The Radiated tortoise that lives in Madagascar is amongst the most attractive of tortoises. Its high-domed, dark carapace has brilliant yellow markings that radiate out from the center of all its plates to make this tortoise's distinctive pattern. The shell’s dark pigment fades as the individual grows older, producing a shell of a lighter color. Males have longer tails and their under shell or plastron has a notch below the tail. Hatchlings are black and off-white, but soon develop the striking adult coloration.
Endemic to Madagascar, this tortoise lives only in the south of the island. They have been introduced to some other places, including Mauritius and Réunion. Their preferred habitat is dry forests, especially woodlands and thorn (diderae) forests in southern Madagascar.
Like many other species of tortoise the Radiated tortoise typically lives a fairly solitary life, though it is not uncommon to see a number of them grazing together (particularly at the time of the breeding season). They regularly graze in the same area, serving to keep that vegetation closely trimmed. These animals are diurnal, they like warmth, and drink a lot whenever they can, although they can go for long periods without water. At the hottest times of the year, they burrow to avoid the excessive heat and dehydration. Radiated tortoises are extremely adaptable to the changing of the seasons from arid and dry to the heavy monsoon rains, when they are described as almost dancing in the rain in order to shake it off. They screech loudly when startled to intimidate and scare off a predator. A Radiated tortoise is a peaceful animal but becomes aggressive towards individuals they perceive as a threat.
Radiated tortoises are primarily herbivores, they eat vegetation such as grasses, leaves, flowers, fruit and cacti. Dead leaves are a big part of their diet for much of the year.
Radiated tortoises seem to be both polyandrous (one female to multiple males) and polygynous (one male to multiple females). During courtship, males fight for the females, attempting to roll each other onto their backs and ramming one another with the front of their shells. Courtship is initiated by head bobbing and the smelling of a female’s hind area. After mating, the female digs a hole of 6 to 8 inches to make a nest and lays 3 to 12 eggs. Incubation lasts from 145 to 231 days. The hatchlings are 3 to 4 cm in long and their carapace develops quickly after hatching.
These tortoises are critically endangered due to habitat loss, being poached as a source of food, and over exploitation in the pet trade. Asian smugglers collect tortoises for their livers and for the pet trade. The burning of their spiny forest habitat for charcoal production also threatens this species.
According to the WWF Panda resource, the total population size of the Radiated tortoise is approximately 6.3 million individuals. According to the IUCN Red List, the conservative total population size of this species is around 1.6-4 million individuals and another piece of research gives the total number of radiated tortoises as around 12 million individuals. Overall, currently this species is classified as Critically Endangered (CR) on the IUCN Red List and its numbers today are decreasing.