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While some animal species are found in almost every corner of the world, these 8 species are impressively isolated. Join Michael Aranda for a new episode of SciShow, and learn about these species that can only be found in one place on Earth!
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 Introduction (0:00)

[SciShow intro plays]

Michael: Some animal species are found in almost every corner of the world. We humans are generalists, for example, using our big brains to find ways to live in lots of different environments. But other animals are isolated from their relatives on islands and mountain tops, or tucked away in deep caves.  And when a species lives in only one place, whether it's a single lake or a whole continent, we say it's endemic to that area.

Over time, these animals can develop special adaptations to their unique habitats, and these eight have done just that. Each one lives in a very specific spot, and it's really, really good at living there.

 The Santa Cruz Kangaroo Rat (0:42)

Let's start with the Santa Cruz Kangaroo Rat. It's a small rodent that you can find in the Santa Cruz Sandhills, a small swatch of land in California. Kangaroo rats get their name because they use powerful legs to hop around and long tails to stay balanced, like kangaroos do.

Of the 23 species of kangaroo rat, these guys are especially suited for the sandy soil and shrub-filled landscape they call home. Santa Cruz kangaroo rats are slow to mature and reproduce, which helps them conserve energy and survive during droughts. But this also makes it harder for populations to recover from threats like habitat loss, which isn’t great news for them or the environment.

As it turns out, this kangaroo rat is a keystone species – an animal with a big effect on the ecosystem where it lives. In other words, if they disappeared, their habitat could permanently change. See, kangaroo rats make lots of burrows, and bury seeds to eat later. So they’re unintentionally helping plant populations grow and stay healthy.

In the late 1900s, researchers even ran an experiment where they excluded three species of kangaroo rats from small areas of desert shrubland over ten years. Without these rodents, the regions were converted into much grassier terrain, with different plants and animals living nearby. So these critters aren’t just endemic to the Santa Cruz Sandhills, they’re also really important to make sure a bunch of other living things have a sandy, shrubby home.

 The Texas Blind Salamander(1:55)

In the water-filled caves of the Edwards Aquifer in Hays County, Texas, there lives a creature that looks like it crawled right out of a sci-fi movie. The Texas blind salamander is a ghostly pinkish-white and doesn’t have eyes, because who needs pigment or vision when you live in the pitch black?

Instead of relying on their eyesight, these bizarre salamanders hunt tiny aquatic invertebrates by sensing movement in the water around them. They’re also really sensitive to pollution, and need really clean water full of oxygen to thrive.

Droughts in the 1950s nearly dried up the aquifer, and people were concerned about these endemic amphibians’ chances of survival. In fact, Texas blind salamanders were on the very first list of federally-protected species, after the Endangered Species Act was passed in 1966. These salamanders are still considered to be vulnerable, because of their small population size and limited range. But even if a disaster hits the wild population, captive breeding by humans hopefully means this species will continue to survive.

 The Marine Iguana (2:47)

Unlike amphibians, only one lizard in the world is at home in the ocean – the marine iguana. These peaceful herbivores are endemic to the Galapagos Islands, and are probably descended from a South American iguana that somehow drifted over and adapted to a watery lifestyle. Over time, these lizards evolved powerful, slightly-flat tails to propel them deep below the ocean surface, so they can forage for algae and seaweed.

Not to mention, they have special glands in their heads that let them filter out all the extra sodium chloride and potassium chloride they suck in from the salty water and their food. These glands are connected to their noses, so they get rid of all the salt by sneezing it out.

In the late 1900s, scientists observed that this iguana species occasionally interbreeds with terrestrial iguanas on one tiny island, where their mating seasons overlap. Like mules or ligers, though, the hybrid iguanas are sterile.

Even though these marine iguanas are the surfer dudes of the reptile world, they had a bad rep with Charles Darwin, who described them as "hideous-looking.” But, hey, we think these guys and their salty sneezes are pretty neat.

 Palau's Golden Jellyfish (3:43)

Thousands of years ago, rising sea levels filled a lake in the South Pacific island of Palau with saltwater – and a few jellyfish. Today, the lake is cut off from the ocean, but it’s still home to some unique golden jellyfish that have evolved to thrive here. They get their yellowish hue from a bunch of tiny protists called zooxanthellae living inside their tissues.

It’s a mutualistic relationship, which means both organisms benefit from the close quarters. Over the course of each day, the jellyfish migrate to follow the sunlight, so the protists can photosynthesize and make lots of energy-containing molecules. The jellyfish sometimes hunt, but also use some of these chemicals to fuel their metabolism, and their waste cycles back to help feed the protists.

You might have heard of this lake before, because snorkelling with the jellyfish is a popular tourist attraction. Their stinging cells aren’t powerful enough to harm humans. Visitors just have to be careful not to dive too deep, because at the bottom of the lake is a layer of toxic hydrogen sulfide and other chemicals, where lots of other microorganisms live.

