Juvenile sulcata tortoise, Geochelone sulcata
The African Spurred Tortoise (Geochelone sulcata) is a species of tortoise which inhabits the southern edge of the Sahara desert, in northern Africa. Their diet provides them with water, and they coat their skin with mud when available to cool off. When mud wallows are not available, they retreat to cooler burrows. Spurred tortoises are important to deserts because their burrows provide shelter for other animals. They do not hibernate, like many other types of tortoises, due to their natural environment being so close to the equator. They love to dig, and make very long burrows, often much damper than the ground surface, and other species frequently sublet, making dens in alcoves off the main burrow.
Due to the availablility of these animals in the pet trade, more and more sulcata tortoises are brought home as pets. However, these animals provide significant challenges to their keepers, due to their dietary and temperature requirements, and their size. For one thing they make quite effective battering rams at 100 lb or more. They are very powerful and very persistent if they think you have something tasty in your house or on the other side of the fence.
They require high fiber diets and many vegetables can cause health problems in large quantities. Red leaf lettuce, cucumbers, hay and clovers are some of the better foods to make up the bulk of their diet. They will attempt to eat most types of plants eventually and some common garden plants can be very toxic to them, such as azeleas. They will eat such things as caterpillars and snails if given the opportunity, but this also should be a very small portion of their diet. Sulcatas need a large enclosure as they get bigger and should be given a generous grazing area. Sulcatas should be kept above 60F, which means most areas will require special winter accommodations.
Unfortunately many people do not research them properly and purchase them without an understanding of the responsibility they are taking on. This is compounded by the relatively low price for a large exotic tortise.
A captive diet for G. sulcata should be organized around five important factors: high dietary fiber, low protein, low fruit or sugary foods, adequate calcium, overfeeding.
The sulcatas' native habitats are semi-arid, and the plant life available to this terrestrial herbivore are primarily dry grasses and weeds. Grasses should make up at least 75% of a captive sulcata's diet, to provide the high dietary fiber found in the wild.
Protein is lacking in their natural diet. A captive diet with a high protein content will quickly overpower the tortoise's renal system, as unused amino acids in the bloodstream are strained out and deposited in the kidneys. The high availability of protein can also cause a shell deformity common in captive tortoises, called pyramiding.
Fruit, and other sugary foods not present in their natural diet can be harmful to the tortoises if they change the pH balance of the sulcata's gut. If the pH changes kill off their intestinal flora, they can be subject to toxic shock, which can be fatal.
Young sulcatas grow very fast - they can easily double in size each year for the first three. For proper bone and shell development, their diet must include adequate calcium. In the wild, this is provided by a high calcium content in the soil, and therefore in their diet, but in captivity calcium supplementation is required.
Last, the diet that is available to captive sulcatas can be much more nutritious than in the wild, which offers its own challenges. Sulcatas are naturally voracious, to offset the dearth of nutrients in their habitat; care must be taken to insure the tortoise does not overfeed. Bedding, or other plant material in their enclosures, should be restricted to grasses or grass-based hay, to ensure that the animal does not take in too much nutrition.
Temperature and Humidity
Coming as they do from the southern Sahara, G. sulcata is well adapted to hot, dry climates. They derive most of their moisture from their diet, and they regulate their temperature and humidity needs by retreating into burrows. Most sulcatas, especially hatchlings, spend much of their time in these burrows, and the humidity requirements for hide boxes in captivity are higher than might be expected - around 40-60%. In other words, no special care needs to be taken to ensure their areas are dry enough - in reality, care must be taken to humidify their enclosures, as hatchlings especially are prone to dehydration.
In much of the United States, their temperature requirements are of greater concern to their keepers. Given their large size, sulcatas are most easily kept out of doors, but should not overnight outside when the temperatures drop below 60 degrees fahrenheit. As this describes most of the US, especially during winter, prospective sulcata keepers may find housing them to be impossible after their first few years of age.
G. sulcata is the third largest species of tortoise in the world, behind the Galápagos Giant Tortoise and the Aldabra Giant Tortoise. Adult specimens are usually 18 inches in shell length, and 70 to 100 pounds in weight, with 24 to 30 inch, 150 pound specimens not unknown. They grow from hatchling size (2-3 inches) very quickly, reaching 6-10 inches within the first few years of their lives. An adult sulcata will need a great deal of space. Several web sites list the record size between 230 lb and 240 lb.
Tortoise & Freshwater Turtle Specialist Group (1996). Geochelone sulcata. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Listed as Vulnerable (VU A1cd v2.3)