Rick Emmer is the lead keeper of The RainForest at Cleveland Metroparks Zoo and an avid observer of amphibians. He provides the following answer.
Frogs are amazing animals. Despite their fragile appearance and inoffensive ways, they have countless strategies to deal with the most severe climates this planet has to offer. They can be found at the Arctic Circle, in deserts, in tropical rain forests and practically everywhere in between. Some of their survival strategies are nothing short of ingenious. Various frog species use two strategies to deal with environmental extremes: hibernation and estivation.
Hibernation is a common response to the cold winter of temperate climates. After an animal finds or makes a living space (hibernaculum) that protects it from winter weather and predators, the animal's metabolism slows dramatically, so it can "sleep away" the winter by utilizing its body's energy stores. When spring weather arrives, the animal "wakes up" and leaves its hibernaculum to get on with the business of feeding and breeding.
Leopard Frog |
Aquatic frogs such as the leopard frog(Rana pipiens) and American bullfrog (Rana catesbeiana) typically hibernate underwater. A common misconception is that they spend the winter the way aquatic turtles do, dug into the mud at the bottom of a pond or stream. In fact, hibernating frogs would suffocate if they dug into the mud for an extended period of time. A hibernating turtle's metabolism slows down so drastically that it can get by on the mud's meager oxygen supply. Hibernating aquatic frogs, however, must be near oxygen-rich water and spend a good portion of the winter just lying on top of the mud or only partially buried. They may even slowly swim around from time to time.
Terrestrial frogs normally hibernate on land. American toads (Bufo americanus) and other frogs that are good diggers burrow deep into the soil, safely below the frost line. Some frogs, such as the wood frog (Rana sylvatica) and the spring peeper (Hyla crucifer), are not adept at digging and instead seek out deep cracks and crevices in logs or rocks, or just dig down as far as they can in the leaf litter. These hibernacula are not as well protected from frigid weather and may freeze, along with their inhabitants.
American Toad |
And yet the frogs do not die. Why? Antifreeze! True enough, ice crystals form in such places as the body cavity and bladder and under the skin, but a high concentration of glucose in the frog's vital organs prevents freezing. A partially frozen frog will stop breathing, and its heart will stop beating. It will appear quite dead. But when the hibernaculum warms up above freezing, the frog's frozen portions will thaw, and its heart and lungs resume activity--there really is such a thing as the living dead!
Estivation is similar to hibernation. It is a dormant state an animal assumes in response to adverse environmental conditions, in this case, the prolonged dry season of certain tropical regions. Several species of frog are known to estivate. Two of the better-known species are the ornate horned frog (Ceratophrys ornata) from South America and the African bullfrog (Pyxicephalus adspersus).
When the dry season starts, these frogs burrow into the soil and become dormant. During the extended dry season, which can last several months, these frogs perform a neat trick: they shed several intact layers of skin, forming a virtually waterproof cocoon that envelopes the entire body, leaving only the nostrils exposed, which allows them to breathe. These herpetological mummies remain in their cocoons for the duration of the dry season. When the rains return, the frogs free themselves of their shrouds and make their way up through the moist soil to the surface.
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16 Comments
Add CommentI found this article to be very helpful in answering my questions about how frogs survive the winter. I have a small bird pond in which I've noticed three small frogs. I don't know if the water is deep enough for them to survive as described. It has a rocky bottom and usually freezes solid in the winter.
Reply | Report Abuse | Link to thisI have the same problem but I have a hard plastic bottom pond.
Reply | Report Abuse | Link to thisWe have a frog (Penelope, if you're interested in her name) that spends every day in a pottery piece up on one of our steel garden tables. Apparently she climbs up every night and spends the day in the pot and then goes out at night for (we assume) food and sex. We are wondering what Penelope will do when our weather gets really cold -- the pot she lives in will follow the air temperature and in the winter here (Nashville, Tn) we think she may freeze. Help! What can we (or you) do for Penelope? Or, should we just leave her alone? Her pot is right near our koi pond but the koi pond has a rubber lining and no mud. Help! Suggestions??
