The chirping gecko on your porch light is quietly conquering the tropics
In warm countries, a small lizard stalking moths around a porch lamp and chirping is usually the common house gecko. Harmless to people, it has hitched rides on cargo from its Asian home to the American Deep South, Mexico, Australia, Africa, the Middle East and the Caribbean, often pushing aside native geckos wherever it lands.
Native to South and Southeast Asia and Near Oceania, Hemidactylus frenatus reaches 7.5 to 15 centimetres and lives around seven years. Its species name means bridled, for the dark streaks running from eye to nostril. It hides by day and hunts at night, and it is truly a house gecko: most populations sit in or near towns, where lights draw cockroaches, termites, moths, flies and spiders. Individuals favour lit spots close to a crack they can bolt into, and those without an escape route come out later and retire earlier.
Mexico shows how the spread works. The first specimen there was collected at Acapulco in March 1895, probably after arriving by ship, and by the early 1940s the species was well settled in the region. It has now been recorded in 21 of the country's 32 states, almost always on houses, hotels and other buildings. A winter dormancy called brumation helps it cope with cooler places, and warming climates combined with growing cities are expected to widen its range further.
Its success comes at native species' expense across tropical Asia, Central America and the Pacific. Its males are more aggressive than the females of rival species, particularly all-female ones that reproduce without mating, and sexual females compete harder too. It tolerates bright light, packs in at high densities, and can make the mourning gecko avoid feeding spots, while being unbothered by neighbours itself. It fails only against bigger natives such as the robust velvet gecko.
Males face a trade-off. Territorial ones grow broader heads for a stronger bite but sprint away more slowly, so they are likelier to stand and fight. Females whose heads grow larger also get longer hind legs, and lose no speed.
Source: Common house gecko
