| Angonoka tortoise | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Testudines |
| Suborder: | Cryptodira |
| Family: | Testudinidae |
| Genus: | Astrochelys |
| Species: | A. yniphora |
| Binomial name | |
| Astrochelys yniphora Vaillant, 1885[1] |
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| Synonyms[2] | |
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The angonoka tortoise (Astrochelys yniphora) is a critically endangered species of tortoise endemic to Madagascar.[3] It is also known as the angonoka, ploughshare tortoise, Madagascar tortoise, or Madagascar angulated tortoise.[4]
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This species was originally described in 1885 by French zoologist Léon Vaillant, who proposed it as the species Tesudo yniphora based on the distinguished shape of the anterior part of the plastron.[5]
The angonoka tortoise (A. yniphora) along with the radiated tortoise (A. radiata) are the only species in the genus Astrochelys. Astrochelys is attributed to John Edward Gray who used the name in his 1873 book Hand-list of the specimens of shield reptiles in the British Museum.[6][7] The parent family for Astrochelys is Testudinidae, the tortoise family.[1]
The name angonoka comes from the Malagasy word which is used as the local name of the species.[8] The alternative common name ploughshare tortoise refers to the appearance of the gular scute of the plastron.[9]
The carapace is highly domed and light brown in colour with prominent growth rings on each scute. The outer parts of the vertebral is a darker brown.[10] The gular scute of the plastron projects forward between the front legs and curves upward toward the neck.
Males are larger than females, reaching a carapace length up to 17 inches (43 cm).[11] Fully grown male angonoka tortoises are larger, as well as heavier, than females. The average weight of an adult male angonoka tortoise in 414.8 millimetres (16.33 in) and the average weight of one is 10.3 kilograms (23 lb). Females measure at a 370.1 millimetres (14.57 in) average and weigh a 8.8 kilograms (19 lb) average.[4]
In the wild this species is only found in Madagascar where it is endemic to the dry forests in the Baly Bay area of northwestern Madagascar, near the town of Soalala.[1][12][13] The distribution is a 25 to 60 square kilometres (9.7 to 23 sq mi) range around Baly Bay.[4]
The Baly Bay region is made up of savanna, mangrove swamps, and dry deciduous forest. They make use of bamboo-scrub habitat which is made up of different types of shrubs, savanna grasses, bamboo, and open areas with no vegetation. The flora includes shrubbery usually under 2 metres (6 ft 7 in) in height, such as Bauhinia and Terminalia species, and Perrierbambus madagascariensis bamboo, which forms dense thickets. The elevation of this area is under 50 metres (160 ft) above sea level.[4]
The population estimate for the angonoka tortoise in the wild is about 600 individuals, ranging from 440 to 770, but is still decreasing. The tortoise is at an extremely high risk of extinction; it is thought it will become extinct in the wild in the next 10 to 15 years. It can be found in five sub-populations, two east of the and three west of the Andranomavo river. The two to the east are Beheta and Sada; the three to the west are Ambatomainty, Andrafiafaly, and Betainalika.[4]
The angonoka tortoise has been observed feeding on grasses found in open rocky areas of bamboo scrub. It is also known to eat shrubs, forbs, and herbs. While it has been seen eating dead bamboo leaves, it has never been observed eating living bamboo. As well as these plants, the tortoise has also been seen eating the dried feces of bushpigs and carnivores.[4]
It is expected to become sexually mature at at least 15 years old. The tortoise can produce one to six eggs per clutch and up to four clutches every season. The reproductive season is from January 15 to May 30.[4] The angonoka tortoise's reproductive patterns coincide with the seasonal rainfall patterns of the region, with both mating and hatching occurring at the onset of the rainy seasons.[14] With a 71.9% fertility rate and a 54.6% hatching success rate, about 4.3 hatchlings are produced per female tortoise.[4]
In captivity males must be separated due to aggression towards each other, including ramming, pushing, and overturning with the enlarged gular scute. The aggression is used to establish dominance.[10]
This species is one of the rarest land tortoises in the world, classified as Critically Endangered on the IUCN Red List.[4] The principal threats to the species are believed to be fires started to clear land for cattle grazing, and collection for the pet trade. The tortoise has a restricted distribution, likely a result of past collection for food, the expansion of agriculture, and accompanying fires.[4] Fires made to clear land can get out of control, turning into wildfires, which cut back more of the angonoka tortoise's habitat. Following efforts to create firebreaks through controlled fires in savanna fringes by conservation groups, out-of-control fires have decreased, until less than 50 hectares (120 acres) of its habitat were burnt in 2004.[4] The angonoka tortoise is often captured to be sold in the international pet trade. Even though there is some successful enforcement of restrictions on illegal trade, including the confiscation of the illegally obtained tortoises, they remain in incredibly high demand for the global pet trade. This is a major threat to the tortoises remaining in the wild.[4]
In addition to its Red List listing, the angonoka tortoise is now protected under the national law of Madagascar and listed on Appendix I of CITES, prohibiting international trade in the species. For the conservation of the angonoka tortoise, the Durrell Wildlife Conservation Trust created Project Angonoka in 1986. The Water and Forests Department, the Durrell Trust, and the World Wide Fund for Nature (WWF) work together on this project.[4] A captive breeding facility was established for this species in Madagascar in 1986 by the Jersey Wildlife Preservation Trust (now the Durrell Trust) in collaboration with the Water and Forests Department.[12] In May 1996, 75 tortoises were stolen from the facility. The thieves were never found, but 33 tortoises later appeared for sale in Holland.[15] The project ultimately was a success, achieving 224 captive-bred juveniles out of 17 adults in December 2004. After the 1990s, Project Angonoka started ecological research on the tortoise and the development of conservation plans that involved the communities surrounding the habitat. The work with the community involved local people in making firebreaks, along with the creation of a park proposed by the community to protect the tortoise and the forests. Although all these improvements have been made, monitoring of the angonoka tortoise in the global pet trade is still needed.[4]
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