Metal Animals

Look — These 6 animals can survive the most extreme conditions on planet Earth

Lyubov Shmakova

Earth is teeming with more than 8 million species of plants, animals, protists, and fungi alone. Most species are relegated to a small region where they can live by the particulars of their environment, but some hardy animals can thrive in places where no other creature can survive.

Here are 6 of the toughest critters on planet Earth.
6. Bdelloid rotifers

Bdelloid rotifers are microscopic organisms that dwell in the Arctic. Researchers recently discovered that these Arctic rotifers can survive in the Siberian permafrost for more than 24,000 years.

Lyubov Shmakova

Michael Plewka

The tiny organisms survive by entering into a state of low metabolism known as “suspended animation” when normal bodily functions cease. This process prevents ice from freezing their cells, which would normally lead to death.

5. Mexican cavefish (Astyanax mexicanus)

The blind fish often dwells in caves throughout central and northeast Mexico, though its native habit also extends to the southern US and Central America.


Alex Keene, Florida Atlantic University

Lacking sight or pigmentation, the cavefish survives through a more sensitive “lateral line” — a unique organ in fish — which can sense vibrations in the water. The cavefish also evolved a unique form of “sleeplessness,” allowing them to sleep less than relatives that live in rivers.

4. Pompeii worm (Alvinella pompejana)

The hardy Pompeii worm lives in toxic hydrothermal vents with extremely variable temperatures on the Pacific seafloor — 2,500 meters (8,200 feet) below the surface.

National Science Foundation / Wikimedia Commons

Scientists suspect the Pompeii worm — the most heat-tolerant animal on Earth — survives due to the prominent bacteria coating its back, which provide some insulation for the worm. In return, the worm secretes mucus to feed the bacteria.

3. Wood frogs (Lithobates sylvaticus / Rana sylvatica)

Wood frogs live in cold climates across Canada and parts of the United States, including Alaska and New England.


Woods frogs cope with the cold by freezing themselves — literally. The frogs produce antifreeze that prevents ice from freezing their cells. Their hearts stop beating and their lungs cease to function. When winter ends, the frogs thaw and resume daily life.

2. Bar-headed geese (Anser indicus)

The geese spend summers in Mongolia, Tibet, and other parts of Central Asia, then migrate to India in the fall. To get to India, the geese must fly over the Himalayas at some of the highest, oxygen-deprived altitudes in the world, reaching 7,000 meters (23,000 feet).


The birds fly at night and use wind deflections off the mountains to fly higher and conserve energy, but recent research also shows their bodies' metabolic rates can uniquely adapt to these oxygen-deprived environments in ways other birds cannot. They’ve even been spotting flying over Mount Everest.

1. Tardigrades

Also referred to as “water bears” or “moss piglets,” these microscopic invertebrates live in the watery film covering lichen, leaves, and moss in freshwater and semiaquatic ecosystems. You can find them in pretty much every corner of planet Earth (and recently thanks to an accident, on the Moon).


Tardigrades can survive freezing temperatures down hundreds of degrees below zero degrees Fahrenheit or hot temperatures exceeding 300 degrees. They can also withstand thousands of times more radiation than humans. Researchers think certain aspects of their bodies, such as their limb movements and ability to enter into a low-metabolism state, may help them survive.

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