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  • When desert locusts are well fed, they're solitary creatures.

  • But when food becomes scarce,

  • hungry, desperate locusts crowd onto small patches of land

  • where they can still find something to eat.

  • Contact between different locusts' hind legs set off a slew of reactions

  • that change their appearance and behavior.

  • Now, instead of shunning their peers, they seek each other out.

  • The locusts eventually start marching and then fly away in large numbers

  • seeking a better habitat.

  • These gigantic swarms can host millions of insects

  • and travel thousands of miles,

  • devastating vegetation and crops.

  • They stay close to each other, but not too close,

  • or they might get eaten by their hungry neighbors.

  • When many individual organisms, like locusts,

  • bacteria,

  • anchovies,

  • or bats,

  • come together and move as one coordinated entity,

  • that's a swarm.

  • From a handful of birds to billions of insects,

  • swarms can be almost any size.

  • But what they have in common is that there's no leader.

  • Members of the swarm interact only with their nearest neighbors

  • or through indirect cues.

  • Each individual follows simple rules:

  • Travel in the same direction as those around you,

  • stay close,

  • and avoid collisions.

  • There are many benefits to traveling in a group like this.

  • Small prey may fool predators by assembling into a swarm

  • that looks like a much bigger organism.

  • And congregating in a large group

  • reduces the chance that any single individual will be captured.

  • Moving in the same direction as your neighbors

  • saves energy by sharing the effort of fighting wind or water resistance.

  • It may even be easier to find a mate in a swarm.

  • Swarming can also allow groups of animals

  • to accomplish tasks they couldn't do individually.

  • When hundreds or millions or organisms follow the same simple rules,

  • sophisticated behavior called swarm intelligence may arise.

  • A single ant can't do much on its own,

  • but an ant colony can solve complex problems,

  • like building a nest

  • and finding the shortest path to a food source.

  • But sometimes, things can go wrong.

  • In a crowd, diseases spread more easily,

  • and some swarming organisms may start eating each other if food is scarce.

  • Even some of the benefits of swarms, like more efficient navigation,

  • can have catastrophic consequences.

  • Army ants are one example.

  • They lay down chemicals called pheromones

  • which signal their neighbors to follow the trail.

  • This is good if the head of the group is marching towards a food source.

  • But occasionally the ants in the front can veer off course.

  • The whole swarm can get caught in a loop following the pheromone trail

  • until they die of exhaustion.

  • Humans are notoriously individualistic, though social, animals.

  • But is there anything we can learn from collective swarm-based organization?

  • When it comes to technology, the answer is definitely yes.

  • Bats can teach drones how to navigate confined spaces without colliding,

  • fish can help design software for safer driving,

  • and insects are inspiring robot teams that can assist search and rescue missions.

  • For swarms of humans, it's perhaps more complicated

  • and depends on the motives and leadership.

  • Swarm behavior in human populations can sometimes manifest as a destructive mob.

  • But collective action can also produce a crowd-sourced scientific breakthrough

  • an artistic expression,

  • or a peaceful global revolution.

When desert locusts are well fed, they're solitary creatures.

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B2 US TED-Ed swarm stay close crowd ant scarce

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

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    ktyvr258 posted on 2019/10/17
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