Captive Maintenance of the Radiated Tortoise
Dan Sterantino
Field Associate in Herpetology
AZA Accredited Trevor Zoo
Millbrook, NY
[email protected]
With thanks to, and significant contribution by:
Dr. William Zovickian
&
Tom Roach
Dan Sterantino
Field Associate in Herpetology
AZA Accredited Trevor Zoo
Millbrook, NY
[email protected]
With thanks to, and significant contribution by:
Dr. William Zovickian
&
Tom Roach
(Tap each picture for better clarity)
Introduction:
This is a document aimed at providing keepers of Astrochelys radiata (The Radiated tortoise) the optimal characteristics for hydration, temperature, lighting, diet and supplementation. The results the author has experienced, following these guidelines, are easily repeatable if the reader sticks to the basic husbandry characteristics presented herein. The results you can expect using the metrics outlined here are healthy, thriving, smooth, happy tortoises.
Figure 1 - A young Radiated tortoise raised by the author using the methods described herein. Photo by Dan Sterantino
This document is not a review of natural history or a detailed description of the myriad methods used to achieve the optimal characteristics. It is expected that the reader has a solid understanding of tortoise husbandry and the common methods and terminology used today. If you do not have this level of understanding, there are plenty of online resources, especially the Tortoise Forum, that can provide definitions and debate on methods.
Radiated tortoises are CITES I listed and, in most states, require permits to possess. Interstate commerce is highly regulated by the US Fish and Wildlife Service (through the CBW permit) and in recent years, has become nearly impossible for all but AZA accredited institutions and their agents. For all practical purposes, finding a breeder/tortoise in your state of residence is the only legal means of purchasing a radiated tortoise.
The specific Radiated tortoise knowledge contained in this document comes from many years of research and experience caring for hundreds of Radiated tortoises by my mentor Dr. William Zovickian and in-turn, many years’ experience caring for them myself. Dr. Zovickian is credited with being the first person to breed the Radiated tortoise in captivity.
The hypothesis that humidity and hydration might be a factor in the smooth growth of some tortoises was considered by a number of people in the past 30 years. My friend and regular contributor to “The Tortoise Forum”, Tom Roach, was one of them. Tom tested this hypothesis for many years putting together a string of research projects, involving hundreds of young tortoises, that eventually exposed the magnitude of the beneficial effects. Tom’s working theory explains that “Pyramiding is caused by growth in conditions that are too dry”. It is this statement (and Tom’s persistence in teaching it) that popularized the high humidity method of raising young tortoises. Customizing and applying this theory to my young radiated tortoises has proven to be game changing. As you can see in Figure 1, the results speak for themselves.
Hydration
If you were to look back 30 years at the state-of-the-art tortoise care and compare it to today, the most significant and impactful change in our understanding of the way tortoises live and grow has to do with hydration. No other variable in our care of tortoises has the dramatic impact on health that hydration does. Even with sub-optimal diet, temperatures, lighting or supplementation, a keeper could still raise reasonably healthy tortoises if hydration is sufficient.
When talking about hydration, we must consider both internal hydration (drinking) as well as proper keratin (shell) hydration. Radiated tortoises will drink considerable amounts of water on a regular basis. Radiated tortoises of all ages need to stay hydrated and have the opportunity to drink at a frequency commensurate with their size.
Proper shell hydration, specifically the keratin layer of the shell, is achieved through the relative humidity of the air in which the tortoise spends its time. Radiated tortoises can and will pyramid if the carapace is allowed to desiccate.
*Note: In my opinion the phrase “Hatchling failure syndrome” should be eliminated and replaced with “Dehydration”. Hatchling failure syndrome insinuates an uncontrollable, mysterious and fault-free condition that kills young tortoises. They simply “fail”. I see no basis in science for this. Dehydration and the subsequent systemic issues that arise from it kill young tortoises. We know it, there’s nothing mysterious about it and we can control it.
