Buzz
When humans experience throbbing fingers and stammering speech, overwhelmed by shivers, they might wonder why animals rarely seem to suffer the same fate during winter. It's true that many animals thrive in freezing conditions better than humans, but it's not simply about insulation and hibernation.
In reality, nature has provided numerous solutions to this issue. Some species have unique ways of preparing for cold spells, while others endure it by sleeping through it and facing the resulting challenges. Some animals, however, have no choice but to live with the cold every single day. Here are ten extraordinary ways animals have adapted to life in freezing climates.
10. Reindeer: Ultraviolet Vision and Feeding in a Resting State
Reindeer, when not aiding Santa, wander across snowy and dark regions. As herbivores, they face a difficult task—digging through the snow to find unfrozen vegetation. The challenge intensifies when they seek their favorite food. Lichens, which are a combination of algae and fungi, form a crucial part of their diet, but their white color blends into the snow. Researchers have found that reindeer possess a unique ability: ultraviolet vision, which helps them spot lichens and predators, such as white wolves, against the snowy backdrop.
Snow reflects UV light, while lichens and wolves absorb it, causing them to stand out against the snowy backdrop for reindeer. Nevertheless, reindeer also have an excellent strategy for making the most of the summer months when food is plentiful. They can sleep while they chew, enabling them to consume enough to fatten up during the warmer months when vegetation is abundant.
9. Bears: The Surprising Ability to Recycle Urine
Bears, like humans, are mammals. However, unlike humans, they can remain inactive for up to five months without suffering from severe muscle and bone degradation. Surprisingly, they even emerge from hibernation with an increase in lean body mass, despite not eating, drinking, or moving at all during this period. Unlike other hibernating mammals, such as squirrels, a bear’s body temperature barely drops, allowing them to burn up to 4,000 calories per day. How do they manage this?
The answer lies in something they don't do during hibernation—urinate. Waste products from bone degradation and protein, which would normally be expelled through urine, are instead recycled while the bear hibernates. As a result, although their bones do undergo degradation due to inactivity, the byproducts of that degradation are repurposed to generate new bone.
Another waste product, urea, results from protein metabolism and can be toxic if it accumulates in the body. However, bears exhibit no signs of urea buildup during hibernation, suggesting that this waste product is also being efficiently recycled during their dormant period.
8. Snakes: Brumation
Though often associated with scorching deserts or dense rainforests, some snakes are also faced with the challenge of surviving bitterly cold winters. As cold-blooded creatures, their body temperature fluctuates with the surrounding environment. This makes them vulnerable to freezing when the temperature drops below a certain point, putting them at risk of dying from the cold.
To endure the winter chill, snakes seek out a sheltered spot where they can hibernate until the weather warms. This process is called brumation, which differs from hibernation in a few key ways. Snakes don't eat before brumation because their digestion slows dramatically in the cold. Another notable distinction is that some snakes may emerge from brumation on warmer days to bask in the sun and raise their body temperature.
7. Fish: Natural Antifreeze
In the freezing depths of the Southern Ocean, water temperatures hover just above freezing, and shelter is nowhere to be found. For most fish, this would be a fatal situation, as being cold-blooded, they'd simply freeze. However, certain fish, like notothenioids, have evolved to survive and even thrive in the frigid Antarctic waters. They possess a remarkable natural antifreeze within their bodies that prevents harmful ice crystals from forming in their bloodstream, allowing them to endure the harshest conditions.
When an ice crystal starts to form, a unique protein quickly surrounds it, attaching itself to the tiny crystal and preventing additional water molecules from joining and turning it into ice. This crystal, now harmless, is transported to the fish’s spleen. For the fish to freeze, the water temperature would need to drop to 27.1°F (-2.7°C). However, seawater's freezing point is 28.6°F (-1.9°C), ensuring that notothenioids are completely safe.
6. Wood Frogs: Freezing Yet Surviving
While most animals have evolved mechanisms to avoid freezing, the wood frog has remarkably adapted to endure freezing temperatures. These frogs inhabit the forest floors of North America, extending to the Arctic Circle. Although they do seek shelter beneath leaves before winter, they are unfazed when temperatures drop below freezing. If ice intrudes into their shelters, they curl into a crouched position, tuck their toes under their bodies, and lower their heads.
Once ice reaches their bodies, up to 70% of the water in their cells freezes, rendering them motionless, breathless, without blood circulation, and devoid of brain activity. They appear lifeless. This process includes storing urine in their bloodstream before winter begins. As the cold settles in, the ice pulls water from the frog’s cells. To prevent this, the frog’s liver starts to produce large amounts of glucose, which binds with the urine to form antifreeze. This prevents water from leaving the body, which would otherwise result in death.
