Radiated Tortoise

Astrochelys radiata

Order: Testudines Family: Testudinidae

Radiated tortoises are the closest living relative of the Ploughshare tortoises, the most endangered tortoises in the world.

Overview

This striking species gives the perfect opportunity to talk about the unique biodiversity of Madagascar and the plight of endangered species across the globe. Radiated tortoises are personable and allow guests a hands on experience with a critically endangered species. This is a relatively large species of tortoise that does require space and can only be used in warm conditions. Radiated tortoises are one of the few SAFE species guests can be hands on with! 

Natural History Information

This is a typically shaped tortoise: they have a high-domed carapace, a blunt head, and elephantine feet. The legs, feed, and head are yellow except for a variable-sized black patch on the top of the head. The carapace is brilliantly marked with beautiful, radiating yellow/white lines contrasting over a jet black shell. Yellow lines radiate from the center of each scute. This is what gives this species their common name. A radiated tortoise has a moderately sized head with a protruding snout and a slightly hooked upper jaw.

Their skin is a dark yellow coloration, with a dark black marking on their blunted head.

Range and Habitat

 Radiated tortoises are found on the south and southwest coasts of Madagascar. They inhabit xerophytic spiny forest habitat, which receives little rainfall throughout the year.

Longevity

 Radiated tortoises are a long-lived species, typically reaching lifespans of 60 to 80 years old in human care. Around 10-11 inches (plastron measurement) they will reach maturity and will top out between 12-16 inches and a weight of 35 pounds.

Ecosystem Role

Radiated tortoises feed on dead leaves and succulents.

Husbandry Information

Housing Requirements

Life Cycle Natural History Relevant Information

  • Radiated tortoises are long-lived animals that take up to 15 years to reach mature size and sexual maturity.
  • Radiated tortoises tend to be crepuscular, foraging for food early in the morning and in the evening. During the heat of the day, they find shelter and rest.

Habitat

Indianapolis Zoo Exhibit
  • Wild radiated tortoises live in xerophytic spiny forest habitat as well as inland plateaus and sandy dunes close to the coast. This habitat experiences a wet and dry season with most rainfall occurring between November and April. Temperatures range from 59 to 91 degrees on average.
  • Indianapolis Zoo: Radiated tortoises are housed on exhibit and behind the scenes in our Deserts Dome, and outside in the summer. On exhibit, the tortoises are in large, naturalistic enclosures, with natural light and access to heat lamps, substrate to lay eggs in, and plants for browse and shade. These are mixed species exhibits with iguanas, chuckwallas, bearded dragons, and blue tongued skinks. Ambient temperatures in the winter are 86-88 during the day and 72-76 at night. During the summer, temperatures are 95. Radiated tortoises do not begin to go outside until night temperatures are in the 50s. They remain outside overnight.

Temperature, Humidity, Light Cycles

Indianapolis Zoo Off Exhibit Holding
  • Temperature: Ambient temperatures in the high 70s to low 80s are appropriate for this species. A basking spot of around 95 degrees should be offered.
  • Humidity: Young tortoises should have access to microclimates with high humidity to help prevent pyramiding.
  • Light: Tortoises should have UVB exposure. If weather conditions are suitable, this species should have access outdoors seasonally.

Substrate

Substrate can be sand, mulch, topsoil, peat moss, or any combination of those materials. A sand, topsoil, peat moss mix seems to work well for nesting females. 

Diet Requirements

Diet in the Wild

  • Radiated tortoises are herbivores, feeding primarily on low-lying vegetation such as leaves, grasses, flowers, and fallen fruits. They will opportunistically feed on carrion, animal bone, and shells which may provide calcium and other nutrients. 
  • Radiated tortoises prefer food with higher contents of digestible energy during the dry season. This includes new growth over old growth as it provides higher protein and lower fiber.

Diet under human care

  • Radiated tortoises need a high fiber diet with as much variety as possible. They are grazers and will spend a lot of the time during the day feeding. If possible, planting a wide variety of edible plants in their environment allows them options for feeding throughout the day.
  • Indianapolis Zoo: Adults are fed 200 g each of a mix of collards, bok choy, kale, broccoli, carrots, and tortoise pellet. They are offered browse throughout the year, but up to 4x per week during the summer.
  • Grapes have been a successful high-value reinforcement during training.
Tortoise browsing on snake plant at Indianapolis Zoo

Veterinary Concerns

  •  Like many tortoises in human care, radiated tortoises are susceptible to pyramiding, which is the excessive vertical growth of keratin scutes. The first few years of life are critical to preventing pyramiding. Young tortoises should have access to humid microclimates, including a hide with high humidity. Enclosures should be sprayed down several times a week.
  • Respiratory problems may occur when a tortoise gets chilled or is kept in suboptimal conditions. Minor problems may be corrected with increased temperatures. If not corrected, minor problems can progress to more serious conditions such as pneumonia. Signs of a respiratory problem include labored breathing, a nasal discharge, a gaping mouth, puffy eyes, lethargy and a loss of appetite.

