Astrochelys radiata only occur naturally in the extreme southern and southwestern part of the island of Madagascar. A. radiata have also been introduced to the nearby island of Reunion (LPZ 1999).
Biogeographic Regions: ethiopian (Native )
Distribution: Madagascar (Antandroy Territory in the south between the Mandrare and Menarandra waterways). Endemic.
Type locality: "Madagascar"; restricted by Bour 1978 to "Soalara (Baie de Saint-Augustin) sud-ouest de Madagascar".
Growing to a carapace length of up to 16 inches and weighing up to 35 pounds, A. radiata is considered to be one of the world's most beautiful tortoises. A. radiata 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 A. radiata is brilliantly marked with yellow lines radiating from the center of each dark plate of the shell, hence the name radiated tortoise. 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. A. radiata 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 A. radiata usually have longer tails and the notch in the plastron beneath the tail is more noticeable (Kirkpatrick 1992).
Other Physical Features: ectothermic ; bilateral symmetry
A. radiata prefer dry regions of brush, thorn (Diderae) forests and woodlands of southern Madagascar (LPZ 1999).
Habitat and Ecology
Radiated Tortoises are herbivores feeding predominantly on grasses and in some areas on the alien invasive Opuntia. On occasion they are also known to ingest animal matter. During the rainy season wild tortoises drink from water that collects on rocks after it rains (Leuteritz 2003).
Adult female tortoises range in carapace length from 24.2 - 35.6 cm and males ranged in from 28.5 - 39.5 cm (Pedrono 2008). Males exhibit distinct secondary sexual characteristics by about 26 cm carapace length (Leuteritz 2002). Mature females produce up to three clutches per season with 1–5 eggs per clutch (Leuteritz and Ravolanaivo 2005), leading to an estimated average production of two clutches of four eggs each per breeding female; an estimated 82% of mature females breed in an average year (Randriamahazo et al. 2007). No solid data exists on longevity but estimated life span is believed to be up to 100 years (Randriamahazo et al. 2007). A detailed overview of natural history is presented by Pedrono (2008).
A. radiata is an herbivore. Grazing makes up approximently 80-
90% of their diet. They feed during the day primarily on
grasses, fruit, and succulent plants. A favorite food in the
wild is the Opuntia cactus. In captivity A. radiata is known to eat sweet potatoes, carrots, apples, bananas, alfalfa sprouts,
and melons. According to some sources A. radiata seem to be
partial to red foods. 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 (Behler and Iaderosa 1991).
Life History and Behavior
Status: captivity: 12.8 years.
Lifespan, longevity, and ageing
Males first mate upon attaining lengths of about 12 inches; 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 will then proceed to mount the female from the rear while striking the anal region of his plastron against the females carapace. Hissing and grunting by the male during mating is common. Females lay from 3 to 12 eggs in a pre-excavated hole 6 to 8 inches deep and then depart. Incubation is quite long in this species, lasting usually between 145 and 231 days. Juveniles are between 32 to 40 mm 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 (Kirkpatrick 1992).
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate)
Molecular Biology and Genetics
Barcode data: Astrochelys radiata
Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen.
Other sequences that do not yet meet barcode criteria may also be available.
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Download FASTA File
Statistics of barcoding coverage: Astrochelys radiata
Public Records: 1
Specimens with Barcodes: 2
Species With Barcodes: 1
Unfortunately, A. radiata is severely endangered due to loss of
habitat, being poached for food, and being over exploited in the
pet trade. A. radiata is listed in Appendix I of the Convention
on International Trade in Endangered Species (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 stud book, 400 specimens are listed as participating in captive breeding programs such as the Species Survival Plan in zoos. Captive breeding of A. radiata has shown great promise (Behler and Iaderosa 1991).
CITES: appendix i
IUCN Red List of Threatened Species: critically endangered
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1996Vulnerable(Baillie and Groombridge 1996)
- 1994Vulnerable(Groombridge 1994)
- 1990Vulnerable(IUCN 1990)
- 1988Vulnerable(IUCN Conservation Monitoring Centre 1988)
- 1986Vulnerable(IUCN Conservation Monitoring Centre 1986)
Population models were calculated at the 2005 Population and Habitat Viability Analysis (PHVA) workshop based on a number of variables including estimated population size and annual harvest intensity. Depending on the variables selected, the species was predicted to reach extinction at various times, with most estimates clustering around 45 years into the future (range 20-100+ years) (Randriamahazo et al. 2007).
International collection has been documented with Asian smugglers collecting tortoises for the pet trade and for their livers (Behler 2002).
