by  Dana

Scientifically Speaking:

                    With the onset of winter upon us all, the question of hibernation is one that has frequented our forums and one we think we should address.  This article is designed to present the scientific side of hibernation, pros and cons that come with hibernating your turtle, and a poll which will allow us to  see how the subject of hibernating captive turtles stands with our readers.

                      Hibernation is defined as the passing through winter in a resting state, or becoming inactive for a distinct period of time.  I have read in many articles and publications that "reptiles don't hibernate- they brumate" (they don't undergo the same physiological changes that occur when mammals hibernate).  For reading ease, however, I will continue to refer to it as hibernation.   I know when I think of animals that hibernate, I think of a bear retreating to his cave to nap through the cold winter months.  We know from our basic biology classes that animals that hibernate store up lots of fat reserves so that when the weather gets cold and intolerable, their metabolic rates lower and they are able to sleep through the harsh conditions. 

                    Aquatic turtles, however, are extremely different than our cave-dwelling bears.  They are air-breathing animals, yet they hibernate underwater, and escape the cold weather by burying themselves under the mud at the bottom of ponds.  One reason it is possible for turtles to stay underwater is the fact that water is capable of absorbing and storing huge amounts of heat- so that it cools as slowly as it warms, and there is only a moderate fluctuation in temperature.  Water is at its greatest density at 39F- meaning that it sinks when it reaches that temperature.  At any other temperature, it rises.  So, as long as our turtles stay at the bottom of the pond (deeper than the frost line), the bottom water will always stabilize at 39F.  If the water becomes cooler than that 39F, it will rise.  Therefore, the turtle can never become frozen in ice given they are burrowed below the local frost lines.

                    The properties of water are not the only thing that enables a turtle to stay underwater for the winter season.  Since they are air-breathing animals, the presence of oxygen is key to survival.  The stabilization of the water at 39F helps.  If water was warmer, the turtle would use up too much oxygen; if it was cooler, it would cause the turtles cells to freeze (as they are primarily composed of water) and most certainly kill the little guy.

                    Since the turtle is submerged, its' lungs are unable to breath.  This presents the problem of slow oxygen starvation and a deadly build-up of carbon dioxide.  Amphibians that hibernate (like frogs) have the ability to breath through their skin.  This is not possible for turtles, so they must adapt in a couple of ways.  The first way a turtle can obtain oxygen from the water is through their throat cavity.  Their throat cavity is lined with lots of small blood vessels that allows oxygen to be extracted from the water.  Similar tissue is also present in the thin-walled sacs near their anus and this allows the turtle to take in oxygen through the water.  Since the water at the bottom of the pond is cold, it traps more dissolved oxygen than warm water- assuring enough oxygen to last our hibernating buddy through the long winter. 

                    When it comes to the metabolism of turtles, it is shown that their metabolism is ten times lower than that of a warm-blooded animal of about the same size.  In hibernation, it drops 10-20% of this rate.  A turtle's heart on a warm, sunny day in June beats forty times, whereas it beats ONE time per every TEN MINUTES during hibernation in the winter! 

                    For those who wish to hibernate their turtles, they should do some research on the species the keep to ensure that their species is actually capable of hibernating.  Some people assume that just because they are a reptile, they must hibernate naturally.  For example, some species from the hot regions of Australia and Central America do go into brief hibernation cycles (such as Hydromedusa tectifera, Cheldina longicollis, Elseya novaeguinea, etc).  On the other hand, species like Testudo greaca and Geochelone sulcata do not hibernate, as they are from Africa and are not exposed to drastic temperature changes.  It is imperitive that you do much, much research before considering hibernating your pet.

                    So, now that we have all been educated on exactly what happens to turtles as they hibernate, we should gather some information from other turtle-keepers to see what works for them and what opinions they seem to have. 



    Breeding - There is a higher success rate for reproduction when a turtle has gone through a cycle of hibernation.  This comes as a result that the breeding instincts are enhanced after the turtle comes out of the  hibernation cycle.  Most individuals that breed their turtles often administer medications two weeks prior to hibernation- usually two weeks before the temperature is expected to fall (if they hibernate outdoors) or two weeks prior to manual temperature adjustment if they are to hibernate indoors.  Medications like Baytril (Enroflocaxin) or Cephtazadine are antibiotics that will be able to treat anything and everything the turtle may be carrying to ensure he enters hibernation in a healthy state.  Medication like Injacom (supplying vitamins A, D3, and C) can also be administered.  It is important, however, that this medication not be given too much or too often as high levels of vitamins can be toxic to your turtle.

    Shorter Hibernation Periods - There are psychological and physiological benefits to hibernation.  If you do not wish to hibernate your turtle for the entire winter season, it is possible to 'trick' the turtle's body into thinking it hibernated.  You can start off by giving them shorter 'light' times (turning off their basking lights and overhead lights earlier each night), begin to start restricting food supplies,  and by lowering both air and water temperatures gradually.  Once that is done, you sustain them for a period of time (determined by the keeper) and then gradually begin to raise them.  This will trick the turtle's body in thinking it has gone through a cycle of hibernation, but not to the extent that a full cycle would have.



    Health - As hibernation sets in, the digestion of the turtle comes to a halt, circulation slows down, and the immune system begins to slow down drastically.  Since the immune system begins to shut down, it is easy for disease to develop unchecked.  It is also possible that your turtle- although showing no symptoms prior to hibernation- can be carrying a minor illness which will turn into a very severe and life-threatening problem if he goes into hibernation without our knowing.  For this reason, it is always advised that we should not hibernate sick or injured turtles.  It is also a risk we take when we hibernate - if there aren't visual symptoms that worry us, something that is easily treatable in normal conditions can possible cause death to our shelled friends if we allow them to hibernate.

    Predators - When turtles are allowed to hibernate in outdoor ponds (or when tortoises hibernate outdoors as well) there is the chance of them falling prey to predators.  It is also possible for a hibernating turtle to suffer a parasitic infection during hibernation.  The threat of predators and parasites is a great one as the hibernating turtle is far from being able to fend for himself.  It is imperative that we supply a safe, sterile environment when hibernating our turtles outdoors.