Sleeping Beauty Awakens

From approximately mid-November to the beginning of February, my tegu displayed signs of slowed activity. As this is my first winter period with her, I do not believe I allowed her to achieve full hibernation, and now have been doing more extensive research regarding tegu hibernation. This topic is something I researched prior to bringing my tegu home, though it was daunting and, honestly, got pushed aside to topics I found more preceding.

There is significant debate on the importance of hibernation with overall tegu health, longevity, and fertility. While research pertaining specifically to tegus is limited, hibernation is still a very important aspect of tegu care where every tegu owner should be learned, whether they chose to participate in yearly hibernation or not. In my research, I have also found large debate on whether the correct term for tegus is brumation or hibernation. With the articles I have read, my opinion is that hibernation more closely describes the behavior observed in tegus when going into a state of slowed metabolism and dormancy.

Here is an article that debates the difference between brumation and hibernation, and the opinions of other tegu owners, researchers, and breeders regarding the vocabulary:

Difference between brumation and hiberbation

Tegus often go through a period of hibernation ranging from a few months to several. By manipulating a captive tegus environment, as well as providing means for tegus to "cool" themselves off, hibernation can be achieved. Although there are claims that breeding can occurred without hibernation of a tegu, it is recommended to hibernate your tegu prior to breeding if you desire successful results. Many tegus will go into a state of hibernation without intentional manipulation done by the owner, most likely due to other subtle external causes. Hibernation can be dangerous, and there are theoretical methods of preventing hibernation, although I am not promoting this as I personally am not knowledgable enough to determine the long-term effects of skipping hibernation periods. If this is something you intend to do, research thoroughly; be aware that any external factors can push your tegu towards hibernation, and it is not recommended to wake your tegu once in hibernation.

"As for stopping/preventing them from hibernation, well, it seems relatively simple if you have the means. Remove all external environmental cues, maintain a steady artificial environment, and they don't hibernate. The caveat is in removing all external environmental cues. A simple window to the real world will tell them it is time to hibernate and they likely will." -- tupinambis

If a tegu begins showing signs of reduced activity, staying burrowed for longer periods of time, and reduced appetite, the tegu may be preparing for hibernation. **Please understand this could also be symptoms of illness, so do not assume it is hibernation.** While there are many facets of research pertaining to hibernation, there are a few topics that every tegu owner should be aware of. There are preparations that should be made prior to hibernation in order to ensure the safety of your tegu.

1) Tegus should be properly "fasted" prior to hibernation. The recommended period of fasting varies between different people, although a generally accepted minimum is a week -- some recommend up to a month fasting period or longer (depending on the size of the tegu). There has been debate on whether fasting is required, and if a hibernating tegu with food still in the digestive tract is harmful. Here is a post by Tupinambis regarding the subject; most hibernation posts I link will be from him, as this is his main area of study:

Unfortunately, I know first hand that these breeders don't know what they are talking about. Yes, you can feed your tegu during hibernation and yes, there may not be a problem. However, this is the same logic that for those people who smoke and didn't get lung cancer, that it is then fine for everyone to smoke and no one will get lung cancer. It's an exception and it also probably does not take all aspects and details into account. 

In nature, as the winter or dormant period approaches, tegus start eating less and less and voluntarily undergo aphagia (stop eating). This period of "eating less" is substantial. It isn't the week before, it isn't a couple weeks before. At my study site, hibernation usually was in full swing ("started" for lack of a better descriptor) by the month of May (remember, this was in the southern hemisphere and so their winter was mid-year). The voluntary reduction in food intake (not forced by me, they chose this themselves) started in February. Food was available, they just wouldn't eat it. Now, this doesn't give us any indication of why they were doing this, or ramifications that could happen if they were continuously eating before entering hibernation, but this does strongly contradict what most people like to believe in in that hibernating animals gorge themselves before entering hibernation and it also shows that upon entering hibernation, their digestive tracts are likely void (empty). 

Now, in lab studies where we did things a little differently, there is more conclusive evidence. There was one experiment wherein the animals were kept under steady/constant conditions (lights and high temps during day, dark slightly cooler nights), feeding regularly (about every other day, large regular quantities). When then put into "hibernation" simulating conditions, cooling temps, no food, no light, with little change over period (about 2 weeks), the results were disasterous. Not soon after, and admittedly under this regimine they were not given the ability to thermoregulate or bask as they naturally might (the idea was to force hibernation, not give them a choice between hibernating or not), but after a couple of months we had catastrophic die-offs. Suddenly, within a couple of days of each other, about half our study colony died (roughly 20 animals out of 40 died). Admittedly, I did not get a professional necropsy done to be absolutely sure what was the accurate cause of death, but upon post-mortem dissection by myself, all the dead tegus had the exact same condition. All their tissues appeared fine and healthy, except for the digestive tracts. The digestive tracts showed hemoraging, what looked liked localized septicemia, occassional bloating, and necrosis. Again, admittedly, I didn't get pathogen work done or anything like that, so I cannot say with 100% accuracy what had happened. The remaining animals were "rescued" by resumption of regular temperatures, hydration (both injected and oral), flushing the digestive system with mild laxative, and daily "deep" enemas to flush out as much as possible. I recall a number of the animals I had thought were gravid because I could feel small, hardened ovoid objects by palpitation of their abdomen. Upon flushing out, these were discovered to be masses of undigested matter. Now, again I stress I cannot say with 100% certainty exactly what occured here, what actually killed the tegus, but this evidence is pretty strongly pointing in one direction. 

