The radiated tortoise (Astrochelys radiata) of Madagascar is one of the most attractive of all the tortoises. The high-domed, dark carapace is marked by brilliant yellow lines that radiate from the centre of each plate and create this tortoise's distinctive pattern. As individuals age, the dark pigment in the shell fades, producing a lighter coloured shell. The legs, feet and blunt-shaped head are also yellow in colour with the exception of a dark patch on the top of the head. Males can be distinguished by their longer tails and a notch in the under shell (plastron), below the tail. Juveniles are black and off-white when they hatch, but quickly develop the adult's striking coloration.

Biology Edit

Males reach sexual maturity once they have attained a carapace length of around 30 cm. Rival males will fight during the breeding season and attempt to roll one another onto their backs. They initiate courtship by a head-bobbing display and smelling the female's hind legs. This is followed by energetic circling and butting of the female's carapace. Once mating has occurred, the female lays her clutch of 3–12 eggs in a nest dug into the ground. Eggs are laid at the end of the wet season, between February and April, and hatch after 10 months or more. Hatchlings emerge within a few weeks of one another at the onset of the next rains, in November or December. Radiated tortoises graze on vegetation such as leaves and grasses, flowers, fruit and cacti. During much of the year dead leaves also make up a substantial part of their diet.

Reproduction Edit

Males first mate upon attaining lengths of about 12 in (31 cm); females may need to be a few inches longer. The male begins this fairly noisy procedure by bobbing his head and smelling the female's hind legs and cloaca. In some cases, the male may lift the female up with the front edge of his shell to keep her from moving away.

The male then proceeds to mount the female from the rear while striking the anal region of his plastron against the female’s carapace. Hissing and grunting by the male during mating is common. This is a very dangerous procedure and cases have been recorded where the female's shell has cracked and pierced the vaginal and anal cavities. Females lay from three to 12 eggs in a previously excavated hole 6-8 in (15–20 cm) deep, and then depart. Incubation is quite long in this species, lasting usually between five and eight months. Juveniles are between 1.25 and 1.6 inches (3.2 to 4 cm) upon hatching. Unlike the yellow coloration of the adults, the juveniles are a white to an off-white shade. Juveniles attain the high-domed carapace soon after hatching.

Range and Distribution Edit

Radiated tortoises occur naturally only in the extreme southern and southwestern part of the island of Madagascar. They have also been introduced to the nearby island of Reunion. They prefer dry regions of brush, thorn (Diderae) forests, and woodlands of southern Madagascar.

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