Ploughshare tortoise (Astrochelys yniphora)
|Also known as:||Angonoka, Madagascar angulated tortoise, Madagascar tortoise|
|Synonyms:||Angonoka yniphora, Geochelone yniphora, Testudo yniphora|
|French:||Tortue À Éperon, Tortue À Plastron Éperonné, Tortue À Soc De Madagascar, Tortue De Madagascar|
|Spanish:||Tortuga De Madagascar, Tortuga Globulosa Malagache|
|Size||Shell length: up to 43 cm (2).|
Classified as Critically Endangered (CR) by the IUCN Red List (1) and listed on Appendix I of CITES (3).
This species is one of the rarest land tortoises in the world (4). Its common name refers to the appearance of the 'gular scute' (5) at the lower part of the shell (plastron), which is drawn out into a plough-shaped projection between the front legs (6). The upper shell (carapace) is hard, highly domed and brown in colour, with prominent concentric growth rings on each scute (5). Males are larger than females (2).
This extremely rare tortoise is endemic to Madagascar. It is thought that only around 600 individuals remain in the wild (7). These individuals occur in just five isolated and small populations in a 30 kilometre radius of Baly Bay in north western Madagascar (8).
The ploughshare tortoise is found in dry forests in course grass and in scrubby habitats close to bamboo forests (6).
This species feeds on grasses and a wide range of other plants (2). Males compete for access to females; during these wrestling matches, males try to flip their opponent over using the plough-like projection of the lower shell below the neck (9). Each breeding season, females lay up to seven clutches of between two and six eggs (6). She lays the eggs in a pit that she digs with her hind legs, covers them with soil and abandons them (2). Young ploughshare tortoises are around the size of a ping pong ball when they hatch at the beginning of the wet season (5) (6). They are fully independent immediately after emerging, but it takes as long as 20 years for them to reach sexual maturity (6).
The main threats affecting this very rare species include habitat loss, largely as a result of uncontrolled bush fires, predation of eggs and young by the introduced bush pig (Potamochoerus larvatus) and illegal collecting by people (5) (8). Like other tortoises and turtles, this species has a slow growth rate and low breeding potential. In addition, it takes individuals a long time to reach sexual maturity. All of these factors reduce the capacity of populations to recover from human-induced effects on the population (5) (7).
A recovery programme was established for this species in 1986 by the Jersey Wildlife Preservation Trust in collaboration with the Malagasy Department of Waters and Forests. A captive-breeding facility was established in Madagascar and within eight years over 100 young ploughshare tortoises had been bred. A study into the habitat of the species and interactions with humans was also established, and a grassroots-level environmental education programme was set up (10). Experimental reintroductions of captive-bred tortoises have been successful to date and large-scale release to re-establish extirpated populations are being planned (5). Although international trade in the ploughshare tortoise is illegal due to its listing under Appendix I of the Convention of International trade in Endangered Species (CITES), poor enforcement of the exotic pet trade is causing great problems. In 1996, 73 individuals were stolen from the captive breeding programme in Madagascar and as recently as 2003 reptile collectors have been arrested with wild ploughshare tortoises in their possession destined for the international exotic pet market (5). When a species is this rare, outrageous crimes such as these have serious implications for the already precarious state of the species (11). These incidents have highlighted weaknesses in wildlife law which must be urgently addressed (11).
For more information on this species see:
- Angonoka tortoise (Geochelone yniphora). Wildlife Preservation Trust- the wild ones:
Information authenticated by Richard Gibson, Curator of Herpetology, Zoological Society of London.
- Carapace: the top shell of a turtle.
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Plastron: in reptiles, the ventral shell of a turtle or tortoise.
- Scute: One of the large keratinous scales on the carapace (the top shell of a turtle or tortoise).
IUCN Red List (May, 2009)
Ploughshare (Angonoka) Tortoise - Enchanted Learning (March, 2004)
CITES (April, 2009)
Vital veterinary training for Madagascar tortoise team. Jersey Wildlife Preservation Trust. (March, 2004)
- Gibson, R. (2004) Pers. comm.
Angonoka tortoise (Geochelone yniphora). Wildlife Preservation Trust- the wild ones (March, 2004)
- Pedrono, M., Smith, L.L., Clobert, J., Massot, M. and Sarrazin, F. (01/01/0001 00:00:00) Wild-captive metapopulation viability analysis. Biological Conservation,.
- Smith, L.L., Reid, D., Bourou, R., Mahatoly, J. and Sibo, C. (1999) Status and distribution of the angonoka tortoise (Geochelone yniphora) of western Madagascar. Biological Conservation, 91: 23 - 33.
Endangered Species Handbook (April, 2008)
- Durrell, L. (1994) A is for angonoka: the ploughshare tortoise project and the ABCs of species conservation. Testudo, 14(1).
Behler, J.L. Troubled times for turtles (March, 2004)