One predator of ploughshare tortoises is the introduced African bushpig (Potamochoerus larvatus), which kills eggs and juveniles. There is a large population of Potamochoerus larvatus because local Muslims seldom hunt them. Rarely, snakes and birds prey on eggs and young tortoises. Humans are predators because many tortoises are hunted for the illegal pet trade or to eat. Although there are laws prohibiting it, there is still smuggling going on today. Additionally, humans are responsible for bush fires, which result in habitat destruction. Since ploughshare tortoises take a long time to mature sexually and reproduce, populations take a long time to recover even if predation is controlled. Ploughshare tortoises have a population growth rate of only 1% each year (A. Mandimbihasina, pers. comm.).
Known Predators:
The heads and snouts of ploughshare tortoises range in color from black to various shades of brown with yellow spots near the ear. As with all tortoises, they lack teeth, but their beaked jaw is extremely powerful. The neck, limbs, and tail are usually brown with some tan or yellow. They have flattened legs with scaly, armored skin and clawed toes on each foot. Ploughshare tortoises have a distinctly large gular scute, which curves up towards the neck. This creates a plough-shaped projection between the front legs, hence the name ploughshare. The oval, high-domed carapace usually has eleven marginals on each side with an additional larger one on the posterior. Each marginal is yellowish-brown darkening towards the edges with thin, black hexagonal growth rings on each scute. The plastron is yellow with some brownish tint. With age, the carapace becomes darker in color and more monotone (A. Mandimbihasina, pers. comm.).
Male, adult ploughshare tortoises have a weight that ranges from 7.2 to 18.9 kilograms (mean 10.3 kilograms). Adult females weigh from 5.5 to 12 kilograms (mean 8.8 kilograms). Males are larger than females, possessing a longer gular scute as well as longer, thicker tails. The length of ploughshare tortoises also varies between males and females. Adult females range from 30.7 to 42.6 centimeters long (mean 37 cm). Adult males range from 36.1 to 48.6 centimeters (mean 41.5 cm). Another way to differentiate between sexes is by flipping the tortoise over and looking at the plastron, anal notches, and anal forks. Females have a flat plastron, while males have concave plastrons. Additionally, males have longer anal forks, and females have larger anal notches that are big enough for the eggs they produce (A. Mandimbihasina, pers. comm.).
Range mass: 5.5 to 18.9 kg.
Range length: 30.7 to 48.6 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: male larger; sexes shaped differently
Although ploughshare tortoises live a long time, the actual lifespan is unknown. It is estimated that ploughshare tortoises live between 50 and 100 years. The lifespan is longer in zoos due to veterinary care, adequate nutrition, and lack of predators. Ploughshare tortoises reach sexual maturity around twenty years of age. Growth rings can be used to measure how old a tortoise is. However, the carapace becomes smooth when the tortoise reaches about thirty years old, making growth rings hard to count (A. Mandimbihasina, pers. comm; D. Uyeda, pers. comm.).
Adult ploughshare tortoises have an annual survival rate of 97%. Juvenile tortoises have an annual survival rate of 44 to 96%, which is determined by their size. Usually, the larger the individual, the higher the annual survival rate.
Ploughshare tortoises are terrestrial and live in bamboo scrub (Perrierbambos madagascariensis) savannahs with palms (Bismarckia nobilis) and shrub thickets (Terminalia boivinii) in a hot-tropical, semi-humid zone. This xeric scrub forest includes the plant species Chadsia grevei, Alloteropsis semialata, Clerodendron incisum, Casaythra species, Heteropogon contortus, and Bismarckia nobilis. Ploughshare tortoises find protection in dense thickets but prefer to forage in open grassy areas.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: savanna or grassland ; scrub forest
Ploughshare tortoises are endemic to the Baly Bay area of northwestern Madagascar. There are five isolated populations within thirty kilometers of Baly Bay that consist of less than 600 total individuals in the wild. The five populations include Cape Sada (150 hectares), Ankasakabe (50 hectares), Beheta (200 hectares), Betainalika (340 hectares), and Ambatomainty-Andranolava (500 hectares). Each population is separated by a geographical barrier such as the Andranomavo River, which isolates the west and the east populations. The total world range of ploughshare tortoises lies within an area of only about one hundred square miles.
