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 deep in 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.
Let’s start with the Santa Cruz kangaroo rat.
It’s a small rodent that you can only find in the Santa Cruz Sandhills, a small swatch
of land in California.
Kangaroo rats get their name because they use powerful hind 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.
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.
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.
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.
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.
[nosy harr-uh] 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.
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.
**
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.
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.
The power of evolution means that animals have been able to adapt to life almost anywhere,
from lightless 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.
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