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When winter descends upon Europe,
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many animals have no choice but to leave.
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(majestic music)
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The migrations of many discrete creatures
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have been a mystery until now.
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And yet they cross oceans and deserts,
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brave intense weather,
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and travel thousands of kilometers unabated.
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Thanks to recent scientific progress,
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we are finally able to follow their journey
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and discover the secrets behind their incredible migrations.
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(upbeat music)
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The painted lady hides its secrets well.
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Untraceable in winter, this butterfly reappears each spring
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as if by magic.
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Behind this mystery lies an extraordinary story.
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The re-conquest of an entire continent
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by an insect that weighs less than a gram.
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(speaking in foreign language)
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How does the tireless painted lady manage to fly for hours?
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To orient itself confidently, and to reach altitudes
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of over 1,000 meters?
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To find out we're going to accompany this creature
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on its incredible journey from Morocco to the Arctic Circle.
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(gentle music)
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The painted lady's journey begins far from Europe,
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on the other side of the Mediterranean in Southern Morocco.
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In early April and south of Marrakesh, spring came early.
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Temperatures averaged 24 degrees
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and numerous plants are already flowering.
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Oh there is some larva but--
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Constanti Stefanescu,
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a researcher at the Granollers Museum of Natural Sciences
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in Catalonia has studied the painted lady for 20 years.
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Now, like every year,
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he combs Southern Morocco's grassy hills
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in search of butterflies.
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The difficulty of finding painted ladies
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depends very much on the season.
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(flighty music)
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There are some years where the butterfly is extremely common
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and then for example here in Morocco,
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you can find it everywhere
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and some years where the butterfly is really scarce.
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(contemplative music)
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In a country like this that is so big
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the chances of finding things are tiny.
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(contemplative music)
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Well this is a very fresh butterfly.
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It probably emerged today or yesterday.
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He's a very new one
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and it was feeding on lavender
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which is one of the preferred nectar sources.
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I guess this butterfly will start migrating
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as the conditions are good for it.
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(wind whispering)
(gentle music)
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Butterflies are remarkable creatures
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whose body temperatures change
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in relation to their surrounding environment.
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They need a lot of sunshine to stay warm.
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It's common to see butterflies still numb
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from the evening cold warming themselves in the morning sun.
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(gentle music)
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If the temperature does not reach minimum
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which is about 35 degrees or even more in some species
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butterflies cannot move.
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One of the first things that they do
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is to search for nectar
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because the nectar is rich in energy.
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(bright music)
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Found in all the Maghreb countries from September to April
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the painted ladies enjoy a mild winter and lush ecosystems
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that are favorable to the particular types of plants
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they need to reproduce.
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After warming themselves and boosting their energy,
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recently hatched painted ladies
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immediately set about fulfilling their primary mission,
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to reproduce.
(cattle lowing)
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In the afternoon the males go to the hilltops
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to establish territories and to defend them
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against other males waiting for females to come and mate.
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(dynamic music)
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You can see that the males have very speedy flight.
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They interact between them, they make acrobatic flights
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that last sometimes several minutes.
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They just come here because this place can be seen
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from the distance.
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At the moment you can see from here
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that the everything is green.
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There are flowers, there are the host plants
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that are needed by the females to lay the eggs
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but probably in two weeks or three weeks at the most
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all this will become withered, will become--
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Hi.
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Yellow and dry and so the opportunities
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for the painted ladies will diminish dramatically
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in three weeks.
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Migrating is the only option.
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Oh, see.
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Okay, here is again.
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Migration is common behavior for birds
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but surprisingly it also pertains to certain insects.
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We know today that a small number of dragonflies
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and butterflies are capable of undertaking journeys
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that are thousands of kilometers long
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in search of more favorable environments.
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(contemplative music)
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How do these migrating creatures know when it's time
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to begin their journey?
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Many factors can influence the moment of migration.
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Excessive temperatures or precipitation,
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the number of hours of daylight,
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a reduction in the amount of food supply
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or any combination thereof.
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But migration can be triggered by other causes.
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For the painted lady,
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the presence of parasites attacking its caterpillars
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is a deciding factor.
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The main enemy of this butterfly
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is a tiny wasp, is a parasitic wasp
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that lay the eggs inside the body of the caterpillar.
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Then when the eggs emerge, the larvae of the wasp
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start to eat the body of the caterpillar from inside.
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When they complete the development
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they kill the larva and they emerge as adult wasp
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that start to search for another caterpillar
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and repeat the process.
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At the end of the winter sometimes
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more than 50% of the caterpillars die because of that.
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(dramatic music)
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The butterfly that have survive for them
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it's much better to leave the country
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and to colonize a new area which is at the moment
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free of these parasites.
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(contemplative music)
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The butterflies that emerge in April
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know that the survival of their species
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depends on a rapid departure.
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The proliferation of parasitic wasps,
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rising temperatures, and local drought
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could prove to be fatal.
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(sheep bleating)
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(contemplative music)
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Constanti meets with one of his colleagues
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who's taking a census of Southern Morocco's butterflies.
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The team has gathered
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because the painted ladies' migration is imminent.
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(contemplative music)
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There's a cocoon here.
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Come see.
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There's a cocoon here I said.
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Oh yeah, over here.
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Let me see.
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(speaking in foreign language)
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A cocoon and an A5 type caterpillar.
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We're lucky.
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How long will it take?
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The caterpillar should make its cocoon tomorrow I think.
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And this cocoon has three or days left at the most.
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This is one species of thistle of the genus Carduus
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and is one of the most common host-plants that are used
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here in Morocco and also in Spain.
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In places like this that there are so many of these plants
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sometimes there are important emergences
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of many butterflies.
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(playful music)
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(speaking in foreign language)
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Look, there it is.
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Got it!
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Great!
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Well done my friend.
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According to our censuses that have been done
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in the last years now is the timing
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when migration starts
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so last days we were in the south
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and there were no butterflies at all
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because most of them had already left to Europe.
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(speaking in foreign language)
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Here they are emerging right now
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but probably in one, two weeks
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there will no longer be butterflies
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because these too will start the migration to Europe.
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(bright music)
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Some butterflies are more willing to migrate than others.
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Hey!
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This one for example was a female that was egg-laying.
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This one probably will not migrate
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and will stay here laying all the eggs before she dies.
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In fact there is like conflict between migration
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and reproduction.
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Butterfly that is migrating has to invest
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all its energy in migration.
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A butterfly that is breeding has to invest all its energy
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in breeding so when butterflies migrate
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they do it in theory before they reproduce
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and then when they arrive to the destiny
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they feed on nectar, they get energy,
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and then they start the breeding period.
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(bright music)
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There's two of them interacting.
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Look, look!
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It's lasting a long time.
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I don't see them.
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They're over here.
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That's pre-migration behavior, look.
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The butterflies have engaged
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in a strange frantic chase in the last few days.
