The
radiated tortoise (
Astrochelys
radiata) is a
species in the
genus of the
Astrochelys tortoises.It is fairly large
and considered by many to be one of the most beautiful
tortoises in the world.
Although this species
is native to Southern Madagascar
and mainly only found there, it can be found in the
rest of this country and has been introduced to the islands of
Réunion
and Mauritius
. As the Radiated Tortoises are
herbivores,
grazing
constitutes 80-90% of their
diet,
while they also eat
fruits and
succulent plants. These tortoises are,
however,
endangered, mainly
because of the destruction of their
habitat by
humans and
because of
poaching.
The oldest tortoise ever recorded, indeed the oldest reptile ever
recorded, was a radiated tortoise,
Tu'i
Malila, there is controversy over whether she lived 150, 188,
or 250 years.
Anatomy and morphology
Growing to a carapace length of up to 16 inches (41 centimeters)
and weighing up to 35 pounds (16kg), the radiated tortoise is
considered to be one of the world's most beautiful tortoises.
This tortoise has the basic "tortoise" body shape, which consists
of the high-domed carapace, a blunt head, and elephantine feet. The
legs, feet, and head are yellow except for a variably sized black
patch on top of the head.
The carapace of the radiated tortoise is brilliantly marked with
yellow lines radiating from the center of each dark plate of the
shell, hence its name. This "star" pattern is more finely detailed
and intricate than the normal pattern of other star-patterned
tortoise species, such as G. elegans of India.The radiated tortoise
is also larger than G. elegans, and the
scutes
of the carapace are smooth, and not raised up into a bumpy,
pyramidal shape as is commonly seen in the latter species. There is
slight sexual dimorphism. Compared to females, male radiated
tortoises usually have longer tails and the notch in the plastron
beneath the tail is more noticeable.
Range and distribution
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.
Opuntia cactus. They are known to graze regularly in the same area,
thus keeping the vegetation in that area closely trimmed. They seem
to prefer new growth rather than mature growth because of the
high-protein, low-fiber content.
Reproduction
Males first mate upon attaining lengths of about 12 inches (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 there have been recorded
cases where the female's shell has cracked and pierced the vaginal
and anal cavities. Females lay from three to 12 eggs in a
pre-excavated hole six to eight inches (15 to 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 to 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.
Radiated tortoises may live as long as 40 to 50 years.
Conservation
Unfortunately, these tortoises are severely endangered due to loss
of habitat, being poached for food, and being over exploited in the
pet trade. It is listed in Appendix I of CITES, which prohibits the
import or export of the species under most conditions. However, due
to the poor economic conditions of Madagascar, many of the laws are
largely ignored.
No estimates of wild populations are available, but their numbers
are declining, and many authorities see the potential for a rapid
decline to extinction in the wild. In the North American studbook,
332 specimens are listed as participating in captive breeding
programs such as the SSP. Captive breeding has shown great promise.
The radiated tortoises on exhibit at the Zoo are all females and
are not part of the SSP breeding program at this time.
References
- Fritz, U. & O. R. P. Bininda-Emonds 2007. When genes
meet nomenclature: Tortoise phylogeny and the shifting generic
concepts of Testudo and Geochelone. Zoology
110, pages 298-307.
- Egeler, 2000
- EMYSystem Species Page
Bibliography
External links
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