Later studies in the lab simulating hibernation (long term, that is) were only successful if the tegus had reduced temperatures, reduced or eliminated photoperiod, and the animals were fasted for several weeks prior to inducement.
Now, I will admit, under a different regime, where tegus can bask and warm up daily if need be, with reduced food intake, etc., that it is likely a tegu can eat during hibernation and not develop complications. However, from what I have seen, I would say doing so while not being entirely sure of proper conditions is extremely risky. As shown above, even under the most strenuous conditions the rate of lethality was only about 50%, but I'll also say the surviving 50% were NOT the picture of health. From other studies done, I know tegus can easily withstand several months of not eating as long as water is available. Taking all these actual scientifically determined facts together, many of them seen first hand by myself, my recommendation is to not feed during hibernation. 

Conversely, most of the time I've been given a "fact" by a breeder, I've learned those "facts" were not so, and instead merely assumptions. Some other "facts" I've seen presented by breeders of tegus: if tegus don't hibernate they become sterile because their gonads stretch; tegus regurgitate on their nests to moisten them; don't give your tegus vitamin D3 because it is toxic but do give them plenty of fish liver oil (a substance immensely high in vitamin D3); vitamin D3 can be supplemented in the place of and instead of UVB exposure; the only fruit tegus eat in the wild is dates (which are from the middle-east, not South America); blue tegus are subspecies of the Colombian tegu; temperatures have nothing to do with hibernation because tegus enter hibernation when temperatures are the same as summer (when they actually measured temps at my insistence, they learned the temps are NOT the same as when active); all of this is nonsense or contradictory. I could go on and on, but really, it should be clear there is an endless litany of pure jibberish passed off as fact by breeders. Not all breeders are bad, and I will admit that many produce excellent tegus and know good husbandry. However, most breeders like to be considered experts and know everything, but the sad fact is usually quite the opposite. To say you can feed tegus during hibernation and there will be no problems....I'm betting there are a number of other things going on that are "flying under the radar". To their credit it can likely be done. However, given how I often see people interpret things (ie. the usual "if a little is good, then a lot must be excellent" and such), the much safer course to take is to recommend witholding food during hibernation. Link to Thread.

My tegu actually decreased her food intake on her own, without my interference, and I did not force her to eat. If you believe your tegu is about to go into hibernation, and is not showing significant interest in food, it is generally safe to stop offering food in anticipation of hibernation.

2) Once your tegu buries itself, wait about one week (7 days) before shutting of the lighting/heat source. Occasionally, tegus will wake up before actually going into full hibernation.

3) Temperatures should be kept consistently between 13 and 18 Celsius. DO NOT allow temperatures to get below ~5 C. Some breeders recommend turning on the basking light occasionally during hibernation to allow your tegu to bask if desired, but this is not necessarily a requirement.

4) You can choose to hibernate your tegu in his/her original enclosure. It is not necessary to move your tegu to a different enclosure unless you have reasons to do so.

5) Make sure your tegu has a readily available source of clean water throughout the whole hibernation period.

If you are interested in learning more about hibernation in tegus, username: tupinambis is a great person to follow on thetegu.com/forum [in my opinion]. He has always been very knowledgable and helpful, and has conducted studies on argentine tegus in their native habitat. Located below are links to a few of his threads and/or posts:

Hibernation in tegus:a rebuttal based on logic and fact ¹ -- a must read
Suggested readings for hibernation/thermoregulation/seasonal
So uh.. Hibernation? -- this is probably one of my favorites, particularly page 3 post #19. There tends to be a lot of banter between Tupinambis and Varnyard in all their threads, though their posts are often very educational as Tupinambis has to s-p-e-l-l everything out for Varynard. My personal opinion is very positive towards Tupinambis, and I'd rather not share my personal opinion on Varnyard's "knowledge" regarding tegus.

Hibernation is honestly a very tedious subject, and there is what feels like an infinite amount of information to be learnt. After reading numerous articles regarding hibernation, there was one statement that really clarified the process of hibernation [to me] and how successful hibernation is achieved:

"Under conditions of changing photoperiod but constant high body temperatures, you do not see suppressed metabolism or hibernation.Under conditions of changing photoperiod and temperature, you can get hibernation." ¹

A photoperiod can be defined as the amount of exposure an animal or plant of light received during a 24-hour period. Note that the temperature stated in the second sentence is the tegus internal body temperature, not the external environmental temperature. This essentially means that regardless of external cues from nature (reduced light exposure, temperature variations . . .), hibernation will not occur if the tegu's internal temperature is unable to lower.

I do not believe my tegu hibernated this winter, as her activity was too great to be considered hibernation. I believe the lack of hibernation was due to her inability to achieve a consistently lower body temperature. While her appetite was reduced, as well as her activity, she removed herself from her burrow daily and accepted meals a few times a week. Despite not achieving full hibernation, there was still been a dramatic change in her activity level and appetite that was quite obvious. During the period of reduced activity, I had to coax her to eat and her meals were drastically smaller; now, she has reverted back to her voracious self, eating significant amounts of fruits and fish daily. Another observed characteristic of this time period was her lack of shedding -- prior to this, she was shedding bi-monthly, whereas shedding ceased for a full > three months during her hibernation-like period.

I apologize for all of the redundancy, but every post containing a forum thread with Vanyard posting or mentioned will come with a disclaimer.

WARNING! Do NOT purchase a tegu from Vanyard Herps (Bobby Hill). Though he was previously a reliable breeder, there have been numerous people scammed by Varnyard who, still, have yet to be compensated. Please view the links located on my previous post -- Commitment Issues.