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This disorderly agitation is instinctive behavior
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that seems to stimulate the butterflies' desire
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to begin their migration.
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The main difference between the migration
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of birds for example and that for the painted lady
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and other insects is that the migration of butterflies
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as exemplified by the painted lady
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is a multiple generation migration.
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This means that every generation makes a part
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of the complex sequence so our butterflies that are emerging
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here in Morocco will fly to Spain, to the South of France,
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will breed there.
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They will die and the offspring of these butterflies
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when they emerge will continue to migrating to the north.
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Each leg of the migration represents these 10s of
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about one thousand kilometers more or less.
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(bright music)
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Over the course of several weeks
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waves of hundreds of thousands of butterflies
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make their move from Northern Africa
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towards the European continent.
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Europe offers the butterflies cooler temperatures
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and ecosystems that are in full-spring bloom.
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Painted ladies coming from the Eastern Maghreb
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don't hesitate to take on the Mediterranean
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which they sometimes cross in a single attempt,
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carried by favorable winds.
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Butterflies born in the west may be a bit less bold
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and some choose to cross at the easiest passage,
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the Strait of Gibraltar.
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(dynamic music)
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For the painted lady, the strait is no major obstacle.
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This famous rock which marks the entry point to Europe
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is only 15 kilometers away
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on the other shore of the Mediterranean.
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Only three days after their departure from Africa,
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the first butterflies have already reached Northern Spain
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and Catalonia.
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The protected Garrotxa Volcanic Zone Natural Park
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is an ideal environment for the butterflies
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to rest and recuperate as they replenish their energy.
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The painted ladies
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have already traveled over 1,000 kilometers,
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despite their flight appearing hesitant or random.
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That impression is certainly deceiving.
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This tireless butterfly actually flies very efficiently.
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The painted lady flies using four wings that are powered
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by extremely strong chest muscles.
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The butterfly which only weighs a quarter of a gram
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has a full wingspan of 5-7 centimeters.
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These four large wings beat about 20 times per second,
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giving this ultralight insect the gift
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of highly effective flight.
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The wings are made of a transparent membrane
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that's covered with miniature scales
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forming colored patterns that change depending on the side.
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There could be up to 600 scales per square millimeter,
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overlaying each other like tiles on a roof.
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These scales are hollow
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which gives them a large surface area
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that's both light and resistant.
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These characteristics also mean that the scales
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can quickly accumulate the heat that's essential
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to the butterfly as it flies.
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Despite its fragile appearance,
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00:17:59,100 --> 00:18:01,530
this insect is a very robust
274
00:18:01,530 --> 00:18:03,453
high performance flying machine.
275
00:18:04,297 --> 00:18:07,047
(dramatic music)
276
00:18:08,160 --> 00:18:11,480
London's Royal Veterinary College is home to a team
277
00:18:11,480 --> 00:18:14,433
that specializes in studying animal flight.
278
00:18:22,760 --> 00:18:25,410
Richard Bomphrey and Masateru Maeda
279
00:18:25,410 --> 00:18:27,790
developed a tool that can be use to analyze
280
00:18:27,790 --> 00:18:29,730
how butterflies fly.
281
00:18:29,730 --> 00:18:32,440
I'm just feeding him or her,
282
00:18:32,440 --> 00:18:35,130
just started and looking good.
283
00:18:35,130 --> 00:18:36,690
Yeah, they're looking healthy and well.
284
00:18:36,690 --> 00:18:37,523
Yeah.
285
00:18:41,300 --> 00:18:43,107
One of the tools that we have here
286
00:18:43,107 --> 00:18:44,850
and the one we're gonna use today
287
00:18:44,850 --> 00:18:47,370
is this small-scale wind tunnel.
288
00:18:47,370 --> 00:18:51,274
Now we built it ourselves, switch it on over here.
289
00:18:51,274 --> 00:18:53,850
When you switch that on, power gets delivered
290
00:18:53,850 --> 00:18:55,890
to these four fans here.
291
00:18:55,890 --> 00:18:59,130
And then it moves along and it passes through a gauze.
292
00:18:59,130 --> 00:19:02,040
So the honeycomb is to straighten the flow
293
00:19:02,040 --> 00:19:04,710
and the gauze is to equalize the pressure
294
00:19:04,710 --> 00:19:07,850
across the cross-section of the wind tunnel.
295
00:19:07,850 --> 00:19:11,140
When it gets accelerated by the contraction cone
296
00:19:11,140 --> 00:19:14,130
it comes out this end beautifully laminar,
297
00:19:14,130 --> 00:19:17,820
smooth, coherent jet and this is the environment
298
00:19:17,820 --> 00:19:21,640
just next to the outlet where we can fly animals
299
00:19:21,640 --> 00:19:24,463
and visualize the flow patterns that they're making.
300
00:19:25,450 --> 00:19:28,390
To visualize the flow what we do
301
00:19:28,390 --> 00:19:30,620
is using this Nichrome wire,
302
00:19:30,620 --> 00:19:32,130
which is like a fuse wire,
303
00:19:32,130 --> 00:19:34,850
and when you pass current through it it gets hot.
304
00:19:34,850 --> 00:19:37,340
And what we do is dribble oil
305
00:19:39,490 --> 00:19:41,590
which we dribble down it like this
306
00:19:43,660 --> 00:19:46,750
and when we turn the power on if you could do that Masi
307
00:19:47,600 --> 00:19:50,323
what you'll see is the smoke comes through.
308
00:19:54,150 --> 00:19:57,187
Can see the smoke bending around my finger.
309
00:19:58,150 --> 00:20:00,550
Strings glued to the butterfly's back
310
00:20:00,550 --> 00:20:01,713
hold it in place.
311
00:20:02,569 --> 00:20:05,243
Okay, time to turn the wind tunnel on.
312
00:20:08,860 --> 00:20:10,560
The procedure is painless
313
00:20:10,560 --> 00:20:13,973
and the strings will be removed after the experiment.
314
00:20:16,449 --> 00:20:17,828
I think we can do better than that one
315
00:20:17,828 --> 00:20:19,143
I should think so--
Yeah.
316
00:20:19,143 --> 00:20:20,803
Am I in the right place now?
317
00:20:21,970 --> 00:20:23,720
Slightly forward.
318
00:20:23,720 --> 00:20:24,990
Yes, exactly.
319
00:20:24,990 --> 00:20:26,227
Okay?
Okay.
320
00:20:26,227 --> 00:20:29,156
Three, two, one.
321
00:20:29,156 --> 00:20:31,463
(beeping)
322
00:20:31,463 --> 00:20:34,630
(contemplative music)
323
00:20:42,000 --> 00:20:43,950
Let's go and have a look 'round here.
324
00:20:45,800 --> 00:20:47,500
Well it's taking it out of the lights this time.
325
00:20:47,500 --> 00:20:48,790
Yeah, good idea.
326
00:20:48,790 --> 00:20:51,023
Beautiful.
Yeah, actually nice.
