'Hibernation' at various temperatures

[Anita Sayles]

Well I'm going to overwinter this year (spur thighed tort, 18 months old) and for the last 6 weeks I have introduced 1 day a week no feeding and no UVB. And for the last 2 weeks I have increased this to 2 days.
Marley still wakes up and is active.
He moves around the table all day, but is not on a mission looking for food, he is slower and calmer. He always has fresh water and still drinks on the non feeding days.
His weight gain has slowed during this time.
There are cooler/rainy/overcast days in their natural habitat and they don't do much at all, and I think with a long winter on a tort table it is better to contol conditions rather than have a really active tort and have to limit food.
Just my thoughts

[romski]

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Originally Posted by Bindi

Strictly speaking they're not hibernating at all, they are brumating


Taken from Wiki

Brumation
Dormancy in reptiles is an example of brumation, which is similar to hibernation.[2][3] It differs from hibernation in the metabolic processes involved.[4]
Reptiles generally begin brumation in late fall (more specific times depend on the species). They will often wake up to drink water and return to "sleep". They can go months without food. Reptiles may want to eat more than usual before the brumation time but will eat less or refuse food as the temperature drops. However, they do need to drink water. The brumation period is anywhere from one to eight months depending on the air temperature and the size, age, and health of the reptile. During the first year of life, many small reptiles do not fully brumate, but rather slow down and eat less often. Brumation should not be confused with hibernation; when mammals hibernate, they are actually asleep; when reptiles brumate, they are less active, and their metabolism slows down so they just do not need to eat as often. Reptiles can often go through the whole winter without eating. Brumation is triggered by cold weather, lack of heat, and the decrease in the amount of hours of daylight in the winter.

Please forgive me jumping into your thread but I have come across this and find it interesting and would like to add to it.

Whilst I am a long term Chelonia keeper and have kept and hibernated tortoises in wild condition in USA I am mostly a turtle keeper and I write from that perspective.


Ernst and Lovich - Turtles of the United States and Canada second edition refers to winter dormancy as hibernation for both tortoises and turtles. Donald C.Jackson also uses the term hibernation in his many papers and also in his recent book "Life in a Shell" which is much recommended to all.


The Wiki extract quoted is correct but the section on brumation cites the Bearded Dragon as an example. The example does however have its limitations and does not consider other forms of reptile life such as turtles and the crocodilians.


A few of us are trying to get a consensus on this subject and I offer this as a working definition.

Cooling
The temperature is reduced for a period, usually co-incident with winter.
The animal reduces activity and feeding may cease, but it does not necessarily go into an extended, torpid state
Brumation
The animal becomes torpid for a period which may last weeks and is often co-incident with winter.
Hibernation
The animal undertakes preparation and goes in to a torpid state for an extended period - duration in months.
Physiological changes occur within the animal.
Co-incident with winter and seen mostly in animals of northerly latitudes..
Aestivation
The animal becomes torpid for a period of days or weeks. Co-incident with hotter weather.


I agree that temperate or Mediterranean climate tortoises in their winter conditions seem to go into a brumation state but Ill come back to this.

Torts and turtles have a liver that forms about 4% of body mass, this, bodily fluids and their muscles store huge quantities of glycogen which is used as an energy reserve for the winter. It's commonly thought that fat is the energy store but fat cannot be metabolised without oxygen.

A recent paper has shown that with lower temperatures less energy is consumed thus less glycogen is used and less oxygen is required. There is a significant difference of energy usage between 10c and 3c of at least 20%. This will be true for tortoises also. Turtles deliberately seek out the colder water to reduce their metabolic rate and hence oxygen and glycogen use. This is particularly important for the pond dwellers, it will be remembered that up north winters can last many months so any energy saved can be reserved for the first days of spring. In addition in anoxic conditions glycogen is used significantly faster so lactic acid is produced faster. These animals actively seek out the coldest water with the highest oxygen content for overwintering. Stories are often told about turtles moving about under the ice, now we have a reason.