However, domestic utilization of this species is of greater concern. Within Madagascar, the Mahafaly and the Antandroy, whose land covers the range of the Radiated Tortoise do not utilize the tortoise. They have a taboo (teremed a 'fady') against eating or touching the tortoises (Nussbaum and Raxworthy 1998, Lingard et al. 2003). However, large quantities of Radiated Tortoises are gathered by people from other areas of Madagascar who recently moved into this region, or by Malagasy people who are passing through. O’Brien et al. (2003) estimated that up to 45,000 adult Radiated Tortoises are harvested each year. Anecdotal information indicates that annual harvest numbers have increased since then; estimates calculated at the 2005 PHVA workshop ranged from 22,000 to 241,000 tortoises collected annually. Tortoise meat is especially popular around Christmas and Easter (Lewis 1995). Declared protected areas are insufficiently patrolled and resourced to deter large-scale collection right inside these nominal strongholds.
Besides being used as food, the Malagasy often keep the tortoises as pets and in pens with chickens and ducks as a means of warding off poultry diseases (Durrell et al. 1989, Leuteritz et al. 2005).
Habitat loss includes deforestation for use as agricultural land, the grazing of livestock, and the burning of wood for charcoal (Nussbaum and Raxworthy 1998). Recent analyses by Conservation International (May 2007) of the state of the spiny forest biome, using aerial imagery, indicate that deforestation rates have significantly increased over the last five years (compared with the period 1990-2000) (H. Crowley pers. comm. to Leuteritz). The 2001 Conservation Assessment and Management Plan (CAMP) workshop estimated habitat loss at 21-50% during the period 1990-2000, and forecast a habitat loss rate of 51-80% for the period 2001-2010. Harper et al. (2007) documented a consistent annual forest loss rate of 1.2% for the spiny forest (primary Radiated Tortoise habitat) throughout the period 1970-2000, and measured an overall reduction from 29,782 to 21,322 sq km over this period, a 29% reduction in less than one tortoise generation.
Invasive plant species affecting habitat suitability were considered a significant threat at the 2001 CAMP workshop.
The species is protected nationally under Malagasy law (Decree 60126; October, 1960). Internationally, the Radiated Tortoise was listed as Category A of the African Conservation Convention of 1968, and, since 1975, it has been listed on Appendix I of CITES, which affords species the highest level of protection (Durrell et al. 1989, Hilton-Taylor 2000).
Four protected areas and three additional sites (Lac Tsimanampetsotsa National Park 43,200 ha, Beza-Mahafaly Special Reserve 67,568 ha, Cap Sainte Marie Special Reserve 1,750 ha, Andohahela National Park 76,020 ha, and Berenty Private Reserve 250 ha, Site of Biological Interest – (1) Hatokaliotsy 21,850 ha and (2) PK3 north of Tulear 12,500 ha) fall within the range of this species. A captive breeding centre (Village de Tortues de Mangily) was established in Ifaty.
In August 2005, an international meeting of the Population and Habitat Viability Assessment (PHVA) group produced an alarming prediction that without immediate and significant intervention, viable populations of Radiated Tortoises will likely be extirpated from the wild within one tortoise generation, that is, 45 years (Randriamahazo et al. 2007). It was suggested that a systematic monitoring program be established. This will have to involve the training of local people so that the programme can be viable. This and other recommended conservation measures are detailed in the PHVA workshop report (Randriamahazo et al. 2007). In addition, monitoring of exploitation trends at the wholesale and consumer parts of the trade chain (surveys of markets, traders and restaurants in Madagascar; monitoring international pet trade) is important.
Additionally, ensuring adequate coverage of Radiated Tortoise populations as Madagascar expands its protected area network is essential. Research on habitat usage, specifically the impacts and benefits from Opuntia and other invasive vegetation, is desirable.
The radiated tortoise (Astrochelys radiata) is a species in the family Testudinidae. Although this species is native to and most abundant in southern Madagascar, it can also be found in the rest of this island, and has been introduced to the islands of Réunion and Mauritius. As the radiated tortoises are herbivores, grazing constitutes 80-90% of their diets, while they also eat fruits and succulent plants. A favorite food in the wild is the Opuntia cacti. 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. These tortoises are, however, endangered, mainly because of the destruction of their habitat by humans and because of poaching.
The Radiated Tortoise
Growing to a carapace length of up to 16 in (41 cm) and weighing up to 35 lb (16 kg), 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 notches beneath their tails are more noticeable. The Radiated Tortoise is endemic to Madagascar.
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.
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.
These tortoises are critically endangered due to habitat loss, being poached for food, and being over exploited in the pet trade. It is listed in Appendix I of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora), 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 Species Survival Plan. Captive breeding has shown great promise as in the captive breeding program for the radiated tortoise at the New York Zoological Society's Wildlife Survival Center. In 2005, the Wildlife Survival Center was closed, and the radiated tortoise captive-breeding program was continued with the inception of the Behler Chelonian Center.
In March 2013, smugglers were arrested after carrying a single bag containing 21 radiated tortoises and 54 angonoka tortoises (Astrochelys yniphora) through Suvarnabhumi International Airport in Thailand.
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