Taxonomic name: Hemidactylus frenatus Duméril and Bibron, 1836
Synonyms: Gecko caracal Tytler 1865, Gecko chaus Tytler 1865, Hemidactylus auritus Poeppig (in Obst) 1977, Hemidactylus bowringii Stejneger 1907: 172, Hemidactylus fraenatus Bleeker 1857, Hemidactylus fragilis Lnaza 1990, Hemidactylus fragilis Calabresi 1915, Hemidactylus frenatus Cogger 2000: 246, Hemidactylus frenatus Cox et al. 1998: 84, Hemidactylus frenatus Glaw & Vences 1994: 277, Hemidactylus frenatus Lanza 1990, Hemidactylus frenatus Liner 1994, Hemidactylus frenatus Boulenger 1885: 120, Hemidactylus frenatus De Rooij 1915: 28, Hemidactylus frenatus Manthey & Grossmann 1997: 235, Hemidactylus frenatus Schlegel in Dumeril & Bibron 1836: 366, Hemidactylus hexaspis Cope 1869: 320, Hemidactylus inornatus Hallowell 1861, Hemidactylus javanicus Fitzinger 1826 (nomen nudum), Hemidactylus longiceps Cope 1869: 320, Hemidactylus mabouia Barbour & Loveridge 1929 (partim), Hemidactylus nigriventris De Rooij 1915: 31, Hemidactylus nigriventris Lidth De Jeude 1905, Hemidactylus okinawensis Okada 1936, Hemidactylus papuensis [Macleay] 1877, Hemidactylus pumilus Hallowell 1861: 502, Hemidactylus punctatus Jerdon 1853, Hemidactylus tristis Sauvage 1879, Hemidactylus vandermeermohri Wermuth 1965, Hemidactylus vandermeer-mohri Brongersma 1928, Hemidactylus vittatus Gray 1845, Hemidactylus (Pnoepus) Bojeri Fitzinger 1843, Hemidactylys cf. frenatus Andreone et al. 2003, Pnoepus bojeri Wells & Wellington 1985, Pnoepus caracal Wells & Wellington 1985, Pnoepus fragilis Wells & Wellington 1985, Pnoepus frenatus Wells & Wellington 1985, Pnoepus frenatus Wells 2002, Pnoepus inornatus Wells & Wellington 1985, Pnoepus papuensis Wells & Wellington 1985, Pnoepus pumilus Wells & Wellington 1985, Pnoepus punctatus Wells & Wellington 1985, Pnoepus vittatus Wells & Wellington 1985
Common names: Asian house gecko (English), Asiatischer Hausgecko (German), bridled house gecko (English), Chichak (Asia), common house gecko (English), geco-casero bocón (Spanish), Gewöhnlicher Halbfingergecko (German)
Organism type: reptile 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 urbanisation 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.
Description
Hemidactylus frenatus is a gecko which measures 7.5-15 cm long with males larger than females. Their scalation is uniform, with distinctive enlarged scales along their backs and arranged in bands on their tail. Its coloration may be gray or light brown to beige with greenish iridescence and a white underside (Csurhes & Markula, 2009). H. frenatus may be identified by several detailed characteristics. It has vertical pupils. Its digits have widened subdigital lamellae, medial subcaudals which are distinctly enlarged, and are arranged in a series. The subdigital lamellae of digit IV extends to base of digit. It has small dorsal tubercles which are restricted to dorso-lateral rows, and a second pair of anterior chin shields in contact with infralabials. Other characters include divided lamellae; dorsum and venter light in coloration, sometimes semi-transparent; a light line through eye; dark lateral stripe may be present; and maximum size of 60 mm SVL (Krysko & Daniels, 2005). H. frenatus has a very distinctive “chuck, chuck, chuck” call (Wilson, 2006) which is most commonly emitted at dusk and dawn. This call is one of the key indicators that house geckos are present in a particular area (N.C. Cole, pers. comm.). Occurs in:
natural forests, planted forests, range/grasslands, ruderal/disturbed, urban areas Habitat description
Hemidactylus frenatus may occur in tropical, subtropical, and temperate environments. It is most abundant in urban, suburban, and developed locations. It is nocturnal and introduced populations are almost always found on building walls near artificial lighting. H. frenatus is also known to inhabit natural environments, including in woodlands, patches of forest, on trees in open fields, rocky and forested areas, coconut palm trunks, under rotting logs, and among dense, low ground-cover such as Ipomea and Canavalia Canavalia often associated with grasses and a rocky habitat. H. frenatus prefers habitats with open hunting surfaces such as walls or vertical rocks near concentrated populations of insects (Csuhres & Markula, 2009; Frenkel, 2006; Newberry & Jones, 2007). General impacts
Hemidactylus frenatus has demonstrated a high propensity for competitive displacement of similar-sized and urban-adapted geckos. The ability of H. frenatus to replace locally native gecko species seems most pronounced in urban areas. H. frenatus is very well adapted to predation on concentrations of insects that gather along building walls near artificial lighting, seemingly more so than most endemic gecko species. H. frenatus also tends to be more aggressive and territorial, as well as, more tolerant of interspecific cohabitation and competition than endemic geckos. Such features allow it to successfully outcompete native species and exclude them from concentrated food sources. Studies have demonstrated aggressive, dominant behavior in H. frenatus over native geckos Nactus spp. on the Mascarene Islands and Lepidodactylus lugubris throughout Pacific islands. H. frenatus was frequently observed stalking, lunging towards and biting at other geckos. In some instances H. frenatus bit off their tails or ate them entirely. H. frenatus was also found to aggressively exclude endemic geckos from daytime refugia, making these native species more vulnerable to predation and adverse climatic conditions (Cole et al. 2005; Newberry & Jones, 2008). H. frenatus are also known to predate upon other small, usually juvenile lizards, such as Cryptoblepharus boutonii (Cole et al. 2005b).There are many records of H. frenatus displacing or causing decline in native geckos throughout its introduced range ostensibly by competitive displacement. H. frenatus displaces endemic and 'Vulnerable (VU)' lesser night gecko (see Nactus coindemirensis in IUCN Red List of Threatened Species) and the endemic night gecko Nactus durrelli in the Mascarene Islands. It displaces both Nactus spp. from favored environments increasing their risk of predation and has proven to be a major cause in the decline of, the once thought extinct in the wild, N. coindemirensis (Cole et al, 2005; Jones & Cole, 2004). H. frenatus displaces Pacific island native Lepidodactylus lugubris in many locations and has demonstrated superior predation abilities. Experiments have demonstrated that H. frenatus consumes a disproportionately higher amount of insect prey than L. lugubris, thereby leaving it with less potential prey which decreases its body condition, fecundity, and ability to survive (Hanley et al 1995; Harvey et al 1998; Petren & Case, 1996). A similar predation study with Australian gecko Gehyra dubia also found H. frenatus to be a more formidable forager (Canyon & Hill, 1997). The displacement of Hemidactylus garnotii by H. frenatus throughout the Pacific basin has been attributed to behavioral interference from aggressive males. Furthermore, H. frenatus was also found to hybridize with H. garnotti in laboratory experiments (Dame & Petren, 2006). Uses
Hemidactylus frenatus are kept as pets in some locations. Geographical range
Native range: Hemidactylus frenatus has a natural range which extends through parts of Asia and the Indo-Pacific.
