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HIBERNATION GUIDELINES - Paula Morris
Copyright © 2003 World Chelonian Trust. All rights reserved
Hibernation is nature's mechanism to protect its cold-blooded creatures (and some warm-blooded animals as well) in cold weather or when food and water are scarce.
Dormancy also seems to affect the reproductive cycles of chelonian species, whether non-tropical or tropical, and zoos often provide a "cooling period" to stimulate breeding activity when temperatures normalize. To keep the information general, I'm dividing turtles and tortoises into only two categories: non-tropical (those species that do hibernate), and tropical (those species that do not).
Turtles and tortoises can hibernate up to a full eight months of the year, depending upon latitudinal location. The rule-of-thumb to guide you on your research should be: The farther from the equator the species occurs naturally, the more likely it is to hibernate; the closer to the equator, the less likely.
WHICH SPECIES NEED HIBERNATION OR A PERIOD OF DORMANCY?
A Horsfields tortoise (Testudo horsfieldii) in Kazakhstan can stay underground for all but three months of the year, although it's not necessarily hibernating the entire period; it emerges only to drink when it rains and vegetation becomes available, then digs back into the soil to a depth where the temperature is stable and the humidity level comfortable. In a like manner, some turtle and tortoise species will do the same thing during periods of drought.
Whether as a response to extreme cold or extreme heat, a turtle or tortoise is going to try to create for itself a "microclimate" when it digs into the soil. 80% soil humidity seems to be the norm. Soil humidityNOT to be confused with the rain-soaked soil of our California winters--is a critical factor in their ability to survive in the wild. But in captivity you're taking a chance allowing your animals to hibernate in the back yard. A combination of wet and cold will kill a digging or burrowing chelonian, even though our California winters are temperate by the nation's standards.
Some commonly kept species that will try to hibernate are the Desert tortoises (Gopherus); the Russian tortoise (T. horsfieldii); the Box turtles; the Wood turtles (Clemmys insculpta); the Spotted turtles (Clemmys guttata); the Snapping turtles (illegal/protected in several states, by the way); and Red-eared sliders (Trachemys scripta elegans).
You must be able to determine which of your animals needs to hibernate. Your local club or any number of sources on the internet can help you. Joining a forum dedicated to the species you keep is also a great way to learn what's working for others.
Tropical species like Refoots (Geochelone carbonaria), Yellowfoots (Geochelone denticulata), Elongatas (Indotestudo elongata), South American Wood turtles (Rhinoclemmys), and the African species don't hibernate, but can slow down for a period of time when the weather cools and the daylight shortens. In non-tropical climes they need to be kept artificially warm and/or humid indoors. A humidity gauge in the terrarium will help you keep track of their comfort.
Arid-dwelling, non-hibernating species like Egyptian tortoises (Testudo kleinmanni), Radiated tortoises (Geochelone radiata), Pancake tortoises (Malacochersus tornieri), Sulcata (Geochelone sulcata), and Leopards (Geochelone pardalis), to name a few, must also be sheltered from wet and cold and are particularly vulnerable to respiratory trouble and infection when damp. They must never be left outside. But even these species have a humidity requirement, albeit not as high as the tropical species. You will have to set up "microclimates" for them that will offset the dryness caused by indoor heating. This can be accomplished by having ready access to water for drinking, soaking and voiding, plus a dry area where there is heat and shelter. A good humidity gauge and a thermometer are valuable tools, no matter what species you're keeping.
As a keeper you are responsible for determining the geographic range of the species you have, and whether your animal should hibernate. You must make provisions based on locale and climate for its safe sleep or period of dormancy. But if you have recently acquired an animal, have one that is ill or recovering, or a hatchling that is under three years old, do not hibernate them; this group is highly vulnerable to dying if allowed to hibernate.
Any species that is being kept in a climate not endemic to its evolution (which applies to the majority of captive animals) is going to require research on your part. You have some careful decisions to make based on the species, its health and weight, its age, and its known history.
Examination by either you, a qualified vet, or an experienced keeper is mandatory. If there's any discharge from either the nose, mouth, eyes or cloaca you may have to overwinter the animal and put it on a regimen of antibiotic treatment; respiratory distress is fatal in hibernation. Wounds or lesions or any shell rot must also be treated until healed prior to hibernation.
If the animal is light for its size or hasn't been eating well and hasn't adequate fat reserves to see it through the months of hibernation, it must be kept awake or fed up to sufficient weight. You can then allow it a shorter sleep period, usually several weeks, in a place where you can monitor its well-being. The immune system isn't effective in hibernation and a sleeping animal has no resistance to infection, either internal or external.
If the animal has eyes that appear sunken (enothalmic), it's a sign of major dehydration or a physical problem that has reduced blood volume or fluid in the cells. A healthy well-hydrated chelonian has bright, clear eyes, and plump and supple limbs and tail.
Be sure to feed foods during the summer that contain a lot of vitamin A. Vitamin A especially becomes depleted during hibernation; it's stored in the body tissues, fat and liver, and the animal draws upon it while asleep. Offer carbohydrate-containing foods such as grated carrots, squash, alfalfa, apples and peaches to your omnivores (the fruit is all right for turtles, but not for tortoises); all contain vitamin A. Encourage your herbivores (tortoises) to eat some carrots and squash, plus the drier high-fiber weeds, grasses, timothy hay and alfalfa towards summer's end. Alfalfa contains more protein than timothy hay or orchard grass, so the latter are preferable, although alfalfa can be mixed into the forage in small amounts. In the wild an herbivorous tortoise will have fed upon vegetation dried by the summer heat; this mass will "swab out" the intestines prior to hibernation.