*Note: Also remember that relative humidity is “relative” to the temperature of the air. The warmer the air gets, the more water it can hold. A relative humidity of 85% at 85 F° means that the air is holding 85% of its potential, at 85 F°. If the temperature drops with no change in the available water, then the RH will rise. If the temperature rises with no change in the available water, then the RH will fall. Dew point can also be a very informative metric. If you have never read about RH and dewpoint, you should – I find it a fascinating topic.
Hatchlings
Figure 2 - A Radiated tortoise emerging from the egg. Photo by Dan Sterantino
Hatchlings have the most critical need for hydration and due to their low body mass, can become dehydrated very quickly. From the minute they emerge from the egg, hatchling radiated tortoises should be offered drinking water at all times in their enclosure and kept in high humidity. I have witnessed many hatchlings, prior to the yolk sac being absorbed, drinking and eating. In addition, radiated tortoises should be soaked for 30 minutes, every day.
The relative humidity for hatchlings should be kept at or above 85% at 85 F°. 85% at 85 F° is a good calibration point that is easy to remember. This is the most impactful characteristic in this document. It is this knowledge that removes any excuse for raising pyramided Radiated tortoises, even for inexperienced keepers. In addition, misting the carapace with water a few times a day will aid in shell hydration and the growth of healthy smooth tortoises.
Juveniles
Juveniles, 2 years and older, should follow the same regimen as hatchlings but soaking 3 or 4 times a week, rather than every day, will suffice.
Adults
Once a radiated tortoise reaches 10” SCL, regular soaking is no longer necessary but drinking water should be made available regularly. At this point the relative humidity and misting of the shell become less important as the periods of rapid growth have passed and the shape of the shell (which includes the underlying bone) is pretty well set. However, if conditions are too dry, even adults can show signs of pyramiding. It won’t be as noticeable as pyramiding in younger animals, but it can occur and indicates the potential for other dehydration related systemic issues.
There is no downside to keeping adults in the same conditions as juveniles if that is convenient for you. Though adult tortoises can tolerate lower RH percentages and go longer periods of time without drinking, I see no reason to test it. I keep my adults in a room humidified to 65% at 85 F° and provide drinking water at least 3 times a week. I also spray them down once a week with a garden sprayer – an activity they seem to “enjoy”.
Temperatures
Many care sheets focus on four critical temperatures – warm side, cool side, basking area and night-time. Knowing and managing these temperatures is an important part of successful tortoise husbandry, but Radiated tortoise hatchlings do not need separate basking lamps – they will bask under the correctly set UVB/Ambient light fixture when desired. I do not utilize basking lamps for my radiated tortoises until they are over 8” SCL, and even then, it is only for an hour in the morning and an hour in the afternoon coinciding with natural activity periods, (a process utilized by Dr. Zovickian that I adopted in my care regimen). Basking lamps are desiccating and pose a risk of hyperthermia should the tortoise become stuck or inverted under the lamp. When keeping a species that benefits from a basking lamp, these risks can be mitigated to a point, but since Radiated tortoises thrive without basking lamps, there is no need to use them.
*Note: Some keepers are starting to experiment with LED ambient and UVB lighting. Be aware that many LED lights do not generate much heat and may not provide any valuable basking potential. Do your own experimentation and adjust your setup accordingly.
Hatchlings and juveniles:
Daytime (6:30am to 7:30pm) ambient temperature: 88 F°
Nighttime – Slowly drops to a low of 70 F°
Adults:
Daytime (6:30am to 7:30pm) ambient temperature: 85 F°
Basking area (on from 8am to 9am and 4:00pm to 5:00pm): 100 F° to 105 F°
Nighttime – Slowly drops to a low of 70 F°
Outdoors
Being outside eliminates the ability, and need, for such specific control over conditions. My tortoises are outdoors 24x7 once they are 6” SCL and the weather is such that daytime temperatures are above 70 F° AND the nights are above 50 F°.
