Radiated tortoise

Radiated tortoises live in dry, spiny forests.

It does not rain much there.

They live only in the south of Madagascar.

Radiated tortoises live only in southern and southwestern Madagascar, usually within about 50 to 100 kilometers of the coast. Their home is the dry spiny forest, where rain is low and does not come regularly, and many plants are spiny and suited to dry conditions.

They live both on high plateaus inland and on sandy dunes close to the sea. Rivers seem to keep many of them apart: a genetic study found three separate groups.

The IUCN text (2008) describes a range in the dry spiny forests of southern and southwestern Madagascar, from around Amboasary in the south across the Karimbola and Mahafaly plateaus north of Tuléar to Morombe, usually in a narrow band about 50 to 100 kilometers from the coast, with a core range of about 10,000 square kilometers. The habitat has low, irregular rainfall and xerophytic spiny vegetation dominated by Didiereaceae and Euphorbia (Durrell et al. 1989), on inland high plateaus and coastal sandy dunes (Leuteritz et al. 2005).

A microsatellite study (Rioux Paquette et al. 2006) identified three distinct conservation units and supported the Menarandra and Manambovo rivers as major barriers to dispersal for most radiated tortoises.

Radiated tortoises eat plants.

They munch grass and fruit.

They drink rainwater from rocks.

Radiated tortoises are plant eaters that feed mostly on grasses. In some areas they also eat prickly pear cactus, a plant that was brought to Madagascar from elsewhere. They eat fruit and juicy plants too, and once in a while some animal food.

In the rainy season, wild tortoises drink the water that collects on rocks after rain.

The IUCN describes radiated tortoises as herbivores feeding predominantly on grasses and, in some areas, on the alien invasive Opuntia, occasionally ingesting animal matter; during the rainy season wild tortoises drink from water that collects on rocks after rain (Leuteritz 2003). The Animal Diversity Web (citing Behler and Iaderosa 1991) states that grazing makes up about 80 to 90% of the diet, that they feed by day on grasses, fruit and succulent plants, and that they graze the same areas regularly, keeping the vegetation closely trimmed, preferring new growth.

Radiated tortoises are busy in the daytime.

They graze on grass.

Radiated tortoises feed during the day, grazing the same patches again and again, which keeps the plants there cut short.

In courtship, a male bobs his head and sniffs the female. He may even lift her up with the front edge of his shell to stop her from walking away, and males often hiss and grunt while mating.

The Animal Diversity Web describes daytime grazing over the same areas, keeping vegetation closely trimmed (Behler and Iaderosa 1991), and a fairly noisy courtship: the male bobs his head and smells the female's hind legs and cloaca, may lift her with the front edge of his carapace to stop her moving away, and commonly hisses and grunts during mating (Kirkpatrick 1992).

The IUCN notes that the species shares its range with the spider tortoise (Pyxis arachnoides), and that radiated tortoises were once often found along roadways in the south, which by 2008 was no longer the case.

Radiated tortoises are in great danger.

Many have been taken from the wild, and much of their forest has been cut down.

Laws protect them, and people care for tortoises that were taken.

The radiated tortoise is critically endangered. The 2008 IUCN assessment found it had vanished from about 40% of its old range. Large numbers were being collected, mostly for food, by people from outside the area, and others for the pet trade. Its spiny forest was being cleared for farmland, grazed by livestock and cut for wood to burn for charcoal.

It has been protected by Madagascar's law since 1960, and international trade has been banned in most cases since 1975. A 2022 study describes a center in its homeland that cares for tortoises confiscated from illegal collection.

Leuteritz and Rioux Paquette assessed Astrochelys radiata as Critically Endangered (A4d; E) for the IUCN Red List (assessed 15 January 2008, published 2008; needs updating): it had disappeared from about 40% of its past range, a reduction of 80% over two past and one future generation (generation 42 years) was judged conservative, and population models at a 2005 workshop predicted extinction in about 45 years on average (range 20 to 100+; Randriamahazo et al. 2007). Earlier population estimates ranged from 1.6 to 4 million (Lewis 1995) to 12 million (Leuteritz et al. 2005). Collection was mainly for domestic consumption, by people from other areas: up to 45,000 adults a year (O'Brien et al. 2003), with 2005 estimates of 22,000 to 241,000 a year; there was also international collection for the pet trade. The spiny forest shrank from 29,782 to 21,322 square kilometers between 1970 and 2000 (Harper et al. 2007).

The species is protected under Malagasy law (Decree 60126, 1960) and listed on CITES Appendix I since 1975; its range includes Tsimanampetsotsa and Andohahela national parks and the Beza-Mahafaly and Cap Sainte Marie special reserves. In 2022, Brenn-White and colleagues described radiated tortoises as confiscated in alarming numbers in recent years, and reported on 120 previously confiscated subadults cared for at the Tortoise Conservation Center within the species' native habitat, part of the pathway from confiscation to release.