The daily migrations of the jellyfish churn up nutrients and microbes in the lake and help fuel its unique food chain. But this year the population isn’t doing too well, and scientists aren’t exactly sure why there’s a decline. Some think it’s because of a drought caused by El Niño, which has made the lake saltier and thrown off the nutrient balance. And if the jellyfish population doesn’t bounce back, the fate of the whole lake’s ecosystem might be in jeopardy.

 The World's Tiniest Chameleon (4:56)

Now, golden jellyfish endemic to a single island lake might seem cool, but you ain’t seen nothing yet. In fact, this next animal is kind of hard to see at all: the world’s littlest lizard is a chameleon tiny enough to sit on the head of a match.

It’s only a couple centimeters long – including its tail. And it’s one of the smallest possible complex vertebrates on Earth. Its home is a small island called Nosy Hara off the northwest coast of Madagascar, where it was recently discovered in leaf litter and bushes by scientists in 2012. These guys are an extreme example of island dwarfism – a trend of isolated island species evolving to become smaller, to thrive in a limited environment.

The island of Madagascar has some other very small chameleon species. So scientists think that this especially tiny lizard might actually be the result of double island dwarfism. In other words, maybe the already-mini chameleons from Madagascar hopped over to Nosy Hara at some point, and became even tinier.

 The Tree Lobster (5:48)

Island dwarfism may have produced tiny lizards, but island gigantism is also a thing. Case in point: the tree lobsters of Lord Howe Island, a little spot off the east coast of Australia. Now, before you go imagining giant crustaceans leaping from branch to branch, I’m gonna break it to you: Tree lobsters aren’t actually lobsters, even though they’ve got big, sometimes-reddish exoskeletons. They’re giant, flightless stick insects.

Islands can be limited in resources, but that also means fewer predators and less competition, so sometimes animals that colonize islands become bigger over time, instead of smaller. And measuring at around 12 centimeters long, these guys are among the heaviest insects in the world. Though these enormous stick insects were well-known to early colonists on the island, no one had seen any since the 1960s. People thought that invasive rats drove them to extinction. But not all hope was lost!

In 2001, some scientists followed some rumors and discovered just two dozen of them living under a bush on a nearby rock spire called Ball’s Pyramid. Now, there’s a colony of tree lobsters at the Melbourne Zoo, thanks to captive breeding. And eventually, researchers hope to reintroduce them to their original home, after getting rid of those invasive rats.

 The Gelada (6:55)

You may picture most monkeys swinging through trees, or living in forests. But troops of geladas spend most of their time on the ground, endemic to the highlands of Ethiopia. At one point, troops of ground-dwelling, grass-eating monkeys roamed most of Africa. But today, geladas are the last surviving species in their genus.

About the size of baboons, they travel across high-elevation meadows in large, herd-like groups. Mostly they spend days sitting down on their plump rear ends, and grazing on abrasive plants with specialized teeth. And at night, they sleep on ledges of cliff faces for protection from predators.

Despite the remoteness of their mountain home, geladas are still starting to feel the pinch of human encroachment. The edges of their habitat are slowly being taken over by agriculture, so there are some conservation efforts to try and protect these monkeys.

 The Inaccessible Island Rail (7:35)

Last but not least, the Inaccessible Island rail’s name says it all: this bird lives in a place that is very, very hard to get to. Rails are ground-dwelling wetland birds related to cranes. Many of them can fly, but the Inaccessible Island rail is actually the world’s smallest flightless bird, at about 17 centimeters long. I mean, why bother flying when you live on a tiny island with no predators?

This bird lives in small family groups, builds dome-shaped nests out of grass, and spends its time eating small invertebrates, berries, and seeds. Now, that’s not the most exciting life, but they’ve managed to survive in pretty incredible place. Inaccessible Island is an extinct volcano ringed by sheer cliffs in the middle of the South Pacific ocean, and it’s only about 16 kilometers square. And the only way to get there is by boat from South Africa, which takes about a week. So if you’re a birdwatcher looking to add this rail to your list – well, good luck.

 Outro (8:23)

The power of evolution means that animals have been able to adapt to life almost anywhere, from light-less, water-filled caves in Texas to rocks off the coast of Australia. But living in only one place does have a downside: Like they say, don’t put all your eggs in one basket, because your species might be wiped out by a natural or man-made disaster. So that’s why some researchers are looking out for the welfare of these unique animals, because ecosystems might suffer, and Earth would be a little less interesting without them.

Thanks for watching this episode of SciShow, and thanks especially to all our patrons on Patreon who protect this show from extinction. If you want to help us keep making videos like this, just go to And don’t forget to go to and subscribe.