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All living things reproduce—it’s literally one of the requirements to be considered alive. And outside of bacteria, most species specifically practice sexual reproduction, where two individuals mix genes to produce the next generation.

But the contributions from both partners aren’t equal. One partner invests way more at the beginning—the one whose egg is fertilized—and that individual is the one scientists consider “mom.” In some species, making eggs is basically the extent of mom’s involvement in her kids’ life. But some moms take mothering to a whole new level.

So in honor of the upcoming mother's day in the US, we thought we’d talk about some really amazing animal mothers. Whether they’re pregnant for years or producing millions of offspring per month, here are seven of the planet’s most extreme moms. Number one, my mom!

You're great. She was pregnant for about 9 months, but African elephant pregnancies last an amazing 22 months. That’s right -- imagine being pregnant for almost two years!

There are a couple shark species that could give them a run for their money, but among mammals, elephants are the undisputed champions of gestational length. As a result, their babies are born with highly developed brains so they’re able to participate in the complex social life of the herd almost right away. But staying pregnant for 22 months requires some biological modifications.

For a 2012 study, scientists performed ultrasounds on pregnant elephants in zoos around the world to learn more about how they keep a pregnancy going for so long. Female mammals get a lot of the hormones they need to maintain a pregnancy from the corpus luteum, a little ball of cells that forms at the former site of a released egg. And it turns out elephants have a bunch of these clumps.

In addition to the main one that forms in the ovary where the egg was released, they produce up to a dozen “accessory” corpus lutea every time they ovulate. This helps ensure that they’ll have plenty of estrogen and progesterone, important hormones for pregnancy, over the long haul. And once the baby is finally born, mom gets a lot of help.

You’ve heard the saying “it takes a village.” Well, for elephants, it takes a herd. Since herds are matriarchal, all those female relatives pitch in, taking turns babysitting and helping protect calves from predators. The Surinam toad is one really weird-looking frog -- its flat, brown body looks like a leaf floating in the water.

But its reproductive strategy is even weirder than its appearance: mom basically implants her babies in her skin for months. Things start out with pretty standard frog sex. The males grasps the female’s back, a position called amplexus.

Egg laying is surprisingly acrobatic. The two somersault as she lays one to ten eggs, which he catches with a fold of his belly skin and fertilizes. He then nudges them onto her back, where they stick to her back skin.

The pair repeats these egg-laying twists many times, as the whole process of mating can take the entire day. Then, over the course of the next few days, the mom’s skin grows up and around her eggs, eventually totally enclosing them in little pockets. She can end up with more than a hundred eggs embedded in her back, where they’re kept safe from predators while they develop.

The young frogs even hatch in there and continue to grow under her skin for the next three to four months. Eventually, fully formed toadlets pop out of the skin, ready to fend for themselves. Whew!

Then the mom sheds her ruined, pockmarked skin to prepare to do it all over again. This gives a whole new meaning to the concept of baby wearing! It's like you've got the wraps... you've got the packs.... and then you've got the toadlets popping out of your skin...

Hornbills are a family of birds found in the Old World tropics. They get their name from the big horn-like casque that some species have on top of their huge bills. But that’s not what makes them extreme moms.

To keep their chicks safe from predators and rival birds, before they lay their eggs mother hornbills seal themselves inside their nesting cavities with their poop. Depending on the species, the female may plaster up the opening from the inside by herself, or her mate may help from the outside. They actually swallow their own feces, dirt, and other material and regurgitate it as pellets which they plaster into the opening with their huge bills.

A small slit is left open, which lets the male pass food to the incubating mom, and the mom poop outward to keep the nest clean. Because, you know, you don’t want poop on the floor. Just the wall.

Months later, when the mother and growing chicks can no longer fit comfortable in the cavity together, she finally breaks free. In most species the chicks are ready to fly as soon as they emerge. So, parents, remember that as exhausting as taking care of a newborn can be, it could be worse — you and the baby could be sealed inside your house behind a wall of poop.

Caecilians might look like worms, but they’re actually amphibians, kind of like legless salamanders, that mostly live underground in the tropics. Thanks to their subterranean habits, they’re not very well studied. But we do know that at least four caecilian species share a really freaky parenting strategy called maternal dermatophagy.