Reply | Report Abuse | Link to thisMy wife and my ages combined, 143, would make one believe that we at least knew a few things about frogs. Well we do now. Great info in a easily read organized form. Thanks because I know that when the spring thaw comes those frogs in our little farm pond will indeed croak again as they they did not croak this winter.
Reply | Report Abuse | Link to thisWe live in Blackfoot, Id. My son found a frog on the snow in Dec. We had had a rather warm week ( about 40 ) and he was in a ditch near our house on a snow drift. We did not know what to do with him so to let my son "Keep" him to turn loose in better spring conditions we put him in our horse water trough that had a heater. About a week later the plug for our heater went out and the trough froze solid ( day time highs where about 10-15 ) The frog lived!! we now have water back in the ditch, and plan to turn Frogie loose when the water trough is low enough to reach in and get him. We took Vidio and have shared with my son's second grade class.
Reply | Report Abuse | Link to thisI have 2 American bullfrogs that I am trying to keep thru the winter. My little pond is not very deep (maybe 10") and has no mud at the bottom. The pond has been known to freeze completely into a chunk of ice during extremely cold temps. Do I need to remove the frogs into something deeper that doesn't freeze completely, or put mud in there?
Reply | Report Abuse | Link to thisAre you saying that the frog froze solid in the horse trough? My pond is about 9" deep and does freeze in the winter, I move my fish to a tub indoors (garage). I would like not to have frogs hopping around in the garage. If they don't hibernate, do they have to eat or are they like fish and turtles who do not eat when weather is cold? Should I put them in a
Reply | Report Abuse | Link to thistool shed in a tub? Can they figure it out if I leave them in the pond?
Thanks this helped me with part of my research paper :)
Reply | Report Abuse | Link to thisThanks this helped me with part of my research paper :)
Reply | Report Abuse | Link to thisI found this very useful. We found a very lethargic frog on the side of an ice-bound creek while out on our New Year's Day Paddle on the Sassafras River, Maryland. Here is a picture http://picasaweb.google.com/ralph.heimlich/NewYearSDayPaddle2010#5422158943754167218
Reply | Report Abuse | Link to thisI have three frogs on the bottom of my pond are they dead or just hibernating
Reply | Report Abuse | Link to thisWe live in the UK, we have had our worse winter for years. our garden pond froze over, ice about 2" thick for months. Today I went to check and clean the pond, and amazingly, there is at least one frog and a HUGE amount of frogs bourne. Amazing!!
Reply | Report Abuse | Link to thisi have a one and half foot deep pond, what might happen to my 4 pet frogs during the winter am i best to bring them in and put them in an aquarium. HELP!
Reply | Report Abuse | Link to thisI'm very interested in TnE's comments because my two adult bullfrogs live in an above ground pond I created using a 150 gallon Rubbermade farm animal drinking trough. I'm trying to find a heater that will keep the water from freezing and need to know what kind of heater to purchase. If anyone can help me please respond. I live in the Nashville, TN area which doesn't get nearly as cold as Idaho. You can even email me at mbshanley@msn.com. I want to keep my two frogs comfy during the winter. Already, with the recent cold snap, their staying underwater and won't eat. I hand feed them grasshoppers in a can. HELP!! Anyone...
Reply | Report Abuse | Link to thisI have two bullfrogs living in an above ground pond. The pond is actually a 150 gal Rubbermade large farm animal drinking trough. I am searching for a means of keeping the water relatively warm and prevent it from freezing. I live in the Nashville, TN area so the temperatures, although in the teens at times, doesn't get as consistently cold as the northern states. In searching for submergible heaters, I can only find deicers. Any suggestions?
Reply | Report Abuse | Link to thisThanks for a great article. I live in the mojave desert and a toad has appeared in our yard. At a 3000 foot elevation our winters can get very cold at times. I was worried about it freezing this winter and had told my husband I was going to buy an aquarium and bring it in. We found this article while doing a web search on frog/toad care. Now I know I don't need to worry about it and will just enjoy watching it. Thanks again.
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