16 November 2014

Yellow-bellied House Gecko – Dhahran Hills

This Yellow-bellied House Gecko Hemidactylus flaviviridis was found and caught inside my house in Dhahran in September. It had been living in the house for some time and skilfully avoided being caught for some weeks before I eventually managed to trap it. They are a relatively large lizard which demonstrates distinct variation in body colour depending on the time of day. At night, they are typically greyish, olive or brown, patterned with indistinct bands on the back and yellowish on the underside; however, when seen during the day, the gecko is usually much darker in colour, with contrasting, chevron-shaped bands on the body. The yellow-bellied house gecko is covered in small, keeled scales and the head and body are flattened, while the tail is fat and swollen at the base, with enlarged tubercles (wart-like bumps and ridges) along the upper side whilst the toes have broad pads and small claws. Active at night, they feed primarily on insects which congregate around sources of light, aided by its extraordinary capability to climb vertical walls and walk on ceilings. This amazing feat is achieved by having specialised toe pads, which are covered in small scales called ‘scansors’. On the underside of the toe, each individual scansor can have up to 150,000 microscopic, highly branched, hair-like structures, known as setae, which form hundreds of saucer-shaped ‘end plates’. This gives the Yellow-bellied House Gecko an enormous surface area in relation to its body size, enabling it to grip all kinds of surfaces. They have particularly large and sensitive eyes, with pupils which open wide at night to let in maximum amounts of light, giving it excellent vision in the dark. The pupils contract to vertical slits during the day to protect the retina (the light-sensitive part of the eye) from harsh sunlight, while the eyelids are fused to form a transparent cover, called a spectacle, for additional protection. Any dust or debris in the eye is licked away by the gecko’s extremely mobile tongue. It is found throughout parts of the Arabian Peninsula, Afghanistan, Egypt, Ethiopia, India, Iran, Iraq, Nepal, Pakistan and Somalia. They are particularly associated with man-made structures such as houses, warehouse complexes, hospitals and schools (3), where it is commonly observed on walls and ceilings. During the day, the yellow-bellied house gecko will retreat to undisturbed crevices, often hiding in or behind fixtures and fittings such as air conditioning units and picture frames, or under the eaves of buildings.