Dave in Coffs Harbour has written to us about a critter most Aussies have become familiar with as a regular in their homes and gardens… the Asian House Gecko.
Dave has come to expect the nightly back and forth of chuk-chuk-chuks as his resident Asian House Geckos (AHG) bark away. And each morning, the light of day reveals their ubiquitous calling card on skirting boards, walls, lampshades and outdoor settings. But as Dave has noticed, there seem to be a few different species at his place. Depending on where you live in the country you are likely to have a mixture of native and introduced gecko housemates.
The AHG (Hemidactylus frenatus) is believed to have travelled to our shores as a cargo ship stowaway in the 60’s. Darwin was first to be colonised, then they showed up in Brisbane, radiating along transport corridors. By the 90’s AHGs had become common place from Northern NSW toTorres Strait. Populations are now present in all of our states and territories and even Norfolk Island.
Their swift invasion of the urban environment has been facilitated by a ready food source. The insect-attracting lights that fill our cities provide an endless smorgasbord for the skilled hunter. Scientists are concerned that AHGs may be displacing the native geckos that previously ruled the house gecko niche eg Dtellas (Gehyra spp.) and Velvet Geckos (Oedura spp.).
AHGs have also hitched a ride to the Americas, Pacific islands and Africa, making them the most invasive reptile in the world with the broadest distribution. In the Mascarene Islands, two native gecko species are no longer found on islands where AHGs exist.
While we’re talking geckos, their fascinating anatomy is worth a mention. We’ve all seen them run across smooth vertical surfaces but how do they do it? No, it’s not suction. I will let David Attenborough explain…
But I digress. What Dave (and probably you) really wants to know is how to tell the difference between the natives and the stowaways:
1. Looks: AHGs resemble native geckos, they are similar in size, but if you look closely AHGs have enlarged spines on their back and in bands around their tail. In comparison to the native Dtella Gehyra dubia, all AHG toes have claws but the inner toes of G. dubia are clawless.
2. Call: AHGs are much louder and more talkative than natives; their chuk-chuk-chuk is aptly described as ‘scolding’. Native geckos tend to chatter softly.
3. Eggs: AHGs lay eggs that are round, hard shelled and much more resistant to moisture loss. Native gecko eggs are parchment-like and soft and must be deposited in moist sites.
If you’re still having trouble, find yourself a reptile field guide.
So if AHGs could pose a threat to native geckos in urban areas what are we doing about them? Well…not much really. In QLD (where AHGs are most prevalent) a 2009 risk assessment deemed them a ‘serious’ threat however they are not a declared pest. The report found that the extent and significance of competition with native geckos requires further study.
This is definitely one to keep an eye on. Take the time to find out who you are sharing your house with.