The Accidental Immigrant

Geckos and Anoles are accidental immigrants to the Llano Estacado

Published Nov 10th 2002 in Wildlife

“How do you get rid of geckos?” In the past month we have had two different couples visit the Sibley Nature Center seeking such advice.

“They are weird, slimy, icky, nasty-looking – they give me the creeps and the heebie-jeebies.” Mediterranean Geckos are pinkish to white, with some darker blotches. The skin is so translucent that a person can see one or two eggs in the abdomen of the females during the spring and summer. White-edged knobby tubercles are in rows down their back. The round tail has more tubercles with some bands of color that are brighter in juveniles. The nocturnal geckos have non-movable eyelids, so their eyes (like those of snakes) are always open, which adds to the spooky otherworldliness of the creatures. And on top of that, the males squeak when squaring off in territorial battle!

Mediterranean Geckos are one of five species of geckos that have been introduced to the United States. They board ships in their home range, but then abandon ship in our semi-tropical ports. Over the years the Mediterranean Gecko population grew and spread until finally taking up residence in plant nurseries. Many of the houseplants sold in local nurseries are grown in the Houston area. Some come all the way from Florida and California as well. The geckos traveled beyond the ports by hiding either in the soil of the plants, or clinging to the plant material. The refrigerated trucks kept the geckos immobile until delivery. The plants were often kept inside of the nursery in airconditioning, so they still did not move much. Mediterranean Geckos arrived in Midland in the 1980s. When folks took the plants home, the geckos finally became warm enough to begin exploring.

When local amateur naturalists first became aware of the geckos and Green Anoles (another non-native lizard well established in Midland), we assumed they would not be able to survive our cold winters. The geckos and anoles are small enough, however, to crawl into tiny spaces that protected them from the cold, and have managed to survive quite well. Both species are constantly expanding their range in town.

Folks in the semi-tropical ports love their geckos, for also abandoning ship are a number of European and Asian cockroach species, as well as other insects – remember the Medfly in both Florida and California? The geckos become housepets, little helpers that keep the insects at bay. When we reported this fact to one of the visitors that were squeamish about sharing living space with geckos, the gentleman did a double-take and said, “You are right, we haven’t even seen a cockroach since the geckos showed up!”

Several years ago we kept a Mediterranean Gecko in captivity for a month. It resided in a 50 gallon aquarium filled with a mixture of native soil, dead leaves, a few rocks, and some half-decayed compost with bits of rotted vegetables. A box turtle lived in the cage, along with a number of species of beetles, pillbugs, worms, ground spiders, and earwigs. The gecko spent most of its time sleeping underneath the sleeping turtle, or underneath a rock. In the morning we would find it at the top of the container, where the lid met the glass walls.

When disturbed, it ran about wildly, often attempted to dig but only half-heartedly, and then would run for the turtle or one of the rocks. We never saw it eating, but it seemed to get plumper, while the numbers of smaller creatures declined. (The turtle ate some, too, I am sure.) Due to its lid-sitting habit, it eventually escaped, to roam the building. We never found it – not even its carcass -- even when we moved every bit of furniture to put tile on the floors.

Geckos can climb surfaces as smooth as glass. Their foot pads are covered with hundreds of thousands of microscopic hairs that have two tiny suction cups at the end. Each cup is about 7.8 millionths of an inch in diameter. The cups are set at a jaunty angle to the hair. The Green Anoles also can climb glass. They have single cups that are 29 millionths of an inch in diameter on their hair. With both species, the cups are very malleable, able to fit against any irregularity of any surface.

Mediterranean Geckos can not survive on the Llano Estacado away from human habitation. It is too dry, especially in this nine-year drought. Despite reports from many Midlanders that the geckos have just moved into their neighborhoods, we wonder if they are surviving beyond the realm of the automated watering systems.

The geckos probably will not affect native wildlife. Areas of town near a playa or drainage ditch still have toad reproduction, so geckos might present some competition to toads. Geckos climb walls and catch insects near porch lights, while toads have to wait on the ground below. With the exponential increase of gecko population any small predator that learns to eat them might increase. The foxes, skunks, and raccoons that roam the alleys at night will only find the geckos useful as an apertif, but long-nosed snakes and kingsnakes would find them tasty. But those snakes are rarely found in town, having lifestyles visible to humans, and so many of us kill every snake we find under the misguided belief that all snakes are poisonous and therefore evil.

That brings us back to the folks that wished to get rid of their geckos. We advised them to learn to live with the fascinating and useful little creatures. In our dry air their droppings dry quickly, so the chance for contamination of living surfaces are slim. They are not carriers of bacteria or viruses. In fact, their skin, like that of toads and frogs, most likely exude substances with antibiotic properties. (A new class of antibiotics recently discovered naturally occurring in amphibian skin is now being studied for possible synthesizing.) Make friends with your geckos!