Asian Giant Softshell Turtle

The Asian giant softshell turtle is a large freshwater species belonging to the family Trionychidae. Native to river systems of South and Southeast Asia, it is one of the world’s most threatened turtles and has disappeared from much of its historical range. Known commonly as Cantor’s giant softshell turtle or the frog-faced softshell turtle, it is recognised for its distinctive morphology, unusual behavioural traits and significant conservation urgency.

Taxonomy and Evolutionary Background

Pelochelys cantorii is one of three species in the genus Pelochelys. Unlike the New Guinea giant softshell turtle (Pelochelys bibroni) and Pelochelys signifera, both of which are restricted to New Guinea, P. cantorii does not naturally occur there. Earlier reports of its presence in New Guinea were re-evaluated in the 1990s and attributed instead to misidentified P. bibroni specimens.
The species remains poorly studied, and some evidence suggests that populations currently grouped as P. cantorii may represent several distinct taxa. Genomic studies have revealed heightened activity in genes associated with tumour resistance, growth and ageing, including VWA5A, ABCG2, A2M and IGSF1. Phylogenetic analyses indicate that P. cantorii diverged from its closest turtle relatives around 59 million years ago, while turtles as a whole diverged from the common ancestor shared with birds and crocodilians approximately 256 million years ago.
Genetic assessments of Philippine populations suggest that these turtles may possess unique traits, raising the possibility of an undescribed endemic form; further research is required to clarify their taxonomic status.

Physical Description

The Asian giant softshell turtle has a broad, flattened head with small eyes positioned close to the snout’s tip. Its carapace is smooth and olive-coloured, lacking scales and covered by a soft, leathery skin typical of trionychid turtles. Juveniles often display dark spotting across the shell and head, sometimes highlighted by yellow margins.
Claims that P. cantorii is the world’s largest freshwater turtle have been complicated by misidentified specimens. Extremely large individuals once attributed to the species are now regarded as suspect or have been reassigned to the Yangtze giant softshell turtle. A more reliable adult carapace length range is markedly lower than some early reports suggested, though the species still ranks among several giant softshell turtles capable of reaching exceptional size and mass.

Behaviour, Ecology and Reproductive Biology

This species is a specialised ambush predator, feeding predominantly on fish, molluscs and crustaceans, although some aquatic plant matter may supplement its diet. One of its most remarkable behavioural features is its tendency to remain buried and immobile for extended periods: it spends approximately 95% of its life submerged beneath sand or mud with only the snout and eyes exposed.
Turtles surface only twice daily to breathe, a pattern facilitated by their sedentary lifestyle and capacity to absorb oxygen through the pharyngeal lining. Nesting typically occurs in February or March, when females lay between 20 and 28 eggs on sandy riverbanks. The eggs are spherical and relatively large compared with those of many freshwater turtle species.
Morphological variation among populations has been noted, including differences in neural bone counts between Philippine specimens and those from mainland Asia, potentially reflecting long-term geographic separation.

Etymology

The species name cantorii honours the Danish zoologist Theodore Edward Cantor, who made significant contributions to 19th-century Asian natural history. The English common name highlights the species’ soft, leathery shell.

Geographic Distribution and Habitat

The Asian giant softshell turtle primarily inhabits slow-moving freshwater rivers, streams and associated wetlands, though some populations may venture into brackish or coastal ecosystems. It is distributed widely across South and Southeast Asia, including:

• Eastern and southern India
• Bangladesh and Burma
• Thailand, Malaysia and Laos
• Cambodia and Vietnam
• Eastern and southern China
• The Philippines (confirmed on Luzon and Mindanao)
• Indonesia (Kalimantan, Java and Sumatra)

In the Philippines the presence of the invasive Chinese softshell turtle has complicated conservation efforts, as the two species are similar in appearance and easily misidentified by local communities.

Conservation Status

Classified as Critically Endangered by the IUCN, the Asian giant softshell turtle has suffered drastic declines due to:

• Habitat destruction, including sand mining and river modification
• Overharvesting for food and trade
• Nest predation
• Competition and confusion with invasive species

By the early 2000s it had disappeared from many areas. Notably, a 2007 survey along a Mekong River section in Cambodia revealed unexpectedly high numbers, offering hope for population recovery in that region.
In the Philippines the species is protected under national law. Nevertheless, accidental collection persists because of misidentification with the invasive Chinese softshell turtle, which authorities permit communities to cull under controlled conditions. Conservation strategies increasingly emphasise local education, habitat protection and genetic monitoring, particularly given evidence that Philippine populations may possess unique evolutionary significance.
The species has also been designated an EDGE species by the Zoological Society of London, highlighting its evolutionary distinctiveness and the urgency of its conservation.

Significance and Research Needs

The Asian giant softshell turtle represents an ancient lineage with distinctive genetic traits relevant to studies of longevity, disease resistance and reptilian evolution. Yet major gaps remain in understanding its ecology, taxonomy and population dynamics. Effective conservation will require expanded field surveys, habitat restoration, community engagement and further genetic research to clarify potential cryptic diversity within the species.