"Night Creatures of the Kalahari"
ANNOUNCER: Tonight, on NOVA. The African sunset signals the beginning of something wild: exotic predators, expert architects, masters of camouflage. Witness inhabitants of a mysterious underworld surface and take center stage, a rare glimpse of events few have ever seen: Night Creatures of the Kalahari.
Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television. This program is funded in part by Northwestern Mutual Life, which has been protecting families and businesses for generations. Have you heard from The Quiet Company? Northwestern Mutual Life. And by the Corporation for Public Broadcasting, and viewers like you.
NARRATOR: There is no end to an African day. Across the grasslands of the Kalahari, the sunset merely signals a new beginning. As the earth cools in the fading light, zebras, wildebeest and other grazing animals move on. They are relinquishing the night to a new cast of characters. Hidden in the shadows, there is a world which few have ever seen, an endless labyrinth of tunnels and burrows, home to the Kalahari's creatures of the night. The dry season is ending in central Kalahari. As winter turns to spring, warmer night air will soon be greeting the dwellers of these moonlit portals. Not all live underground. A tree gives shelter to this wide-eyed curiosity, nine inches of lesser bush baby, a tiny primate, one of our distant relatives. Excellent eyesight, grasping hands, and an amazing agility make them superb catchers of insects. On the ground, another creature has woken up. These are spring hares. About as big as a rabbit, the spring hare looks like a small kangaroo. It feeds on the remaining dried grasses, and if pursued, it can leap as far as thirteen feet in a single bound. To the left of the bush baby is a tree mouse, one of the smaller and therefore more careful desert predators. Less timid than its neighbor, the bush baby illustrates the art of foraging. The tree mouse scrambles to the ground. Here, it will either find a meal or become one. Larger predators are now emerging. The brown hyena, a rarely-seen scavenger. The hole it calls home is not its own creation. The hyena is merely a squatter in this vast underground burrow stretching out hundreds of yards. Many of Kalahari's smaller inhabitants could not survive without the protection of these ready-made shelters. And this is the master digger, the principle architect for Kalahari's underworld. It is the aardvark. Translated, its name is "earth pig," although the name "antbear" is often used. But it is no relation to pig or bear. The aardvark's nearest relatives are all extinct. It has a long snout to sniff out food and a long, sticky tongue to gather its prey. The aardvark is a timid creature, relying on sound, rather than sight, to alert it to danger. Its diet consists of mostly ants and termites. But despite its vigorous probing, the termites in this mound are not to be found. As the aardvark widens its search, a brown hyena prowls nearby. It is one of the least-glimpsed animals of the Kalahari. Brown hyenas are primarily scavengers, favoring meat from abandoned carcasses over all other food. But they will also consume eggs, fruit, insects—even the occasional mouse. Guided by its keen sense of smell, the aardvark has stumbled upon this: a hill seething with ants. More often, the aardvark must dig for its meal. But tonight, the ants are within easy reach. Many ants attempt to repel the invader. Ineffectual, but irritating nonetheless. A few seemingly-gentle strokes from its sharp claws opens up the hard shell of the mound. Once inside, its long, sticky tongue goes to work. Satisfied, the aardvark prepares for the coming day. It doesn't need to find the entrance to its most recent home. It will simply make a new one, demonstrating its well-earned reputation of master digger. Burrows vary in design. Many are created to serve as temporary shelter, penetrating only a few yards into the ground. Deeper, more elaborate burrows are excavated for use as maternity dens in the rearing of their young. Aardvarks can dig at a prodigious rate and could easily escape capture from anyone with a shovel intent on digging them out. The tail and the hind legs help clear away the soil the massive claws are digging. In less than thirty minutes, the aardvark has disappeared underground, leaving a mound of earth in its wake. Burrows are not kept for long. Once abandoned by the aardvark, they provide life-giving shelter for Kalahari's other nocturnal inhabitants. Porcupines, although capable of digging their own homes, will readily take advantage of these pre-existing burrows. The male porcupine is the largest rodent in Africa and can grow up to 25 pounds. The offspring will need their parents' care for about six months, protected from both heat and cold in this second-hand nursery. Above, the brown hyena is checking for messages. On the grass stems, other hyenas have left special glandular secretions. One longer-lasting scent tells whose territory this is. Another short-lived odor indicates how long ago other hyenas were feeding here. Scent-marking helps the brown hyena keep track of other group members, which may number as many as twelve. It also helps reduce the need to defend their territory. An unwary gerbil is caught