Taiwan japalure

Diploderma swinhonis: The Taiwan Japalure

The Taiwan japalure, scientifically known as Diploderma swinhonis, is a species of draconid lizard native to the island of Taiwan. It is also recognized as an invasive alien species in Japan, having likely been introduced from its native habitat. This diurnal, arboreal lizard is characterized by its foraging ambush predation style, typically found at the bottom of forests, though it has demonstrated adaptability to a range of environments, including urban settings.

Physical Characteristics and Sexual Dimorphism

Diploderma swinhonis exhibits notable sexual dimorphism. While both sexes share brown backs, males are physically distinct, being considerably larger than females. Adult males typically measure around 73 mm in snout-to-vent length (SVL), compared to approximately 62 mm for females. Males also possess a prominent yellow stripe on each side of their body, a feature absent in females. Further differences include larger dewlaps in males and a more laterally compressed body shape, whereas females have more cylindrical bodies. A unique characteristic among its genus is the presence of enlarged scales scattered across the dorsal side. While the maximum total length, including the tail, can reach about 31 cm, the body itself is around 8 cm long.

Habitat and Behavior

This species primarily inhabits lowland forests below 1,500 meters in elevation. Its arboreal nature means it often resides on tree trunks and forages on the ground. The Taiwan japalure is known to adapt well to various habitats, being found not only in natural wooded areas but also in human-altered environments such as schools and shopping malls. Males tend to occupy higher altitudes on trees, while females and juveniles stay closer to the ground and near bushes. Male D. swinhonis are territorial, engaging in aggressive displays to defend their space, which is believed to be primarily for increasing mating opportunities rather than resource protection. In the presence of intruders, males may expand their throat to display white spots as a deterrent. In Taiwan, these lizards typically hibernate from November to March.

Diet and Reproduction

As a sit-and-wait predator, the Taiwan japalure feeds mainly on mobile arthropods. Its diet commonly includes ants, grasshoppers, crickets, bees, and spiders. While generally feeding on diurnal arthropods, variations exist, with populations on Orchid Island showing a preference for crickets. The species reproduces seasonally, with females being reproductively active between March and August. They are oviparous, laying an average of 4.27 eggs per clutch, usually producing two clutches annually. Significant mortality occurs before maturity, with approximately 88% of eggs not surviving the initial 30-day incubation period. Males mature between 140 and 260 days, while females take around 350 days to mature.

Distribution and Conservation Concerns

Native to Taiwan, Diploderma swinhonis is found on peripheral islands like Orchid Island and Green Island. Its presence in Japan, first noted in 2006, is considered an invasive threat, potentially impacting local ecosystems. In its native Taiwan, the species faces threats from invasive predators, including the frog Polypedates megacephalus and the agamid lizard Physignathus cocincinus. There is also concern that the invasive arboreal anole, Anolis sagrei, could outcompete D. swinhonis, leading to population declines.