327
00:20:59,340 --> 00:21:01,680
The first thing that you notice is that
328
00:21:01,680 --> 00:21:06,410
these streaks at the top turn downwards
329
00:21:06,410 --> 00:21:07,730
and they get thrown down.
330
00:21:07,730 --> 00:21:10,530
That process generates a lower pressure above the wing
331
00:21:10,530 --> 00:21:12,360
and a higher pressure beneath the wing
332
00:21:12,360 --> 00:21:16,150
and the result of that is it accelerates air downwards
333
00:21:16,150 --> 00:21:18,220
and by Newton's Third Law,
334
00:21:18,220 --> 00:21:19,770
if you accelerate something downwards
335
00:21:19,770 --> 00:21:23,440
you experience the acceleration, the reaction upwards
336
00:21:23,440 --> 00:21:26,783
and that's how the butterfly is generating its lift.
337
00:21:28,310 --> 00:21:31,600
In fact, when it wants to accelerate up,
338
00:21:31,600 --> 00:21:35,220
what it will do is increase the amplitude of the stroke
339
00:21:35,220 --> 00:21:37,350
so instead of flapping like this
340
00:21:37,350 --> 00:21:38,960
it will almost clap the wings together
341
00:21:38,960 --> 00:21:40,750
and sometimes does clap the wings together
342
00:21:40,750 --> 00:21:42,540
at the top and bottom of the stroke
343
00:21:42,540 --> 00:21:43,950
so that's how they would go up
344
00:21:43,950 --> 00:21:48,520
and when they're settled into their long-distance migrations
345
00:21:48,520 --> 00:21:50,730
they might choose to reduce that amplitude
346
00:21:50,730 --> 00:21:52,510
when they're in fast forward flight
347
00:21:53,440 --> 00:21:55,272
which can save them some energy.
348
00:21:55,272 --> 00:21:58,000
(contemplative music)
349
00:21:58,000 --> 00:21:59,930
The painted lady's flight technique
350
00:21:59,930 --> 00:22:02,520
is incredibly energy efficient
351
00:22:02,520 --> 00:22:04,330
which means this little insect
352
00:22:04,330 --> 00:22:06,533
has exceptionally high endurance.
353
00:22:08,870 --> 00:22:11,898
It can flap its wings for many hours at a time,
354
00:22:11,898 --> 00:22:14,830
all the while traveling at an average speed
355
00:22:14,830 --> 00:22:16,943
of 20 kilometers per hour.
356
00:22:16,943 --> 00:22:20,110
(contemplative music)
357
00:22:21,500 --> 00:22:24,430
Having arrived from Morocco five days ago,
358
00:22:24,430 --> 00:22:27,300
the butterflies have had time to recuperate
359
00:22:27,300 --> 00:22:30,283
and are now eager to resume their frantic journey.
360
00:22:34,590 --> 00:22:38,870
Ahead lies a seemingly insurmountable obstacle,
361
00:22:38,870 --> 00:22:40,690
the Pyrenees Mountain Range
362
00:22:40,690 --> 00:22:43,233
which separates Spain from the rest of Europe.
363
00:22:45,510 --> 00:22:47,650
How will these frail travelers tackle
364
00:22:47,650 --> 00:22:51,350
this mountainous wall of rock over 400 kilometers long
365
00:22:51,350 --> 00:22:53,173
and thousands of meters high?
366
00:22:55,990 --> 00:22:59,023
Most painted ladies will avoid it all together.
367
00:23:00,380 --> 00:23:02,790
They head towards the passage where it's easiest
368
00:23:02,790 --> 00:23:04,983
to cross the Pyrenees Mountain Range.
369
00:23:09,250 --> 00:23:12,720
Some travel east along the coast of the Mediterranean
370
00:23:12,720 --> 00:23:16,396
while others travel west by following the Atlantic coast.
371
00:23:16,396 --> 00:23:19,563
(contemplative music)
372
00:23:23,523 --> 00:23:25,911
(train whirring)
373
00:23:25,911 --> 00:23:28,820
The painted ladies' itinerary often coincides
374
00:23:28,820 --> 00:23:31,900
with the main routes built by mankind for travel
375
00:23:31,900 --> 00:23:33,713
or communication purposes.
376
00:23:37,520 --> 00:23:41,300
Over hilltops, through deep valleys dug by rivers,
377
00:23:41,300 --> 00:23:44,560
and along coastlines, these natural itineraries
378
00:23:44,560 --> 00:23:47,353
are used by butterflies and men alike.
379
00:23:52,550 --> 00:23:55,860
One of the butterflies most studied migratory pathways
380
00:23:55,860 --> 00:23:58,633
follows the Atlantic coastline through France.
381
00:24:03,300 --> 00:24:06,800
It is difficult to predict when the butterflies will arrive
382
00:24:06,800 --> 00:24:09,240
but some people know with great certainty
383
00:24:09,240 --> 00:24:10,533
where they will appear.
384
00:24:11,420 --> 00:24:14,070
Yves Lanceau and Nathalie Truchet,
385
00:24:14,070 --> 00:24:15,640
two naturalist passionate
386
00:24:15,640 --> 00:24:17,570
about the painted ladies' migration
387
00:24:17,570 --> 00:24:19,700
are often waiting for them.
388
00:24:19,700 --> 00:24:22,473
They only capture butterflies to admire them.
389
00:24:24,440 --> 00:24:26,973
Look there, I'm going to try to catch it.
390
00:24:28,096 --> 00:24:29,030
Lets see.
391
00:24:29,030 --> 00:24:31,770
Is it a cabbage white or a green-veined white?
392
00:24:31,770 --> 00:24:32,730
Look.
393
00:24:32,730 --> 00:24:35,020
It's an enormous cabbage white.
394
00:24:35,020 --> 00:24:37,673
Those black spots mean it's a female.
395
00:24:38,740 --> 00:24:40,290
Shall we release her?
396
00:24:40,290 --> 00:24:41,200
Go on.
397
00:24:41,200 --> 00:24:42,660
Don't move too much.
398
00:24:42,660 --> 00:24:44,163
There, bye.
399
00:24:45,411 --> 00:24:48,078
(playful music)
400
00:24:53,470 --> 00:24:55,363
I see flying over there.
401
00:24:56,670 --> 00:24:57,840
That's a nice area.
402
00:24:57,840 --> 00:25:00,020
Yes with lots of flowers.
403
00:25:00,020 --> 00:25:01,053
Excellent.
404
00:25:08,720 --> 00:25:10,220
That's a painted lady, right?
405
00:25:10,220 --> 00:25:12,153
Yes, that's a painted lady.
406
00:25:23,635 --> 00:25:27,218
And I missed it, I missed the painted lady.
407
00:25:28,178 --> 00:25:30,761
(bright music)
408
00:25:34,540 --> 00:25:37,480
Migrations take place through these migratory corridors
409
00:25:38,420 --> 00:25:39,930
which are not very big,
410
00:25:39,930 --> 00:25:42,283
usually 50 or 100 meters wide.