Biogeographic Regions: ethiopian (Native )
Other Geographic Terms: island endemic
Ploughshare tortoises are largely herbivorous. Their diet consists of many types of fruits, leaves, and the feces of some animals including lemurs (Lemuriformes) and introduced bushpigs (Potamochoerus larvatus). They eat the leaves of shrubs but rarely eat bamboo leaves, which can contain high levels of cyanide. They forage on the grass Heteropogon contortus, but favor the shrub Bauhinia pervillei (A. Mandimbihasina, pers. comm.).
At the Honolulu zoo, a female ploughshare tortoise is fed on alternate days with browse and a mixed diet. Browse includes sweet potato vines, flowers and leaves of hibiscus, dandelion, Opuntia, or hau. The mixed diet consists of ground carrots and celery as well as cut up orange, apple, and banana. This mixed diet also includes horse pellets, made of bionate and calcium (D. Uyeda, pers. comm.).
Plant Foods: leaves; fruit
Other Foods: dung
Primary Diet: herbivore (Folivore , Frugivore ); coprophage
Amblyoma geochelone is a recently discovered species of tick that is a host-specific ectoparasite of ploughshare tortoises. Given its host-specificity, it is thought that A. geochelone may also be endangered. This parasite does not seem to substantially harm ploughshare tortoises. Ploughshare tortoises may be important in dispersing the seeds of the fruits they eat.
Ecosystem Impact: disperses seeds
Commensal/Parasitic Species:
Astrochelys yniphora is also known by the common names: angonoka (Malagasy), angulated tortoises, plowshare tortoises, and Madagascan tortoises.
The only communication known is that males vocalize during mating by projecting singular continuous calls. So far, no further study has been done on the vocalizations of ploughshare tortoises. Like other tortoises, ploughshare tortoises likely use vision and smell extensively in their foraging and navigation (A. Mandimbihasina, pers. comm.).
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical
The IUCN Red List 2008 classifies Astrochelys yniphora as critically endangered. This species is also listed on Appendix I of CITES, and Malagasy law prohibits hunting and collecting of ploughshare tortoises.
Ploughshare tortoise are the world’s rarest tortoises and are being bred in captivity for release into the wild. The Forestry Station at Ampijoroa, located only 150 kilometers from Baly Bay, is the main captive breeding center of ploughshare tortoises. They did not take any tortoises from the wild. Instead, they obtain tortoises from Malagasy authorities who confiscate them from illegal captivity. Besides one hatching at the Honolulu Zoo, ploughshare tortoises had never before bred successfully in captivity. Starting in 1986 with only eight tortoises, the Forestry Station had successfully raised sixty-two young by 1992. Hatch and survival rates increase each year with increased research and techniques on health, diet, breeding, and hatching. Currently, there are seventeen adults, which consist of seven females and ten males, as well as over two hundred offspring. This is enough juveniles to start a release program. Over a four year period, twenty tortoises will be released each year to the same location in the wild (A. Mandimbihasina, pers. comm.).
US Federal List: endangered
CITES: appendix i
IUCN Red List of Threatened Species: critically endangered
Ploughshare tortoises are amniotes. They progress through vertebrate embryonic development to hatching. Adults grow about 5% per year, while juveniles grow 15% each year. Sexual maturity is reached at about 20 years. Growth is slowed at that point but does not come to a halt.
The sex of ploughshare tortoises is determined by incubation temperature. However, temperature ranges that determine sex are not known. Additionally, all eggs in a particular hole are the same sex. Sex cannot be determined until tortoises reach sexual maturity around 20 years of age (A. Mandimbihasina, pers. comm.).
Development - Life Cycle: temperature sex determination; indeterminate growth
There are no known negative impacts of ploughshare tortoises on humans.