Enrichment & Training

Enrichment

Behavioral Relevant Information

  • Radiated tortoises spend the morning and late afternoon hours foraging for food and spend the mid-day heat resting. Radiated tortoises should have access to basking spots.
  • Radiated tortoises will forage on fallen vegetation as well as young growth on the plants.
  • Check out the Reptelligence Facebook page and Reptelligence website for enrichment and training inspiration.
  • Advancing Herpetological Husbandry July 2018 Quarterly Newsletter- Article Environmental Enrichment for Reptiles By Charlotte James

Environmental Enrichment

  • Indianapolis Zoo: We offer different substrates including mulch, pine shavings, shredded paper, sand, soil, and leaves. Tortoises may also receive scents and audio recordings of other animals.

Behavioral Enrichment

  • Indianapolis Zoo: Natural browse is planted within the exhibit and provided throughout the year.

Schedule

  • Indianapolis Zoo: Tortoises at the Indianapolis Zoo receive enrichment once a week.

Training

Behaviors Trained

  • Indianapolis Zoo: One tortoise is target trained. Education or keeper staff can demonstrate targeting with the public. Public has been allowed to hold the target pole as the tortoise trains.
Training with tortoise at Indianapolis Zoo

Reinforcers used & schedule of reinforcement

  • Indianapolis Zoo: Tortoises receive halved or quartered grapes as reinforcement.

Other

Social Housing/Colony Management

  • While radiated tortoises exclusively breed during the wet season in the wild, they have been known to reproduce year round in human care.
  • Enclosures for a single adult should be at least 6’ long x 2’ wide x 2’ tall. Pairs should be housed in enclosures at least 8’ long x 3’ wide x 3’ tall. 
  • Radiated tortoises are sympatric with spider tortoises in the wild and have been found sharing the same shelters. Radiated tortoises have been housed successfully with a wide variety of species including chameleons, geckos, lemurs, iguanas, and other lizards. This species should not be housed with the Ploughshare tortoise because of the risk of interbreeding.

Colony or Breeding Management

  • Multiple radiated tortoises may be housed together. Males should be monitored for aggression. Multiple male, multiple female groups may lead to unknown parentage. Look to SSP for recommendations.

Individual Identification

  • Some radiated tortoises can be distinguished easily by their shell markings and coloration. 
  • Indianapolis Zoo: Individuals are microchipped and have individualized shell filings to identify them.

Programmatic Information

Messaging Themes

  • Endemism: Some species can only be found in one specific place. Radiated tortoises are only found in Madagascar. 85% of Madagascar’s reptiles are endemic.
  • Endangered Species: Radiated tortoises went from one of the most common species of tortoises on the planet to one of the most endangered in just a few decades. They have experienced a 75% decline in just the last 20 years.
  • Unsustainable Harvest: Radiated tortoises were once one of the most common species of tortoises in the world, but their numbers have decreased mostly due to poaching for bushmeat and the pet trade. Despite being a protected species, radiated tortoises are collected by local peoples for food. Juveniles are targeted to be sent abroad for the pet trade. The large numbers of animals harvested from the wild has caused a sharp decline in populations. Because radiated tortoises take a long time to reach sexual maturity, it is difficult for their numbers to rebound quickly. Up to 500,000 radiated tortoises are taken from the wild every year.
  • Many regions of Africa including the Congo and the island of Madagascar are extensively mined for coltan and other minerals that go into cell phones, tablets, and computers. Natural habitat, frequently in areas that are legally protected, is lost for wildlife, trees and topsoil scraped away. In addition, toxins from discarded electronics leach out of local landfills and contaminate waterways here at home. Please ask guests to think twice before replacing their electronic devices and to recycle their old ones when they do. http://www.houstonzoo.org/wp-content/uploads/2012/10/Why-should-I-recycle-my-cell-phone.pdf
  • In general, animals seen at the zoo do not make good pets. Most have specialized dietary, veterinary, housing, and social needs that are difficult or impossible for even dedicated pet owners to meet. Always ensure that your future pet has not been taken from the wild. Captured animals are typically mistreated by profit-motivated traffickers and dealers, resulting in many animal deaths; well-meaning animal lovers may feel like they are rescuing animals by purchasing them but are really perpetuating the cruelty. In addition, many exotic pets are released by their owners when they become too dangerous or demanding, often with devastating effects on local ecosystems. Reptiles have specialized needs, are frequently wild-caught, and damage the local environment if released; guests should be advised to educate themselves and proceed with caution. Domestic dogs and cats are almost always the best option! Many deserving animals are available for adoption at animal shelters. http://www.philadelphiazoo.org/Save-Wildlife/Images/PetWalletBro2012.aspxhttp://pin.primate.wisc.edu/aboutp/pets/index.html
  • One of the best ways for people to help the rainforest is to reduce their use of tropical woods. Many rainforest trees are felled each year for lumber, furniture, and other products that end up in countries all over the world. Flooring, musical instruments, picture frames and other products made of rosewood should be particularly avoided to slow deforestation on Madagascar and to avoid the extinction of endangered or vulnerable rosewood tree species from forests all around the equator. Ask guests to consider used or vintage furniture or new furniture made of wood that has been reclaimed from old structures. There are many alternatives to conventional lumber including flooring and other products made from fast-growing bamboo, and decking made of recycled plastic formed to look like wooden boards. http://environment.nationalgeographic.com/environment/habitats/rainforest-threats/http://www.globaltrees.org/tp_d_nigra.htmhttp://www.rainforestrelief.org/What_to_Avoid_and_Alternatives/Rainforest_Wood/What_to_Avoid_What_to_Choose/By_Tree_Species/Tropical_Woods/R/Rosewood.html

