Meet the Philippine Forest Turtle: A Critically Endangered Species

Philippine Forest Turtle (Siebenrpckiella Leytensis)

• Did you know? Turtles are thought to have exceptional night vision due to the unusually large number of rod cells in their retinas. They also see in color.

Siebenrockiella leytensis is a species of freshwater turtle endemic to the Philippines. It is classified as critically endangered. It is known as the Philippine forest turtle, the Philippine pond turtle, the Palawan turtle, or the Leyte pond turtle. Despite the latter common name, it does not occur in the island of Leyte but is instead native to the Palawan island group. It is locally known as bakoko in Cuyonon.

Philippine forest turtles are readily recognizable by their ginkgo-shaped vertebral scutes and a pale white to yellow line traversing across its head behind the ears. The previous characteristic has earned it the nickname of 'bowtie turtle'.

Philippine forest turtles are classified under the subgenus Panyaenemys. Together with the smiling terrapin (Siebenrockiella crassicollis), it is one of the two species in the genus Siebenrockiella.

Description

Philippine forest turtles have brown to reddish brown to black carapaces that reach a length of 21 cm (8.3 in). Larger individuals can reach 30 cm (12 in) in length, though this is relatively rare. A dorsal ridge (the keel) is only present in the posterior vertebral scutes or absent altogether. The front margin of the carapace is slightly to strongly serrated, with the marginal scutes projecting beyond the cervical scutes. The vertebral scutes are broader than long.

The plastron is reddish brown to black, sometimes with blotches of yellow. In juveniles, the plastron is a uniform yellow. The bridge (the hinge connecting plastron and carapace) is the same color as the plastron. It is significantly smaller than the carapace and narrow at the front and back. It possesses deep notches between the projecting gular scutes as well as between the gulars and humerals, but it is more distinct in the former.

The skin of the legs, body, and neck are rough in appearance, being covered in tiny tubercles. The head is brown in color, sometimes speckled at the temples with light brown, orange, or red spots. A thin white to pale yellow line traverses through the width of the head just behind the openings of the ears; it may be divided at the center in some individuals. This has led to the species being nicknamed as the 'bowtie turtle'. The line is more prominent in younger individuals.

The upper jaw is hooked and the skin on the sides of the neck and the chin are lighter in color. The lower jaw may also sometimes possess a pair of small yellow spots on the sides.

The legs possess irregular enlarged transverse scales and are darker in color at the front. Four transverse scales are present on the forelimbs and more at the hind limbs (though absent at the heels). All limbs are webbed and possess large claws on all toes. The tail is uniformly light brown in color.

Philippine forest turtles are relatively easy to recognize. They can be distinguished from all other turtles by their strongly projecting epiplastra, vertebral scutes shaped like ginkgo leaves, the absence of temporal arches in the skull, and the aforementioned light lines behind its head.

The Malaysian giant turtle (Orlitia borneensis) and the smiling terrapin (Siebenrockiella crassicollis) are the only other turtle species with ginkgo-shaped vertebral scutes, but they do not possess the white to pale yellow line on the back of their heads.

History of Discovery

Philippine forest turtles were first described by the American herpetologist Edward Harrison Taylor in 1920 as Heosemys leytensis. He described them on the basis of two specimens (male and female) collected by Gregorio Lopez, allegedly from the swamps of the municipality of Cabalian in Southern Leyte (now known as the municipality of San Juan). These specimens were unfortunately destroyed in World War II during the firebombing of Manila.

No other specimens were reported until 1988 when a specimen was bought from a local resident in Taytay, Palawan. Believing that the turtle got there through interisland trade, numerous herpetologists searched Southern Leyte for other individuals. Their lack of success led to fears that the turtle was already extinct.

In 2001, during an assessment of endemic wildlife of the island of Palawan, live specimens of Philippine forest turtles were rediscovered. It soon became apparent that natural populations of the species existed in Palawan. Diesmos et al. (2004) have concluded that Taylor and/or Lopez may have somehow confused the type locality of the original specimens. Lopez also collected turtle specimens from the islands of Coron and Busuanga in Palawan. Specimens from Palawan may have been mistakenly exchanged with actual specimens from Leyte (which were probably Cyclemys dentata). It is now presumed that Philippine forest turtles have never been introduced outside of Palawan, and thus were not actually from Leyte.

Distribution and Habitat, Ecology and Behavior

Philippine forest turtles are known only from northern Palawan and surrounding islands. This includes the island of Dumaran where the species is still relatively abundant in creeks. Elsewhere, it is believed their populations are declining sharply, particularly in the areas of Taytay and San Vicente. Its distribution area is estimated to be less than 100 km².

Philippine forest turtle populations often exist alongside other more common native turtle species, including Asian leaf turtles (Cyclemys dentata) and Southeast Asian box turtles (Cuora amboinensis).

Due to its rarity and its status as newly rediscovered, little is known of the life cycle of the Philippine forest turtle. From observations, however, Philippine forest turtles appear to exhibit long life spans and high adult survival rates. Like most turtles, their sexual maturation is delayed, but they are able to mate multiple times before death (iteroparity).

Captive adults confiscated from illegal traders were provided a large outside pool with well-planted islands and numerous underwater rock formations in Malabon Zoo in Manila. But they proved to be very shy and retiring, spending considerable time hiding under rocks, both in and out of the water. They took some months to adjust to confinement. Observations indicate that they are omnivorous, favoring commercial turtle food, aquatic plants, and they have been observed hunting small fish and crustaceans. They became active in the early morning and late evening, foraging for food, and moved about during the night. They were not observed to be keen on basking in the sun, but this may have been the result of being in a captive environment.

Known food sources of Philippine forest turtles in the wild include figs.

Threats and Conservation

The Philippine forest turtle is an enigmatic freshwater turtle species that exerts great fascination for turtle hobbyists. Due to the previous inability to locate it in the wild, probable threats from habitat loss, and potential pressure from collectors, this turtle is listed as critically endangered.

Due to the species' susceptibility to stress and the extremely aggressive territorial behavior of male individuals, Philippine forest turtles do not do well in captivity. Nevertheless, as of 2009, a considerable number of these turtles (over 171 individuals documented in a span of four years) were found for sale illegally in major Manila pet markets, particularly in the main Chinese markets (where the turtles are sold cheaper). The animals are not sold openly, and some of the buyers are overseas collectors. Most of the individuals were juveniles or young adults. Between 2009 and 2011, this species ranked sixth among the most commonly confiscated species in the Philippines. These animals had been collected from mud wallows in northern Palawan, and it is believed that they hide during daylight hours.

Additionally, many specimens (from Palawan) offered for sale had small holes bored in the carapace, indicating that some, at least, had been held captive as pets and tethered accordingly. Local Palawan people are known to keep these animals in water troughs for domestic pigs, as these are supposed to bring luck for the household and the pigs, although it is not known if this luck is shared by the turtles.

The unconfirmed existence of illegal trade of Palawan turtles to Borneo, Malaysia, is also a cause of concern. Although some studies into their habitats have been commenced by several Philippine academic institutions, lack of funding has prevented full study, and they must still be considered endangered, especially from collecting, until further research has been carried out.

Trade is banned internationally under the CITES convention, as well as domestically under the Philippines Wildlife Act.

Some eighteen individuals have been donated to the Malabon Zoo north of Manila.

Recent legislation in the Philippines requires pet owners and traders to register their animals with the authorities and pay for licenses to keep the more "exotic" pets. It is hoped that this may prove to reduce the collection of various endangered species, including the Philippine Pond Turtle. The entirety of the Palawan group of islands is also a nationally protected area.