00:00About 128 million years ago, snakes suddenly appeared and began to thrive on Earth,
00:07ending up diversifying into a few 4,000 species that we know today.
00:11Nevertheless, it is not only by losing their members and adopting a long and serpentine form that they succeeded.
00:18Although there are 25 groups of lizard without members, it is the snakes that have truly won the palm in terms of diversity.
00:26To understand what makes snakes so efficient, scientists have studied more than 60,000 reptile specimens from museums around the world.
00:35According to them, snakes would have evolved faster than lizards in key areas,
00:40offering them an advantage to exploit new opportunities.
00:44If you find this frightening, I fully agree with you.
00:47But let's continue.
00:50A major factor in their success lies in their eating habits.
00:55With their flexible skull and their sharp sense of smell,
00:58snakes can ingest prey larger than their heads and track their victims like pros.
01:04When dinosaurs disappeared, about 66 million years ago,
01:08snakes were about to adapt to this changing world and occupy vacant niches.
01:13Although we are not sure why snakes evolve so fast,
01:18it is obvious that they represent a singularity in the great curve of evolution.
01:22Just like the sudden explosion of flowering plants,
01:25these macro-evolving singularities have shaped life on our planet in an unexpected way.
01:30Today, snakes are present almost everywhere on Earth, exhibiting a wide variety of characteristics and habitats.
01:37They are found in deserts, tropical forests, meadows and even in the depths of the oceans.
01:44All snakes are predators, feeding on various prey,
01:48including insects, small vertebrates, other snakes and sometimes even large mammals, even humans.
01:57However, you will not see any snakes in Ireland.
02:00Why?
02:01One of the most famous legends says that St. Patrick would have hunted his reptiles from the island.
02:06However, experts believe that snakes never inhabited Ireland at first,
02:11making this story a symbol rather than a reality.
02:15There are also other regions of the world where snakes are absent,
02:19such as Iceland, Greenland, New Zealand and Antarctica.
02:23The absence of snakes in New Zealand is particularly intriguing,
02:26given its proximity to Australia, where snakes abound.
02:30The reason for this absence seems to be the constantly changing climate of the country,
02:34making the survival of snakes difficult.
02:37Although New Zealand is devoid of terrestrial snakes,
02:40it sometimes happens that sea snakes visit its waters.
02:43The black and yellow sea snake and the yellow-lip striped tricot are known to visit the island from time to time.
02:52As for the country with the largest number of snakes, Brazil wins the palm.
02:57With more than 375 species, it has an assortment of harmless and dangerous snakes.
03:03The vast tropical forests of the country offer an ideal habitat for these reptiles,
03:08including famous constrictors such as Anaconda, Boa Constrictor and Boa Emeraude.
03:14Brazil is also home to venomous snakes such as spearhead and coral snake.
03:20However, if you are afraid to participate in the carnival in Rio because of the fear of Brazilian snakes,
03:25know this.
03:26Of the 4,000 species of snakes in the world, only about 600 are venomous
03:31and about 200 are capable of harming us.
03:34The bites of deadly snakes are therefore less frequent than one might think.
03:38The chances of encountering a dangerous snake are barely 5%.
03:42It is difficult to precisely evaluate the total population of snakes because they tend to remain discreet.
03:49However, scientists can estimate the number of individuals within certain specific species.
03:55Thus, they think that there could be up to a million common striped snakes in the wild.
04:01Charming little reptiles.
04:04Contrary to the widespread striped carnivore, the St. Lucie's snake is one of the rarest snakes in the world.
04:10Its history is full of twists and turns.
04:12First considered extinct, it was rediscovered and then lost again,
04:17before finally being found in 2012.
04:20The survivors of this species are now on the small island of Mariamajor,
04:24after being eradicated from the continent by mongooses and other invasive creatures
04:29that feed on these harmless snakes.
04:32Another factor in the evolutionary success of snakes is their fascinating ability to be fed by the sun
04:38because they depend on external sources of heat or light.
04:42Although they are often called cold-blooded animals, this term is misleading.
04:47The appropriate term is that of ectothermic,
04:49which means that their body temperature is regulated by their environment.
04:53Unlike mammals and birds that maintain a constant temperature,
04:58reptiles must warm up in the sun or find other ways to increase their body temperature.
05:05In addition, some snakes challenge the traditional taxonomy of reptiles by not laying eggs.
05:10Although we are taught at school that all reptiles lay eggs,
05:13nature likes to make exceptions.
05:15About 70% of snakes are actually oviparous,
05:19but those living in colder environments give birth to their young,
05:23because eggs would not survive in such conditions.
05:26Nature always has a way of dispelling our expectations and our nomenclatures.
05:30Snakes form a group of prosperous tetrapods,
05:33although they do not present the four characteristic members of tetrapods.
05:37Despite, or perhaps thanks to this, snakes are extremely diversified.
05:42Although this diversity seems to go back to the era of dinosaurs more than 100 million years ago,
05:48modern snakes seem to have appeared more recently.
05:53Fossils and DNA suggest that snakes would have begun to diversify
05:58and evolve after the massive extinction that ended the dinosaurs.
06:02They would have benefited from the habitat and niches left vacant by the missing species.
06:07In terms of locomotion, snakes are extremely flexible
06:11and can crawl, dig, climb, swim, and some are even able to glide.
06:16The ancestors of snakes were quite different from those we know today.
06:21Some species even had very developed limbs.
06:24They continued to evolve throughout the upper cretaceous,
06:28various species developing all over the world.
06:31Only a few modern snake families appeared later,
06:35millions of years after the extinction of dinosaurs.
06:38The fossil record of snakes is fragmented,
06:41making the reconstruction of their evolutionary history complex.
06:44To clarify this enigma, scientists use DNA analysis.
06:49Molecular clock techniques allow us to estimate when different snake lines merged,
06:55suggesting that most of the diversity of modern snakes would have appeared after the dinosaurs.
07:00Only a few snake lines survived the mass extinction of the late Cretaceous.
07:05But these few survivors gave birth to the incredible diversity of snakes that we know today.
07:11Some families lasted for millions of years before extinguishing,
07:15while others prospered and branched out after the event of extinction.
07:20This pattern of rapid survival and diversification is similar to what we observed in birds and mammals
07:26after the extinction of dinosaurs.
07:29The ability of snakes to dig, hunt in the dark, and survive for a long time without food
07:35helped some species to cross the chaos following the extinction.
07:40Their flexibility and their ability to adapt allowed them to find refuge
07:45and prosper where other species failed.
07:50Snakes may seem frightening to many people,
07:53but most species are harmless and do not interact with humans.
07:58And even if they wanted to, most snakes are too small to pose a real threat.
08:04Some large snakes can nevertheless swallow prey, at least surprisingly.
08:09The biggest animal ever eaten by a snake was a 70 kg hyena,
08:14swallowed by a seba python.
08:17I bet the hyena stopped growling at that moment.
08:20Before that, the biggest meal ever observed was a 60 kg impala
08:24devoured by a python of the same species.
08:27Amazing!
08:28The world's largest snakes are constrictors,
08:31which kill their prey by suffocation.
08:34To consume large prey, the snake must be huge.
08:38Seba pythons, green anacondas, reticulated pythons,
08:42Burmese, Indian, and Amethyst
08:45are all claimed to be the world's largest snakes,
08:48sometimes reaching impressive lengths and weights.
08:52And that's it with snakes.
08:54Burk.
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