In order to survive this, the animals have developed particular strategies that require physiological changes. Many turtles, in particular the northern pond turtles, have the ability to utilise the calcium carbonate (CaCo3) within the shell. Their shell is about 40% of body mass and its calcium is used to buffer the lactic acid in the blood and raise the pH thus reducing the effect of acidosis. In addition the shell can sequester some of the acid and store it for disposal when oxygen becomes available again after the winter thaw.

The build up of lactic acid can take days or weeks depending on the temperature and the level of anoxia in the water (caused by iced up ponds). The lactic acid in the blood and in the shell can take equally long to dispose of once conditions are better in spring. The calcium used must also be replaced so for females about to produce eggs this is a particularly hard time.

Turtles also have the ability to manage the flow of blood to the lungs once oxygen is depleted and they have become anoxic.

The above points illustrate the fact that these animals go through physiological changes and are therefore hibernating in the full sense of the meaning.

I also keep my turtles in naturalistic conditions in the UK and despite them being in hibernation mode I still see them moving about seeking optimal conditions. This weirdly gets us back to the proposition made by Caledonia originally and drawing me to conclude that hibernation as defined is valid but in some species there is a geographical or season driven overlap with the state of brumation. Such animals would be the Painted Turtle, the Spotted Turtle and the Snapper, all of which will not need to hibernate in the southern states.

That brings us back to the tortoises. My G.Aggassizii when they hibernated dug themselves in and did not move about, what's more they seemed covered in dirt. My T.Graeca also hibernate themselves deep into the soil where they stay for months. My box turtles do likewise and as it gets colder they do move downwards in the soil.

So here's my question; if they are covered in soil where the heck do they get their oxygen from? Do they use glycogen in the same way as the pond turtles and buffer any resulting lactic acid with calcium carbonate from their shell?

If we artificially "hibernate" them under human control are we forcing them into a brumation state where in real life they would be hibernating?

As was stated by Bindi and with the same sentiment please correct or add or inform if you have more info.

Rom

[Ozric Jonathan]

Thats really interesting Rom. We have often discussed how mediterranean tortoises in natural conditions dig down quite far into the soil and are covered over in such a way as there must be hardly any air.

Many keepers say that their tortoises dig down deeper when it gets colder and in this way access soil which is less cold than the soil exposed to the air in a hard winter.

I'm not totally clear on the differences between hibernation and brumation but thats not a criticism of your definitions.

[Kirkie]

I read this article last year on the cellular changes that occur in T.Graeca before, during and after hibernation. It includes a reconfiguration of the cellular oxygen requirement during hibernation.

http://www.tandfonline.com/doi/abs/1...50008709355603

[Geomyda]

as Romski has recommended, I too would commend the reading of Life in a shell, by Donald C Jackson. Furthermore, wouldn't it be great if one of the National Chelonia Groups or Herpetological societies were able to get Prof Jackson, to present a lecture here in the UK?
Perhaps, on the physiology of Chelonia. The topic has great interest and in particular, the adaption of these Vertebrate forms to the natural process of hibernation.

[romski]

Whilst there seems to have been loads of work done on hibernating turts in the winters of USA (funding availability), there does not seem to have been the same level of investigation on temperate terestrial tortoises. As I scratch the surface of this I get to think that we still know bugger all about torts.

We in the hobby have, over time, developed hibernation strategies that work. We are still refining them with the use of refrigerators for example as we have learned that animals hibernated thus lose less weight (=less glycogen usage at colder temps)

The wider use of the web has meant that the hobbyist now has access to the work done by scientists and we can start adding to their knowledge to paint a better and more informed husbandry picture.

I think we are now moving from having knowledge of what works in order to hibernate these creatures to an understaning of why it works -and thats a good thing.

Kirkie do you have a copy of the paper? The implication is that physical changes occur along similar lines that have been described by Jackson for turts.

Another question; if they do have a capability for dealing with lack of oxygen, have a heart beat that slows to a beat a minute and bugger all matabolic rate then why open the fridge door every day?


Rom

[Alan1]

Surely they will get their oxygen underground in the same way plants do? All the plants that die off in winter above ground but their roots under ground are still alive must be getting oxygen from the soil?