Ploughshare Tortoises are consumed by humans. In the past, sailors ate the tortoises as a source of fresh meat. Additionally, Arab traders exported ploughshare tortoises as food to the nearby Comoro Islands. Although this ended in the nineteenth century, many people still eat the tortoises; this does not include the local Malagasy people (A. Mandimbihasina, pers. comm.).
Although trade in ploughshare tortoises is illegal by international convention, there is a black-market in captive tortoises. In January 2008, a Nigerian man was arrested with three different passports each from different countries with a separate identity. He had 300 tortoises, 8 of which were ploughshare tortoises. He could have sold them in the exotic pet trade market making as much as $200,000. Additionally, 3 more ploughshare tortoises were confiscated in Bangkok in April 2008. More recently, in February 2009, two were confiscated from a man in Hong Kong. Juveniles sell for at least $1,000, while adults can sell for up to $30,000 each in Bangkok, Thailand.
Positive Impacts: pet trade ; food ; ecotourism
Ploughshare tortoises mate from October to February, mostly in the months of November and December. Courtship begins with the male sniffing and then circling the female five to thirty times. The male pushes the female, sometimes biting at the female’s head and forelimbs. When mating, the male’s enlarged epiplastron penetrates under the female’s carapace. The male uses his gular scute as leverage to overturn the female. The female lifts her hind legs in order to hoist the posterior shell. Only the male vocalizes, projecting single, continuous calls. Both males and females have multiple mates, however there are many days between each partner (A. Mandimbihasina, pers. comm.).
Mating System: polygynandrous (promiscuous)
Nesting occurs three months after mating in open areas within grasslands, bamboo stands, burnt areas, or savannah. Nesting is usually near a bush, log, or tree and usually takes place in the late morning. The female digs a shallow pit with her hind legs and urinates to moisten the soil during excavation. The average hole width is 11.43 centimeters and 10.92 centimeters deep. She packs the soil tightly over the eggs and then abandons them. Female ploughshare tortoises may lay four to five clutches, each one month apart. The clutch size can range from 1 to 6 (mean 3.2) spherical white eggs that have a diameter of about 4.19 to 4.7 centimeters and mean egg weight of 36.2 grams (range 20 to 54 grams).
The incubation period ranges from 197 to 281 days, with an average of 237 days. Rainfall in the beginning of November usually leads to hatching. Young emerge during the daytime and typically have a carapace length of 42 to 46 millimeters. They are completely independent upon hatching.
In a study of two populations for five years, ploughshare tortoises had an egg fertility rate of 71.9 percent and a hatching success rate of 54.6 percent. Each year, a female averages 4.3 hatchlings.
Breeding interval: Female ploughshare tortoises lay 4 to 5 clutches each year, about 1 month apart.
Breeding season: Ploughshare tortoises mate from October to February, mostly in the months of November and December.
Range number of offspring: 1 to 6.
Average number of offspring: 3.2.
Range gestation period: 197 to 281 days.
Average gestation period: 237 days.
Range time to independence: 0 (low) minutes.
Average age at sexual or reproductive maturity (female): 20 years.
Average age at sexual or reproductive maturity (male): 20 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Ploughshare tortoises are completely independent upon hatching. Females invest significant energy in supplying eggs with nutrients and laying clutches in protected places.
Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female)
In 2012, Astrochelys yniphora was included among the world's 100 most threatened species in a report by the IUCN Species Survival Commission and the Zoological Society of London.
The angonoka tortoise (Astrochelys yniphora) is a critically endangered species of tortoise severely threatened by poaching for the illegal pet trade. It is endemic to Madagascar.[5] It is also known as the angonoka, ploughshare tortoise, Madagascar tortoise, or Madagascar angulated tortoise.[1] There may be fewer than 400 of these tortoises left in the wild. It is found only in the dry forests of the Baly Bay area of northwestern Madagascar, near the town of Soalala (including Baie de Baly National Park). A captive-breeding facility was established in 1986 by the Jersey Wildlife Preservation Trust (now the Durrell Trust) in collaboration with the Water and Forests Department. In 1996, 75 tortoises were stolen, which later appeared for sale in the Netherlands. The project was ultimately successful, achieving 224 captive-bred juveniles out of 17 adults in 2004. Project Angonoka developed conservation plans that involved local communities making firebreaks, along with the creation of a park to protect the tortoise and the forests. Monitoring of the angonoka tortoise in the global pet trade has also continued to be advocated.
