Thanks to Brilliant for supporting this episode of SciShow.

Go to Brilliant.org/SciShow to check out their Science Essentials course. [ ♪INTRO ]. If you were to imagine the perfect place to build a nursery… an active volcano probably wouldn't be your first choice.

But it turns out that lots of animals use the heat from volcanoes to incubate their unborn babies! And they aren't being terrible parents. They're just letting nature do some of the work for them, because all developing embryos benefit from a bit of heat!

It turns out, heat is pretty important for development. And that's because heat is just molecules moving around faster, and that means, it speeds up all sorts of chemical reactions — including the ones inside of eggs that transform yolk compounds into baby animals. So eggs in super cold environments can take a very long time to incubate.

For instance, the eggs of some skates — a kind of fish related to stingrays — can take four plus years to hatch! That's because they live in the deep ocean, where the water temperature is similar to the milk in your refrigerator. But deep-dwelling Pacific white skates have figured out a way to fast-track their young's growth.

They tuck their egg cases into the rocks of a kind of undersea volcano called a hydrothermal vent. In fact, when this was first observed in 2015, the researchers noted that the egg cases were mostly placed within 20 meters of an active vent chimney, where hotter-than-boiling water is shooting out of the seafloor. And they're not the only ones taking advantage of these deep-ocean hot spots.

In 2018, Nautilus Live stumbled upon over a thousand otherwise-solitary deep sea octopuses grouped together at a hydrothermal vent. They were all tucked weirdly into the rocks with their eight arms flipped backwards, protecting their eggs! And deep-sea animals aren't the only ones getting in on volcanic nurseries.

For creatures like us that maintain a pretty constant body temperature regardless of their environment, it seems to be even more critical to keep embryos warm while they develop. In some species, eggs won't develop at all unless they're kept close to their parent's body temp. That's because embryos lack the ability to regulate their own temperature.

Most mammals have solved this problem by incubating their embryos inside their bodies, which are body temperature, whereas birds generally sit on their eggs to keep them warm. But not the maleo. It's a stocky, chicken-sized bird found on two of the islands in Indonesia, and it uses volcanically-heated soils to incubate its enormous eggs.

A mated pair will “test” soils with their temperature-sensitive mouths until they find a spot that's a toasty 33°C. Then, they dig a hole for one egg — which is five times the size of a chicken's egg! When that's laid, they'll cover it up and leave it to incubate — and hatch — all on its own.

No need to stay by the nest if you've got volcanic soils to keep everything perfectly toasty! It's even thought that massive sauropods — those iconic, long-necked dinosaurs — used similar, hydrothermally-active nesting grounds. Places like the hot springs of Yellowstone.

Paleontologists think that's because, with eggs and embryos that big, these animals may have especially benefited from speeding up development with a little extra warmth! Now of course, you will be unsurprised to hear that there are risks to this. The trick is getting close, but not too close, to the heat source.

Most enzymes have a limit to how much heat they can tolerate. So, if you heat an egg up too much, it won't develop normally, or at all. Also, if the volcano acts up, you could literally end up with hard-cooked eggs!

But thankfully, volcanoes are fairly well behaved — on biological time scales, anyway. And that's allowed this strange parenting behavior to evolve in these diverse animal species. If all this talk about heat has you warmed up for learning, you might want to check out the Science Essentials course offered by Brilliant, the sponsor of today's video.

It contains a whole chapter on heat, so you can better understand what it is and why these eggs benefit from being so close to their volcanic incubators. And, with a premium subscription, you get access to it as well as dozens of other engaging, interactive STEM courses. Plus, if you're one of the first 200 people to sign up at Brilliant.org/SciShow, you'll get 20% off the annual price!

So get your subscription while it's hot! [ ♪OUTRO ].