Geckos: The Animal Answer Guide

5. Gecko Ecology

62 Chapter 5 Gecko Ecology Where do geckos sleep? When sleeping or resting, geckos try to find places that will shelter them from potential predators and protect them from temperature extremes or bad weather. Terrestrial geckos usually shelter in burrows underground or beneath stones or fallen logs. Some, like the Australian Fat-tailed Gecko, Diplodactylus conspicillatus, use their tails to plug burrow entrances. Rockliving geckos retreat to cracks or crevices. Depending on the species, these may be shallow or deep, horizontal or vertical, or limited to particular types of rock. Many geckos prefer vertical cracks that open downward because they are harder for some predators to climb up and because they are protected from wind and rain and will not accumulate dirt or debris. Arboreal geckos often sleep beneath bark or in the axils of leaves, although they may also sleep in the open on branches, trunks, or leaves, particularly if they have some sort of camouflage. The live-bearing New Caledonian geckos, Rhacodactylus trachycephalus, sleep in family groups in tree holes. Pygopods that live in spiny grasses will generally sleep or rest deep in the grass tussocks . Even some arboreal geckos will come to the ground to seek out shelter in dense vegetation at the base of bushes. The choice of a sheltering site can also depend on other factors. Since geckos store heat they obtain from their surroundings, sheltering under thin rock flakes or bark may be especially advantageous, as these will warm quickly in the sun and transfer heat to animals sleeping beneath them. 63 Gecko Ecology Which geographic regions have the most species of geckos? Given that most geckos prefer warm climates, it is not surprising that geckos are most species-rich in tropical and subtropical regions. The country with the most gecko species is Australia, with more than 175, but there are also many geckos in Madagascar (more than 100), India (>90), southern Africa (South Africa has more than 80 and Namibia has more than 60), southeast Asia (Vietnam, Thailand, and Indonesia each have 60 or more species), and Iran (65). Some of these areas have moist forested habitats, but many are mostly drier and semiarid to arid. On the whole, more geckos live in deserts than in rainforests. Partly because of this, places like tropical South America have fewer geckos than might be expected, with the most in Venezuela (36) and only 35 in all of the huge territory of Brazil. Grasslands and savannas have among the fewest gecko species, probably because these more homogeneous, open habitats do not provide much three-dimensional diversity in microhabitat types. They also are poor in sheltered sites needed by geckos to thermoregulate, lay eggs, and rest. Likewise, desert dunes are also quite gecko-poor for just the same reasons. Do geckos burrow? Certain terrestrial geckos do occupy burrows. In some cases these may be abandoned by other small animals, such as spiders, scorpions, or other Arboreal geckos often sleep head downward, stretched out along a tree branch or trunk. Here a wellcamou flaged Gargoyle Gecko (Rhacodactylus auriculatus) rests on a lichen-covered trunk (center) in New Caledonia. This animal has a small radio transmitter on its back used to study its movements. Courtesy of Josh Snyder. 64 Geckos: The Animal Answer Guide lizards, but generally they excavate their own burrows or at least modify existing ones. Geckos that burrow usually have modified feet to help them dig. Minimally their toes have reduced adhesive scansors, as these structures are not useful on sand or soil and would become clogged by dirt and sand grains. In extreme cases, the toepads are lost entirely. The African Giant Ground Gecko, Chondrodactylus angulifer, has lost the toepads of its ancestors and instead the skin of the feet bears small raised spines. Other burrowing geckos, like the Wonder Geckos or Frog-eyed Geckos, Teratoscincus, of the deserts of Asia, have fringes on the toes that are used like rakes to help move sand as the animals dig. Even more specialized are the webbedfeet of the Namib Desert–dwelling Pachydactylus rangei. In this species, there are no adhesive pads and the feet are completely webbed to form small shovels for excavating of sand. Not only is there skin linking each toe to the next but the toes also have extra skeletal elements called “paraphalanges” that help to support the webs and provide attachment points for muscles controlling its movements. The...