411
00:25:43,190 --> 00:25:45,860
If we wait perpendicular to the corridor,
412
00:25:45,860 --> 00:25:48,683
we can actually count how many butterflies are going by.
413
00:25:49,780 --> 00:25:51,770
Usually there's a few each minute.
414
00:25:51,770 --> 00:25:55,088
Sometimes as many as one or two every second.
415
00:25:55,088 --> 00:25:58,255
(contemplative music)
416
00:26:00,740 --> 00:26:01,963
There, I got it, yes.
417
00:26:04,100 --> 00:26:07,341
The colors fade from brown to orange with hints of red.
418
00:26:07,341 --> 00:26:10,250
(speaking in foreign language)
419
00:26:10,250 --> 00:26:12,210
They travel thousands of kilometers
420
00:26:12,210 --> 00:26:14,710
and even though this one was probably born here
421
00:26:17,000 --> 00:26:19,740
its mother is most likely from Morocco.
422
00:26:19,740 --> 00:26:21,910
It will presumably continue north
423
00:26:21,910 --> 00:26:23,433
which is really amazing.
424
00:26:24,356 --> 00:26:27,360
(playful music)
425
00:26:27,360 --> 00:26:28,470
The painted ladies
426
00:26:28,470 --> 00:26:31,040
that have completed the first part of their migration
427
00:26:31,040 --> 00:26:33,053
now begin to reproduce.
428
00:26:34,790 --> 00:26:36,920
It's the second generation butterflies
429
00:26:36,920 --> 00:26:38,470
that will continue the journey.
430
00:26:39,830 --> 00:26:43,630
This clever strategy means the butterflies recolonize
431
00:26:43,630 --> 00:26:45,963
every European country they cross.
432
00:26:49,460 --> 00:26:53,723
Here, the parasitic wasps are rare and food abundant.
433
00:26:54,570 --> 00:26:57,123
The conditions are perfect for reproduction.
434
00:27:02,003 --> 00:27:04,890
A brief nuptial parade precedes mating
435
00:27:04,890 --> 00:27:08,833
between the male and female facing away from each other.
436
00:27:08,833 --> 00:27:12,000
(contemplative music)
437
00:27:18,790 --> 00:27:22,350
As soon as her eggs are fertilized the female flies away
438
00:27:22,350 --> 00:27:24,983
to find a good plant where she can lay them.
439
00:27:28,070 --> 00:27:30,090
She carefully chooses the habitat
440
00:27:30,090 --> 00:27:31,903
for her future caterpillars.
441
00:27:35,060 --> 00:27:38,773
The egg is minuscule, barely over one millimeter.
442
00:27:42,370 --> 00:27:44,560
Laid on the upper side of a leaf,
443
00:27:44,560 --> 00:27:46,423
the egg is very vulnerable.
444
00:27:47,530 --> 00:27:50,730
It often falls victim to predators like this bug larva
445
00:27:50,730 --> 00:27:53,776
which can drain the egg in a single sip.
446
00:27:53,776 --> 00:27:56,526
(dramatic music)
447
00:28:03,080 --> 00:28:06,696
The rare survivors only need a few days to hatch.
448
00:28:06,696 --> 00:28:09,363
(playful music)
449
00:28:21,880 --> 00:28:23,800
The tiny caterpillar that emerges
450
00:28:23,800 --> 00:28:25,913
quickly begins searching for food.
451
00:28:30,530 --> 00:28:33,060
Caterpillars have voracious appetites
452
00:28:33,060 --> 00:28:35,430
that drive consumption of as much food
453
00:28:35,430 --> 00:28:37,223
in as little time as possible.
454
00:28:42,490 --> 00:28:45,760
When the caterpillar's skin becomes too tight,
455
00:28:45,760 --> 00:28:46,593
it molts.
456
00:28:49,530 --> 00:28:51,960
It sheds its skin four times
457
00:28:51,960 --> 00:28:54,468
before entering the pupal stage.
458
00:28:54,468 --> 00:28:57,635
(contemplative music)
459
00:29:01,260 --> 00:29:05,140
In just 10 days the caterpillar quadruples in size
460
00:29:05,140 --> 00:29:07,343
and totally changes appearance.
461
00:29:10,425 --> 00:29:13,342
(wings flittering)
462
00:29:18,300 --> 00:29:21,130
Extremely vulnerable, it builds a shelter
463
00:29:21,130 --> 00:29:23,130
by folding a leaf over itself
464
00:29:23,130 --> 00:29:26,393
and attaching it with silk threads produced by its mouth.
465
00:29:29,730 --> 00:29:31,420
This disguise keeps it sheltered
466
00:29:31,420 --> 00:29:33,677
from predators and the rain.
467
00:29:33,677 --> 00:29:36,427
(pensive music)
468
00:29:42,030 --> 00:29:44,530
After two weeks of frantic fattening,
469
00:29:44,530 --> 00:29:46,440
the caterpillar has enough reserves
470
00:29:46,440 --> 00:29:50,160
to pass through the last stage of its metamorphosis,
471
00:29:50,160 --> 00:29:51,120
the cocoon.
472
00:29:51,120 --> 00:29:53,787
(bright music)
473
00:30:07,190 --> 00:30:10,123
40 days has passed since the eggs hatched.
474
00:30:10,970 --> 00:30:14,161
Metamorphosis is a long and complicated process.
475
00:30:14,161 --> 00:30:16,744
(gentle music)
476
00:30:40,170 --> 00:30:43,010
When the butterfly emerges from its cocoon,
477
00:30:43,010 --> 00:30:46,133
its wings are damp and seem smaller than its body.
478
00:30:48,630 --> 00:30:51,000
They require about an hour to unfold
479
00:30:51,000 --> 00:30:52,933
and take on the definitive shape.
480
00:31:01,390 --> 00:31:03,350
Before making its first flight,
481
00:31:03,350 --> 00:31:06,610
the young butterfly enjoys a moment in the sun's warmth
482
00:31:06,610 --> 00:31:09,433
to complete the process of drying its wings.
483
00:31:15,525 --> 00:31:18,108
(gentle music)
484
00:31:38,410 --> 00:31:39,850
Oh you're beautiful,
485
00:31:39,850 --> 00:31:42,140
yes, you're beautiful.
486
00:31:42,140 --> 00:31:43,183
Very beautiful.
487
00:31:44,100 --> 00:31:45,310
Freshly hatched,
488
00:31:45,310 --> 00:31:47,550
the second generation of painted ladies
489
00:31:47,550 --> 00:31:50,620
are now ready to pick up where their parents left off
490
00:31:50,620 --> 00:31:53,317
and carry on their northerly migration.
491
00:31:53,317 --> 00:31:56,067
(pensive music)
492
00:32:02,070 --> 00:32:03,640
When they run into an obstacle,
493
00:32:03,640 --> 00:32:05,930
they're so fixated on their destination
494
00:32:05,930 --> 00:32:07,850
that they simply go over it.
