The Skill that Helps Them Survive the Winter

Introduction

Ever notice during the winter the lack of bugs, spiders and even amphibians? Where do they all go? The answer might surprise you.

What You Need To Know

Some species of frogs produce an enzyme that allows them to freeze themselves to survive winter

• Some species of frogs produce an enzyme that allows them to freeze themselves to survive winter
• Wood frogs can freeze themselves for up to eight months
• Scientists are studying these frogs to assist the medical communities of organ donation and diabetes

Habitat

Frogs don’t go away just because it’s winter; they hibernate or freeze themselves to survive the cold season.
According to Assistant Natural History Biologist Matt Ormsby, with the Missouri Department of Conservation, most of the frogs are found in large urban areas. Noting that “these species are normally only found in or near water during their breeding season, and outside of that can be found in forested woodlands.”
During the winter, these frogs have somewhat of a superpower. With no food available and the inability to migrate south to warmer climates, they literally freeze themselves into hibernation.
A tree frog crosses a rural road in St. Charles County, Missouri in 2022. Photo courtesy of Matt Ormsby with the Missouri Department of Conservation.
The frogs will burrow into shallow mud with some aquatic species, finding the spot under the ice where it stays just about freezing. “They slow down their metabolism and heart and absorb the oxygen from the water through their skin,” explains Ormsby.
The most extreme example of suspended animation is the wood frog. Found in eastern Missouri, this frog has a widespread range, encompassing most of the northeastern U.S., Canada and Alaska. “It is the only frog that lives within the Article Circle,” emphasizes Ormsby.
A cold-blooded creature would need some sort of survival tactic in such harsh condition and this frog has evolved to do it.

Freezing Process

The “freezing” part has to do with a special enzyme that the frog secretes. Ormsby breaks it down for us.
“The biggest part of the process is the special glucose that the frog’s liver produces just before the freezing process. This special glucose is sent to all tissues, organs, and cells in the frog’s body, which acts somewhat like a natural antifreeze and keeps the water inside the cells from freezing and causing damage.”
Adding, “Water outside the cells does freeze inside the frog, but the cells are protected. Nearly 65% of the frog’s body is frozen solid. Most of this is in the abdominal cavity surrounding the organs and in the eye lenses and water between the skin and muscle. The heart and lungs stop while the frog freezes.”
Emphasizing, “wood frogs can remain ‘frozen’ in this fashion for up to eight months.”
The wood frogs begin this process, usually in late November or early December, when temperatures cool to near freezing levels. Sometimes it may not happen until January.

Thawing

Emerging from hibernation happens when temperatures during the day stay above freezing and close to freezing at night. For reanimation, “the heart starts back up and begins to deliver oxygen-rich blood to help flush out the cells and the special glucose and cell wastes,” says Ormsby.
He adds, “Wood frogs start breeding often in the middle of February and are the first to start in Missouri, even before the spring peepers.”
A wood frog captured in 2022. Photo courtesy of Matt Ormsby with the Missouri Department of Conservation.
With inconsistent weather of extreme cold and warmth, the frogs seem adapted to the fluctuations. “The frog can freeze, thaw and refreeze multiple times without issues,” he says.
Adding, “wildly fluctuating extreme weather events back-to-back could prevent them from being able to start or end the process quickly enough. As it takes about a day to start and finish the thawing and waking up process.”

Assist the Medical Community

This entire method might seem like science fiction, but scientists are studying these amphibians for medical purposes. With one study focusing on organ donation and how this process could give longer viability to organs before getting to the recipient.
This frog could also help with diabetes, says Ormsby. “When the wood frog starts producing its special glucose, its blood sugar levels go to more than 100% of its normal levels and suffers no ill effects. This is being studied in relation to how to better control or stop diabetes in humans without serious side effects.”
Come mid-February when the first songs of these frogs sound, think about how these amphibians spent their winter, frozen in time.
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Conclusion

The wood frog’s ability to freeze itself during the winter months is a fascinating survival tactic that has evolved over time. This unique process, which involves the production of a special glucose that acts as a natural antifreeze, allows the frog to survive in extreme cold conditions. The study of this process has the potential to assist the medical community in areas such as organ donation and diabetes research.

FAQs

Q: How do wood frogs survive the winter?
A: Wood frogs survive the winter by freezing themselves, using a special glucose that acts as a natural antifreeze to protect their cells from damage.
Q: How long can wood frogs remain frozen?
A: Wood frogs can remain frozen for up to eight months.
Q: What is the purpose of the special glucose produced by the wood frog?
A: The special glucose produced by the wood frog acts as a natural antifreeze, protecting the frog’s cells from damage caused by freezing temperatures.
Q: How do scientists plan to use the study of wood frogs to assist the medical community?
A: Scientists plan to use the study of wood frogs to assist the medical community in areas such as organ donation and diabetes research, by studying the frog’s unique survival tactics and adapting them to human medicine.