Life in the Cooler
BCG Newsletter
2001
Having started my chelonia interests some 25
years ago with water turtles, box
turtles and tropical tortoises, it was some time before the peculiarly ritualistic
autumn events of boxing up one’s tortoise for the winter came to my attention,
or indeed, required me to take part in the ceremony. I am of course talking
about hibernation. As an ‘outsider’
therefore, I can perhaps cast a fresh insight into an event so steeped in tradition
and dogma that often the reason for hibernation has been completely overlooked
or misunderstood.
All tortoises have survival mechanisms to get them through adverse times
in their life cycle. Essentially, these rough periods will either consist of
cold, heat, and (or) drought. If a
tortoise is too cold, its digestion will not work, and, its ability to move will
be slowed to a painful crawl. This is because nearly all reptiles are
endothermic- they obtain energy from the surrounding heat. Under these
conditions the tortoise will attempt to stabilise its temperature at a such a
level at which energy loss is at a minimum. This usual requires the tortoise to
dig below the topsoil into cool but
frost free soil. Here its internal systems will slow to imperceptible levels. It
becomes comatose- but not asleep as such.
Similarly, under conditions of extreme heat and subsequent
drought, the tortoise behaves in the same fashion, burying itself in the cool to
conserve energy until conditions improve, when it can revive, and continue with
its life. It is this revival stage which is the most critical time, in which the
waiting environment should match the tortoises expectations, and in which
captive husbandry should match conditions in the wild.
The abilities, expectations and capabilities of tortoises to survive the cold
(hibernation), or to endure the heat (aestivation) vary wildly from species to
species, and from one part of a single species’ range to another. The
horsfield’s tortoise for instance, plays both cards- living in burrows to
survive the long fierce Siberian winters, and using these same burrows to avoid
the searing heat of the arid summertime. They emerge in bursts of mild weather,
mornings and evenings, to conduct their frantically compressed lives. In
complete contrast, the Yellow Footed tortoise from Brazil suffers terribly from
drought, and will die overnight if left to experience an autumn chill in the
back garden- they seem to have little ability to hibernate or aestivate
at all.
Our most common captive tortoises have ranges stretching from the South of
France, through to Yugoslavia (T.hermanni), and from the plains of Libya
and Egypt, through to the mountains of Iran and Turkey (T. graeca).
Despite these vast differences in climate, conditions and habitat, the
traditional wisdom for hibernation has been the same for all- place in a box of
straw for 5 months. No wonder that everyone has developed their own recipe for
success in hibernating these species of tortoises. What we must realise is that
for every one tortoise alive in this country today, nine died in their attempt
to survive. The primary cause of death has been hibernation related. The
survivors are here today because of a series of chance factors- genetic (a
little more cold hardened), luck (in a garden with plenty of natural food) or,
amazingly, having their owner select by chance some bizarre method of
hibernation that matched that of their natural habitat and climate. How would
your tortoise fare if hibernated in a warm airing cupboard, being fed only once
in four months (on Christmas Day!)? I know of one such who has done perfectly
well for 20 years with this treatment- clearly by chance a T.g.graeca who is
adapted to aestivate for long periods.
Considering all of this, how was I to proceed with my own plans for tortoise
hibernation. Traditionally, dogma says that tortoises should end up in one of
four places- the garden shed, the garage, under the stairs, or in the loft.
Unlike the home of my childhood, when tortoises were common pets, my
house is double glazed, cavity filled, and centrally heated (there goes the
loft), with open plan stairs (enough said), and a garage turned into a tropical
house (no help there). The garden shed was there, but it was not frost proof,
and early attempts to correct this with lights and thermostats simply did not
work- the temperature fluctuations were severe enough to leave my poor tortoises
confused and exhausted.
