Is It Spring Yet?—Increasing temperatures and longer days are environmental triggers that prompt hibernating wildlife like California ground squirrels to become active again. Photo: Sundry Photography/iStock/Getty Images Plus
Spring is a time of awakenings. As flowers begin bursting into bloom, many wildlife species once again get out and about after taking a long winter break. Whether they hibernate, brumate, enter diapause, or estivate, some animals use unique adaptations to survive during months when food is scarce and extreme temperatures make their normal daily activities impossible. And some of those species just might surprise you.
Waiting Out Winter—Greater horseshoe bats hibernate in a sheltered winter roost, such as a cave. During hibernation, their heart rate slows significantly and they do not require food. Photo: Remus86/iStock/Getty Images Plus
Hide-bernation
Hibernation is one of nature’s most fascinating survival tactics. It allows some wildlife species to enter a dormant state until conditions in their ecosystem change for the better. They may stay hidden in a burrow beneath frozen earth or spend the winter in a secret den, but their key to survival is the same.
Imagine putting your body in "low power mode." Hibernation involves slowing critical body functions to near standstill levels while still supporting life. By lowering body temperature—often to within just a few degrees of the freezing conditions around them—along with slowing heart rate and breathing, and consuming energy stores from fat, some species can survive for months without eating or drinking.
For example, during hibernation, a bat’s heart rate plummets from approximately 200 beats per minute to just 10, helping it go for long periods without food. Additionally, many hibernators hide themselves in burrows or dense vegetation, where they don’t give off a scent or appear to move. This has the added benefit of making it harder for predators to detect them.
Seasonal Slowdown—North American brown bears, including grizzlies, enter a state of torpor in cold climates.
Famous Hibernators – Kind Of
When you think of hibernation, North American brown bears might come to mind. While they’re well known for their winter slumber, these bears technically enter a state of torpor, a lighter dormancy from which they can awaken if disturbed. It can last four to six months in cold climates and during this time, they don’t eat or drink. Instead, their fat stores provide the energy they need, even enabling females to give birth to cubs during winter down time.
Long Live the Queen—Not all bumblebees can survive a cold winter, but the queen can. She buries herself in the ground at the end of summer and becomes active again in spring, ready to start a new colony. Photo: Wirestock/iStock/Getty Images Plus
Bumblebees have a fascinating hibernation strategy—but only for the queens. After mating in late summer, they bury themselves in the soil. Emerging in spring, they’re able to start brand-new colonies which are essential for pollination and healthy ecosystems. Meanwhile, koi fish survive cold winters by entering a slow-moving state of torpor at the bottom of ponds, reducing their oxygen needs and energy use. Each species that enters topor is uniquely adapted to survive in its own habitat.
Swim Slower, Stay Deep—Koi reduce their oxygen and energy needs by entering a state of torpor in cold weather.
Stayin’ Alive
Hibernation might be the best known, but it isn’t the only way wildlife adapt to extreme temperatures. Nature offers some fascinating ways for species to cope with seasonal challenges—in both warm and cold climates.
Cold-blooded Strategies
Brumation is a survival strategy specific to reptiles, amphibians and other ectothermic or “cold-blooded” animals, whose body temperature fluctuates with that of their surroundings. Unlike hibernating species, brumating wildlife don’t remain entirely dormant. They limit their movement to conserve energy and slow their breathing. They don’t need food, but they occasionally wake to drink water and sometimes change location within their habitat.
Spring Awakenings—Mountain yellow-legged frogs survive chilly winter days through brumation, hiding in deep pools or in rock crevices until warmer weather returns.
In Southern California, endangered mountain yellow-legged frogs in the San Jacinto, San Bernardino, and San Gabriel mountains survive frigid winter temperatures by brumating inside rock crevices or in deep pools with underwater vegetation. Changing sunlight and temperature conditions help trigger resumed activity in the spring.
Keeping Their Head Up—Several species of crocodiles and alligators brumate during cold weather, keeping their snout above the chilly—and sometimes freezing—water's surface to continue breathing.
Some crocodilians, including American alligators, survive when their home waters freeze over by keeping their snouts above the frozen surface to continue breathing. It’s both a surprising sight and a fascinating way to thrive in extreme winter conditions!
Taking a Break
Diapause is a state of suspended activity and development that primarily benefits arthropods. As the name implies, this process temporarily pauses insects’ growth—as eggs, in the larval stage, or as adults—when environmental conditions are unfavorable. It’s triggered by environmental signals such as seasonal changes in temperature or day length.
Woolly Sweater Weather—When a woolly bear caterpillar goes into diapause, it temporarily stops developing as a strategy to survive freezing conditions. Photo: Holcy/iStock/Getty Images Plus
A remarkable example of this is the woolly bear caterpillar, which can freeze almost solid for extended periods. Once conditions improve, it thaws out and continues developing, eventually metamorphosing into an Isabella tiger moth.
Surviving in Water or Dirt—The West African lungfish estivates during intense seasonal heat that dries up the bodies of water where they live. It can live suspended in mud until conditions improve and rain restores its habitat.
Beating the Heat
These biological survival tactics also help animals survive periods of intense heat and drought, in a process called estivation. The West African lungfish is a champion at it. When water sources dry up, the fish burrows into mud and secretes a protective mucous cocoon to protect itself. Amazingly, this state can last for years if drought conditions persist, with the lungfish reawakening once rains return.
Summer Hideaway—When seasonal heat becomes intense, desert tortoises sit out the extreme weather in a burrow. During their estivation, they can live without food or water.
Desert tortoises estivate during the hottest periods of summer when no water is available. They enter a burrow and remain inactive, living off their stored fat until cooler, wetter days return.
This spring, as wildlife venture out and about once again, take a moment to reflect on the amazing adaptations that help them survive and thrive in their unique ecosystems. Together with partners across the globe, and the support of allies like you, we’re working to save, protect, and care for wildlife and their habitats through our eight Conservation Hubs.
