Photographer: Vicki Nunn Source: www.commons.wikimedia.org Copyright: CC BY-SA 3.0
Hemidactylus frenatus is a gecko which measures 7.5-15 cm long with males larger than females. Overall the scalation is uniform, with distinctive enlarged scales along the back and arranged in bands on the tail. The coloration of common house gecko may be gray or light brown to beige with greenish iridescence and a white underside. It has vertical pupils and dorsum and venter light in coloration and sometimes appear semi-transparent.
Hemidactylus frenatus has demonstrated a high propensity for competitive displacement of similar-sized and urban-adapted geckos. The common house gecko is very well adapted to predation on insects that gather along building walls near artificial lighting, seemingly more so than most native gecko species. Also, H. frenatus also tends to be more aggressive and territorial, as well as, more tolerant of inter-specific cohabitation and competition than native geckos. Such features allow the common house gecko to successfully out-compete native species and exclude them from concentrated food sources. Studies have demonstrated aggressive, dominant behavior in H. frenatus over native geckos like Lepidodactylus lugubris throughout the Pacific islands. In some instances H. frenatus bit off their tails or ate them entirely. Their aggressiveness and their ability to cohabitate while out-competing makes H. frenatus a dangerous invasive species. With H. frenatus being established on all continents (except Antarctica), it is a clear and present threat to native geckos and their ecosystems.
Hemidactylus frenatus mating includes a short courtship during which males repeatedly touch the female with his snout and may bite and hold her by the neck. Three to four weeks after fertilization females lay two hard-shelled that are partially fixed to a solid surface. Breeding occurs throughout the year in tropical environments and is seasonal in cooler conditions. Females are able to store functional sperm for up to a year and lay two eggs per clutch. Eggs are round and hard-shelled, unlike most reptile eggs, making them resistant to moisture loss and better able to survive traveling long distances. Juveniles become sexually mature after six months to a year and adults live up to 5 years. Hemidactylus frenatus is predominantly a nocturnal, opportunistic hunter which preys on a wide range of insects and spiders. This gecko is also known to consume juveniles of other geckos and skinks and also known to consume sugar-based products and nectar.
The common house gecko is now established in at least 87 locations around the world outside of its natural range in Asia and the Indo-Pacific. Many of these new locations have been small remote islands in the Pacific and Indian Oceans. Where the common house gecko has been introduced to islands of the Pacific Ocean, researchers have shown that this lizard has been responsible for the competitive displacement of other similar sized or smaller gecko species in urban and suburban environments. It was shown that habitat simplification and clumped food resources around artificial light sources as a result of urbanization have enabled the common house gecko to gain an indirect competitive advantage over other nocturnal gecko species. The ability of the house gecko to persist outside of its natural range poses a threat to the survival of ecologically similar endemic geckos.
U.S. Habitat: Hemidactylus frenatus has flourished in the Deep South because it is a tropical gecko that thrives in warm, humid areas where it can crawl around on rotting wood in search of the insects it eats. This gecko is very adaptable and may prey on insects and spiders, displacing other reptiles.
The common house gecko is a native of Southeastern Asian countries like India, Malaysia and Thailand but has extended far beyond its native range. Hemidactylus frenatus is now confirmed in Pacific Islands, Australia, South Africa, United States, Costa Rica, Venezuela and many other countries. The widespread expansion of this gecko shows that it is a fierce competitor and a dangerous threat to native gecko species worldwide.
U.S. Present: AL, GA, FL, LA, MS, TX
The common house gecko had previously been an imported reptile for the pet industry; but now, the majority of introductions of Hemidactylus frenatus are the result of it finding its way onto boats or shipping containers that are transported to new locations. It is recommended that incoming cargo should be examined for H. frenatus and that any individuals or eggs found be exterminated to prevent its establishment. Its superior ability to cling to surfaces allows it access to high crevice spaces for refuge and egg deposition, which gives it high potential to stowaway undetected in cargo and shipping containers.
The use of naturally or artificially occurring substrates with a crumbly particulate surface may be used to exclude the pad-bearing H. frenatus from specific locations. By having a different substrate it allows claw-bearing gecko species to forage unchallenged. This method of substrate substitution was tested to preserve populations of threatened Nactus spp in the Mascarene Islands. To prevent this gecko from becoming more established worldwide and give the native gecko species the upper hand; it will take vigilant eyes searching on shipping containers, and innovative plans to create an inhospitable environment for Hemidactylus frenatus.
Cole, N. 2005. The new noisy neighbours: Impacts of alien house geckos on endemics in Mauritius. In: Aliens newsletter, No. 22, Invasive Species Specialist Group (ISSG)
Csurhes, Steve and Anna Markula., 2009. Pest animal risk assessment: Asian house gecko Hemidactylus frenatus. Biosecurity Queensland, Queensland Primary Industries and Fisheries, Department of Employment, Economic Development and Innovation
Newbery, Brock and Jones, Darryl. 2008. Presence of Asian House Gecko Hemidactylus frenatus across an urban gradient in Brisbane: influence of habitat and potential for impact on native gecko species. Pest or Guest: the zoology of overabundance, Pp 59 - 65.
Ota, H. 1994. Female reproductive cycles in the northernmost populations of the two gekkonid lizards, Hemidactylus frenatus and Lepidodactylus lugubris. Ecological Research 9:121-130.
Yamamoto, Yurie; Ota, Hidetoshi., 2006. Long-term functional sperm storage by a female common house gecko, Hemidactylus frenatus, from the Ryukyu archipelago, Japan. Current Herpetology. 25(1):39-40.