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By Jonathan Rheins
INTRODUCTION All reptiles and amphibians are ectothermic; that is, the environment in which they are found dictates their body temperature. These animals have perfected the art of altering body position and their location within their surroundings to establish an ideal body temperature. In the terrarium, this behavior is often demonstrated by animals moving in and out of localized “basking" spots. In nature, this amounts to where the animal chooses to position itself in relation to the sun or other source of radiant heat.
During weather extremes many ectothermic animals seek refuge from the elements either underground, deep within rock fissures, or within any other acceptably insulated space. This behavior is known as brumation, when the period of inactivity occurs during cold weather, and aestivation, when the weather is too warm for regular activity.
IN THE WILD
For wild herps, brumation and aestivation are basically survival tactics. These behaviors are natural adaptations that allow them to slow down their metabolism drastically and survive for extended periods when conditions are simply too unfavorable for regular activity. While reptiles are generally rather tough creatures, they also often inhabit some of the harshest environments on Earth.
Central Asian (aka Russian) tortoises, Agrionemys horsfieldii, serve as a prime example of these principles. During the winter months in most of their range temperatures can drop far below 0 degrees F with many feet of snow covering the ground. Conversely, in the summer months, the temperature regularly soars over 100 degrees F. When the weather reaches these extremes, A. Horsfeidii will be burrowed as far as 6' under ground, and emerge only for 3 to 4 months after winter to eat, breed, and lay eggs.
When maintaining reptiles in a terrarium setting, we must keep in mind that the activity of many herps is seasonally dictated. This is part of their hard-wired instinct and it is much easier to embrace this fact than try to combat it by “tricking" an animal by manipulating lighting and heating. By gaining a thorough understanding of an animal's natural history and behavioral patterns, it becomes easier to interpret their behavior and adjust husbandry accordingly.
There are two general approaches to dealing with brumation behavior in the terrarium setting. With species that undergo a true brumation in the wild, it may be acceptable to replicate this rest period for captive animals housed indoors. Animals such as tortoises and box turtles that live outside may be allowed to enter brumation on their own, with minimal involvement on the part of the keeper. For some species, such as cornsnakes, this annual fluctuation of temperature and photoperiod induces breeding and subsequent egg-laying. In the wild, most temperate and sub-tropical herps reproduce during the spring and summer months, ensuring the young have ample time and resources prior to facing their first winter.
If captive propagation is not your goal, most pet reptiles can be kept awake year-round. This alternative is the more typical approach, and requires fewer changes to the husbandry routine. In these cases, photoperiod and temperatures are mainatained the same throughout the year. However, it should be noted that even if no adjustments are made on your part, some animals will experience a “slow down" exemplified by inactivity and decreased appetite.
A thorough understanding of an animal's natural range and the weather patterns therein can aid greatly in making brumation preparations for any herp. Every attempt should be made to replicate the natural environment as much as possible. The specifics regarding brumation timing and procedures will vary from one species to another, but some generalizations can be made.
Changes in lighting and heating regimens should be done gradually, as they occur in the wild. Transitioning a reptile from “normal" summer temperatures to winter temperatures overnight can be not only stressful to the reptile, but can have negative health implications as well. Additionally, feeding should be slowly reduced as the temperatures are decreased. Brumating herps do not hunt or eat in the wild, and having an empty digestive tract prior to entering brumation will ensure that no undigested food is left to decay in the gut and potentially cause illness.
In the spring, this procedure is essentially reversed; temperatures and photoperiod are gradually increased and feeding is resumed once all environmental conditions are stabilized. For many reptile species this return to warmer temperatures and longer day length triggers courtship and breeding behavior. The actual cooling process plays a significant role as well, specifically with spermatogenesis and ovulation in male and female herps respectively.
Only animals in ideal health and of good body weight should be considered for any sort of artificial or natural brumation. Typically, herps eat and grow during the spring and summer in preparation for cooler months when food is scarce. Although baby herps do brumate in the wild, it is out of necessity. Most hobbyists and breeders wait until an animal is in its second or third year prior to allowing it to undergo a full winter cool-down.
CASE STUDY: BEARDED DRAGONS
As one of the most popular and prevalent pet lizards in the US, it seems only fitting that we look at the details of brumation in bearded dragons, and its implications for the average keeper. Many first time bearded dragon owners become understandably alarmed when their normally ravenous dragon suddenly begins sleeping all day and losing interest in food. However, the vast majority of mature dragons will show marked changes in behavior during different parts of the year.
In the United States, most bearded dragons that have reached sexual maturity (typically 12-18 months) will begin to show signs of impending winter dormancy beginning in mid-fall. In southern California, where the author lives and breeds bearded dragons, animals begin slowing down by the end of September. External cues such as shortened day length, lower temperatures, and fluctuations in barometric pressure all contribute to the onset of brumation in bearded dragons.
During this transitional time, most dragons will still enthusiastically eat their favorite foods, but may lose interest in less appealing fare. Basking behavior will often change as well, with animals spending less time underneath heat sources and more time in the cooler regions of the enclosure.
By mid-November most male bearded dragons will have stopped eating almost completely. Female dragons tend to brumate as well, but males are more likely to exhibit more drastic changes in behavior. Food should still be offered on a semi-regular basis as per the interest in food shown by the animal.
As the days continue to get shorter, and nighttime temperatures drop, one should not be alarmed to see their bearded dragon go for weeks, sometimes months, without eating. Animals that are going through a normal brumation period will lose minimal body weight, and at no point should they appear skinny or weak. However, it is normal for them to remain hunkered down in a cold and dark corner of the cage for days on end.
It is important to ensure that brumating herps, bearded dragons included, remain properly hydrated. The majority of their normal water intake is via the foods that they eat. So when they are off food for the winter, a water bowl should always be available. Alternately, adult dragons can be given a 10-minute soak in warm water once or twice a week to allow ample opportunity to drink.
Most of the author's adult dragons begin “waking up" around the beginning of March. As the ambient temperature begins to increase and the days begin getting longer again, the dragons will begin basking more often, and showing a gradually increasing interest in food. By April, male bearded dragons will begin displaying their full breeding behavior. Darkened beards, head bobbing, and courting of any receptive female can be expected.
When temperatures have stabilized in mid to late spring the majority of lizards will have resumed a normal feeding schedule, and should exhibit more typical basking behavior. It should be noted that some male dragons will be less inclined to eat when they are housed with a female. These animals will often be more concerned with breeding than with eating.
To the uninitiated, the entire brumation or aestevation process seems quite unusual, and entirely foreign. As mammals, we find the idea of going for extended periods of time with little to no food to be alarming, and a great cause for concern. However, we must remember that reptiles are a very ancient and well-adapted group of animals that have evolved in such a way as to survive when and where most other organisms could not.
By familiarizing yourself with the underlying biological implications of the brumation process, one can become better prepared to recognize and accommodate these behaviors in the terrarium setting. While some concessions must be made, overall, the best results are observed when herps are allowed to follow a natural seasonal cycle.
Behavioral and physiological changes in tune with the environment are part of what make reptiles and amphibians the creatures that they are. If we can identify and embrace these behavioral changes, rather than allow them to concern us, it will only allow us to better care for our charges, and ensure that our herps live the most natural, and comfortable life that they can.