This species was originally described in 1885 by French zoologist Léon Vaillant, who named it Testudo yniphora (from Ancient Greek ὕνις (húnis)[6] 'ploughshare', and -φόρος (-phóros) 'bearer') based on the distinguished shape of the gular scute in the front of the plastron.[7]
The angonoka tortoise (A. yniphora) and 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.[8][9] The parent family for Astrochelys is Testudinidae, the tortoise family.[3]
The name angonoka comes from the Malagasy word used as the local name of the species.[10] The alternative common name, ploughshare tortoise, refers to the appearance of the gular scute of the plastron.[11]
The carapace is highly domed and light brown in colour with prominent growth rings on each scute. The outer parts of the vertebral are a darker brown.[12] 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 in (43 cm).[13] The average length of an adult male angonoka tortoise is 414.8 mm (16.33 in) and the average weight is 10.3 kg (23 lb). Females measure at a 370.1 mm (14.57 in) average and weigh 8.8 kg (19 lb) on average.[1]
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 (including Baie de Baly National Park).[3][14][15] The distribution is 25 to 60 km2 (9.7 to 23.2 sq mi) in range around Baly Bay.[1]
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 m (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 m (160 ft) above sea level.[1]
The first population surveys of this species were performed by Juvik & Blanc in 1974 and Juvik et al. in 1981, in which they estimated the total wild population to be a few hundred, based on a population density of around five tortoises per km2 and a potential range of approximately 100 km2 (39 sq mi) in suitable habitat. In 1983 (published 1985) Curl et al. estimated a total population of 100–400 individuals in a range of 40–80 km2 (15–31 sq mi), found in five subpopulations, two east and three west of the Andranomavo River. The two to the east were Beheta and Cape Sada; the three to the west were Ambatomainty, Andrafiafaly, and Betainalika. The most accessible and most studied area was on Cape Sada, and numerous surveys in the 1990s estimated a population there of around 30 individuals.[16]
In 1999 Smith et al. performed an exhaustive survey of the population on Cape Sada, counting 96 individuals, of which approximately half were adults. They concluded that the Cape Sada population, which was split into 3 subpopulations by Juvik et al. in 1997 on the basis of what they considered suitable habitat, was a single group because the animals utilized the more open habitat in the centre of the Cape and moved from between the three more forested areas. They also concluded the remote Ambatomainty and Andrafiafaly sites were in fact were two ends of an extensive tract of contiguous habitat. Smith et al. did not provide a total population estimate, but based on their research a population of 400–1500 tortoises could be extrapolated.[16]
According to Leuteritz & Pedroso, writing for the IUCN in 2008, estimates of the wild population by Smith et al. in 1999 and Pedroso in 2000 ranged from 440 to 770 (giving an average of around 600). In 2005 the Durrell Wildlife Conservation Trust (DWCT), which helps run the main captive breeding program, estimated a wild population of 800 individuals. In 2004 Pedroso used a Population Viability Analysis to predict it would be extinct (in the wild, presumably) by 2014 to 2019. In 2008 Pedroso estimated that his estimate of 440 in 2000 had decreased to 400 (half being adults), and using this estimated decrease, among other factors (such using a population model split into more subpopulations), Leuteritz & Pedroso in 2008 considered it to be critically endangered.[1]
In 1986 the DWCT (then known as the Jersey Wildlife Preservation Trust) established a captive breeding centre at the Ampijoroa in Madagascar, which was able to breed the first captive ploughshare tortoises the following year. In 1997 the Madagascar government created Baie de Baly National Park to conserve to tortoise, and the first five captive-bred tortoises were released back into the wild in the park in 1998 by the DWCT. By 2005 the DWCT release programme had been significantly expanded and by 2011 the first baby tortoises had been born in the wild from captive-bred and released animals. In 2015 20 more animals were released, bringing the total number of released tortoises to 100 at the time.[17]