* Note: When housing tortoises outdoors in dry climates, make sure they have microclimates to retreat to where they can maintain higher levels of humidity. Radiated tortoises can and will start to pyramid rather quickly when kept outdoors if the carapace is allowed to desiccate.
Lighting
Figure 3 - An amazingly colored tortoise raised by the author. Photo by Dan Sterantino
Hatchlings and Juveniles
I use a high-quality dual-bulb, polished metal reflector, high output (HO) 4’ fluorescent fixture containing a UVB bulb and a 6500k Grow bulb. The 6500k bulb provides a nice natural ambient light. I set the fixture height such that the UV index, as read with a Solarmeter 6.5 at the carapace, is between 2.5 and 3.0. I also fill my enclosures with hides and plants so the tortoises can always get out of the light when desired. I run my lights 13 hours a day.
Adults
I use a high quality, 4-bulb, polished metal reflector, HO 4’ fluorescent fixture containing 1 UVB bulb and 2 6500k grow bulbs. I leave one socket empty. I set the fixture height such that the UV index, as read with a Solarmeter 6.5 at the carapace, is between 5.0 and 6.0. I do not keep plants in my indoor adult radiated tortoise pens as they are too destructive for such things. I place the light fixture to one side of the pen so that they can retreat to the opposite side to get out of the light. I do not provide any form of hide or other decorations in my adult pens. I run the lights 13 hours a day. As mentioned earlier, I do provide a 150w basking lamp (simple incandescent flood bulb) for adults for an hour in the morning and an hour in the afternoon. I set the bulb height such that the substrate temperature directly under the lamp is 105 F°. Some tortoises utilize it regularly and others avoid it.
Diet
Housing your sub-adult and adult Radiated tortoises outdoors for as much of the year as possible, temperature permitting, is highly beneficial. Likewise, natural graze including an assortment of grasses, weeds, leaves and flowers, is an essential part of a quality diet for as many months as possible. If these wild items do not grow in your area for a significant part of the year, its best to grow, or otherwise procure your own!
My radiated tortoise diet remains consistent throughout their lives with the only difference being the size and amount of certain food items. Any food items that smaller tortoises cannot swallow whole, bite through or easily tear, like grass, is cut into bite sized pieces. In the event you offer any prepared tortoise pellets – make sure they are right-sized for the tortoise or soaked so they can be easily bitten through.
As often as possible, my radiated tortoises get natural grasses and weeds. I do not supplement with other foods when natural graze is available. Some common weeds and flowers in my area include various dandelion greens and flowers, various plantain, red and white clover and clover flowers, sow thistle, roses, rose of Sharon (hibiscus) leaves and flowers, and I grow opuntia cactus in their outdoor pens during the warmer months.
When natural graze is not available, I rely heavily on grass hays. My radiated tortoises will eat grass hay, but they do not enthusiastically feed on it, so I do utilize some grocery store items and prepared tortoise pellets in the winter months. I also tend to stock opuntia cactus and feed that once in a while throughout the winter.
Grocery items primarily include dandelion greens, escarole and chicory with occasional spring mix and mustard greens. On rare occasions, I feed mushrooms, carrots, squash, prickly pear and pumpkin.
I do feed Mazuri Tortoise LS, as a small portion of their diets, twice a week. LS, in my experience, has a better formulation and yields much better stool consistency. The original Mazuri can lead to lose stools, especially when natural graze is not available.
Your tortoises may initially reject hay and/or Mazuri LS – but they will eventually accept it and some animals prefer it over the grocery store greens. Be careful with the amount of Mazuri you feed. Prepared tortoise pellets are very nutritious, and some tortoises get overly fond of it. Overfeeding can lead to accelerated growth. In Radiated tortoises, this presents itself as raised growth at the scute boundaries rather than flat growth as desired. This appears exactly opposite of pyramiding and is a topic of continued research.
