Emperor penguin (Aptenodytes forsteri), adult and young baby in Snow Hill Island, Antarctic Peninsula
Cold weather drains animals' energy supplies by sucking away their body heat. To conquer the cold, animals evolved astounding survival skills such as antifreeze blood, lounging by hot springs, and even having gender-bender orgies.
Emperor penguins survive in the Antarctic by leaning back and keeping their cool. The outer surface of the bird's feathers drops to lower temperatures than the surrounding air. A team of biologists used heat-sensitive cameras to observe the bird's chilly exteriors. The super cold feathers may help the birds warm up on cloudless days by a physical process known as convection, suggested the authors of the penguin study published in Biology Letters. Feathers don't protect the penguin's feet, though. The biologists noted that the birds would lean back and pick their toes up off the ice. The non-perpendicular penguins could reduce heat loss from their feet by fifteen percent using this technique.
A young icefish.
Beneath the penguins in the depth of the Antarctic seas, species of icefish thrive in deep waters that average -2 degrees Celsius. The water doesn't freeze because of the intense pressure from the water above. The Antarctic icefish evolved antifreeze proteins flowing in their blood and bodily tissues that keep the fish from freezing.
On the other side of the planet, the northern cod developed a nearly identical form of the antifreeze protein. Cod and icefish aren't closely related, and the production of antifreeze protein follows different genetic pathways in the fish, according to research in the Proceedings of the National Academy of Science. Northern cod and icefish provide an example of convergent evolution, when two distantly related species reach a similar biological solution to a problem.
The European common lizard (Lacerta vivipara)
Unlike icefish and cod, many cold-blooded animals die in subzero temperatures because the water in their blood turns to ice. The ice crystals puncture the cells of the animal's body like millions of tiny razor blades. However, some reptiles and amphibians evolved a sweet way to survive being frozen.
To avoid being stabbed from the inside out, some frogs and lizards increase the amount of glucose, a type of sugar, and glycerol, a sugary alcohol, in their blood. Glucose and glycerol in the blood can help prevent the formation of ice crystals. The European common lizard (Lacerta vivipara) went a step further and developed specialized mitochondria, the energy producing part of the cell, according to a study in the Journal of Experimental Biology. These mitochondria help the lizard continue producing energy without creating harmful byproducts even when half of the lizard's body water freezes.
A Burmese python on a clutch of eggs.
Not just northern lizards need to beat chills. Even in the balmy tropics, reptiles evolved ways to overcome their fate as cold-blooded creatures. The Burmese python (Python bivittatus) can warm its eggs using its own body. Although most snakes must use the environment to warm up, the python developed a way to raise the temperature of its nest.
The mother python wraps around her nest of eggs and rapidly flexes her muscles to produce body heat that can warm the nest by several degrees. After hatching though, the baby pythons must fend for themselves, as the mother python's maternal instincts only cover incubation.
Alpine Marmots (Marmota marmota) in Hohe Tauern National Park, Grossglockner High Alpine Road, Carinthia, Austria.
Some animals evolved to sleep right through the cold. The alpine marmot (Marmota marmota), a small rodent from the mountains of Europe, sleeps through eight harsh months. In the four months of marmot activity, the animals scurry to mate and gorge on food to build fat reserves for the long winter's nap.
While most cold-hating birds migrate, the common poorwill (Phalaenoptilus nuttallii) of western North America enters a state of torpor, similar to hibernation. The bird hides under rocks to sleep through the winter.
Even animals in the tropics hibernate. The fat-tailed dwarf lemur (Cheirogaleus medius) sleeps through the winter of its native Madagascar, even though the air temperatures can rise to over 30 degrees Celsius (86 degrees F), according to a study published in Nature. Hibernating may help the lemur save energy during the dry season when little fruit and other food is available.
Red-sided garter snakes (Thamnophis sirtalis parietalis) at a hibernaculum in Inwood, Manitoba, Canada.
Sleeping through the winter, or hibernation, can be a social affair for some snakes. Dozens of garter snakes (Thamnophis sp.) den together to hibernate. After the cold passes the snakes emerge with an urge. The snakes form squirming mating balls as males attempt to fertilize females.
Some sneaky males will emit female scent chemicals that trick other males into trying to mate with them. These gender-bender garter snakes benefit by sapping some of the other males heat, which gives the tricksters an advantage as they warm up after winter.
A snow monkey relaxing after a nice bath in Jigokudani hot spring, Nagano, Japan.
Japanese macaques (Macaca fuscata) live further north than any other primate species, except humans. In one of the coldest areas of the macaques' habitat, the Jigokudani valley of Nagano prefecture, one group of macaques learned to use man-made, hot-springs pools to warm up during the winter. Using the hot springs seems to be a learned behavior that the monkeys teach to each other.
In 1965, primatologists first documented juvenile monkeys taking dips in the hot springs. Now, approximately one-third of local macaques use the hot springs habitually, according to a 23-year-long study of the monkeys published in the American Journal of Primatology. Infants of mothers that bathed were more likely to grow up to use the hot springs as well. However, male monkeys that emigrated into the region in adulthood rarely bathed in the warm water.
Bison and winter snow at Yellowstone National Park.
Hot springs also serve as a winter lifeline for bison and elk in Yellowstone National Park. The animals congregate near geyser basins, such as Scalloped Spring, to take advantage of the warm ground near the geothermal springs, although often the water itself is too hot for bathing. The heat radiating from the spring saves the animals from burning up their own calories to stay warm, according to the National Park Service. However, a misstep can prove fatal. Bones of beasts litter the scalding waters of the some of the hot-spring pools.
The hot springs and geysers of Yellowstone receive their heat from geologic activity beneath the park. That same geological activity also slowly pushed the land beneath the park skyward. As the region goes higher, it also gets colder. Adding to the area's winter ferocity, the mountains around Yellowstone form a giant, stone bowl that traps the frigid air from the surrounding Rocky Mountains.
Adult humpback whale (Megaptera novaeangliae) breaching in the AuAu Channel between the islands of Maui and Lanai, Hawaii.
Whales also use a layer of fat, called blubber, to keep warm in the icy depth of the polar oceans. Blubber insulates the whales and traps their heat energy from escaping into the cold waters, like a scuba diver wearing a wet suit. Without the blubber, the whales would burn too many calories just trying to stay warm.
The cold-busting benefits of blubber can be modeled at home. First, fill a plastic bag with shortening or lard, these materials will mimic the effects of body fat. Then insert another bag and tape the tops of the two bags together so the fatty substance can't escape. Then, put a hand into the bag and squish the fat around until it surrounds the hand like an oven mitt. Put an ice cube into the blubber glove to see how well fat can protect an animal from the cold. The New England Aquarium provides more detailed instructions.
Infrared image of a polar bear.
Beneath its fur, the polar bear also has a layer of fat, known as blubber. To keep even warmer, the polar bear wears two fur coats. The bears sport short, fuzzy hairs close to their skin. Over that coat the bears have a thick layer of long, stiff hairs. This outer fur has a strange structure. The hairs are hollow, like drinking straws. The tiny tubes help to repel water, while the fuzzy undercoat traps heat.
Both of the bear's fur coats lack coloration. The fur reflects all the light that strikes it which makes the fur appear white. The polar bear's skin actually has a black hue. However, polar bears in captivity sometimes take on a greenish coloration because algae grow inside the tubes of the outer fur.