Let’s be clear on which “herp”—reptile or amphibian—we’re dealing with. As common as they are, geckoes are often confused with another lizard seen clinging to walls and plants, the brown anole. But they’re easy to tell apart; if the gecko is the reptile equivalent of a Cooper MINI, the anole, with its sleek lines and clawed toes, is a Corvette. Geckoes, on the other hand, are distinguished by their rounded toe pads and chunky bodies. Look closer and you’ll note that they also don’t have eyelids, hence their cute, Japanese manga-girl expression. (More precisely, they do have eyelids; they just can’t move them. They clean their eyes by using their tongues like a windshield wiper.) And as anyone who’s spent an evening on a länai in Hawai‘i knows, their chirp sounds a bit like laughter. Geckoes in fact are the only lizards that vocalize beyond brute hissing; the name “gecko” derives from the Javanese tokek, a word that mimics the call of the Tokay gecko native to Indonesia.
There are eight gecko species established in Hawai‘i today, all of them likely introduced by humans. Four probably got here as stowaways on Polynesian sailing canoes: the mourning gecko (Lepidodactylus lugubris), the stump-toed gecko (Gehyra mutilata), the tree gecko (Hemiphyllodactylus typus) and the Indo-Pacific gecko (Hemidactylus garnotii). To the casual observer they look alike: diminutive and in shades of cream, beige, brown and charcoal. They’re nocturnal, so they don’t need to be flashy, and their drab coloration is good camouflage during the day. Three of these species—the mourning, stump-toed and Indo-Pacific geckoes—are likely to be spotted hunting in the glow of porch lights. Or at least were; while all of the founding four are still around if one goes looking, only the mourning gecko remains common in and around houses.
Fragile bones found in sinkholes on O‘ahu’s ‘Ewa plain indicate that geckoes existed alongside early humans, possibly introduced as early as 400 AD, not long after the first canoes landed. So far nothing has been found to suggest that they were here before then, and it’s unlikely: Apart from marine iguanas, saltwater crocs and perhaps Godzilla, lizards and seawater don’t mix. But some gecko eggs could have survived the journey across the world’s largest saltwater moat, says Susan Brown, a UH Hilo professor who’s studied the mourning gecko. Its eggs are salt-tolerant and have a surprisingly long gestation period—up to 125 days. So it’s at least “theoretically possible that they crossed the Pacific on a log and hatched in Hawai‘i,” she says.
But getting here would have been only half the battle. Establishing a colony usually requires two arrivals, male and female. Not so for certain gecko species, because they’re parthenogenic; that is, they reproduce without mating. All of Hawai‘i’s mourning geckoes, tree geckoes and Indo-Pacific geckoes are “unisexual”—all female. And because they reproduce without the introduction of new genes, unisexual geckoes are also clones; some of the animals we see today could be carbon copies of geckoes that arrived 1,600 years ago. Parthenogenesis gives geckoes a serious advantage in the colonization game, Brown says. “If two males end up someplace, the species isn’t going to get a foothold, but if a unisexual gecko ends up someplace, there’s a better chance it’ll survive. Every member of your population can reproduce. … That’s a really good reason not to have males,” she laughs. If the idea of a world without men makes some people uneasy, those same people might go apoplectic to learn that these geckoes aren’t just unisexual; they’re homosexual. Female pairs engage in “pseudo-sex”; one mounts the other and then they switch, a behavior thought to stimulate egg-laying.
This adaptation would have without doubt helped a gecko once it got here, but whether any made the trip independent from humans, Brown says, “I’m not sure anybody will ever know.”