with surprising speed. Such a kill is unusual for this nocturnal scavenger. The scuttle scarcely disturbs the bush baby above. It's still scoffing insects. Ever hungry, it thinks it's spotted another victim. Or has it? It looks like a stick. But it did move. The insect unfurls its wings. Not designed for flight, they rattle noisily in an attempt to ward off predators. This bush baby's eyes are bigger than its appetite. And so is this giant stick insect. But curiosity soon banishes fear, and the perhaps not-so-hungry bush baby follows the oddity with the passion of a naturalist. The bush baby decides not to bite off more than it can chew. With the coming dawn, the creatures of the Kalahari's night return to their shelters. Although highly adapted to living in this arid region, they would soon overheat if left exposed. They will sleep through the day, safe from predators and protected from the ferocity of the African sun. Oblivious to the underworld beneath them, zebras move out across the plain, foraging from the sea of dry vegetation that surrounds them. Because of their larger body sizes, grazers like the zebra, can tolerate much higher temperatures. But large or small, wildlife must find life-sustaining water in their food. For in most of the Kalahari, which occupies one-third of southern Africa, there is no surface water from which to drink. For this ant-eating chat, moisture is found in the insects its neighbors will soon be uncovering. Even though they are active during the day, ground squirrels also require protection from the sun. The job of hole digging demands constant activity. Vulnerable and exposed, the ground squirrel's work is often interrupted by having to check for hostile predators. A lot of effort goes into these daytime retreats, and when the ground squirrels abandon them, others move in. Meerkats take advantage of the ground squirrels' inadvertently generous nature, and so are neighbors and squatters beside them on the plain. Even in this tinder-dry scrub, they know how to root out a juicy insect or two. Sweeping the horizon with keen eyes, they are constantly on the alert for any approaching threat. This time, the threat comes from above. One of the season's first storms is approaching. Unaware of the advancing rain, some need a cue to disappear. Nature provides it. Generally, rain falls in the warmer months between October and April. Often, it will come in violent, torrential downpours. Because of these seasonal rains, much of the Kalahari is not, in fact, a true desert, despite its reputation. The rains are often local and patchy. Some areas remain dry for years. Highly tolerant, the vegetation is adapted to these drought conditions, renewing itself through seeds when the life-giving storms finally do arrive. What was a dusty plain will very quickly flush green. The freshly-disturbed earth around each hole in the ground is the first to show new growth. It is burrowing animals that provide the water with a path to flow, allowing it to soak the soil and become available for plants. Fortunately, the tunnels don't flood at every level, and the passage is quickly dried. Soon, life resumes with more predictable patterns. Following the torrent of localized rain, the stage is set for a most spectacular event. Winged termites take to the air just once in their lives. These flyers are called "alates" and are produced to leave the mound in order to establish new colonies. In termite mounds all over the Kalahari, this exodus of potential kings and queens happens just once a year, triggered by strong rains. The rain has brought out other arrivals just beyond the swarming mound. The giant bullfrog's arrival is opportune. It has a taste for termites. Without a strong wind, many of these winged termites will not travel far. Once on the ground, the wings are discarded. Now, kings pursue queens, but not unobserved. This annual phenomenon provides the termites with very little chance for success. Only a few couples will escape. Paired kings and queens equipped with huge fat reserves will hide in cracks in the ground or find refuge in trees. There, each will attempt to found a new colony. Animals of all shapes and sizes come to satisfy their appetites. Even a gerbil will risk leaving its home on this particular night. It's the shifting equilibrium between predators and prey that keeps the Kalahari full of life and under natural control. The delicate sound of rustling wings is a clear signal for the bat-eared fox. Although related, it is not a true fox. Its huge ears and small teeth put it in a sub-family all its own. Most of its food is insects. Special jaw muscles allow it to chew rapidly, ideal for coping with termites. Prey is located primarily through hearing. Using their very specialized ears, they can even detect the movements of insect larvae buried in the ground. The last winged termites leave the mound. The workers are busy sealing the doors for another year. In just a few hours, the spectacle is over. The African hedgehog also took its share of termites, and it will eat almost anything else it comes across. It has longer legs and different facial markings compared to its European cousins. The termites were of no concern to the porcupine family. They are vegetarians. The porcupines love to feast