From the freezing ocean floor to the scorching desert, animals live in some the planet’s harshest climates. Over millions of years, they’ve adapted features to fit in with their environments.
Color-changing camouflage, flapping ears, and toxin-killing bacteria are just a few of the mechanisms animals use to survive.
Wood frogs freeze their bodies.
To survive the winter, over 60% of Alaskan wood frogs’ bodies freeze solid. They also stop breathing, and their hearts stop beating. This allows them to survive temperatures as low as 3.2 degrees Fahrenheit. And in the spring, they thaw out.
To achieve this semi-frozen state, the frogs build up high concentrations of glucose (up to 10 times the normal amount) in their organs and tissues.
The sugar acts as a “cryoprotectant,” preventing ice crystals from forming in the cells, which can puncture blood vessels and damage tissue. During their hibernation, the frogs don’t urinate, instead using the urea as further protection from ice.
Kangaroo rats survive with very little water.
Kangaroo rats (Dipodomys merriami) have adapted to survive in the arid desert. They get all the moisture they need from the mesquite beans and grass seeds they eat.
Each gram of seeds provides half a gram of water. The rats’ kidneys produce very concentrated urine, helping to conserve water.
During the hottest, driest months, when kangaroo rats need more water, they’ll get it from eating insects and vegetation.
These critters also have incredible hearing and can jump up to 9 feet, which helps them avoid owls, snakes, and other predators. Creating burrows in the soil allows them to store seeds (which then absorb more moisture) and escape from the unforgiving climate.
Antarctic fish have “antifreeze” proteins in their blood.
Notothenioid fish make their own “antifreeze” proteins to survive in the frigid Southern Ocean encircling Antarctica. At temperatures of about 28 degrees Fahrenheit, the water is too cold for most fish.
The antifreeze proteins bind to ice crystals in their blood, preventing the crystals from growing and harming tissues and cells. Scientists think that those crystals then make their way to the fish’s spleen, where they’re stored until they can safely melt.
This extraordinary adaptation helps explain why these fish make up 90% of the fish biomass of the region.
Scientists have researched the proteins to solve problems as diverse as preventing freezer-burnt ice cream to keeping donated organs cold and undamaged during transport.
Some frogs create mucus cocoons to survive the dry season.
Frogs that live in climates with dry seasons or droughts need to protect their skin when there isn’t much moisture in the air. Some Australian species burrow into the soil and cocoon themselves in layers of discarded skin and glandular secretions like mucus.
The Cyclorana australis frog spends the first few months of the dry season in a shallow burrow, around 1 to 3 inches deep. As the environment grows more arid, it starts to develop its cocoon.
Even before developing their cocoons, the frogs store excess water in their bladders.
Researchers have taken australis frogs from their burrows at between two and four months and weighed them. Their increased weight, up to 136% of their standard body mass, suggests they retain a lot of water to help prevent dehydration or desiccation.
When rains return, the frog emerges, typically after spending about six months underground.
Cuttlefish blend into their surroundings.
Cuttlefish have the amazing ability to change their color and texture to blend into their surroundings. Though colorblind, they can detect different wavelengths of light, then mimic their environment.
Contracting or relaxing the muscles around its pigmented skin cells, called chromatophores, lets the cuttlefish appear yellow, red, black, or brown.
According to some estimates, a cuttlefish has around 10 million of these skin cells, individually controlled by neurons. The animal can create patterns like dots and stripes by manipulating which cells it turns on and off. Think of it like a 4K TV, which has over 8 million pixels.
Some cuttlefish skin also has papillae, which expand like balloons to look rigid, like coral. Together, these features allow cuttlefish to evade predators and sneak up on unsuspecting prey.
Tubeworms thrive in a mix of magma and freezing seawater.
Scientists once thought that the deep ocean floor was empty of life. But in 1977, they found giant tubeworms (Riftia pachyptila) living along the Galápagos Rift, about 1.5 miles below the ocean’s surface. These invertebrates thrive in hydrothermal vents, where freezing seawater mixes with magma.
Reaching lengths of over 6 feet, they have no digestive system. Long white tubes end in red plumes full of hemoglobin. These plumes act similarly to gills, circulating oxygen, hydrogen sulfide, and carbon dioxide.
Inside the tubeworms, chemosynthetic bacteria live symbiotically, oxidizing toxic hydrogen sulfide into carbohydrates and proteins that feed both themselves and the worms. The bacteria detoxify the sulfide and, in exchange, make their home inside the worm.
Okapi have scent glands on their feet to mark their territory.
Okapi (Okapia johnstoni) look like a combination of a giraffe and a zebra. However, at 5 feet tall, they’re much smaller than their long-necked relatives. They live in the Democratic Republic of Congo, where it’s very hot and where predators such as leopards are always lurking.
To survive, okapi have several key adaptations. Their dark, striped coats help camouflage them in the sun-streaked tropical rainforest. Solitary animals, the scent glands on their feet spread a tar-like substance to mark their territory.
With their large ears, they can pick up on soft sounds. The ruminants use low-frequency infrasonic calls, to communicate with their calves without alerting predators.
A 12-to-18-inch tongue helps them pull branches from trees and wash their eyes and ears.
Pufferfish can inflate to more than double their original size.
It can be difficult for slow-swimming fish to escape predators. Pufferfish have elastic stomachs that they inflate with water if they feel threatened.
Some species have spines instead of scales that pop up when they puff to seem extra threatening. Other times, they expand just to stretch their muscles. They can swell up to more than twice their original size.
Additionally, most pufferfish produce a neurotoxin called tetrodotoxin that can cause paralysis and seizures. In some cases, consuming a pufferfish can lead to death, and a few people die from eating fugu, a dish made with the fish, every year.
African elephants use their giant ears to cool down.
African elephants’ ears are the largest of any animal, and they act like a built-in cooling mechanism. Elephants can create a breeze by flapping them.
The African elephant actually has two subspecies, savanna (Loxodonta africana) and forest (Loxodonta cyclotis). Many savanna elephants live in grasslands in sub-Saharan Africa, but some are adapted to desert environments. They require dozens of gallons of water a day for drinking and evaporative cooling.
But their ears also have a network of blood vessels that can dilate to direct up to 12 liters of blood per minute. The increased blood flow helps the pachyderms give off more heat.
Most mammals’ fur keeps heat in, but elephants’ wiry hairs conduct it away from their bodies.
Water can also keep elephants cool. A 2014 study suggests they can detect low-frequency sounds from thunderstorms as far as 150 miles away.
And it’s not just their ears that help elephants communicate. They can pick up vibrations from their herds’ calls through their sensitive feet.
The platypus uses electroreceptors in its bill to detect prey.
Known for their odd mix of bird-like features, beaver-esque tails, and egg-laying reproduction, platypuses are unique mammals endemic to Australia.
When it’s underwater, the platypus closes its eyes, ears, and nose. For hunting, it relies on its bill, which has receptor cells that detect physical changes and electric fields as its prey moves around.
This post has been updated. It was first published on July 15, 2016.