Changing seasons and their impact
It’s hard to explain, but my bearded dragons just don’t seem as active now as they were in the summer. Does their activity level change? I noticed the same thing last year. What can I do? I always know that autumn and winter is on the way when I start receiving questions about unexplained drops in activity and decreased appetite in reptiles housed in vivarium surroundings! Last year, I noticed a huge rise in such questions coming in to me and wrote a piece on the subject in this publication. Interestingly, although not everyone agreed at the time, it seemed that our reptiles knew best! The winter period of 2012-2013 turned out to be a very long, hard season.
I have been thinking increasingly about brumation and its effects upon captive reptiles recently, and have come to a few new conclusions about how and why they seem to enter into these periods. Wild animals by definition have to survive. They are able to change and adapt to their surroundings, depending on the season, with the underlying aim being to survive and reproduce. They also have to make the most of their wild food and water sources, and in the case of cold-blooded creatures like reptiles, they must do all of this with the limitations of obtaining energy from an external heat source – the sun.
Generally, reptiles have thrived in the past and continue to do very well over much of the globe, with a few species even being encountered in the Arctic Circle. Seasonal changes can have a huge effect on a wild reptile that is effectively dependant on the external temperatures within its range. Like all living things, reptiles have to eat. Food is obtained and the nutrients from these food sources are absorbed into the body of the animal. We all know that reptiles rely on the sun for access to UVB. This exposure will start and maintain the vitamin D3 cycle so that they can go on to utilize ingested calcium properly. Being exothermic means they also rely on the heat from the sun to aid digestion.
If temperatures decrease, so reptiles may not only struggle to digest their food properly but this fall in temperature may coincide with a drop-off in the UV index and thereby restrict the vitamin D3 cycle as well. This then leads on to the fact that as temperatures reduce, so sources of food may become scarce as well, and therefore marks the start of a vicious circle.
A survival strategy
Temperatures fall, there is less food and so the reptile has less energy to find or pursue its normal food sources. Reptiles, however, are generally much too clever to allow the seasons to cut their lives short. Rather than try to carry on at their previous level of activity, so they can enter a period of brumation or even a full hibernation.
For some species, this is quite normal and wild breeding seasons are defined by these events, especially in the case of various snakes. Brumation is nature’s way of protecting a reptile that is under stress, and making sure that it survives through in reasonable condition until next breeding season. Unlike hibernation, when activity ceases entirely, brumation reflects a general slowdown in activity. The reptile will tend to spend much of its time sleeping in a hide or burrow.
Its coloration tends to be less bright than normal, but although the individual is not eating so much, it should not actually lose much in the way of weight if it is brumating properly. What is actually happening is that the reptile has slowed its metabolism down in order to protect itself. Some of the fat and mineral reserves that it had built up when conditions were more favorable, to sustain it through the more difficult, cooler seasons will be utilized over this period. Minerals like calcium are essential to the everyday function of the vital organs but if food is scarce, so calcium will not generally be as widely available either.
Stores of calcium kept in the bones are released back into the blood, so as to ensure good muscle contraction for example, thereby assisting the survival of the animal itself. Fats are used at a much slower rate as the heart and respiratory rates are reduced, with activity being kept to a minimum. This is no real problem in the wild. The animal is in effect waiting for the return of spring, when things will improve. The reserves of calcium that have been used through the winter are then very quickly topped up, as are the stores of useful fats, and no lasting damage is done. The reptile has survived and will be ready to breed again very quickly.
In vivarium surroundings
Under these conditions, however, brumation can be a very different process. I typically start to get questions about reptiles beginning to slow down and refusing food from the last weeks of September onwards. On close study, I find this often corresponds with a drop in atmospheric pressure.
It is easy to check on the barometric pressure readings on the Met Office’s website (See http://www.metoffice.gov.uk/ for details). I have noticed a direct link between an early drop in atmospheric pressure, irrespective of the actual fall, and the start of concerns being expressed by keepers. Our reptiles in effect are becoming a very clever, long-range weather prediction service. It seems that they can sense the impending seasons, and perhaps the severity of the winter too, adjusting their behavior accordingly.
This is a natural reaction of course, based the reptile’s aim to protect itself for the following warmer seasons. Brumation in the vivarium can be fraught with issues. This is made worse in systems where the animal is not allowed access to the temperature range or the UV light index that it would experience in the wild. I believe that many incidences of metabolic bone disease (MBD) can start from this basis. The reptile has basically been living in an ‘under-powered’ environment, where it has not been able to lay down adequate reserves.
This in itself will affect the blood calcium level, and there will be an increased tendency for calcium to be broken down from the bones, so as to bring the level in the blood back up to the required level. As this process continues, so calcium levels become increasingly depleted. This of course is then made worse during the winter when, as it spends longer in its hide, the reptile enjoys even less exposure to heat and light. In effect, spring never comes and the risk of MBD increases. Let me illustrate what has happened so far this autumn.
I started to get concerned emails from owners in mid-August, which seems very strange as we were experiencing a wonderful summer, with temperatures approaching around 30°C (86°F) nearly every day. But by September 13th, atmospheric pressure and temperature readings had crashed, and both were forecast to stay relatively low, with the start of October already proving to be very unsettled. These ultra-sensitive animals had indeed predicted a significant change in the climate, as reflected by a marked shift in their behavior.
Is it a good idea?
So should we allow our reptiles to brumate? Well in a way, we simply cannot stop them! Some animals are very sensitive and “dig in” very quickly and just simply cannot be persuaded to become active again. All that you can do is to provide your animals with a full and varied diet throughout the year, and allow them access to a well thought-out system. This will help to protect a reptile during the months when it is not actively basking and seeking out food. Some animals are not affected at all though, and will carry on feeding throughout the entire year. A percentage will seek to slow down, but they can be bought back to a normal level of activity by careful management, unlike members of the first group.
In general terms, I feel that because of a combination of limitations in our dietary knowledge and the food we offer, as well as the restrictions imposed by current technology, some lizards may not be able to obtain enough of the correct fats or lay down enough calcium in their bones over the summer to protect themselves during the winter. Keepers who can provide a wide variety of food and are able to offer a UV index as part of the light and shade method, based on the species’ exposure in the wild, can be less concerned though, as their animals should hopefully remain in good health, even if they display a tendency to start brumating.
How you might break the cycle
Lizards that have pre-existing health concerns are underweight or have calcium issues should be dissuaded from brumating if possible. This is all too easy to say but not so straightforward to achieve in practice! The only method that I have found that will sometimes bring a lizard out of its winter slumber is to trick it into thinking that spring is returning. You can do this by increasing the basking temperature by 5°C (9°F) over a five day period and raising the UV index too.
These changes should be accompanied by a more varied diet and a higher humidity level. Try placing the lizard under the basking zone every day and increasing the night-time temperature slightly as well. This may be enough to convince your bearded dragon into thinking that the sun is back again and food is still abundant. Supplement the food following the recommended guidelines for the supplement that you are using, and make sure that your UV system is changed as necessary, to ensure an optimal output.
Make sure that you have a spare heat source and utilize something like an 80W or 100W D3 basking lamp in the case of bearded dragons, running this for just two hours a day alongside your existing light source. Using this lamp in the morning will increase the vivarium temperature and provide a concentrated beam of light in which the lizard can be placed. If your animal continues to slow down and or starts to lose weight, however, then you should seek the advice of your vet.
© John Courteney-Smith Taken from “Practical Reptile Keeping” magazine