Hemidactylus scabriceps

The Scaly Gecko (Hemidactylus scabriceps)

The scaly gecko, scientifically known as Hemidactylus scabriceps, is a species of nocturnal, terrestrial, and insectivorous lizard found in the arid regions of South India, particularly in Tamil Nadu, and in the northern parts of Sri Lanka. Its discovery in the coastal sand dunes of Ramanathapuram, Tamil Nadu, marked the beginning of its identification, though it was only recently that detailed descriptions and molecular data allowed for its proper classification.

Physical Characteristics

Adult scaly geckos are characterized by a short and stout build. They possess a convex forehead, a blunt and rounded snout that is larger than their eyes, and short limbs. Their tail is cylindrical and tapers to a point. The dorsal surface of the head and neck is covered in small, rounded, granular scales. The eyes are large, positioned laterally, and feature a vertical pupil with a brown iris, surrounded by small yellow scales. The dorsal scales are imbricate, leaf-shaped, and nearly smooth, increasing in size from the snout towards the tail, with the largest scales located above the limbs and on the tail. Adult males are identifiable by up to six pre-anal pores, though femoral pores are absent. The fourth toe shows subdigital lamellae and is partially divided.

In life, the scaly gecko displays a brownish coloration, with hues varying from yellow to red on its dorsum, fading to a creamy white on its venter. The sides often exhibit indistinct mottling of black and bright yellow scales, and the head is mottled with white and black scales. Labial scales are straw yellow, and the scales around the eyes are also yellow. Distinctive markings include two parallel lines running along the dorsum from the base of the forelimbs to near the tail, and white crossbands along the back. The limbs are brown and mottled with black and white.

Habitat and Distribution

This species thrives in semi-arid and open habitats that are dry and sometimes sandy. Its range encompasses Tamil Nadu in South India, with documented sightings in areas such as Ramnad, Adyar, Chennai, Mayiladuthurai, Madurai, Thanjavur, Tirunelveli, Tuticorin, and Vallanadu Wildlife Sanctuary. In Sri Lanka, it has been reported in Marichhukate in the Northern Province. They are frequently found in dry environments, including along coastal sand dunes.

Behavior and Ecology

The scaly gecko is strictly nocturnal, spending daylight hours concealed under rocks. At night, it becomes active on the open ground, moving with a noticeable upright stance. Its diet consists primarily of insects. Evidence of territorial behavior has been observed in males, who engage in vocalizations ('chirping calls') and visual displays, including arching their bodies, stretching their legs, and waving their tails, sometimes lunging at each other. Reproductive activity involves females laying eggs; observations indicate clutch sizes of two eggs in July and also between December and February.

Evolutionary Context

Historically, Hemidactylus scabriceps was sometimes misassigned to different genera due to a lack of clear molecular evidence. However, recent phylogenetic analyses have confirmed its placement within the genus Hemidactylus. It is estimated that this species diverged from its common ancestor approximately 35 million years ago, with its expansion into Sri Lanka likely occurring during the Late Miocene epoch.