Incredibly, the frogs can remain in this frozen state for months, returning to their normal state once the temperature rises and they thaw out. This survival strategy allows them to awaken before other animals that hibernate underground, giving them time to breed safely.
5. Antarctic Midges: Swift Cold Adaptation
Antarctica, known for its extreme environment, is home to some remarkable native species. Among them is the Antarctic midge, a fascinating insect that demonstrates that cold-blooded creatures, like fish, and even frogs that can freeze and remain alive, aren't the only survivors of such frigid conditions.
These minuscule insects, measuring less than a centimeter in length, are flightless and spend most of the year in a state of frozen dormancy. They dwell beneath the surface, where temperatures stay below freezing but are somewhat warmer than the freezing cold above. Their larvae, however, can withstand temperatures as low as 5°F (-15°C).
Scientists attribute the Antarctic midges’ resilience to a remarkable phenomenon called 'rapid cold hardening.' This process allows the insects to avoid injuries while freezing, enabling them to recover quickly once thawed. Research into this process could potentially lead to advancements for human applications, such as better methods for preserving organs for transplants.
4. Snow Flies: The Art of Self-Amputation
Another small insect that defies freezing temperatures is the snow fly. Unlike Antarctic midges, these insects don’t enter a dormant state during the winter. Instead, they remain active, seeking a mate and reproducing. This behavior gives them a significant advantage, allowing them to reproduce when predators are scarce.
Researchers have discovered that snow flies maximize their chances by moving around in search of a mate until the moment they freeze. They even extend their window of opportunity by self-amputating their limbs when they sense them beginning to freeze. This survival strategy enables them to thrive above ground in North America’s mountainous regions, like the Cascades, even when temperatures drop below 32°F (0°C).
3. Ducks: The Secret of Counter-Current Heat Exchange
Ducks are often seen swimming in ponds even during chilly, snowy weather. One might wonder why their feet don’t freeze when the water is near freezing. The secret lies in their unique circulatory system, where arteries carrying warm blood from the heart surround veins that carry cooled blood back toward the heart.
This clever arrangement allows the warmth from the arteries to heat the cool blood in the veins as it returns to the upper body. Consequently, the blood flowing into the ducks' feet cools significantly. Their feet can reach temperatures as low as 33.8°F (1°C), while the rest of their body remains at around 77°F (25°C). This efficient system minimizes heat loss through their feet while they swim in icy waters.
2. Himalayan Songbirds: Specialized Feathers and Altitude Adaptations
Feathers are well known for providing warmth, and certain bird species, like the Himalayan songbird, rely on this feature to survive in colder climates. What makes these songbirds particularly interesting is that the density and color of their feathers are finely tuned not just to the mountain range they inhabit, but also to the specific elevation at which they reside.
At the base of the Himalayan mountains, you’ll find crimson sunbirds living at altitudes below 1,600 feet (487.7 meters). Higher up, between 5,000 and 10,000 feet (1,524-3,048 meters), their cousins, the green-tailed sunbirds, dwell, and the fire-tailed sunbirds inhabit elevations from 11,000 to 13,000 feet (3,353–3,962 meters). Scientists have begun uncovering the factors that influence these birds’ choice of habitat and their ability to survive within these ranges.
One crucial factor is the thickness of the birds' feathers, which becomes more pronounced as they live at greater altitudes. Birds also rely on shivering to generate warmth, but this process consumes energy. Without adequate feather insulation, the birds could burn through so many calories that they would starve. Over time, they have adapted to their specific altitude ranges to avoid such dangers.
1. Bacteria: Cold-Active Enzymes and Transporter Cells
There are even smaller organisms than insects capable of surviving freezing temperatures, potentially for hundreds of thousands of years or more. These remarkable bacteria, known as psychrophiles, which comes from the Greek word for 'cold-loving,' are uniquely equipped to endure environments where no animal could survive—inside ice or within the minuscule veins found in sea ice and glaciers.
Psychrophiles exhibit various adaptations depending on whether they live in saltwater or freshwater. However, they share a few key characteristics. One is an increased number of transporters on their cell surfaces, allowing for more efficient nutrient transport, which is essential as cold temperatures slow down this process. Much like Antarctic fish, certain bacteria also produce antifreeze proteins, and all psychrophiles possess cold-active enzymes. These enzymes are distinct from those found in typical bacteria, as they operate most effectively at temperatures below 68°F (20°C).
