The Amazing Biogeography of Caves

Today we're learning about both the geographic and biologic factors that influence life underground to see if we can get a better understanding of cave biogeography!

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[djtfot]

I remember in an Anthropology class back in college the professor explained that species don't lose something over time because they're not using it, they lose it because it's a detriment to them in their new environment. As such, his example was that cave fish don't lose their eyesight or eyes over the course of evolution because they're not using it anymore, they likely lose it because their eyes can become a source of infection in the cave environment, so they have an advantage if they lose that source of infection. Just an interesting note.

[soft.callus]

My favorite thing about your videos is that you start with simple questions, such as why dont mammals live in caves, and then ask further questions that build into an interpretation of more abstract topics, with insights that are not apparent on surface level.

[TheBrewster]

As a note for why salamanders seems to excel at cave life where other ectotherms have not, salamanders actually prefer cooler temperatures overall as a group. It’s why they’ve more or less have been excluded from the tropics and even where they’re native you’re often hard pressed to find them in the hottest months of the year. Many species actually prefer temperatures in the 50s-60s F. As someone who works with captive species, I even have to be careful temperatures don’t get too high above 70F or else you risk them overheating. I think this preferred temperature zones has made them well suited to cave life. They prefer wet and moist dark habitats as you mentioned, they are ectothermic so they don’t have high energy needs as you mentioned, but also they operate at cooler temperatures than other ectotherms, such as reptiles. Because of this they just set up well to quickly adapt to cave life.

Now, there are some reptiles who do prefer cooler temperatures, such as a genus of Asian geckos, Goniurosaurus, who are collectively referred to as “cave geckos”. Despite being called cave geckos, they’re more so just visitors to caves. Possibly they’re on the way to evolving in that direction, but I think a fact with reptiles is they have to evolve to be more tolerant of constant cool temperatures compared to salamanders who that’s already their ancestral condition, so they’re just in a better position to take over the niche quickly.

[coopernoble]

Another thing to consider is that the water level in caves fluctuates frequently, occasionally fully inundating the system. All other animals would drown, even other amphibians like frogs. This also contributes to making the niche more favorable to salamanders.

[Cy]

At 26:45 you mentioned no other cave predators exist other than salamanders. As of recently, scientists have discovered that there is a population of dwarf crocodiles that spend nearly all of their lives inside of caves in Gabon, and they eat mostly insects and bats. This proves that if competition was low enough, in theory other animals can take the niche of apex predators in caves.

[pablorey]

In Eastern Europe (Romania?) there is a cave that was completely isolated for entire eras. There are no bats, no energy input from the outside, the energy comes from a chemical reaction, which I don't remember, but it was from the minerals in the cave. There are spiders and I think fish... all highly evolved. If you find reliable data on this cave (or cave system) it would make for a very interesting video.

[JKTCGMV]

Imagine this. A species of cave dwellers pass down stories of the caves that include descriptions of how tight and narrow the passages are, but because of erosion the passages have become less narrow, and it makes the people think they’re getting smaller over generations

[icewink]

Wow, as someone from the Southern US, I had no idea how unique this region is for salamander diversity! I mean, I knew that the Smoky Mountains have the highest salamander diversity, but I would have expected the rest of the region to have a similar numbers to the rest of the world.
Thanks for this great video!

[Intelligenthumour]

There are also lava tube caves, iirc Hawaii has some cave critters(like a type of shrimp) that dwell in those.

[joshuagcwong]

I wrote an essay on this in my second year of university and fell in love with these kinds of animals. The Congo River and Lake Baikal in Russia host analogous species to troglobionts too, as these bodies of water are so deep that light does not reach the bottom of them.

[matthewwhiteside]

3:45 just want to say that we pronounce it "Nulla-bore" in Australia, but looking at the way it's spelled, you're probably right that it was meant to be "Null Arbor", or "No Trees".

[sizanogreen]

Great video, just one tiny correction. Karst is not the only geology that forms caves. At the very least there are also lava tubes and stuff.

[MCLegoboy]

It probably doesn't count, or they're still working their way toward it, but there are yellow-red rat snakes that hang from the top of the Kantemó Bat Cave in Mexico, and they snatch the bats right out of the air. It even has the nickname of the Cave of the Hanging Serpents. I have no clue how they really stay in the cracks of the ceiling or how they even reproduce and stay off the cave floor save for a few ledges on the walls, but supposedly they've already gone blind (still have eyes though) and live their whole lives in these caves because there really is no need to leave. They know exactly when the bats are about to depart for the night, get into position just hanging down, and when they feel a breeze close enough, they can just snatch the bats right out of the air. I wouldn't be surprised if the younger snakes feed on bugs and anything else that wonders in until they're old enough to start hanging from above, so this could be contention for your Salemander only apex predator theory.

[eiwtsexiang]

Speaking of geographic isolation, you NEED to make a video about mountains and specifically montane animals and plants!! Mountains behave as islands too, and many mountain-dwelling species get stuck in the highlands, unable to move downwards due to the temperature differences. These species proceed to diversity and develop their own ecological niches seen nowhere else on earth.

Please have a look at the highland Nepenthes (pitcher plant) species in Southeast Asia :)

[DwreckJ]

“In the deep glens where they live, all things are older than man, and they hum of mystery.”

The end of ‘The Road’, McCarthy, and one of my all time favorite quotes.

[goose]

what i love about your videos is how you basically explain the thought process you had throughout your research and the answers you found

[robo-birdie]

Ever heard of the Abanda Cave Crocodile from Gabon? It's a population African Dwarf Crocodile that became isolated thousands of years ago. It has orange skin and along with eating bats and invertebrates lives off tons of algae.

[Harrebs]

Caving isnt for everyone but its something you have to experience even if its very open.

[fakeAratPrime]

*_Now that I know, Im gonna dive down a chasm to find some neat creatures._*

[Knealeriley]

Howdy, from the US state with the most caves Tennessee!!

For every cave humans can get to and explore there are multiples more that are too small for humans or too inundated with snow or ice

Caves are such a large and largely unexplored Refugia for many rarities. Please support your local grotto or spelunking organizations

Help protect caves and their biological inhabitants before they’re lost to errant development