In 2016 poaching intensified, including a foiled attempt to raid the captive breeding centre (a raid in 1996 had 75 tortoises looted).[17][18] It was estimated in 2016 at a CITES conference that the wild population had dropped to 100 adults and the species would be extinct in the wild by 2018.[19]
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.[1]
The introduced bushpig is the main predator of the angonoka tortoise; it eats the tortoises' eggs and young.[20]
It is expected to become sexually mature once reaching 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 15 January to 30 May.[1] 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.[21] With a 71.9% fertility rate and a 54.6% hatching success rate, about 4.3 hatchlings are produced per female tortoise.[1]
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.[12]
This species is one of the rarest land tortoises in the world, classified as Critically Endangered on the IUCN Red List.[1] 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.[1] An additional threat is predation by the bushpig.[20] 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 ha (120 acres) of its habitat were burnt in 2004.[1] Another reason why the Angonoka might go extinct is that the species is concentrated only in one area. They are not dispersed, which means anything such as severe weather and disease could wipe the species out.
The angonoka tortoise is often captured to be sold in the international pet trade. Though some enforcement of restrictions on illegal trade is successful, 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.[1] Conservationists mark the shells with identifying marks which mars the most attractive feature and make them less desirable to poachers and wealthy collectors. The engraving is a last-ditch effort to protect the animals.[22][23]
In addition to its Red List listing, the angonoka tortoise is now protected under the national law of Madagascar and listed on CITES Appendix I, commercial trade in wild-caught specimens is illegal (permitted only in exceptional licensed circumstances). 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 work together on this project.[1] 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.[14] In May 1996, 75 tortoises were stolen from the facility. The thieves were never found, but 33 tortoises later appeared for sale in the Netherlands.[24] 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. Monitoring of the angonoka tortoise in the global pet trade has continued to be advocated.[1]
In March 2013, smugglers were arrested after carrying a single bag containing 54 angonoka tortoises and 21 radiated tortoises (Astrochelys radiata) through Suvarnabhumi International Airport in Thailand. The 54 angonoka tortoises might be as much as a tenth of the world's population of the species.[25]
On 20 March 2016, the Custom officials at Mumbai airport seized 146 tortoises from a mishandled baggage of a Nepal citizen. This bag was said to belong to a transit passenger, who arrived from Madagascar and flew to Kathmandu leaving this bag behind. Out of the 146 tortoises, 139 were radiated tortoises (Astrochelys radiata) and seven were angonoka tortoises (Astrochelys yniphora), both critically endangered tortoise species of Madagascar. Two radiated tortoises were found dead with broken shell.[26]
On 12 June 2016, it was reported that 6 angonoka tortoises and 72 radiated tortoises had gone missing from a breeding facility in Thailand.[27]
{{cite journal}}: Cite journal requires |journal= (help) The angonoka tortoise (Astrochelys yniphora) is a critically endangered species of tortoise severely threatened by poaching for the illegal pet trade. It is endemic to Madagascar. It is also known as the angonoka, ploughshare tortoise, Madagascar tortoise, or Madagascar angulated tortoise. There may be fewer than 400 of these tortoises left in the wild. It is found only in the dry forests of the Baly Bay area of northwestern Madagascar, near the town of Soalala (including Baie de Baly National Park). A captive-breeding facility was established in 1986 by the Jersey Wildlife Preservation Trust (now the Durrell Trust) in collaboration with the Water and Forests Department. In 1996, 75 tortoises were stolen, which later appeared for sale in the Netherlands. The project was ultimately successful, achieving 224 captive-bred juveniles out of 17 adults in 2004. Project Angonoka developed conservation plans that involved local communities making firebreaks, along with the creation of a park to protect the tortoise and the forests. Monitoring of the angonoka tortoise in the global pet trade has also continued to be advocated.
