Despite the fact that there are roughly 49 tortoise species in the world, the majority of keepers are drawn to a relative handful of species, including sulcatas (Centrochelys sulcata), red-footed tortoises (Chelonoidis carbonarius), and Russian tortoises (Testudo horsfieldii). There’s certainly nothing wrong with this; many of these species make fantastic pets –that’s part of the reason they’re so popular!
However, some keepers would rather work with less popular species instead. And for keepers with this mindset, there are few species that can compare with the beautiful radiated tortoise (Astrochelys radiata).
Unfortunately, radiated tortoises are quite imperiled in the wild, and they’re currently classified as critically endangered. However, they are being bred with increasing regularity in captivity, which makes them available to tortoise keepers who want to work with a relatively rare species.
I’ll explain everything you need to know about radiated tortoises below, so that you can decide if you’d like to work with this amazing species.
Radiated Tortoises: Basic Information
While radiated tortoises share a number of similarities with other tortoise species, they also have several unique traits, which help to make them especially endearing.
Physical Appearance
Radiated tortoises are typically categorized as a medium-sized species, who usually reach lengths of 10 to 15 inches and weigh 5 to 25 pounds. However, occasionally animals grow larger than this, with one female reportedly reaching 55 pounds.
Radiated tortoises have highly domed shells with very attractive markings. Each scute typically bears a yellow-colored central spot, with radiating yellow lines stretching from it to the scute edges (hence their common name). However, the amount of yellow present varies from one individual to the next, with some being quite dark and others being clad in tons of yellow.
Radiated tortoise males are often longer and thinner than females. However, these tortoises are often very difficult to sex, and keepers are occasionally surprised to find that their “male” turns out to be a female or vice versa.
Natural Habitat & Range
Radiated tortoises have a very small natural range, as they’ve historically been confined to the southern and southwestern coasts of Madagascar. However, humans have introduced them to the nearby islands of Mauritius and Reunion.
These tortoises prefer arid habitats, including the dry forests that are common in this region. Unfortunately, habitat destruction has eliminated large swaths of suitable habitat, which is one of the primary reasons this tortoise species is declining in the wild (illegal collection for the pet trade is the other important reason for their falling numbers).
Natural Behaviors
Like most other tortoises (especially those hailing from hot, arid locations), radiated tortoises are typically most active in the morning when temperatures are comfortable. They’ll generally retreat to burrows or sheltered spots during peak midday temperatures, though they occasionally become active again in the afternoon.
Interestingly, radiated tortoises often tend to feed repeatedly in the same area. This has the effect of keeping the vegetation closely cropped, as occurs in the home ranges of some other tortoise species. This is thought to be an adaptation that enables the tortoises to feed on new rather than old growth, which they tend to prefer.
Radiated tortoises are noted for performing a “rain dance” in wet weather, in which they’ll stand up high on their legs and repeatedly wiggle back and forth. The purpose of this behavior remains unclear, but it is certainly entertaining to witness.
Captive Care: Maintaining a Radiated Tortoise
Now that you understand some of the key facts about radiated tortoises, I’ll now share some of the things you’ll need to consider when maintaining these remarkable chelonians.
Enclosure & Space Requirements
There are several types of enclosures you can use to maintain young radiated tortoises, including tortoise tables, children’s swimming pools, and stock tanks. Front-opening reptile enclosures will also work, though they’re often expensive.
However, most adults are best housed in large, custom-built enclosures. If you live in an area with a suitable climate, you should strongly consider maintaining your pet outdoors in a predator proof enclosure. Indoor maintenance is acceptable, though it will necessitate the use of lighting and heating devices, which aren’t necessary outdoors.
While different keepers are comfortable with different enclosure sizes, you’ll generally want to provide your radiated tortoises with an enclosure that provides between 30 and 50 square feet of space. Nevertheless, as is almost always the case, larger enclosures are preferable.
Heating, Lighting, & Humidity
Radiated tortoises require appropriate environmental conditions – including suitable temperatures, humidity levels, and lighting – to thrive.
Providing a suitable humidity level for these tortoises is generally easy, as they prefer dry conditions. The heating devices you add to the enclosure will generally help evaporate the water present and, therefore, keep the humidity level relatively low.