[Kirkie]

Hi Rom,

The link in my post above will take you to the study (a .PDF download is available from the link)

http://www.tandfonline.com/doi/abs/1...50008709355603

I can only assume that opening the fridge door regularly is akin to refreshing the air in an incubator. The release of CO2 buildup in a closed system though I see your point that very little is probably being produced. Perhaps it errs on the side of caution. I suppose we see "underground" as a claustrophobic environment but there must be airflow and oxygen replacement taking place.

My own tortoises and box turtles bury deeply into soil to hibernate but it's not a closed system. An experiment that a dispassionate mind like Donald Jackson would relish (not a critisim of him, it needs the detatchment to get the results).

On the "weight loss" in hibernation aspect, I've put this down to dehydration rather than "fat" or indeed glycogen use. Over the past few years I've modified the environment my tortoises hibernate it (a gradual drop down to hibernation temperatures, allowing the animals to dig into deep soil) and I now see very little change in body weight post hibernation. I'd assumed the cocooning in soil prevented a degree of fluid loss (the fabled 10% acceptable weight loss of the box/fridge method). I know other who allow their tortoises to dig into the substrate of greenhouses have recorded the same thing, no weight loss.

[Kirkie]

I think the most interesting point is that the gradual lowering of the oxygen requirement is cued by peak high summer temperatures and continues even if the tortoise is not then presented with winter conditions. It appears to be unconnected to low temperature or day length/light levels.

[Alan1]

Many people refer to torts as hibernating but I am not convinced that they do simply because I've read so many differing articles on it. It has been referred to as hibernation, brumation and dormancy. My Koi carp used to 'hibernate' apparently but my other outdoor fish were described as just slowing down for winter. I have read lots of stuff on what hibernation actually means, some that only mammals truly hibernate, some that they are not truly hibernating if they move around and come out to eat on warmer days (as torts do) and some that animals are simply going through a period of dormancy.

There are plenty articles like this one below and plenty that claim that this isn't the case too.

Reptilian Brumation

Most readers are likely aware of the fact that all reptiles and amphibians are ectothermic (cold-blooded) animals, relying on their environment for thermoregulation. That said, these animals have evolved and adapted incredible survival strategies to ensure survival when environmental conditions become unsatisfactory. One such adaptation is brumation. Brumation is a term used for the hibernation-like state that cold-blooded animals utilize during very cold weather.

On the other end of the spectrum is a state known as aestivation, which like brumation, provides a way for reptiles to handle temperature extremes. However, aestivation occurs when environmental temperatures become too high for healthy physiological function to occur, and thus is beyond the scope of this article.

What is Brumation?

As previously mentioned, brumation can be loosely equated to hibernation among mammals. When a reptile brumates, it becomes lethargic, sometimes not moving at all for the duration of the cold season. In nature, these animals typically find hibernaculums within their environment in which they can be somewhat insulated. A hibernaculum is simply the place where the reptile spends these periods of inclement weather. Burrows, rock crevices, caves and leaf litter are a few examples of hibernaculums documented in nature. Some temperate species can even brumate under water!

The amount of time that a reptile brumates is dependant on a number of factors. Perhaps the biggest variable is in regards to whether the animal is in the wild or being maintained in captivity. In the case of the latter, environmental conditions can be easily manipulated by the keeper at any given time. Other considerations include the age of the animal, its gender, geographical origin, and varying natural conditions. Due to the wide range of species and habits, it is futile to make quantitative generalizations regarding how long a reptile will brumate. In the broadest of terms, reptiles will enter brumation in the late fall (when temperatures drop and the days get shorter) and come out of brumation in spring, triggered by increased temperatures, longer days, and changes in barometric pressure.

Why do Reptiles Brumate?

As ectothermic organisms, reptiles cannot raise their body temperature independently of environmental conditions, and as such must contend with the conditions that nature presents them with. The vast majority of our planet experiences seasonal temperature extremes, from the deserts to the plains to even the tropics. The amount of temperature variation does change from region to region. For example, sub-tropical animals, as well as those found near the equator, often do not undergo what herpeteculturists call a "true brumation." However, these animals are just as receptive to natures cues as those from more northern or southern climates. They may slow down, i.e. reduce food intake, eat less, etc, but not enter a true state of brumation.