Surely technology could provide a solution? The optimum hibernation temperature
has been worked out to be 5 degrees Celsius. Instead of warming tortoises in a
freezing garden, what about cooling them down inside a warm house- by using a
refrigerator! Not sure of the
implications, or the techniques involved, I began some research- looking at
similar existing schemes. It soon became clear that just as with other methods
of hibernation, everyone had their own recommendations on what to use, and what
to do. It became obvious however,
that few had looked into the procedure in any depth. In particular, the use of a
cheap modern ‘fridge was suggested, and indeed used by many, despite the
risks. These risks centered around the operating temperatures of ‘fridges-
which by law need to keep food between 0-4 degrees Celsius. This naturally means
that temperatures outside this range are on the very extremes of the ‘fridges
normal operational boundaries, which for a cheap model, means that its
thermostat is operating outside its design parameters to hold a steady 5 degree
minimum for tortoises. Having spoken to one distraught owner at a Birmingham
health check, whose ‘fridge thermostat stuck ‘open’, freezing to death her
hibernating tortoises, I warily steered clear of that solution.
The very expensive professional ‘fridge is of course another matter. Designed
for catering, they have a more flexible temperature capability, and having seen
one in operation at friends of ours (Ken and Jackie), this seemed the business-
complete with retro-fitted temperature alarms designed to ‘wake the dead’ if
electrical failure lead to freezing (or ‘thawing’) of the tortoises. A visit
to ‘Currys’ however put me off the idea- 500-800 pounds each, these
‘fridges were not an option for us!
Other reptile societies were at that time proud to show off
options they were experimenting with- the drinks chiller cabinet, and we
visited two such in the Birmingham area. With glass doors to view through, the
tortoises literally stacked like coca cola cans within, these seemed the very
essence of 21st century hibernation. The advantage of this type of
cabinet is the fact that they are not designed to go below freezing point, even
on full power- an obvious plus point. The disadvantage was the increased
electrical cost- leaking cold through the glass doors. This seemed however to be
a viable option, provided that the tortoise was insulated against the
temperature fluctuations within the cabinet by providing the usual
box-and-shredded-newspaper for each animal (not always provided in the examples
that we saw).
Back at home, we wondered at the cost of such equipment. Not being whole
societies, with funds at our disposal, but just ordinary members of the BCG, we
had no idea whether we could afford to go along that path. Surveying the wine
cooler in our local pub that night (estimating its capacity in tortoises!), we
read the logo- ‘Whitbread’, a local firm- and decided to write to them,
offering to buy (second hand) one of their coolers. Their reply exceeded our
wildest expectations. Yes, you can have some coolers (we said two), no, you owe
us nothing, BUT, could we use you in some advertising. We of course agreed, and
TV coverage followed, along with national press articles (including the ‘News
of the World’), and even a cartoon in the Independent! The actual firm who provided the coolers (Hereford Coolers)
were even more obliging, not only delivering and installing the Whitbread
logo’d coolers, but they have even provided free maintenance ever since.
Before use, I fitted temperature sensors to the coolers- wired to a laptop,
allowing the range of temperature to be recorded in order to oversee any
fluctuations. In addition, alarm thermometers were added, to give warning of any
equipment failure. The tortoises themselves each enjoy a personal wooden box,
filled with shredded newspaper, and with a loose fitting, perforated lid. The
sliding glass fronts to the cabinets were fitted with a sheet of polystyrene to
reduce the electric bill, and to provide darkness inside.
With every system there are of course drawbacks. A cooler is vulnerable to power
cuts, and to equipment failure. Without adequate ventilation, they can also
produce condensation- all forms of damp must be carefully avoided. This is a
‘cold’ hibernation, not suitable for all tortoises, and certainly to be used
in moderation with new specimens whose history is not known. There is also an
electric bill to pay.
So what are the benefits? The first is that I can select the exact time to
start, and to stop hibernation during the year, giving far greater control over
the tortoises well being. I have the cabinets easy to hand, allowing regular
inspections (removing the polystyrene, I can see if any lids have been
‘popped’, indicating a restless tortoise). Finally, the temperature inside
remains constant, giving a high quality hibernation. This is indicated by very
little weight loss at the end of their time- often just a few grams. Indeed,
sometimes the tortoise actually seems to gain weight in hibernation. I have it
confirmed by other cooler users that this is not just me, but a common
phenomenon. This of course is impossible, unless the tortoises know more about
the use of Einstein’s Theory of Relativity than we do. (conversion of
mass to pure energy requires travelling at light-speed, so perhaps the
opposite is true (energy converted to mass) in our slow moving, hibernating
tortoises!!)
Paul Coleman