Threats and Conservation Status

  • Radiated tortoises are a Critically Endangered species according to the IUCN. Populations have experienced an approximate 75% decline since 2000.
  • From the Radiated Tortoise Studbook: This moderately large and attractive species is under threat because of not only its size, but its beauty as well. In 2008, this species was elevated to Critically Endangered status with the IUCN, as surveys have shown drastic population declines throughout its range. This species as well as the spider tortoise (Pyxis arachnoides) was once protected by traditional fady or local taboo. In recent years, the local taboos have subsided, and the tortoises have been collected by the hundreds of thousands in addition to having vanished from approximately 65% of their historic range. Demand for this species for consumption in Madagascar and the black market pet trade in Asia has been primarily to blame for this recent insurgence in their trafficking.
  • The Turtle Survival Alliance, along with Henry Doorly Zoo’s Madagascar Biodiversity Partnership, Utah’s Hogle Zoo, and Nautilus Ecology are working with the local Malagasy to protect the remaining populations as best as possible.
  • This species is endangered due to habitat loss, the pet trade, and poaching.
  • Radiated tortoises originally became endangered because the Chinese settlers of Madagascar used their meat as an aphrodisiac. This species is found in a very restricted range (naturally occurring in an area of less than 20,000 square miles.) No estimates of the 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, over 300 specimens are listed as participating in captive breeding programs such as the SSP. Captive breeding has shown great promise.

Interesting Natural History Information

  • Just like humans take a long time to reach maturity, tortoises do too. This makes them especially susceptible to population loss as recovery takes a long time.

Did you know…

  • The oldest known radiated tortoise was named Tua Malia. She was an estimated 189 years old at the time of her death.
  • World Turtle Day is May 23rd every year! 

Handling & Presentation Tips

  • Indianapolis Zoo: Handlers are required to be trained on smaller tortoise species before handling and presenting radiated tortoises. The tortoises are allowed to free roam as guests are invited to touch their shells. Handlers reposition the tortoise as necessary. 

Use Guidelines

  • Indianapolis Zoo: Individuals can be handled up to twice a day, three days in a row. There must be at least 2 hours between encounters and a rest day following three days of use. Temperature of encounter space must be at least 70 degrees and no more than 95 degrees.

Public Contact and Interaction Guidelines

  • Indianapolis Zoo: Public is encouraged to gently touch the tortoise’s shell, avoiding the head, tail, and legs. A two finger touch is suggested, especially for children.

The Indianapolis Zoo hosts the Zoopolis500 every year, which coincides with the Indy500. Local announcers and racecar drivers help announce a race between the radiated tortoises as lumber towards a plate of their favorite foods.

Transportation Tips

  • Indianapolis Zoo: Tortoises are transported in large coolers. The bottom is lined with newspaper to improve their comfort during transport and reduce clean-up time.

Crating Techniques

  • Indianapolis Zoo: The bottom of the cooler is lined with newspaper. Tortoises are lifted into the cooler.

Temperature Guidelines

  • Indianapolis Zoo: Radiated tortoises can be presented in conditions between 70 and 90 degrees. The Zoo only does on-ground programming. Radiated tortoises may not be transported outside their building if temperatures are below 20 degrees. 

Acquisition Information

Radiated tortoises are a Green SSP species. Contact the SSP coordinator for acquisition and breeding recommendations.

SSP Coordinator: Michael Ogle, Zoo Knoxville mogle@zooknoxville.org

Studbook Keeper: Stephen Nelson, Zoo Knoxville snelson@zooknoxville.org

Resources

Contributors and Citations

  •  Casey Schmidt, Radiated Tortoise SSP Education Advisor, Indianapolis Zoo 

Photo Credits: 

Header photo by Stephen Nelson. All other photos from the Indianapolis Zoo. 

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