Ploughshare Tortoise
Species Description
The Ploughshare tortoise (Astrochelys yniphora), or Angonoka in Malagasy, is endemic to the tropical dry forests of Madagascar’s northwest coast. Restricted to just a 160 km2 area in Baly Bay National Park, they are currently the most threatened tortoise species in the world. Baly Bay park was established in 1997 specifically to protect the Ploughshare tortoises, and all entry, apart for conservation and research purposes, is controlled. This habitat is made up of a combination of savannah, bamboo scrub and deciduous forest, with pools of water for drinking and wallowing. Their skin is a mixture of brown and tan while their carapace is golden in colour. Each scute has dark brown borders, creating a unique pattern that allows the tortoise to camouflage against dried leaves on the forest floor. Unfortunately, it is their striking shell that makes them so desirable to collectors in the illegal pet trade.
The Ploughshare tortoise has been protected under Malagasy law since 1960, which prohibits the collection, consumption and captivity of wild individuals. They are also listed in Appendix 1 of CITES, making any international commercial trade illegal. Despite these regulations, the Ploughshare is the most threatened of the island’s four endemic tortoises. They are considered ‘Critically Endangered' on the IUCN Red List, with only a few hundred individuals left in the wild. The alarming status of the Ploughshare tortoise is the result of extreme commercial exploitation, coupled with habitat destruction from frequent logging and anthropogenic brush fires. The effects of these disturbances are exacerbated by the tortoises’ slow growth rate, delayed sexual maturity and low fecundity - these characteristics make it difficult for their populations to recover from severe declines.
A Ploughshare’s lifespan is unknown. While the growth rings on juveniles are very visible, these smoothen out over time, making it difficult to age older individuals. They can probably live over 100 years in captivity. Adults can reach a weight of 20 kg and a carapace length of 50cm. They are characterised not only by their unique shell pattern but also by the plough-shaped shell protrusion underneath their head - hence their name. This protrusion is known as the gular scute and is more prominent in males.
Habitat & Home Range
The Ploughshare tortoise inhabits six isolated pockets of dry bamboo forest in Baly Bay, one of the driest regions in Madagascar. The dry bamboo forest habitat is a combination of grasses, shrubs, bamboo thickets and open areas. The climate of this region is harsh and arid. There is little to no precipitation during the dry season and all the streams dry up between May and October. Ploughshares are inactive during this period and will often stay under fallen leaves and other dense vegetation. The wet and hottest season occurs between November and April. During this time of year, Ploughshares are most active. Their monthly home range shifts from around 4 hectares in the dry season to around 20 hectares in the wet season.
Adult Ploughshare tortoises have no natural predators but invasive species such the Indian palm civets, rats, and African bush pigs prey on tortoise eggs, hatchlings and juveniles.
Diet
Ploughshare tortoises are primarily herbivores. Although the major portion of their diet consists of plants and fruits, they are occasionally observed eating the dried faeces of lemurs and African bush pigs. Their preferred foods appear to be shrub leaves, tussock grass and orchid tree (Bauhinia pervillei) seedlings. They have been observed using their beak-like jaw to scrape moss and small plants off low lying tree branches.
Reproduction
Ploughshare tortoises reach sexual maturity at 15-20 years old. Mating occurs between October and February, but is most frequent during November and December. Courtship is preceded by a period of inter-male combat, during which males will ram their gular scutes into one another. The successful male will sniff and circle the female 5-30 times, before biting at her head and forelimbs. He will use his gular scute to lift her into position, producing single, continuous calls while they mate. If mating is successful, the female will lay her eggs 1-3 months later. Nesting occurs mostly in open areas within the grassland, though some females will nest among the bamboo stands, the savannah or in clearings created by brush fires. Ploughshares can lay several clutches per season, with anywhere between 1 and 6 eggs per clutch. The incubation period is approximately 250 days and hatchlings will usually emerge at the onset of the rainy season, during daylight hours. As in most tortoise species, the sex of Ploughshare hatchlings is determined by the nest temperature during incubation; Temperatures of 30-32°C produce females while temperatures of 27-29°C produce males.
Conservation Concerns
Ploughshare tortoises have been exploited since the 1600s. They were once exported to the Comoros Islands where they were used as a source of protein by Arab sailors. This was repeated when European boats arrived in the Indian Ocean. In fact, Baly Bay was one of the first known trading posts in Madagascar. At present, however, the consumption of tortoise meat is considered ‘taboo’ and is therefore no longer a significant threat. Today, their populations are threatened primarily by the international pet trade and anthropogenic brush fires, used to expand the land available for grazing cattle. The pet trade has grown steadily over the last 15 years, with much of the demand now stemming from countries in South and South-eastern Asia. Deemed THE rarest tortoise species in the world, Ploughshares are extremely desirable and can sell for very high prices on the blackmarket. At the current rate of decline and without rigorous enforcement of national and international anti-poaching and anti-trafficking laws, the species will likely go extinct in the wild within the next decade.
Conservation Efforts
ince 2009, there have been increased efforts to employ local people as park rangers to protect the tortoises and their habitat. Permanent field camps have been set up in the Ploughshare’s habitat and anti-poaching patrols occur daily. However, these efforts come with several challenges; Rangers need to cover vast areas of remote habitat during their patrols and there is a lack of rapid response from enforcement agencies, who have limited resources.
The Durrell Wildlife Conservation Trust is the first organisation to successfully breed Ploughshare tortoises in captivity. As of 1984, they have bred over 800 Ploughshares and of those, 105 have been released into the wild. Those remaining at their captive breeding centre are heavily protected by armed guards. Since breeding in the wild is minimal, captive juveniles are at a particularly high risk of being stolen. Durrell and Madagascar National Parks also encourage local communities to take part in anti-poaching patrols and to report any potential smuggling operations. They also engrave the carapaces of wild and captive Ploughshares in an aim to devalue them for the international pet market.
Successful breeding of captive Ploughshares is very limited outside of Madagascar. One exception is the Francois Leguat Reserve in Rodrigues, where they are being bred under an agreement with the Madagascar government. Laying and hatching success have been high over the last two years and since the start of 2023, the reserve has welcomed 16 Ploughshare hatchlings. The aim is to eventually return them to their native habitat in Madagascar, once poaching is no longer a significant threat.
A Story of Home
Hope is a three-legged Ploughshare tortoise living at Chester Zoo, England. He was found in a suitcase by Hong Kong customs officers in 2019, along with 56 other live and endangered tortoises. The owner of the suitcase was a man from the Comoros Islands. He was jailed for two years for smuggling. Hope was missing a front leg when he was found, so he was fitted with under-shell support rollers. He is one of only 63 Ploughshares existing legally outside of Madagascar as part of vital conservation breeding programs, and Chester Zoo is home to four of these individuals. The support rollers worked tremendously well and today, Hope is even faster than his four-legged friends.
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