Si les libellules étaient plus grandes, elles domineraient la chaîne alimentaire

Sympa

Imaginez un monde où les libellules sont surdimensionnées : nous parlons ici de proportions dignes de Jurassic Park. Si ces insectes ninjas étaient plus grands, ils domineraient totalement la chaîne alimentaire. Avec leurs acrobaties aériennes rapides comme l'éclair, elles s'abattraient sur des proies sans méfiance comme des avions de chasse. Moustiques, attention ! Les libellules deviendraient les prédateurs suprêmes dans le monde des insectes, obligeant les araignées et les fourmis à remettre en question leur place dans la hiérarchie. Les jardins et les prairies se transformeraient en champs de bataille épiques lorsque ces libellules géantes se livreraient à des duels aériens. Dans cet hypothétique royaume des insectes, les libellules régneraient en maître, prouvant que la taille compte vraiment dans le monde sauvage des ailes et des merveilles.

Transcript

00:00 Who, or what, is, in your opinion, the most efficient hunter on the planet?

00:05 No, it's not lions, nor sharks, nor eagles, nor wolves.

00:09 Sharp teeth, a powerful roar, huge claws and a terrifying appearance

00:14 don't automatically make an animal a good hunter.

00:18 The main indicator of the efficiency of an animal

00:20 lies in its ability to succeed in catching a prey.

00:24 For example, lions can catch their meal only once in four,

00:28 while sharks only succeed in half of their attacks.

00:32 Wolves and eagles, on the other hand,

00:34 must make considerable efforts to ensure their meal.

00:38 However, there is a creature that systematically succeeds in catching its prey,

00:43 the dragonfly.

00:45 More than 90% of these hunting attempts are crowned with success.

00:49 If dragonflies were the size of giant griffins,

00:52 they would undoubtedly dominate the top of the food chain of our planet.

00:56 Moreover, these insects were even larger in the past.

01:01 But we'll talk about it later.

01:03 For now, let's focus on what makes dragonflies so efficient.

01:08 Two of the main factors contributing to the success of dragonflies when they hunt

01:12 reside in their speed and their manoeuvrability.

01:16 Dragonflies have the wings among the most efficient in the world.

01:19 They can glide in the air, change direction in a few seconds,

01:23 be stopped, fly backwards and even turn in a circle.

01:27 For comparison, birds, on their side, take about a second or more to take off.

01:32 Their flight is certainly graceful, but it lacks manoeuvrability.

01:36 Birds are indeed unable to stop quickly or change direction easily.

01:42 Their movements are fluid but limited.

01:44 However, dragonflies have four wings, two at the front and two at the back,

01:49 and these wings can move independently from each other.

01:53 In just three wings, dragonflies can reach a speed of 50 km/h,

01:58 which is equivalent to the average speed of cars in the city.

02:02 In addition, the braking distance of dragonflies is very short.

02:06 If an ordinary car were to stop at the same speed, it would skid several meters.

02:11 However, a dragonfly is able to stop abruptly at any time,

02:15 with a braking distance almost non-existent.

02:18 Thanks to this remarkable talent, dragonflies rise, dive and perform 360-degree pirouettes,

02:26 which makes them unbeatable hunters to which nothing can escape.

02:30 Finally, just 10%.

02:32 Nevertheless, their super-efficient wings would not be enough

02:35 if they were not complemented by a brain that works wonderfully.

02:39 Almost all insects rely on their odors and touch to hunt.

02:43 Let's take the example of a spider on its web.

02:46 It detects all contact with delicate girls and determines the location of the prey thanks to vibrations.

02:53 Dragonflies, on the other hand, rely mainly on their exceptional sight.

02:58 They can focus on a target just like humans,

03:01 by totally abstracting from external distractions.

03:05 Imagine yourself in a large room with many TVs hanging on the wall,

03:09 each broadcasting a different film.

03:11 In the midst of this chaos, you spot your favorite comedy,

03:15 and you can focus on it while completely ignoring the sounds and images of other TVs.

03:21 A dragonfly has a similar ability.

03:24 If it observes a swarm of flying mosquitos in various directions,

03:28 it is able to focus on a single mosquito

03:31 and follow each of its movements.

03:34 The mosquito will not be able to hide in the crowd.

03:37 Oh oh!

03:38 The part that allows a dragonfly to fly resides in its chest.

03:42 Similar to the bone marrow, this center receives signals from the brain

03:46 and transmits them to various members of its body.

03:49 In addition, the dragonfly's brain is connected to its thorax.

03:53 When the insect focuses on a target,

03:56 16 neurons form a chain through which the signals pass from the brain to the wings.

04:01 This rapid communication guides the wings in their flight

04:04 and allows them to capture the target.

04:08 The dragonfly looks at the mosquito, then calculates the interception trajectory.