495
00:32:07,850 --> 00:32:09,830
Whether it's a house or trees,
496
00:32:09,830 --> 00:32:11,980
they won't go around, but straight over it.
497
00:32:12,880 --> 00:32:15,140
They're obsessed with their direction.
498
00:32:15,140 --> 00:32:16,790
They're better at it than we are.
499
00:32:18,200 --> 00:32:21,150
We can barely go anywhere without a GPS.
500
00:32:21,150 --> 00:32:23,360
They have an internal GPS.
501
00:32:23,360 --> 00:32:26,610
(contemplative music)
502
00:32:30,370 --> 00:32:32,560
It is now mid June
503
00:32:32,560 --> 00:32:34,987
and the migration began over six weeks ago.
504
00:32:43,740 --> 00:32:45,740
Some recently hatched butterflies
505
00:32:45,740 --> 00:32:47,850
take flight almost immediately,
506
00:32:47,850 --> 00:32:50,603
flying over the sea without hesitation.
507
00:32:51,540 --> 00:32:54,200
Their flight plan is ingrained in their genes
508
00:32:54,200 --> 00:32:57,020
and drives them towards a surprising destination.
509
00:32:57,020 --> 00:33:00,493
Southern England where plants are in full bloom.
510
00:33:02,860 --> 00:33:05,600
Butterflies are not the only migratory animals
511
00:33:05,600 --> 00:33:08,720
that instinctively know how to orient themselves
512
00:33:08,720 --> 00:33:11,250
but it is incredible that such small creatures
513
00:33:11,250 --> 00:33:14,030
can rival the precision of other more evolved ones
514
00:33:14,030 --> 00:33:15,037
like birds.
515
00:33:15,037 --> 00:33:17,620
(bright music)
516
00:33:18,740 --> 00:33:22,440
How can an insect with a brain as small as the painted lady
517
00:33:22,440 --> 00:33:24,620
instinctively maintain its direction
518
00:33:24,620 --> 00:33:26,725
as it flies during migration?
519
00:33:26,725 --> 00:33:29,892
(contemplative music)
520
00:33:32,460 --> 00:33:34,920
Rebecca Nesbit long studied this question
521
00:33:34,920 --> 00:33:36,893
through her doctoral dissertation.
522
00:33:38,440 --> 00:33:42,360
Assisted by Jason Lim from Rothamsted Research,
523
00:33:42,360 --> 00:33:45,510
she uses an ingenious device to gain insight
524
00:33:45,510 --> 00:33:48,870
into how butterflies orient themselves.
525
00:33:48,870 --> 00:33:51,783
The device must be placed in a very sunny area.
526
00:33:53,806 --> 00:33:56,140
(dynamic music)
527
00:33:56,140 --> 00:33:59,380
A painted lady which will be released after the experiment
528
00:33:59,380 --> 00:34:02,760
is attached to a pivoting stick that records the direction
529
00:34:02,760 --> 00:34:03,900
of its flight.
530
00:34:03,900 --> 00:34:06,060
Unable to see the landscape around it,
531
00:34:06,060 --> 00:34:08,520
the insect flies in place.
532
00:34:08,520 --> 00:34:09,870
Okay, she's flying.
533
00:34:12,314 --> 00:34:13,870
(playful music)
534
00:34:13,870 --> 00:34:18,000
So we know the direction of the butterfly's body
535
00:34:18,000 --> 00:34:21,310
and as it turns we are recording that.
536
00:34:21,310 --> 00:34:23,800
Every time it turns we've a got a new bit of data
537
00:34:23,800 --> 00:34:25,390
coming into the computer
538
00:34:25,390 --> 00:34:28,684
and that allows us to plot out that flight path.
539
00:34:28,684 --> 00:34:33,107
Okay, and I'm going to three, two, one and let go.
540
00:34:34,350 --> 00:34:35,348
Its rotating?
How's it looking?
541
00:34:35,348 --> 00:34:37,420
Yes, Yes.
Looking good.
542
00:34:37,420 --> 00:34:38,870
From this we're able to tell
543
00:34:38,870 --> 00:34:41,200
what direction the butterflies are heading in
544
00:34:41,200 --> 00:34:44,220
and that means we can look at the directions
545
00:34:44,220 --> 00:34:47,030
of the whole group of butterflies and see whether
546
00:34:47,030 --> 00:34:49,853
they are flying in a favorite direction.
547
00:34:51,240 --> 00:34:52,120
I can see.
548
00:34:52,120 --> 00:34:57,120
Yes, it's moving north, northeast, east something, yeah.
549
00:35:00,610 --> 00:35:02,593
And now stable, yes, yes.
550
00:35:06,020 --> 00:35:08,764
If I move the direction of the butterfly
551
00:35:08,764 --> 00:35:10,443
to a different location
552
00:35:10,443 --> 00:35:13,530
when released the butterfly will tend to go
553
00:35:13,530 --> 00:35:17,685
back to the original location that he wants to fly to.
554
00:35:17,685 --> 00:35:20,852
(contemplative music)
555
00:35:26,520 --> 00:35:28,560
With the sky as the only reference
556
00:35:28,560 --> 00:35:31,170
it seems as though the butterfly uses the sun
557
00:35:31,170 --> 00:35:32,503
to orient itself.
558
00:35:34,910 --> 00:35:37,790
To test their hypothesis Rebecca and Jason
559
00:35:37,790 --> 00:35:41,013
prevent the insect from seeing any of its surroundings.
560
00:35:43,840 --> 00:35:47,381
We put an opaque lid on the top of the simulator
561
00:35:47,381 --> 00:35:49,920
blocking the sky from view
562
00:35:49,920 --> 00:35:52,540
and that allows us to tell whether butterflies
563
00:35:52,540 --> 00:35:55,460
are still able to maintain their migratory direction
564
00:35:55,460 --> 00:35:57,260
when they can't see the sun
565
00:35:57,260 --> 00:36:00,674
and what we found was that the butterflies
566
00:36:00,674 --> 00:36:03,690
are not able to maintain that preferred direction
567
00:36:03,690 --> 00:36:05,271
when they can't see the sky.
568
00:36:05,271 --> 00:36:08,380
(dramatic music)
569
00:36:08,380 --> 00:36:09,880
The experiment proves
570
00:36:09,880 --> 00:36:12,670
that the painted lady orients itself in relation
571
00:36:12,670 --> 00:36:14,103
to the sun's position.
572
00:36:17,140 --> 00:36:19,860
The painted ladies migration is a phenomenon,
573
00:36:19,860 --> 00:36:22,720
the scale of which can be lost on us.
574
00:36:22,720 --> 00:36:26,343
They migrate en masse but often pass by unseen.
575
00:36:27,570 --> 00:36:30,530
In order to observe them we have to use tools
576
00:36:30,530 --> 00:36:31,463
like a radar.