In these species, young caecilians possess a unique set of teeth with the wonderfully gross purpose of tearing off pieces of their mother’s skin. The mom has a specialized, fatty, peeling layer of skin for exactly this reason, and the babies periodically gather round and voraciously rip off bits off to eat. The skin is so nourishing that they can weight ten times as much just after a week.

And in a month or so, they’re strong enough to burrow out on their own. At least one of these skin-feeding species goes a step further, as mom also provides her offspring with a clear fluid that’s secreted from her cloaca—a sort of amphibian milk. And in some caecilian species, the babies start eating their mother even earlier, consuming parts of her reproductive tract while still inside her.

But caecilians are so hard to observe in the wild that skin-feeding was only confirmed in 2006, and who knows -- there could be other species out there with even weirder parenting techniques. After all, there are about 200 species of them, most of which haven’t received such careful study. When it comes to sheer reproductive output, no animal beats the African driver ant.

These ants live in huge colonies—sometimes consisting of more than 20 million workers. Similar to New World army ants, they send out massive raiding parties that can consume seemingly anything in their path. These swarms have been known to kill and eat animals as big as monkeys and pigs, which has given them a pretty fearsome reputation.

Though, the column of ants only advances about a meter every three minutes, so there’s plenty of time to get out of the way if you’re paying attention. Driver ants spend part of their time as nomads because the colony frequently shifts locations. But once they settle down to reproduce, things get really extreme.

They have the biggest queens of any ant species—a little over five centimeters long. And these mega-moms each have up to fifteen thousand ovarioles—the egg-producing structures inside insect ovaries—which they use to lay eggs pretty much continuously while the colony is settled. Queens of one species in particular can produce three to four million eggs over the course of about a month, and other, related species aren’t far behind.

That’s… a lot of baby ants. But at least they have millions of older siblings around to raise them and show them the ropes. Two closely related frog species were discovered in the 1970s and ’80s in the mountains of.

Queensland, Australia, and named for their unique way of raising their offspring. For even among the weird world of amphibian parents, the gastric brooding frogs stand out. Once a female lays a brood of eggs, the male fertilizes them, and then the female swallows them.

A hormone in the eggs tells her stomach to stop producing acid so her twenty-five or so tadpoles can hatch in there and literally develop inside her stomach for the next six weeks, safe from the dangers of the outside world. How did this evolve?! Mom obviously isn’t eating anything during this time, and the tadpoles’ gill mucus helps protect them from any remaining dribbles of stomach acid.

The developing tadpoles take up so much room that over time, the mother’s lungs are squashed, forcing her to breathe directly through her skin. Eventually a series of tiny but fully-formed froglets come crawling out of her mouth, ready to take on the world. But if she’s stressed out, she can speed this process up, projectile vomiting her young with such force that they land over half a meter away.

Sadly, both species of gastric-brooding frog went extinct by the mid-1980s, and nobody is sure why. But scientists are trying to resurrect them using DNA from frozen specimens, so maybe one day these special frogs will live in the mountains of Australia once again. The mothers on this list all make a lot of sacrifices for their offspring, but in at least three species of social spiders, moms and aunts make the ultimate sacrifice.

Unusually for spiders, these species live in family groups that share communal nests. Only about forty percent of the females ever get the chance to mate. But, since all the spiders in a nest are related, even non-breeding females are motivated to help make sure the family genes are passed on.

Once a batch of eggs hatches, both the mother and some of her sisters feed them by regurgitating a nutritious fluid from their mouths. But this ain’t just any old regurgitate! Producing this spider “milk” takes a /lot/ of resources -- the caregivers basically liquefy themselves to do it.

Eventually, when these spider mothers and aunts have nothing left to give, they die, and the babies eat what’s left of them. Only then are they ready to start fending for themselves. The technical term for mother-eating is matriphagy, and it’s pretty rare, for obvious reasons.

Besides spiders, it’s only been documented in a few insects and nematode worms. Maternal care really doesn’t get any more extreme than that! But whether it’s offering their own bodies to nourish their young, or carrying them around for years, all the animals on this list take mommying to a whole new level.

And that extra effort pays off. By giving their all for their offspring—sometimes quite literally—they help their kids make it in this often unforgiving world. And it does kind of put cleaning spit up and managing temper tantrums in perspective.

Thanks for watching this episode of SciShow and thank you to all of our moms! If you like learning about extreme animal parenting, you might like our episode on the animal kingdom’s awesomest dads. ♪.