Turtles and tortoises usually instinctively stop eating on their own prior to hibernation, but it's best if you regulate food availability. The Practical Encyclopedia of Keeping and Breeding Tortoises and Freshwater Turtles draws a correlation between the size of the animal and its metabolic rate (determined by temperature) and the amount of time it takes to start winding down to hibernation through fasting. A larger animal may require up to three weeks to clean out its system while a box turtle or a Horsfields tortoise may need only two weeks. Dr. James Jarchow believes that a bit of grass ingested prior to hibernation isn't harmful, but large of amounts of food are. Omnivorous species like turtles must be kept from feeding at least two weeks prior to being put into hibernation to avoid food decomposing in the upper part of the digestive system; tympanic gas will form and suffocate the sleeping turtle. Fruit whose sugars ferment are particularly dangerous.
Aquatic turtles can hibernate outdoors as long as the water in their habitat doesnt freeze solidly. The turtle will seek cover in the bottom of its pond and reduce its oxygen requirement by reducing its body processes, taking in oxygen through the mucous membranes of its throat and cloaca. In captivity an aquatic can hibernate comfortably in a minimum of 18 inches of water so the temperature doesn't fluctuate and cause a total freeze. Savvy keepers in colder parts of the country keep a small floating pond heater active to prevent their ponds from freezing. If your pond is shallow and your turtle has no way to protect itself at a stable hibernating temperature, set up an indoor aquarium and enjoy the winter together.
EXOTIC AND TROPICAL SPECIES
Unlike species in colder climates, tropical species experience a period of inactivity associated with the dry season. This torpor ends with the arrival of the rainy season. You can encourage this period of inactivity indoors by reducing the light intensity and feeding less frequently. This period lasts about six weeks and can stimulate breeding behavior following a return to normal light levels and accelerated feeding schedule. Internet searches on climate should yield the dry-season information for particular exotic species. You can also search by "Geography and climate of Xxxxx"--just type in the country. Some sites not only show charts of annual rainfall, but temperature as well. This is very useful when printed out for reference.
HIBERNATING TERRESTRIALS AND SEMI-AQUATICS INDOORS AND OUT
Freezing and drowning are the two biggest hazards faced by captive terrestrial and semi-terrestrial turtles and tortoises hibernating outdoors, so keepers often provide containers in which their animals can spend the winters indoors. A box-within-a-box that is filled with wadded or shredded newspaper provides insulation and darkness. Place the box in a little-used room, closet, a shed or a garage and keep a thermometer on the box. Check it frequently, especially if there are external weather changes.
Hibernating species can tolerate a temperature between 39°F and 50°F (3.8°C and 10°C) when artificially hibernated. A temperature above 50°F may precipitate torpor, not a true hibernation, and your turtle or tortoise may use up precious fat reserves with its raised metabolism. If that happens and too much fat has been expended, you'll have to take the turtle or tortoise out of its hibernation container and allow it to gradually come up to a warmer temperature. The animal must then be fed and maintained at non-hibernating temperatures. One way to tell your tortoise isn't truly hibernating is if it is active in its hibernation box or if you find it has urinated . Remove him and hydrate him and move the box to a cooler, protected spot. Provide fresh, dry substrate and monitor him to be sure he will sleep.
It's critical to weigh your turtle or tortoise prior to hibernation and chart its weight throughout the hibernation period. Invest in a digital scale for weighing the smaller species (under 6 lbs.) for best accuracy. Based upon the size-to-weight ratio, your vet or another keeper can tell you if hibernation is safe. During hibernation your frequent checks can be used as a time to gently weigh your tortoise. An excellent rule-of-thumb is that a tortoise or turtle should lose only 1% of its body weight per month of hibernation. For example, a 400 gram tortoise should not lose more than 4g per month. Multiply the animal's weight in grams by 0.01: 0.01 X 400 = 4.0 grams. Chart it on a piece of paper you keep taped close to the hibernaculum/container as a guide for next year's hibernation.
Wild tortoises and turtles will select a burrow that has slightly humid soil or leaf litter to decease evaporative water loss through the skin and lungs. Captives that are being hibernated in unnatural conditions indoors risk dehydration due to low humidity. However, because they're poikilotherms, they mustn't be allowed to become wet and chilled, either; they won't be able to dry off. Check the skin condition of animals spending the winter sleeping indoors. If the skin is drier than usual or the animal has lost too much body mass in that period, wake it and soak it in shallow (below the bridge), room-temperature water for two hours to regain lost fluid. Dry it thoroughly (but do not warm it!) and return it to its box. Younger tortoises and turtles (hatchlings and juveniles) should have this done for them every three weeks if necessary.
Body water partitioning in hibernating turtles and tortoises changes in the fall, allowing them to store more water in winter than in summer, so hydration is critical to a successful hibernation. If your hibernating turtle or tortoise voids its water stores (you find the substrate is wet), you absolutely must bring it out for rehydration in shallow water as previously explained.
If your animal is used to hibernating outdoors, make sure it has access to drinking water at all times, but don't let it hibernate where rain can drown it or wet it to the point it gets chilled. Check the hibernation spot frequently. If you see a turtle or tortoise out trying to bask on a rainy or cloudy day, it's indicative that something's wrong with the hibernation process. Bring the animal indoors for an examination to determine whether hibernation should be allowed to continue. Better to be safe than sorry!
Intimidated? You should be. Attention to detail makes the difference a successful hibernation and one that harms your animal. But you've got several good tools with which to work: a scale, a thermometer, a humidity gaugeand resources like your club and the internet.
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