Conversely, many reptile species inhabit regions that do in fact get very cold in the winter, and accordingly must have behavioral adaptations in order to survive. In the most basic sense, brumation is a survival tactic. A tactic that has been hard wired into the brains of these animals for well over a million years.

Take for example, the Russian tortoise (Testudo horsfieldi). Over much of their range they experience summer highs well over 100 degrees Fahrenheit, and in the winter temperatures fall far below freezing. Without the option of brumation, these animals would perish. Instead, they construct burrows, sometimes as deep as six feet, and remain in them until conditions become favorable. During this time, the tortoises physiological functions grind to nearly a halt. Feeding obviously ceases, as does digestion and defecation. Heart and respiratory rates also drop.

Suspended animation is a phrase often used to describe this state among reptiles. In fact, there are theories suggesting that these long periods of inactivity may actually lengthen the lives of wild herps much the way your car would last you longer if you kept it garaged and purged of all fluids for 5 months of the year.

Reproductive Connotations

Aside form serving as a survival tactic during seasonal weather fluctuations, brumation (and winter slowing in general) does have an affect on reptile reproduction. Please keep in mind that there are exceptions, but in general, cooler temperatures trigger the production of sperm in males, and prepares females fro ovulation in spring.

Despite this widely accepted theory, many breeders have found that only slight drops in temperature are needed to trigger this reproductive behavior, while others have found to be completely unnecessary. Renowned monitor breeder Frank Retes is well known for his successful captive breeding attempts with a number of Australian, Indonesian, and African monitor species. He is equally well known within the monitor keeping circle for his unique methodology. His monitors are kept warm year round. His motto, "Heat them, feed them, breed them" has proven quite successful. In fact, in an interview in The Vivarium Magazine in the mid 90s he shared that his monitors also have light 24 hours a day.

This radical approach to breeding may seem outlandish, but experimental techniques such as those of Mr. Retes have allowed us to better understand reptiles in captivity. It remains clear that a short period of slight reduction in temperature and/or photoperiod can be vital in triggering reptiles to reproduce, but not always completely necessary.

In my experience, and in the experience of many of my colleagues and fiends, true brumation does not seem to be a requirement in maintaining healthy, reproductively active reptiles. Generally a brief, slight change in conditions (as mentioned above) is all that is needed. Furthermore, in most American homes, this requires little work on the part of the keeper, as seasonal fluctuations and physiological cues will occur regardless of husbandry.

This is not to say that allowing temperate herps to brumate at cooler temperatures for longer periods of time is harmful if done properly. In some species, males that have been cooled are much more fertile than those which were not, and therefore more likely to produce viable clutches with a similarly cycled female.

Brumation in Nature

In the wild, reptiles are presented with both internal and external cues that it is time to brumate. Herpetologists have classified these cues into two main categories. The first are endogenous cues, which originate within the animal. Theories regarding endogenous cues suggest that some reptiles (but certainly not all) undergo hormonal changes as well as shifts in neurotransmitter levels and amino acid concentrations. These factors are directly affected by circadian rhythms and the environment, making these biological cues little more than a secondary function of natural climatic changes. The question remains as to whether these internal changes occur spontaneously and trigger brumation, or if the animal begins to brumate and then these physiological changes occur.

It should be made clear that the role of endogenous cues in reptilian brumation is still poorly understood. Exogenous cues on the other hand are those with which we are already familiar and include factors such as photoperiod (day length), barometric pressure, humidity, and temperature. Exogenous cues seem to be of most importance to herps inhabiting temperate zones. Sub-tropical herps, because of the relatively constant conditions they experience, appear to rely more on internal (endogenous) cues.

Brumation is an extremely trying time for all reptile species. As we have discussed, it is a survival tactic at which many species are quite proficient. Nonetheless, many wild reptiles that enter brumation never emerge in the spring. Sometimes the choice of hibernaculum is a poor one, and when conditions become extremely harsh these areas simply do not provide adequate protection. Other times, reptiles may enetr brumation with an injury of illness which would normally require supplemental warmth and nutrition to heal properly. In the brumative state these animals tend to succumb to their ailments.

continued next post...