577
00:36:33,504 --> 00:36:35,660
And now we can open that yes, very good.
578
00:36:36,772 --> 00:36:40,390
Okay, the antenna looks okay so I'm going to go in
579
00:36:40,390 --> 00:36:42,788
and turn on the radar and see how it goes.
580
00:36:42,788 --> 00:36:45,455
(pensive music)
581
00:36:49,204 --> 00:36:51,120
(machine buzzing)
582
00:36:51,120 --> 00:36:54,480
The radar works, operate from 200 meters
583
00:36:54,480 --> 00:36:57,550
to 1.2 kilometers above the ground
584
00:36:57,550 --> 00:37:00,350
and it's actually measuring a very small columns of air.
585
00:37:00,350 --> 00:37:03,170
If you look, imagine your lights going up
586
00:37:03,170 --> 00:37:05,470
so at one kilometers above ground,
587
00:37:05,470 --> 00:37:08,050
so we're looking at 30 meters in diameter
588
00:37:08,050 --> 00:37:11,743
so it's really a very small columns of air we are sampling.
589
00:37:14,900 --> 00:37:16,430
The entomological radar
590
00:37:16,430 --> 00:37:19,140
generates an electromagnetic wave above it
591
00:37:19,140 --> 00:37:21,920
that detects altitude, flight direction,
592
00:37:21,920 --> 00:37:23,730
and the number of butterflies passing
593
00:37:23,730 --> 00:37:25,703
during a specific time-frame.
594
00:37:27,860 --> 00:37:30,230
Extrapolated to the sky as a whole
595
00:37:30,230 --> 00:37:33,200
the radar collected data reveals the true scope
596
00:37:33,200 --> 00:37:34,850
of the painted ladies' migration.
597
00:37:42,840 --> 00:37:44,790
These four diagrams on the right
598
00:37:44,790 --> 00:37:49,790
are data for butterflies and at the top
599
00:37:49,890 --> 00:37:53,760
we have the spring, this is data from April, May, and June.
600
00:37:53,760 --> 00:37:57,820
Each dot represents a single day and the track,
601
00:37:57,820 --> 00:38:00,920
this is the direction the butterflies were traveling in,
602
00:38:00,920 --> 00:38:02,533
the heading, this is the direction
603
00:38:02,533 --> 00:38:04,580
that the butterflies were facing in
604
00:38:04,580 --> 00:38:07,800
and what you can see is as we would expect.
605
00:38:07,800 --> 00:38:11,070
In the spring they are on a northwards migration
606
00:38:11,070 --> 00:38:12,890
moving into Northern Europe
607
00:38:12,890 --> 00:38:17,070
and it was only with the invention of techniques
608
00:38:17,070 --> 00:38:20,133
such as this radar that we were able to monitor this.
609
00:38:20,133 --> 00:38:22,800
(pensive music)
610
00:38:30,270 --> 00:38:32,540
Using the radar also helps scientists
611
00:38:32,540 --> 00:38:35,480
discover that certain years boast much greater numbers
612
00:38:35,480 --> 00:38:37,938
of migrating painted ladies than others.
613
00:38:37,938 --> 00:38:40,605
(dynamic music)
614
00:38:42,870 --> 00:38:46,960
2009 was a record year with millions of butterflies
615
00:38:46,960 --> 00:38:48,610
being observed throughout Europe.
616
00:38:49,800 --> 00:38:52,230
This mysterious massive migration
617
00:38:52,230 --> 00:38:54,870
only takes place once or twice a decade
618
00:38:54,870 --> 00:38:58,188
and scientist still cannot fully explain it.
619
00:38:58,188 --> 00:39:00,855
(dynamic music)
620
00:39:05,620 --> 00:39:08,750
The radar-based study of this spectacular migration
621
00:39:08,750 --> 00:39:12,020
also helped another British scientist, Jason Chapman,
622
00:39:12,020 --> 00:39:14,000
better understand the role of the wind
623
00:39:14,000 --> 00:39:15,913
in the painted ladies' migration.
624
00:39:19,030 --> 00:39:21,070
It seems the butterflies that they fly up
625
00:39:21,070 --> 00:39:23,800
and sample the winds and if it's a favorable direction
626
00:39:23,800 --> 00:39:26,425
and it's fast then they will tend to stay at those height
627
00:39:26,425 --> 00:39:29,490
and that's going to travel, help them travel
628
00:39:29,490 --> 00:39:31,700
a very long distance in a short amount of time
629
00:39:31,700 --> 00:39:33,100
but there's a lot of variation
630
00:39:33,100 --> 00:39:35,480
so we don't have all the butterflies at one height,
631
00:39:35,480 --> 00:39:38,510
there are some go very high, some stay lower down.
632
00:39:38,510 --> 00:39:41,110
So there seems to be a lot of in-built variation
633
00:39:41,110 --> 00:39:42,500
amongst the butterflies.
634
00:39:42,500 --> 00:39:46,350
It's almost as if they are increasing their chances
635
00:39:46,350 --> 00:39:49,560
of some of them survivin' by scattering themselves
636
00:39:49,560 --> 00:39:51,985
over a range of different flight altitudes.
637
00:39:51,985 --> 00:39:54,650
(dynamic music)
638
00:39:54,650 --> 00:39:56,410
If the painted ladies' migration
639
00:39:56,410 --> 00:39:59,860
often goes unnoticed, it's because it takes place
640
00:39:59,860 --> 00:40:02,810
through several superimposed aerial corridors
641
00:40:02,810 --> 00:40:06,483
ranging from the ground to over 1,000 meters in altitude.
642
00:40:09,580 --> 00:40:11,203
It's now end of June.
643
00:40:12,100 --> 00:40:14,990
Encouraged by excellent climatic conditions
644
00:40:14,990 --> 00:40:18,590
and a large number of ideal host plants for egg laying,
645
00:40:18,590 --> 00:40:21,280
the majority butterflies arriving in England
646
00:40:21,280 --> 00:40:22,913
will stay to reproduce.
647
00:40:24,870 --> 00:40:27,550
Other butterflies decide to travel onwards,
648
00:40:27,550 --> 00:40:30,990
crossing the North Sea as they merge with other migrators
649
00:40:30,990 --> 00:40:32,523
from all over the continent.
650
00:40:33,640 --> 00:40:35,640
Carried by favorable winds
651
00:40:35,640 --> 00:40:38,223
the butterflies continue their journey north.
652
00:40:39,220 --> 00:40:43,554
They fly over Belgium, the Netherlands, and Germany.
653
00:40:43,554 --> 00:40:45,300
(ominous music)
654
00:40:45,300 --> 00:40:49,890
Yet, even in the summer, the journey isn't always easy.
655
00:40:49,890 --> 00:40:53,187
Sometimes the weather takes a turn for the worse.
