Species Spotlight Vol. 12

by Jordan Gray

Radiated Tortoise

Radiated Tortoise (Astrochelys radiata)

Countries of Origin: Madagascar

IUCN Status: Critically Endangered

Estimated surviving population: Declining rapidly

Habitat: Xeric spiny forests, sandy coastal scrub, and rocky coastal outcroppings of the limestone-based Mahafaly and Karimbola plateaus of southwestern Madagascar.

Biology and Habits: Radiated Tortoises are most active during the morning hours of 6:30 – 10:00 AM and late afternoon hours of 3:30 – 6:00 PM, when temperatures are cooler and the humidity is greater. The seasonal activity patterns of this species are highly synchronized with precipitation. The greatest amount of activity occurs throughout the rainy season (December – February), during which time the region receives most of its roughly 40 cm (16 in) of annual rainfall. This species is primarily an herbivorous grazer and forager, feeding on grasses, flowers, fruits, invasive Opuntia cacti, as well as dried leaves when soft vegetation is unavailable. Females will lay between 1 – 3 clutches of 1 – 5 eggs during the end of the rainy season. Egg incubation may last up to 10 months, strategically hatching the eggs at the onset of the next rainy season when new soft vegetation and water is in better abundance. A long-lived species, the Radiated Tortoise is known to live well past the century mark, with the oldest known specimen, a female named Tu’I Malila, having lived to 188 years old!

Size: Males ≤ 40 cm (16 in), Females ≤ 36 cm (14 in). **The largest specimen we currently know of is a 24 kg (52 lb) female that currently resides at our facility in Tana after having been a long-term captive at the US Embassy there.**

Factoid: The plight of the Radiated Tortoise is considered by many to be the “American Bison” of Madagascar. An analogous story of extirpation, the tortoise, once numbering in the tens of millions, has disappeared from roughly 65% of its former range, with an estimated population reduction of 80% in the next two decades. For centuries, the tortoise was protected throughout much of its range by a religious taboo of the Mahafaly and Antandroy peoples known as “fady.” This fady prevents the touching of and collection of tortoises. In recent decades however, an influx of outsiders to the region has put the tortoise in peril as their customs do not recognize this fady. Additionally, socioeconomic pressures attributed to the rapid growth of Madagascar’s population have resulted in the erosion of some societal norms and unique customs, and put a greater stress on the sourcing of income and sustenance.

Greatest Threats: Poaching for domestic and international food and pet markets, and habitat loss including the clearing of land for agriculture and livestock, and the harvesting of wood for charcoal.

How you can help: The TSA and Utah’s Hogle Zoo (UHZ) have been working on a strategic action plan for this tortoise known as the “Confiscation to Reintroduction Strategy.” This strategic action plan for Radiated Tortoises is based on a multi-pronged conservation approach with bases in law enforcement, community outreach, reintroduction, habitat preservation, and the new joint TSA/UHZ Tortoise Conservation Center (TCC). Furthermore, this strategy for the survival of the Radiated Tortoise will now be bolstered by collaborative conservation efforts through the Association of Zoos and Aquariums’ (AZA) Saving Animals From Extinction (SAFE) initiative. You can directly help save the Radiated Tortoise from extinction in the wild by DONATING TODAY!