Known introduced range: H. frenatus is quickly becoming a cosmopolitan species with introductions to locations throughout the world including Australasia, Central, South, and part of North America, Africa, many small islands in the Pacific and Indian Oceans, and new locations in Asia. Introduction pathways to new locations
Pet/aquarium trade:
Seafreight (container/bulk): 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 (Csurhes & Markula, 2009). Its superior ability to cling to surfaces allows it access to high crevice spaces for refuge and egg deposition, both of which increase it potential to stowaway undetected in cargo and shipping containers (Newberry & Jones, 2008).
Local dispersal methods
Natural dispersal (local):
Road vehicles: H. frenatus are commonly found on vehicles, from which they are easily transported to new locations (N.C. Cole, pers. comm.)
Translocation of machinery/equipment (local): In Mauritius H. frenatus are transported to new locations with movement of building materials. Management information
Preventative measures: 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 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 (Csurhes & Markula, 2009; Newberry & Jones, 2008).
The use of naturally or artificially occurring substrates with a crumbly/highly concentrated particulate surface may be used to exclude the pad-bearing H. frenatus from specific locations, allowing claw-bearing gecko species to forage unchallenged. This method of exclusion was tested in attempts to preserve populations of threatened Nactus spp in the Mascarene Islands. Simple habitat modifications through the addition of artificial refugia have been proposed as a means to enhance populations of endangered or displaced native reptiles (Cole et al 2005).
Chemical control: The use of Tricaine methanesulfonate (MS222) injected into the intracoelomic cavity of H. frenatus is a chemical euthanasia method consistent with conditions specified by The Public Health Service Policy on Humane Care and Use of Laboratory Animals which require that euthanasia of ectotherms be consistent with the American Veterinary Medical Association (AVMA) Guidelines on Euthanasia. Test subjects were administered a intracoelomic injection of 250 to 500 mg/kg of 0.7% to 1% sodium-bicarbonate–buffered MS222 solution followed by intracoelomic injection of 0.1 to 1.0 ml unbuffered 50% (v/v) MS222 solution. Test subjects were effectively made unconscious by the first injection and respiratory and cardiac functions were eliminated by the second (Conroy et al 2009).
Nutrition
Hemidactylus frenatus is predominantly a nocturnal, opportunistic hunter which preys on a wide range of insects and spiders. It may be commonly found hunting in developed environments on walls near artificial lights. Stomach contents analysis revealed prey of insect orders Blattodea, Coleoptera, Dermaptera, Diptera, Hemiptera, Homoptera, Hymenoptera, Isopoda, Isoptera, Lepidoptera, Neuroptera Orthoptera, Zygoptera, as well as Araneae and other arachnids. H. frenatus is also known to consume juveniles of other geckos and skinks and also known to consume sugar-based products and nectar (Cole 2005 b; Csurhes & Markula, 2009). Reproduction
Hemidactylus frenatus is a sexually reproducing, oviparous reptile. 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 (Csurhes & Markula, 2009). Incubation of the eggs to a temperature of at least 18 °C is required for development (Ota, 1994; N.C. Cole, pers. comm.). 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 (Yamamoto & Ota, 2006). Lifecycle stages
Females lay two eggs per clutch which have an incubation period of 48-90 days in laboratory conditions (Krysko et al., 2003; Church, 1962 in Krysko et al., 2003). Studies conducted in outdoor enclosures hatched after an average of 50 days (48 to 53 days) (N.C. Cole, pers. comm..). Eggs are round and hard-shelled, unlike most reptile eggs, making them resistant to moisture loss and better able to survive travelling long distances (Wilson, 2006). Juveniles become sexually mature after six months to a year. The lifespan of H. frenatus is approximately 5 years (Csurhes & Markula, 2009). Reviewed by: Dr. Nik Cole, Durrell Wildlife Conservation Trust.
Compiled by: IUCN SSC Invasive Species Specialist Group
Updates with support from the Overseas Territories Environmental Programme (OTEP) project XOT603, a joint project with the Cayman Islands Government - Department of Environment
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Last Modified: Monday, 4 October 2010
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