The common house gecko is an immigrant species, originally hailing from Southeast Asia. They are such accomplished travellers that they’ve spread right around the globe, joining the eastern export drive by hitching rides in shipping containers. A female doesn’t necessarily need to bring her mate along for the ride because she can store sperm for up to a year and happily lay fertilised eggs once she’s bypassed customs and immigration. She doesn’t even need to travel herself because gecko eggs have hard outer shells, unlike those of other reptiles, so they’re better able to retain moisture and hence travel well, even when unaccompanied in cargo class.
Southern Africa’s tropical house geckos must be non-plussed with the new arrivals, especially given that the immigrants are particularly well suited to hanging around lights and snapping up insects. They tend to be more on the ball and assertive than their shy and retiring South African cousins, chasing them out of the way and even making a meal of the native young.
Fortunately, urban living isn’t for everyone and most geckos in any event prefer to stick to their own natural niche, living on rocks, in trees and even in the desert. The web-footed gecko has evolved to live only in the intimidating coastal strip of the Namib Desert, relying for the moisture it needs on the fogs that roll in from the sea. It uses its long tongue to lap up drops of condensation from stones, and even from its own body. The webbed feet have nothing to do with swimming, a rather redundant skill in the Namib, but instead enable the gecko to scamper over sand dunes without slipping or sinking in, and act like shovels when its digs a burrow. While geckos come in a wide variety of exciting and exotic colours, the web-footed can be almost translucent, its delicate spine and internal organs dimly visible.
In common with other lizards, all geckos have the ability to abruptly detach their tail in an emergency. This disconcerting self-mutilation isn’t undertaken on a whim. The tail, though clearly not essential for survival, plays an important part in balancing and mating. Rapidly contracting muscles conduct the amputation at a specific ‘crisis point’, where the joint is composed of cartilage; the wound instantly closes up, with virtually no loss of blood. The tail does eventually grow back, reinforced with cartilage rather than bone, but is never as elegantly proportionate as the original.
The point of this sacrifice is to distract predators while the gecko makes its escape, but not all attackers, notably Homo sapiens, are interested in eating the eerily wriggling tail. If the gecko survives the onslaught of rolled-up newspapers, shoes and other assorted missiles, it might creep back later to eat its own discarded appendage. It takes a lot of energy to grow a new tail and geckos, like most wild creatures, firmly subscribe to the ‘waste not, want not’ school of thought, even eating their own discarded skin after moulting. Ascalabus, as a former young member of our own improvident species, probably found this a particularly difficult adjustment as he began his new life by the light on the porch.
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RAIN FROG
A typical frog, at least the kind you see in cartoons and children’s picture books, is bright green, has an inane grin on its face, and squats on a lily leaf in the middle of a pond all day, croaking happily and shooting out its sticky tongue to zap each passing fly. Every now and again it takes an ostentatious leap into the water.
Given a bit of practice, that sounds quite straightforward, so it’s a little surprising to discover that, of the thousands of species of frog in the world, the majority do nothing of the kind. Could it be that they have not read the script?
Rain frogs, judging by the rather grumpy expression on their faces, are definitely not available for such frivolities. They exhibit an aversion to ponds bordering on hydrophobia, and are so rotund that the merest ripple would be sufficient to destabilise a lily leaf and plop them into the water. If that happened, the indignant frog would immediately inflate itself like a little beach ball, and trust a passing breeze to bowl it along to the shore.
As is apparent from this, rain frogs can’t swim. Without their beach-ball trick they’d sink like a stone. Their rear feet aren’t webbed, but instead designed for digging holes. Each heel has a hard projection that helps it to shovel soft earth or sand up and around its body so that it can rapidly disappear backwards into the ground. Although it may sound claustrophobic, being underground certainly beats sitting on a lily leaf in the bright sunlight, exposed to everything with a beak and bad intentions.
Unlike its glamorous, albeit fictitious, Hollywood counterpart, a rain frog doesn’t score high points in the looks department. If a fairy-tale princess were to kiss one, the chances are – following the mandatory puff of sparkling smoke – the resultant prince would look more like Quasimodo than Prince Charming. The frog resembles a small, round baked potato, overdone and allowed to cool, with frayed matchsticks stuck in fore and aft for arms and legs. A grouchy little face, pressed out from the potato skin, serves for a head.
Given its apparent aversion to water, it is not unreasonable for the casual reader to ask why it was named after rain in the first place. The answer is that it usually appears shortly before or immediately after rain, and especially so after heavy rain. Cautious at first, it sticks its nose out of its home in the ground and starts intermittently to whistle, squawk or cheep, depending upon which of the 13 species of southern African rain frog it is. Whatever dialect it speaks, it’s tempting to speculate that the frog is moaning about the water damage done to its lounge carpet, but this is in fact their way of calling for a mate.
Male rain frogs are considerably smaller than the females, more or less in the proportion of a ‘new’ potato to one suitable for roasts or mash. Given this disparity in size, and the fact that the male has small arms, an amorous embrace is out of the question. The compatibility problem calls for a novel solution and this takes the form of a milky skin secretion that has similar properties to those of superglue. The small male literally sticks himself into an appropriate position on the female’s lower back. The resultant bond is so strong that the happy couple cannot be pulled apart without serious damage to one, or both.
The strength of the bond is important because the weird combo then set about tandem digging their way backwards into the moistened ground. The fact that the earth is soft and moist after a downpour may help to explain why these frogs choose the onset of rain as the moment to set about such intricate and delicate activities.
A relatively modest number of eggs, somewhere between 25 and 50, are laid in a gelatinous mass about 12 centimetres underground. Their work complete, the male and female then separate, the unbreakable bond dissolving as miraculously as the wonder adhesive which, in gullible times past, you may have used to reattach the handle on your favourite coffee mug.
Many other species of frog lay thousands of eggs, draping them in an orgy of abundance as flamboyant necklaces across ponds and puddles. Assuming these eggs aren’t immediately eaten, most of the myriad tadpoles that hatch are gobbled up by fish, dragonfly larvae, birds and other predators. Safe underground, rain frog tadpoles sensibly stay in their egg case, feeding on the jelly hampers left by moms and pops, and finally emerge, after about six weeks, as fully formed frogs.
Rain frogs don’t appear every time it rains. The bulk of their calendar is taken up with subterranean activities, including snacking on termites and any other suitable subsurface insect that happens along. A good deal of their time is spent in sleep, disturbed, perhaps, by nightmares featuring lily pads and deep, dark pools of placid water.
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Cat among the pigeons Page 12
