African spurred tortoise

The African spurred tortoise is one of the largest species of all tortoises. Like all tortoises they were created on Day 6 of Creation by God. They mainly inhabit the southern portion of the Sahara desert. 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. Other species frequently sublet (borrow the burrows made by spurred tortoises), making dens in alcoves off the main burrow. The burrows that they make are beneficial to other animals in the desert because they provide a safe shelter. 

Anatomy
The African spurred tortoise is the largest of African tortoises. It has a broad, flat carapace, thick skin that holds water, and spurs (like claws) on their legs. 

The anterior and posterior marginals are serrated, and the posterior marginals upturned. The plastron (the ventral part of the shell of the tortoise) is ivory colored with divided anal scutes and paired forked gulars. They have growth rings on the scutes that are strongly marked with age. Skin color is golden to yellow-brown and very thick. Mature males usually develop reverted marginal scales in the front. The large scales on the front legs overlap. On the rear legs, there are spurs which are not known to serve any particular purpose.

Their head is moderate in size, with a slightly hooked upper jaw and nonprotruding snout. It is brown, with the jaws being a slightly darker brown. Externally, it is hard to tell males from females. Males have slightly longer, thicker tails and a more concave plastron, but otherwise appear similar to females. 

The sulcata is the only tortoise in the world that is fully adapted for terrestrial life. As a defense mechanism against predators, the sulcata will retract its body under its hard horny shell to where the only thing showing is the front surface of its forelegs, which is covered by scales, and the soles of its hind feet. To protect itself from an even bigger predator, the temperature, sulcata is famous for digging burrows. Sulcata can go weeks without food or water, but when they do get ahold of some water, they can drink up to 15% of their body weight. 

Reproduction
Sulcatas breed very well in captivity. Males reach sexual maturity when their carapace is about 35 cm in diameter. Sulcatas are very aggressive toward each other, especially during breeding time. Males ram each other repeatedly and sometimes end up with bloody limbs and heads. Copulation can take place anytime from June through March. However, it occurs most frequently after a rainy season in September through November. When mating, the male first circles the female and will occasionally ram her with his shell.

After mating, the female's body will swell with eggs and she will decrease her food intake. She becomes increasingly restless as she looks for good places to make a nest. Nesting season is in the autumn. She begins by kicking loose dirt out of the way and eventually creates a depression, which she urinates in. She digs until the depression reaches approximately 0.6 m in diameter and 7-14 cm deep. This may take her up to five hours. Four or five nests may be dug before she finally selects one to lay her eggs in. Once she selects one, an egg is laid every three minutes. Her clutch size may reach 15-30 eggs, sometimes more. The eggs are white and spherical with brittle shells. After the eggs are laid, the female will fill in her nest. It may take her more than an hour to cover all the eggs up.

The eggs incubate underground for about eight months. When they hatch, the tortoises are only 4-6 cm in carapace length. They are oval-shaped and weigh less than 25 gm. They are yellow to tan with rounded, serrated carapaces. 

Ecology
The Sulcata is the third largest species of tortoise in the world, and is the largest of the mainland tortoises. Adults are usually 18 inches in shell length, and weigh 70 to 100 pounds. 

Geochelone sulcata ranges from Ethiopia and Sudan westward through the dry regions of Chad, Niger, and Mali to southern Mauritania and Senegal. Its range generally lies along the southern perimeter of the Sahara Desert. 

This species has many adaptations and behaviors for living in a dry environment. Thick skin prevents loss of moisture. They are active in the morning and evening, spending the hottest part of the day underground. Their diet of succulent plants provides them with water, and they coat their skin with mud to cool off. Spurred tortoises are important to deserts because their burrows provide shelter for other animals. 

Diet
African Sulcata Tortoises have voracious (huge) appetites. They require a diet high in fiber and calcium and low in fat and protein. In the wild, Sulcatas graze, similarly to cows or sheep, and the desert vegetation is often coarse and of poor nutritional quality. 

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.