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Wednesday, June 21, 2000

WILD WATCH

The little known giants of the Kalahari


The fine red sand of the Kalahari, dampened by the early morning dew, reveals the tracks of nocturnal and early morning wanderers. The heat of the rising sun soon turns the sand powder dry and the tracks blow away on the slightest breeze, but for those who are out early there are strange stories to be read in the sand.

Parallel tracks, about a centimeter apart, each as thin as a pencil line, yet extending meter after meter in a meandering, criss-crossing mesh of trails, are an intriguing desert sight. Lion and cheetah, gemsbok and springbok, mongoose, meerkat and ground squirrel are well-known track layers in the Kalahari desert sands, but these thin, wandering trails looked as if a young child playing with an old tin toy train in the sand had made them.

Dawn proved to be the time to catch the perpetrators. An early prebreakfast scouting session revealed many more of the "train" tracks in the sand, and some interesting-looking holes, freshly made and still damp beneath the surface. Shunting sheds for the trains? Waiting at one of these holes, I was treated to my most fascinating Kalahari wildlife-watching experience ever.

Now that is not to say that cheetahs and gazelles, eagles and owls and so on hold no interest for me, just that I had not appreciated that some of the smaller life forms were so amazing. After a few minutes' wait, a black shape appeared at the entrance of the hole, shiny, long and black. It backed out toward me, thick as my thumb, longer than a hand-span. Instead of wheels, rows of fine legs propelled it along, waves of motion passing like peristalsis along the line of legs, their tiny footprints so closely placed that the tracks seemed unbroken.

Backing out with deep, thrusting steps, it was dragging sand with it. Fresh excavations were clearly in process. The millipede was digging its underground burrow, and no ordinary millipede but a giant African millipede.

Then came the funniest natural event I have seen in years, as memorable as graceful swans skidding out of control on ice as they turned duck in their landing path into living bowling pins, as funny as a forest wagtail disco-dancing its way along a grass verge.

It was the Romans, I believe, who criss-crossed the Mediterranean by trireme, slave-powered ships propelled by three banks of oars. Images of the potential confusion that could take place while switching between forward and reverse tickled my sense of humor as I watched the giant Kalahari millipede go through a similar reversal.

All several hundred of its legs slowed their backward sculling; my mind supplied sounds of a locomotive slowing and whistles blowing, or of drum beats signaling. Almost before the last of the legs had ceased their reverse motion, at the front end the message was already coming back along the line for forward motion. There was a slight pause, and off it chugged, back to its hole for another load of sand, repeating its journey over and over as it excavated a deeper day hole.

Millipedes are a fascinating group, belonging to the Myriapoda. Evidence of our obsession with species large and furry or feathered is the fact that the approximately 10,000 species of Myriapoda are twice as numerous as mammals and more numerous than birds, yet the average person would be hard pushed to name any of them.

There are more than 1,000 species of millipedes. Although a few species are scavengers or even predators, most are part of the global recycling cooperative. They live by eating decaying plant matter, digesting and processing fallen leaves and plant stems, reducing them to a scale that makes them available to the myriad other soil organisms that live beneath their feet.

Where I grew up in Europe I rarely saw millipedes. Their shiny black shapes, a mere thumb-joint in length, were hard to spot among the leaf litter of the woodland floor. In the forests of southeastern United States there is a more noticeable black-and-red species that grows to 10 cm; even that species is dwarfed, though, by African giants belonging to the genus Archispirostreptus, some of which reach up to 30 cm in length.

In the cool early morning air cape sparrows were chattering noisily and a small gang of yellow mongoose emerged from their den, signaling the changeover from night shift to day shift. The millipedes belong to the night shift. At dawn their tracks were everywhere in the sand, and scouring the area I found more than 25 of them on their ramblings.

Occasionally they bumped into each other, then, disturbed by the unexpected contact, they would rear their heads, curling them under, questing about for a safe route and setting off in a new direction, slowly protruding their curled heads again as they went.

More severe disturbance caused them to curl in on themselves completely, protecting the head and soft underside. They reminded me of the large spiral licorice sweets I used to buy as a boy in England. The shape was the only resemblance, however, for these millipedes are not to be trifled with. They are not aggressive and they do not bite, but when disturbed, their lateral glands produce pungent toxins in liquid or gas form that are capable of repelling almost all predators.

Twice I came across what appeared to be mating pairs, each time a larger millipede coiled around a slightly smaller individual. This was no hurried clasping, but a prolonged embrace. Later the female would excavate a nest and some weeks after mating she would lay hundreds of eggs in it.

Millipedes live life in the slow lane, even as eggs. It takes them up to three months to hatch, several more months to reach maturity and they may eventually live to be as old as seven years old.

If you are wondering how to distinguish between millipedes and centipedes, then the number of legs and the way that they use them is a clue. Not the absolute number, which would be hard to count, but the number of legs per segment. Centipedes have a single pair of legs per segment. These emerge from the sides of the body so the creature appears more flattened, its legs splayed out. Centipedes are carnivorous and they move in a snakelike fashion.

Although the name millipede literally means "thousand-legged," most millipedes have no more than 300 legs, and these are arranged in two pairs per body segment. The legs of the herbivorous millipede emerge from beneath each segment, so that the millipede's cylindrical body stands off the ground as it moves in straight lines.

Within an hour or so of dawn the millipede tracks were beginning to fade or were being overlaid with those of other larger creatures, as the animals that made them rested through the heat of the day in the cool, damp shade underground. Even these giants would have been easily overlooked, yet they were a welcome reminder that while large mammals are better known, there is still much to learn about the smaller creatures which actually play far more significant, though unobtrusive, roles in our lives. The creatures that help return nutrients to the soil are vital for all of our agricultural endeavors, yet we so easily ignore them, even wage war against them.

Send e-mail messages to MarkBrazil@ or by snail-mail c/o The Japan Times.


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