Supplementation
The only supplements I use are Reptomin vitamin powder, Reptocal Calcium with D3, Benebac powder and cuttlefish bone.
Hatchlings and juveniles:
Cuttlebone is available all the time. Vitamin and calcium powder are sprinkled on their food twice a week when I am not feeding Mazuri. If you feed Mazuri weekly, then vitamin and calcium supplements are not necessary as the Mazuri diets contains them. Benebac is sprinkled on their food once a month.
Adults:
When indoors during the colder months, I provide adult females with cuttlebone twice a month. I don’t use any powdered supplement with adults as I tend to feed them more Mazuri LS then I do the younger animals and Mazuri contains the needed vitamins and calcium. Benebac is sprinkled on their food once a month. When outdoors, I do not provide any of these supplements.
Figure 4 - A 7-year-old female owned by the author. Photo by Dan Sterantino
Housing
The most successful method of housing Radiated tortoises of all ages starts with a temperature and humidity controlled dedicated tortoise room. Rooms allow the keeper to avoid heating multiple individual enclosures and the associated expense. In addition, heating individual enclosures requires individual heating elements like CHE’s, basking bulbs, or radiant heat panels. Each of these adds complexity and introduces desiccating effects that are counter to our hydration goals and must be mitigated (which they can be).
Figure 5 - The author's Radiata room. The rack height is adjustable so the top tub can be raised when the lower tubs are in use. You can see 2 closed chambers used for young tortoises in the back. Photo by Dan Sterantino.
My first exposure to this method of keeping Radiated tortoises in dedicated rooms was when I first toured Dr. Zovickian’s collection in the late 1990’s. I replicated every aspect of his room at my own home. The only changes I made over the years was to adopt the higher humidity level’s I reference in this document.
My room is radiant heated, and I heat to 85 F° during the day and let it naturally drop to 70 F° at night. Radiant heat in a large room can be thermostatically controlled to cycle during a 24-hour period in a natural way rather than the sharp spikes in temperature that can be hard to avoid in small enclosures. A large room takes a couple hours to heat up in the morning and a couple hours to cool down at night.
The RH of the room is 65% at 85 F° (during the heat of the day), and naturally rises as the temperature falls during the night.
My adult Radiated tortoises are housed individually in specially designed tortoise tubs that are 18” tall, 4’ wide and 6’ long. These tubs were designed by Dr. Zovickian for housing adult Radiated and Ploughshare tortoises. Commercially available tubs at the time were meant to house large snakes and were awkwardly deep for keeping tortoises. Manufactured by Neodesha Plastics, these tubs are perfect for housing 1 or 2 adult Radiated tortoises. Since the tubs are all in a climate-controlled room, there is no need to heat or humidify each tub separately. A tortoise room is one giant closed chamber.
Within my room, I have smaller (5’ x 3’) closed chambers for my hatchlings and juveniles which I designed and built. Within those chambers, I maintain the higher temperature and humidity levels I described above in the hatchling hydration section. Having higher humidity closed chambers within a humidified room makes temperature and humidity maintenance very easy and stable. Even if you neglect an individual closed chamber, it will never drop below the room humidity level providing some room for error.
Figure 6 - Two closed chambers designed and built by the author to house young radiated tortoises. Closed chambers similar to these are commercially available for purchase. Photo by Dan Sterantino
If you do not have the ability to dedicate a room, young tortoises can be maintained within closed chambers. Closer attention must be paid to maintaining proper temperatures and humidity levels, but well-designed closed chambers retain heat and humidity very nicely.
I am a huge proponent of dedicated tortoise rooms for many reasons. Give it serious consideration, especially when planning to maintain adults.
If you need help or ideas when it comes to closed chamber design, tortoise room design, outdoor heated night boxes, lighting products, humidity holding substrates and much, much more – spend lots of time on the Tortoise Forum. The access to information and knowledgeable people is second to none!
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