656
00:40:53,187 --> 00:40:56,140
(ominous music)
657
00:40:56,140 --> 00:40:58,420
Without the sun to orient themselves
658
00:40:58,420 --> 00:41:00,510
and bombarded by heavy rain,
659
00:41:00,510 --> 00:41:02,640
the painted ladies have no choice
660
00:41:02,640 --> 00:41:05,333
but to momentarily interrupt their traveling.
661
00:41:10,560 --> 00:41:13,180
But it takes more than that to discourage the brave
662
00:41:13,180 --> 00:41:14,313
painted ladies.
663
00:41:16,120 --> 00:41:20,330
As soon as the sun reappears the journey continues.
664
00:41:20,330 --> 00:41:24,380
After a few more days they will reach their destination,
665
00:41:24,380 --> 00:41:25,213
Sweden.
666
00:41:26,700 --> 00:41:29,490
In early July the Scandinavian summer
667
00:41:29,490 --> 00:41:32,890
is particularly favorable to the painted lady.
668
00:41:32,890 --> 00:41:35,640
The days are long and full of sunshine,
669
00:41:35,640 --> 00:41:40,258
creating plenty of ideal ecosystems for insect reproduction.
670
00:41:40,258 --> 00:41:43,425
(contemplative music)
671
00:41:45,610 --> 00:41:48,690
Just east of Sweden on the island of Gotland
672
00:41:48,690 --> 00:41:51,070
biologist Lars Pettersson is conducting
673
00:41:51,070 --> 00:41:53,223
his annual butterfly census.
674
00:41:55,360 --> 00:41:58,273
Many painted ladies end their migration here.
675
00:42:02,000 --> 00:42:04,623
I caught a migrant painted lady.
676
00:42:06,950 --> 00:42:11,950
It has traveled quite far and you can see from the,
677
00:42:11,960 --> 00:42:15,660
still wants to move away, you can see from the pattern
678
00:42:15,660 --> 00:42:19,763
that it has been on its way for quite some time.
679
00:42:21,900 --> 00:42:23,680
One can easily distinguish
680
00:42:23,680 --> 00:42:27,233
a migratory butterfly by observing the state of its wings.
681
00:42:28,280 --> 00:42:29,820
The wings of a painted lady
682
00:42:29,820 --> 00:42:33,980
that has traveled 1,000 kilometers have lost a lot of scales
683
00:42:33,980 --> 00:42:35,960
and their edges are irregular
684
00:42:35,960 --> 00:42:39,063
while the wings of a freshly hatched butterfly are perfect.
685
00:42:40,746 --> 00:42:43,163
(flittering)
686
00:42:45,850 --> 00:42:49,540
Here we have a couple really fresh ones
687
00:42:49,540 --> 00:42:52,850
and they're much nicer looking than the one
688
00:42:52,850 --> 00:42:55,030
that had flown a long way
689
00:42:55,030 --> 00:43:00,030
so this one's probably hatched near here
690
00:43:00,530 --> 00:43:03,093
and haven't flown very long.
691
00:43:03,093 --> 00:43:05,676
(bright music)
692
00:43:12,260 --> 00:43:15,180
I will always see that there are many more butterflies
693
00:43:15,180 --> 00:43:19,790
in autumn and late summer than what we have in spring.
694
00:43:19,790 --> 00:43:23,760
That's because the painted lady migrates here in spring
695
00:43:23,760 --> 00:43:27,780
and in July you have new hatchlings
696
00:43:27,780 --> 00:43:29,820
and they are much more numerous than the ones
697
00:43:29,820 --> 00:43:32,280
that are coming in from the south.
698
00:43:32,280 --> 00:43:35,450
(contemplative music)
699
00:43:35,450 --> 00:43:37,700
Just 10 years ago scientists thought
700
00:43:37,700 --> 00:43:41,083
the butterflies migration ended on the island of Gotland.
701
00:43:42,600 --> 00:43:45,720
But the extraordinary migration of 2009
702
00:43:45,720 --> 00:43:48,940
allowed researchers to see that not all painted ladies
703
00:43:48,940 --> 00:43:50,393
end their journey in Sweden.
704
00:43:53,320 --> 00:43:56,750
That year, there were massive arrivals of butterflies
705
00:43:56,750 --> 00:44:01,123
in Norway, Finland, and even as far as the Arctic Circle.
706
00:44:02,730 --> 00:44:06,350
That is the farthest the painted ladies are know to migrate.
707
00:44:06,350 --> 00:44:09,023
Any further north would be too cold for them.
708
00:44:14,910 --> 00:44:17,680
In a few weeks the temperature in Scandinavia
709
00:44:17,680 --> 00:44:18,910
will start to drop
710
00:44:20,560 --> 00:44:22,740
and the butterflies will have no choice
711
00:44:22,740 --> 00:44:24,763
but to leave again or die.
712
00:44:26,700 --> 00:44:29,753
Much about the return migration remains a mystery.
713
00:44:33,860 --> 00:44:36,210
There was a long-standin' mystery about the migration
714
00:44:36,210 --> 00:44:39,880
of painted lady because there was an absence of observations
715
00:44:39,880 --> 00:44:42,610
of return migrations in the autumn
716
00:44:42,610 --> 00:44:43,820
so the there were two idea,
717
00:44:43,820 --> 00:44:46,510
one was that the migrations were going on somehow
718
00:44:46,510 --> 00:44:49,400
and we were not able to see them for some reason
719
00:44:49,400 --> 00:44:52,680
or the other idea was that the autumn generation
720
00:44:52,680 --> 00:44:54,640
would hatch out and then just die out
721
00:44:54,640 --> 00:44:55,990
when the cold weather came.
722
00:44:58,600 --> 00:45:02,283
So we decided to look in the U.K usin' our radar data.
723
00:45:03,280 --> 00:45:07,290
These plots here show the distribution of
724
00:45:07,290 --> 00:45:10,920
the painted ladies detected by the radars in England
725
00:45:10,920 --> 00:45:12,610
at different heights above the ground.
726
00:45:12,610 --> 00:45:14,630
There is an interesting difference between
727
00:45:14,630 --> 00:45:15,710
the spring and the autumn.
728
00:45:15,710 --> 00:45:17,970
If we look at the spring data on the top,
729
00:45:17,970 --> 00:45:21,850
we see a gradual decline from the very high altitudes
730
00:45:21,850 --> 00:45:24,170
which continues down to the lowest
731
00:45:24,170 --> 00:45:26,710
and that suggest there are many, many painted ladies
732
00:45:26,710 --> 00:45:28,260
flying close to the ground
733
00:45:28,260 --> 00:45:31,593
and only a small number flying at higher altitudes.
734
00:45:32,710 --> 00:45:35,610
Interestingly in the autumn we don't see that pattern
735
00:45:35,610 --> 00:45:38,490
so we see the painted lady butterflies concentrated
736
00:45:38,490 --> 00:45:41,470
at greater altitudes, around about 4-500 meters
737
00:45:41,470 --> 00:45:42,530
above the ground.
