Why do animals form swarms? - Maria R. D'Orsogna

321,088 views ・ 2017-12-18

TED-Ed


Please double-click on the English subtitles below to play the video.

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When desert locusts are well fed, they're solitary creatures.
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But when food becomes scarce,
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hungry, desperate locusts crowd onto small patches of land
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where they can still find something to eat.
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Contact between different locusts' hind legs set off a slew of reactions
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that change their appearance and behavior.
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Now, instead of shunning their peers, they seek each other out.
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The locusts eventually start marching and then fly away in large numbers
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seeking a better habitat.
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These gigantic swarms can host millions of insects
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and travel thousands of miles,
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devastating vegetation and crops.
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They stay close to each other, but not too close,
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or they might get eaten by their hungry neighbors.
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When many individual organisms, like locusts,
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bacteria,
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anchovies,
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or bats,
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come together and move as one coordinated entity,
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that's a swarm.
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From a handful of birds to billions of insects,
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swarms can be almost any size.
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But what they have in common is that there's no leader.
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Members of the swarm interact only with their nearest neighbors
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or through indirect cues.
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Each individual follows simple rules:
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Travel in the same direction as those around you,
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stay close,
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and avoid collisions.
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There are many benefits to traveling in a group like this.
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Small prey may fool predators by assembling into a swarm
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that looks like a much bigger organism.
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And congregating in a large group
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reduces the chance that any single individual will be captured.
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Moving in the same direction as your neighbors
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saves energy by sharing the effort of fighting wind or water resistance.
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It may even be easier to find a mate in a swarm.
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Swarming can also allow groups of animals
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to accomplish tasks they couldn't do individually.
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When hundreds or millions or organisms follow the same simple rules,
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sophisticated behavior called swarm intelligence may arise.
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A single ant can't do much on its own,
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but an ant colony can solve complex problems,
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like building a nest
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and finding the shortest path to a food source.
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But sometimes, things can go wrong.
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In a crowd, diseases spread more easily,
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and some swarming organisms may start eating each other if food is scarce.
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Even some of the benefits of swarms, like more efficient navigation,
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can have catastrophic consequences.
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Army ants are one example.
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They lay down chemicals called pheromones
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which signal their neighbors to follow the trail.
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This is good if the head of the group is marching towards a food source.
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But occasionally the ants in the front can veer off course.
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The whole swarm can get caught in a loop following the pheromone trail
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until they die of exhaustion.
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Humans are notoriously individualistic, though social, animals.
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But is there anything we can learn from collective swarm-based organization?
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When it comes to technology, the answer is definitely yes.
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Bats can teach drones how to navigate confined spaces without colliding,
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fish can help design software for safer driving,
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and insects are inspiring robot teams that can assist search and rescue missions.
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For swarms of humans, it's perhaps more complicated
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and depends on the motives and leadership.
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Swarm behavior in human populations can sometimes manifest as a destructive mob.
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But collective action can also produce a crowd-sourced scientific breakthrough
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an artistic expression,
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or a peaceful global revolution.
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