Philippine Sailfin Lizard
The Philippine sailfin lizard, crested lizard, sail-fin lizard, sailfin water lizard, soa-soa water lizard (Hydrosaurus pustulatus) or its native name ibid is an oviparous lizard endemic to several of the islands that make up the Philippines and is also found in New Guinea and some parts of Eastern Indonesia. The Philippine Sailfin Lizard is a protected species in its native country of the Philippines as it is a target for exotic pet collectors and sought after in the international pet trade.
This is largely because these lizards have unique dorsal crests (otherwise known as sailfins) that give the organism a structure similar to a sail, and the Philippine sailfin lizard also has very bright coloration patterns that make them attractive to the eye.
The Philippine sailfin lizard usually lies close to bodies of water, stays in tree branches, and runs across the ground to get around their habitat. They utilize their sailfins/scales to do territorial displays in the presence of a competitor or a predator. In terms of their reproduction, they utilize sexual reproduction and breed one time each year, but they can produce multiple clutches of eggs with between 2 and 8 eggs. These eggs are buried into the soil for a period of two months before hatchlings are produced. Philippine sailfin lizards are heavily studied by herpetologists and other scientists, as they are unique amongst other reptile lizards with regard to their coloration and form.
Population and Threat
Animals can be very common in appropriate habitat (such as silty, lowland rivers). The density of the species is also considered to vary between islands; field surveys indicate that it is common on Guimaras and Romblon, but rarer on Negros and Cebu.
The threats to the two species of Hydrosaurus in the Philippines are generally very similar. Populations appear to be principally threatened by habitat loss, often the conversion of wooded land to alternative uses (including agriculture), and through logging operations. In addition, animals (especially hatchlings) are heavily collected for both the pet trade (national and possibly international) and local consumption. Because of inter-island trade, there is some possibility of introduced animals mixing with indigenous populations. In some parts of is range it is additionally threatened by water pollution resulting from the use of agrochemicals and increased sedimentation.
Life cycle and reproduction
Philippine sailfin lizards reproduce through sexual reproduction, and they only breed once every year with potentially multiple clutches of eggs. In order for female Philippine sailfin lizards to lay their eggs after mating and birth, they dig relatively shallow holes in soil near their watery-habitats, and these eggs then incubate for approximately two months. The eggs then eventually become hatchlings during the rainy season, which actually are born with a natural swiftness and agility that allows them to evade their predators by running across the water unlike adult lizards that swim. These female Philippine sailfin lizards are able to lay several clutches of eggs a year that each can contain anywhere between 2 and 8 eggs. It’s also important to note that these eggs are laid above the flood line.
This species is endemic to the Philippines, however its distribution is unclear because of confusion in identification between Hydrosaurus amboinensis and H. pustulatus. Populations of H. pustulatus have been reported from the islands of Luzon (with recent records from Bicol), Polillo, Mindoro, Negros, Cebu, Guimaras, Panay, Masbate, Tablas, Romblon, Sibuyan, and Catanduanes. It may be present on the island of Bohol but this requires confirmation.
Habitat and distribution
The Philippine sailfin lizard is found across several of the islands that comprise the Philippines, including Guimaras, Romblon, Negros, and Cebu, but the lizard is not found in Palawan Island. The lizard is also found in New Guinea and some of eastern Indonesia. The Philippine sailfin lizard lives in tropical wooded habitats near water, like rivers, riverbanks, rice-fields and mangrove. The Philippine sailfin lizard also lives in moderately high densities in these habitats.
The Philippine sailfin lizard also prefers the bodies of water that they reside nearby being freshwater. Due to confusion with H. amboinensis, the exact distribution in the Philippines has been labelled with some uncertainty. However, a genetic study that sampled individuals throughout the Philippine archipelago (from Mindanao in south to Luzon in north) found that all were H. pustulatus, which is divided into six clades. Additionally, the Philiippine sailfin lizard is often found near rocky areas close to a stream.