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 39ºF- 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 39ºF. If the water becomes cooler
than that 39ºF, 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 39ºF 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.
- 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.
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.
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.
- 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.