Why did Crocodiles Survive and Dinosaurs Die?

#PaleoAnalysis
I have heard this question asked many times over the years, so I have decided to make my very first Paleo Analysis video about this subject and dive into the reasons why crocodiles still exist today despite being around during the time when the meteor struck the earth and ended the age of dinosaurs.

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[blondbraid]

Gators are pretty hardy animals, Saturn the alligator even survived the bombing of the Berlin zoo in WW2 and somehow managed to survive for years in a European warzone before British soldiers found and recaptured him, and he lived on to the ripe old age of 84 despite all he'd been through.

[Darkkefka]

No over exaggerated intro, No annoying music in the background, no beating around the bush, just straight to the point And very entertaining and interesting information. You sir have earned my sub.

[DocReasonable]

You omitted their ability to burrow as a major factor in their survival. The extant Nile crocodile can burrow to depths of 12 metres, and there's no doubt the surviving Mesozoic crocs had similar capabilities. This would have saved them from all the horrors on/near the surface, such as raining hot glass, noxious gases, extended winter etc. The fact they only need to eat once a year sealed the deal.

[wilkolb]

Crocs had plenty of aquatic animals to eat even when land based animals became scarce, also those that did survive had to drink water, so the crocs food source came to them, they didn't have to go out hunting, they sit back and wait. Ambush strategy works and not wasting calories roaming around hunting, also the crocs are cannibalistic.

[robinsonray]

Here in Florida humans have pushed bears, panthers, armadillos and many other mammals to the brick of extinction in our territories, yet gators are prospering as are turtles, rats and of course several birds. Resilient animals that adapt to change

[DieLuftwaffel]

Hard to imagine the sheer number of massive carcasses that would have filled the world at that time, choking rivers, floating in the ocean, just death everywhere. Granted, as you said carnivores would have been around a while to clean up the mess but with that much death all at once it would have been amazing in a smelly gross way.

[Sarcosuchas]

As a crocodile specialist, this is a question I get asked all the time. Very nicely explained and kept simple and easy to understand. Also, that is a nice gator skull :P

[robertzantay]

Crocodiles and their relatives are also known not only to bury their eggs, which offers a much greater chance for survival, but they will often burrow into the banks of rivers, lakes and streams for protection against predation and intense weather conditions. They share these traits with some other notable survivors, like turtles, snakes, and lizards.

[ReeveProductions]

I think it’s worth noting how small mammals tend to breed fast, some even having multiple sets of offspring in the corse of a year. Also small mammals tend to mature to breeding age quickly. I think a strong argument could be made that warm blooded mammals survive because they could evolve adaptations quickly. Planet is getting colder? Joe survived more winters than bob who had less fur, joe has more offspring, joe’s kids tend to have thicker fur. Larger creatures tend to have fewer offspring and invest more resources into each of them, making it harder to evolve quickly.

[frankhoffman]

I have a theory. Some crocodiles hibernate underground in a shell of hardened mud during droughts. Many small mammals live in burrows in the dirt. Snakes and lizards often live in underground nests. Some birds nest in holes in cliff faces. That seems like it is the commonn theme of the animals that survived the asteroid strike and asteroid winter that followed.. All terrestrial animals alive today evolved, I think, from species that had some kind of underground refuge.

[luisvalentin]

Their metabolism very slow and the fact that they could go months without eating. Not to mention that they could had easily hide underwater or underground

[michaelclark]

Most of the animals that survived the extinction event at 66 Ma, lived or spent a lot of time in water. This included crocs, and turtles. They also laid eggs, but did not really need parents to survive.

[maxyneschaw]

I have never been into dinosaurs until my son came along. I know more species now than ever. Glad I came across your channel, very informative👍🏿

[Sensekhmet]

I imagine the same mechanisms were behind the survival of turtles and tortoises: animals that were (are?) viewed as "slow", "stupid" and "primitive", yet are still going after 200 million years.

[TheSpeep]

My guess, before having watched the video, would be that crocodiles largely managed to survive due to their relatively low metabolism.
I feel like the ability to just chill out for half a year or more without needing to eat might have come in handy during any kind of mass extinction event, whereas more active, warm blooded, large predators would not have had that luxury.

[davidboyle]

It’s likely turtles, lizards, and snakes followed similar routes in surviving the KT event. I’ve always been curious why studies of the survivors hasn’t been more vigorous. Good presentation.

[truthspeaker]

There's another factor when talking about the large dinosaurs and even why the extremely large insects that existed during the cretaceous period and that is the oxygen levels then versus in our modern era. It is estimated that the oxygen level during the dinosaur period was at 30%, whereas our oxygen level now is at 20%. Those extremely large dinosaurs needed higher oxygen levels and of course, the warmth.

[ethanperks]

I would like to add one 'theory'. It seems the most dinosaurs required considerable parental care from adults. While crocodilians receive parental protection they are quite able to survive upon hatching. This would be especially true in a world where most threats to hatchlings have already perished. Plus, they might hibernate as well as only needing to eat once or twice a year.

[ellenbryn]

Two items about Chixulub which I've seen many paleontologists argue played a part:
—It struck a sulfur-rich area, lofting enough sulfur into the atmosphere not only to cool temps for several years but in high enough concentrations for acid rain to strip leaves from plants. For quite a while there's almost no trees, and vegetation is predominantly ferns, with a major knock-on effect on the foodweb. (Luckily seeds can last a long time in the ground, so when the acid rain was finally done plants could recover) Lakes and rivers would have diluted this effect somewhat for aquatic plants.
-- So much material was lofted from the impact that tectites fell all over the earth— that's the iridium layer. The combined friction of that many small meteorites coming in at once was enough to heat the atmosphere to low broil over much of the planet, even on the far side, which is why there's evidence of fires everywhere— except New Zealand seems to have lucked out. Only burrowing animals, animals that nested in caves, animals in canyons or under rocks, and animals that could take refuge in water avoided this.

I know this second is a modified version of the "asteroid nuked the whole earth" hypothesis you dismissed, and maybe the calculations have been run again and it's been disproven.

But there are eyewitness reports of uncomfortable heat from both Chelyabinsk and Tunguska, both of which broke up in the high atmosphere, raining down only tectites and tiny spherules. The latter reportedly caused some 1st degree burns to people many tens of miles away. And those meteors were house-sized. We know the iridium layer covers the whole planet, and it's a lot thicker than the amount of debris from those Russian meteors.

If the broil hypothesis is trus, it explains why crocs, turtles and even frogs survived: enough of them and their eggs were protected by mud and/or water!

Birds are a bit more of a puzzle, but many nest in cliffs and even small caves, and some are burrowers.

Anything too big to find a cool hole to crawl into for a few hours would die of heat stroke. And that really would wipe out every dinosaur.

[jamesdelcol]

Love this question. Things went dry and some areas still had swampy conditions with small things that they normally eat anyway. They reduced in size during this atmospheric condition over a period of thousands of years. They changed size and reduced how much food intake. When the earth's atmosphere became more habitable, they grew and changed a little in size and biology in varying ways in different places. And they stayed small and bigger birthers in other places like Caymans. Amazing evolutionary story of this animal. They survived and have never returned to a super large size like in ancient period, but they are a great predator and a beautiful animal. Crocs are awesome.

I like how they interact with hippos. They have a healthy fear of hippos. Hippos are actually kind of nasty. They will try for their young, but they will not mess with a bull. They run, swim away.