04:12 In case of problem, the dragonfly can adjust the movement of its wings during the flight.

04:17 Its eyes occupy most of its head and are made up of thousands of small lenses.

04:23 They can see at nearly 360 degrees,

04:27 and some species have a field of vision of about 12 meters.

04:31 This distance may seem small, but compared to that of a human being,

04:35 it is an excellent vision for its small size.

04:39 In addition, some dragonflies have an ultraviolet vision

04:43 that allows them to distinguish their environment very clearly

04:46 and to focus on the target while maintaining the viewing angle during the flight.

04:50 Even if it faces the wind or if the target changes position,

04:54 a dragonfly maintains the same angle on the prey

04:56 while adapting its wings to a new flight trajectory.

05:02 All these amazing abilities allow these insects to catch a prey in 95% of cases.

05:11 They attack mosquitos, night butterflies, butterflies, flies and even other dragonflies.

05:17 Their legs are strong and spiky, which allows them to firmly grip their prey.

05:22 However, these advantages do not make them the main predator in nature.

05:29 Dragonflies can become the prey of toads, birds, fish and even turtles.

05:35 As they mainly fly over swamps, lakes and ponds,

05:40 they are not always able to spot a predator climbing into the depths.

05:44 They can easily become the meal of a bird in flight or get caught in a spider web.

05:50 However, dragonflies would have made fewer enemies

05:53 if they were as big as 300 million years ago.

05:56 Before dinosaurs traveled the Earth, insects measuring 0.7 meters in diameter flew in the air.

06:04 They were known as griffons and looked like dragonflies the size of a horn.

06:10 A drawing of these monsters could easily disrupt your barbecue party.

06:15 Hmm, I think we're going to need a bigger fly mat.

06:20 During prehistory, the atmosphere contained 9% more oxygen.

06:25 Insects absorbed it through special respiratory tubes that functioned as an alternative to lungs.

06:32 The high oxygen saturation helped them grow for millions of years.

06:37 However, their heavy weight prevented them from maneuvering and flying as fast as today's insects.

06:43 Griffons were clumsy flying insects.

06:46 About 150 million years ago, I wasn't there at the time,

06:50 insects began to shrink in size.

06:53 It's interesting to note that the oxygen levels in the atmosphere hadn't changed.

06:58 But something seemed to influence the growth of insects.

07:02 Scientists are convinced that insects began to shrink when the great prehistoric birds appeared.

07:09 Giant dragonflies have become easy prey in the sky,

07:14 which has encouraged nature to reduce their size to increase their agility.

07:19 They have become smaller, but their flying skills have improved considerably.

07:24 Now let's look at another insect with exceptional flying skills.

07:28 The domestic fly.

07:30 This annoying insect roams around your room and disturbs your sleep.

07:35 You may have already wanted to crush it with a slipper or a newspaper.

07:40 But it's a real challenge,

07:42 because the attention and reaction speed of this fly are several times higher than yours.

07:46 Imagine two acrobats.

07:49 One performs acrobatics and bold jumps in a gym.

07:53 The other, underwater.

07:55 The underwater acrobat would move much slower,

07:58 with predictable movements and apparently heavier than the one in the gym.

08:03 Isn't it?

08:04 Well, against this annoying insect, you look like an underwater acrobat.

08:09 As fast as the blow you try to give for the fly,

08:13 your hand will move as fast as a balloon inflated and falling on the ground.

08:17 Not to mention that the fly sees better than you,

08:19 thanks to thousands of receivers that capture the light around it.

08:23 You contract your muscles and move your eyes to see something on the side.

08:28 But the fly doesn't need it.

08:30 It sees everything at the same time.

08:32 If you think you're getting close to a fly without it noticing you, you're wrong.

08:37 It sees everything and is ready for any attack.

08:40 Like a dragonfly, the fly can easily change speed and direction, slow down and accelerate.

08:47 It is even able to anticipate the trajectory of your hand.

08:51 When you shake a newspaper to crush it,

08:54 the fly calculates the impact point and its body immediately prepares for an evasion maneuver.

08:58 In a way, it can dodge the attack before you even hit it.

09:02 Can you imagine if flies and dragonflies increased their size

09:06 while maintaining their speed and their ability to react?

09:09 Humanity would be confronted with problems.

09:12 Let's say, size.

09:14 It is the case to say it.

09:16 And do you know why flies love you so much?

09:18 Because your body is a vast clearing where you can find free food all the time.

09:23 Starting with the sweat you secrete and which contains a lot of delicious snacks,

09:28 such as proteins, salts, carbohydrates and a lot of other chemical substances.

09:34 Flies love these things and at the same time have no real threat from the outside.

09:40 Of course, there are giant beings that slowly shake their big hands.

09:45 But is it a reason for them to give up the feast?

09:48 Of course not!

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