738
00:45:42,530 --> 00:45:45,300
So radar told us that actually millions were migrating
739
00:45:45,300 --> 00:45:48,141
high above out head totally invisible.
740
00:45:48,141 --> 00:45:51,308
(contemplative music)
741
00:45:53,000 --> 00:45:55,360
During the autumn conditions deteriorate
742
00:45:55,360 --> 00:45:57,420
so they have to get all the way back down
743
00:45:57,420 --> 00:46:00,180
to the Mediterranean or perhaps even North Africa
744
00:46:00,180 --> 00:46:03,650
in a single adult lifespan.
745
00:46:03,650 --> 00:46:04,950
So that doesn't give them very long
746
00:46:04,950 --> 00:46:06,830
so they have to travel very fast
747
00:46:06,830 --> 00:46:08,920
in order to make that migration
748
00:46:08,920 --> 00:46:10,070
and their only way to do that
749
00:46:10,070 --> 00:46:12,837
is to fly on those high-altitude winds.
750
00:46:12,837 --> 00:46:16,004
(contemplative music)
751
00:46:18,970 --> 00:46:20,910
For Scandinavian butterflies
752
00:46:20,910 --> 00:46:24,070
high-altitude winds are powerful air corridors
753
00:46:24,070 --> 00:46:27,650
capable of carrying them south in record time.
754
00:46:27,650 --> 00:46:31,064
Yet, many of them never make it to their final destination.
755
00:46:31,064 --> 00:46:33,814
(dramatic music)
756
00:46:35,430 --> 00:46:38,873
Whether coming or going, danger is everywhere.
757
00:46:40,070 --> 00:46:42,783
Many butterflies won't survive the journey.
758
00:46:54,640 --> 00:46:56,980
Only the hardiest painted ladies will make it
759
00:46:56,980 --> 00:46:58,233
to their destination.
760
00:47:01,290 --> 00:47:03,570
After traveling for only two weeks
761
00:47:03,570 --> 00:47:05,910
the butterflies converge massively
762
00:47:05,910 --> 00:47:07,923
and head towards the Mediterranean.
763
00:47:11,410 --> 00:47:13,000
In Morocco in autumn
764
00:47:13,000 --> 00:47:15,543
the prairies are still covered in flowers.
765
00:47:16,900 --> 00:47:19,713
This is where the painted ladies will stay until April.
766
00:47:20,563 --> 00:47:24,249
(contemplative music)
767
00:47:24,249 --> 00:47:27,120
Constanti Stefanescu is awaiting them.
768
00:47:27,120 --> 00:47:28,980
He chose to return as well
769
00:47:28,980 --> 00:47:31,659
so he could continue his research.
770
00:47:31,659 --> 00:47:34,826
(contemplative music)
771
00:47:48,550 --> 00:47:52,280
I came to this field to catch some butterflies
772
00:47:52,280 --> 00:47:55,203
that will be used for isotope analysis.
773
00:47:57,120 --> 00:48:02,120
The isotope is one form of one chemical element
774
00:48:03,590 --> 00:48:07,180
so it each chemical element has different forms
775
00:48:07,180 --> 00:48:11,451
depending on a number of neutrons on the nuclei.
776
00:48:11,451 --> 00:48:14,118
(playful music)
777
00:48:28,810 --> 00:48:33,810
So far we are focusing on the deuterium
778
00:48:34,070 --> 00:48:37,620
which is the isotope of hydrogen.
779
00:48:37,620 --> 00:48:41,300
When the caterpillar eats a particular plant
780
00:48:41,300 --> 00:48:45,690
like mallow or thistle the percentage
781
00:48:45,690 --> 00:48:50,070
of the deuterium that was on the plant
782
00:48:51,050 --> 00:48:54,532
passes through the wings and through other tissues
783
00:48:54,532 --> 00:48:58,800
of the butterfly so when we analyze the wings
784
00:48:58,800 --> 00:49:03,510
we know what was the percentage of the plant
785
00:49:03,510 --> 00:49:08,510
so in that way we know the place where the caterpillar
786
00:49:09,230 --> 00:49:12,140
grew and where the butterfly emerge.
787
00:49:12,140 --> 00:49:15,490
For example, as you move to the north
788
00:49:15,490 --> 00:49:18,453
the quantity of deuterium increases.
789
00:49:19,460 --> 00:49:21,590
The wings, which the scientist removes
790
00:49:21,590 --> 00:49:24,810
from dead butterflies contain precious information
791
00:49:24,810 --> 00:49:26,053
about their origins.
792
00:49:28,960 --> 00:49:30,650
The initial results from this study
793
00:49:30,650 --> 00:49:33,053
meet the researchers' expectations.
794
00:49:33,910 --> 00:49:38,620
We have been analyzing isotopes for the last two years
795
00:49:38,620 --> 00:49:41,250
but we are still doing some work.
796
00:49:41,250 --> 00:49:45,090
For example one of the most exciting findings
797
00:49:45,090 --> 00:49:49,430
was that some of the butterflies that we collect in Morocco
798
00:49:49,430 --> 00:49:52,910
also come from south of the Sahara.
799
00:49:52,910 --> 00:49:55,860
That was quite an unexpected result
800
00:49:55,860 --> 00:49:59,400
and what it says is that the
801
00:49:59,400 --> 00:50:03,120
migratory system of the painted lady is huge
802
00:50:03,120 --> 00:50:07,240
because it encompasses not only Europe and North Africa
803
00:50:07,240 --> 00:50:09,850
but also the Sahara region.
804
00:50:09,850 --> 00:50:14,850
So it's a very complex system that can
805
00:50:15,000 --> 00:50:20,000
represent distances of 5,000, 6,000 kilometers
806
00:50:20,940 --> 00:50:24,160
which is the longest distance for a migratory insect
807
00:50:24,160 --> 00:50:26,583
that has ever been described.
808
00:50:26,583 --> 00:50:29,166
(bright music)
809
00:50:31,550 --> 00:50:33,070
Painted lady butterflies
810
00:50:33,070 --> 00:50:34,943
accomplish an incredible feat.
811
00:50:38,330 --> 00:50:42,030
Stage by stage, generation after generation,
812
00:50:42,030 --> 00:50:45,450
these tenacious butterflies travel thousands of kilometers
813
00:50:45,450 --> 00:50:48,912
for their circular migration between Africa and Europe.
814
00:50:48,912 --> 00:50:51,495
(bright music)
815
00:50:52,840 --> 00:50:55,720
Only winter gives pause for a few months
816
00:50:55,720 --> 00:50:58,853
to these incredible insects and their great journey.
817
00:51:00,940 --> 00:51:04,440
But come the new year when it will be too warm in the south,
818
00:51:04,440 --> 00:51:07,020
the painted ladies will take to the road again
819
00:51:07,020 --> 00:51:09,874
like they've been doing for thousands of years.
820
00:51:09,874 --> 00:51:12,457
(bright music)
63113
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