Spiny turtle

Carapace

The spiny turtle is a medium-sized tortoise with a brown shell and red-spotted head.[4] Also known as the “cog-wheel turtle,” it derives its name from its spiky-edged carapace, marginal scutes, and spiny keel.[5][6][7] As juvenile spiny turtles become adults, the black striped and yellow underside of their shell fades in color.[5] In addition, the juveniles’ serrations, or jagged edges, at the carapace margin decrease in size and become restricted to the carapace’s rear margin.[8] These changes of the spine and carapace serve as evolutionary adaptations attempting to prevent predators from preying on juvenile turtles.[6]

The spiny turtle belongs to the kingdom of Animalia, the order of Testudines, and the genus of Heosemys.[9] The classification of Heosemys incorporates four species: Heosemys annandalii, Heosemys depressa, Heosemys grandis, and Heosemys spinosa; however, relationships between the four are undetermined.[10] Variation among the Heosemys spinosa is also uncertain, but it has been suggested that there are two types: a “mainland form” dwelling in Malaysia, Thailand, and southern Myanmar, and an “insular form” found in Indonesia and the Philippines, possibly in Brunei and Singapore as well.[10]

Adult spiny turtles’ carapace length usually falls between 175 mm to 220 mm and their mass ranges from 1.5 kg to 2.0 kg.[7]

The spiny turtle buries itself in leaf litter to camouflage during the day and only emerges at night, foraging for food.[4][6]

While often portrayed as a herbivore, the spiny turtle also eats carrion and insects alongside fruits and plants.[4] Fruit from the yin-ngan tree is especially important for the turtle, and in Myanmar, the turtle often dwells beneath these trees when the trees are fruiting.[11] Similarly, captive juvenile spiny turtles consume fruit salads multiple times a week, particularly those containing tomatoes.[7] At the Kubah National Park in Sarawak, analysis of fecal content revealed the turtles’ role as seed dispersal agents, for their fecal matter contained five different seed types.[12] Arthropods and hair were also found in the samples, suggesting consumption of mammals and other animals.[12]

young spiny turtle

Mating occurs in December and February, and appears to be triggered by rain.[7] Regarding nesting behavior in the wild, the female lays one or two eggs in a nest and produces up to three clutches annually.[7]

In captivity, it has been observed that spraying males with water results in them chasing females and attempting to mount.[7] To ease the delivery of the egg, a hinge forms in the female turtle’s plastron before it is laid.[13] The egg is usually covered with a partial layer of substrate, and researchers have found eggs laid in a so-called “protected spot” underneath cork bark or thick foliage.[4]

Many attempts at reproduction in captivity have proved unsuccessful due to the eggs’ shells being thick and prone to bursting if the substrate is too damp.[4] The first successful copulation in captivity occurred in 1991 at Zoo Atlanta, where incubation lasted for 106 days in a medium of peat moss, long fiber peat moss, and damp sand.[7] For the first 35 days, the egg was incubated at a temperature of 28-30°C, and for the last 71 days, the temperature was decreased to 26-28°C.[7]

The spiny turtle is known from Brunei, Indonesia, Malaysia, Myanmar, the Philippines, Singapore, and Thailand.[1][14] It lives along brooks in forested areas, usually in mountains with altitudes of 170 m to 1,000 m above sea level.[4][15]

Labeled as “vulnerable” by the IUCN in 1996, the spiny turtle became endangered in 2000 when the supply of the species declined by a half in the Chinese food market.[4] It is suggested that the main threat to the spiny turtle has been the destruction of natural forests to create oil palm plantations, common in southern Myanmar.[11] The spiny turtle’s participation in the international pet trade and its use in traditional Chinese medicine has also led to its decline.[4] However, numerous conservation efforts have been undertaken because the turtle is protected by the Philippines Wildlife Act and other initiatives.[6][15] A spiny turtle hatching at the Chester Zoo in the UK in 2013 has also given hope to conservationists that the species may be retained.[16]

Bibliography

• Rhodin, Anders G.J.; van Dijk, Peter Paul; Inverson, John B.; Shaffer, H. Bradley; Roger, Bour (31 December 2011). "Turtles of the world, 2011 update: Annotated checklist of taxonomy, synonymy, distribution and conservation status" (PDF). Chelonian Research Monographs. 5. Archived from the original (PDF) on 31 January 2012.
• Fritz, Uwe; Havaš, Peter (2007). "Checklist of Chelonians of the World" (PDF). Vertebrate Zoology. 57 (2): 149–368. doi:10.3897/vz.57.e30895. S2CID 87809001. Archived from the original (PDF) on 1 May 2011.

• ARKive - images and movies of the spiny turtle (Heosemys spinosa)