Philippine sailfin lizard

Geographical Origin and Habitat: This species is endemic to the Philippine archipelago, where it is distributed across several islands including Luzon, Mindoro, Negros, and Panay. Its habitat is closely associated with clean, fast-flowing freshwater streams within pristine tropical rainforests. This semi-aquatic lizard spends much of its time on branches overhanging the water, ready to dive at the slightest sign of danger to swim or dive to the bottom.

Taxonomy and Genetics: Hydrosaurus pustulatus belongs to the family Agamidae and is the type species of the genus Hydrosaurus, known for sailfin dragons or lizards. Genetically, the species features isolated populations among the various Philippine islands, with minor morphological variations. It is considered a vulnerable species (VU) by the IUCN due to massive deforestation and illegal collection for the exotic pet trade.

Behavior and Habits: It is an extremely alert, shy, and agile reptile that possesses extraordinary swimming abilities thanks to its laterally compressed tail which acts as a rudder. Juveniles are capable of running for short distances across the water's surface, using speed and fringed skin on the toes of their hind legs. They have diurnal habits and love basking in the sun on logs and rocks near water.

Morphology: It is a large lizard, capable of reaching a total length of 80-100 centimeters in adults, of which two-thirds consist of the tail. The most spectacular morphological feature of adult males is the presence of a large erectile skin crest supported by vertebral spinous processes located at the base of the tail, resembling a sail. The coloration is olive-gray with purplish or bluish hues on breeding males.

Terrarium Setup: Given the size and activity of the species, it requires a massive enclosure, ideally a room or a large custom terrarium of at least 200x100x200 cm in height. At least one-third of the terrarium's surface must be occupied by a large water basin 30-40 cm deep, equipped with a powerful aquarium filter since sailfin lizards tend to defecate in water. The land area must be rich in sturdy climbing logs.

Lighting and Heating: It requires a powerful heat source to create a land basking area with temperatures of 38-40 °C, while the ambient temperature must have a gradient of 26-28 °C in the air. At night, the temperature must not drop below 22 °C. The use of high-output UVB lamps (such as metal halide or T5 10%) is mandatory, positioned so the animal can get close at a safe distance to synthesize vitamin D3.

Humidity and Hydration: Humidity must be constantly high, between 80% and 95%, recreating the environment of the Philippine rainforests. This requires installing automatic misting or artificial rain systems operating several times a day, and an ultrasonic humidifier. Monitoring with digital hygrometers is necessary to avoid humidity drops that hinder shedding.

Feeding and Supplementation: The diet is omnivorous. Juveniles are predominantly carnivorous and should be fed live insects (crickets, locusts, roaches), small fish, and earthworms. Adults tend to become more vegetarian: about 60% of the diet should consist of leafy green vegetables, edible flowers (hibiscus), and fruit, while the rest consists of insects and occasional rodents of appropriate size. Supplement with calcium and D3 at every meal for juveniles.

Compatibility: Males are strongly territorial and must never be housed together in the same terrarium to avoid deadly fights. It is possible to keep one male with one or two females within a properly sized terrarium, provided there are multiple basking spots and visual hides. Single specimens adapt better and suffer less stress from competition.

Health and Common Diseases: One of the most common problems in captivity is rostral trauma (nose-rubbing): the animal, frightened by the presence of glass or humans, runs frantically, hitting its snout against the walls, causing injuries that can become infected and lead to stomatitis. Other frequent pathologies are MBD (metabolic bone disease) due to lack of UVB and skin infections caused by dirty or cold basin water.