However, you will still want to mist the enclosure periodically (perhaps once or twice per week) to prevent it from becoming too dry. Additionally, you should always keep the substrate under one of your pet’s hides damp to provide a high-humidity hiding spot, as the animals would enjoy in the wild.
Radiated tortoises not only need heat sources to allow them to maintain proper body temperatures, but they also require access to full-spectrum lighting, which includes rays in the UVA and UVB portions of the electromagnetic spectrum. This complicates the choice of lights used in an enclosure, as some types of lights produce heat while others do not produce (very much) heat.
Accordingly, some keepers use one kind of light to satisfy their pet’s lighting and heat needs, while others opt to use separate lights to provide heat and full-spectrum lighting.
Here are the six basic options available:
- Radiant heat panels: Radiant heat panels only produce heat, so they must be used in conjunction with some type of full-spectrum lights.
- Mercury vapor lights: Mercury vapor bulbs are growing in popularity, as they’re the only option that produces substantial heat and full-spectrum light.
- Incandescent heat lights: Incandescent bulbs produce heat, but they do not produce full-spectrum light, so you have to use them in conjunction with some other light source.
- LED lights: LED lights produce beautiful, energy-efficient, full spectrum light, but they do not produce appreciable amounts of heat.
- Linear fluorescent tubes: Linear fluorescent tubes are waning in popularity, as they do not produce heat and require special fixtures to work.
- Compact fluorescent tubes: Compact fluorescent bulbs must be used alongside heat lamps or radiant heat panels, but they can be used in typical fixtures, unlike linear fluorescent tubes.
No matter which kind of lights and heating devices you decide to use, it is important to set up all heating devices at one end of the enclosure. This creates a “thermal gradient,” or range of temperatures. This way, your tortoise can adjust his temperature as he sees fit.
Also, note that tortoises reared outdoors do not require full-spectrum lights, as the sun will provide all the UV radiation your pet needs.
Substrate, Decorations, & Enrichment
While bark may serve as a suitable substrate for radiated tortoises, most keepers elect to use a soul-sand mixture instead. If at all possible, try to include enough substrate to allow your pet to dig burrows.
On top of the substrate, you’ll want to include decorations and enrichment items to prevent your tortoise from having to live in a barren enclosure. Always incorporate at least two hiding spaces (with one placed at the warm end of the enclosure and the other placed at the cool end), but you may also want to include smooth stones, driftwood, or live (non-toxic) plants.
Just be sure that any heavy items (especially stones) actually rest on the bottom of the enclosure, rather than on top of the substrate. This will prevent your tortoise from becoming trapped or crushed, should he tunnel beneath the stones.
Food & Water
Even though radiated tortoises hail from arid habitats, they still require drinking water. So, always provide your pet with a wide, shallow dish of fresh, clean water.
Feeding radiated tortoises is generally easy. They’re largely herbivorous, though they may consume insects, worms, or carrion on occasion in the wild (this is not necessary or recommended in captivity). So, you’ll generally want to provide a diet comprised of a rotating mixture of non-toxic grasses, weeds, sedges, leafy green vegetables, and flowers. The occasional bit of tortoise-safe fruit is unlikely to cause serious problems, but this type of high-sugar, low-fiber food should be fed very sparingly.
Hatchlings and juveniles should be fed six to seven times per week, but adults will often thrive when fed five to six times per week.
Ongoing Radiated Tortoise Care
Of course, your work as a keeper isn’t complete once you’ve set up the enclosure – there’s plenty of on-going work to be done. This includes:
- Clean the enclosure on a daily basis, taking care to remove any feces, uneaten food, or shed scutes.
- Monitor the temperature regularly and ensure that it is within the proper range.
- Provide food and water on a proper schedule based on your pet’s age and size.
- Observe your pet for signs of injury or illness and obtain veterinary care whenever necessary.
- Measure and weigh your pet periodically to track his growth – young animals should steadily increase in size, while adults should maintain their size or grow larger very slowly.
- Completely break down the enclosure, clean all of the components, and replace the substrate at least two to four times per year.
Citations
- Zoo Atlanta – Radiated Tortoise
- Smithsonian’s National Zoo & Conservation Biology Institute – Radiated Tortoise
- The Turtle Room – Radiated Tortoise