on tsama melons. With a water content of more than 90%, they are a valuable source of moisture. Porcupine pairs are monogamous, and it is the female that initiates mating. She will typically conceive only once a year with litter sizes varying between one and three. They young arrive well-developed, attaining adult body mass in just over a year. Due to the porcupine's effective, defensive spines, suckling begins with a bothersome search. The sought-after nipples are not on the mother's underbelly, but positioned further up on the side of her body, covered and surrounded by sharp quills. Their desire for milk is so strong, they'll put up with this for nearly five months, although they've been able to take solids since they were four weeks old. Baby hedgehogs are totally reliant on their mother's milk. These newborn are waiting for her return. Despite their quills, hedgehogs and porcupines are quite unrelated. Unlike porcupines, the hedgehog mother has no mate to help raise the family she's going back to. When born, the babies' sharp spines have not yet cut through the skin. But over the first two weeks, the eyes open, hair grows, and the spines push through and harden. Very soon, they will have the defensive knack of rolling into an inedible, spiky ball. The burrow will be their den for six to seven weeks. After that time, they'll be expected to venture out on their own. So warm and safe is this home, that when the time comes, their mother may have to push them out. When not raising young, these nocturnal creatures will change their resting places daily, curling up in holes, under bushes, or beneath matted grass. An abandoned termite mound is the home for this familiar-looking creature. But this is no house pet. Called the black-footed cat, it is the smallest member of the Kalahari's wild cat family. What it lacks in size, it makes up in ferocity. Because of its aggressive nature, it is unmanageable in captivity, despite its appearance. Mice are its favorite food, but it will readily attack other small mammals, with a few exceptions, such as this nearby hedgehog, puffing along contentedly in search of food. The black-footed cat approaches. But unwilling to risk the sharp, prickly spines of the hedgehog, it quickly retreats. Black-footed cats have two or three kittens in a litter, and this one can't wait to leave home. The other kittens are not quite as brave and stay home. The bolder kitten is ready for a lesson in hunting technique. He must learn to hunt very quickly in this forbidding environment. Playing follow-the-leader, the kitten duplicates its mother's every move. For the less adventurous, there's always a brother or sister to practice on. The mother returns home, but the kitten is not yet ready to follow. The sound of potential prey prompts the mother to investigate. Another sound, this time of a potential predator, encourages the bold kitten to call it a night. The black-footed cat's larger and more common relatives are feeding tonight. Though sometimes active during the day, lions are primarily nocturnal. As they squabble among themselves, others are tempted out by the smell of blood in the air. Unlike spotted hyenas, which hunt and kill in packs, the brown hyena won't disturb the meal. They'll wait until the lions leave before approaching the carcass. Until then, it's time to be patient and indulge in a display of affection. Hyenas are perhaps one of the most misunderstood and maligned of creatures. Because of their eerie nighttime calls and secretive, scavenging nature, they are considered animals of doom and misfortune among many African natives. Their true nature is rarely, if ever, seen. The lions leave. Now they can venture in and sift through what's left. Brown hyenas have remarkable digestive systems and an unusual range of tastes in food. They will even eat fruit, an important supplement in this arid region. After finding a kill, they will readily eat what other animals have discarded. Their powerful jaws can crush bone, which contains nutritious marrow inside. Not much is left of this springbok ram, but it's a better meal than many. Sometimes, brown hyenas will travel as much as thirty miles in a single night. Even then, they may only pick up a few scant insects for their efforts. Nothing goes to waste in the Kalahari. As the wet season runs its course, the sun rises over a sea of green. This lush, flowered garden will be put to good use until the plains, once again, dry out. A feast awaits the mostly vegetarian ground squirrel. It may eat an insect now and again, but its diet consists primarily of leaves, grass, bulbs, roots, and on this day, seeds. Like most of Kalahari's creatures, it receives moisture from its food and can live without the presence of standing water. Aptly named, ground squirrels are poor climbers, but they will scramble up the occasional bush in search of berries. Otherwise, feeding is strictly a terrestrial activity. After the meal, it returns to work on the den. The damp soil is easy to remove. But for the moment, play takes precedence. But these days of plenty will soon be over. In March, as the dry season descends, temperatures soar to over 100 degrees. Only a ruffled dry carpet of grass remains. Hard at work on these grasses are harvester termites, one of many insect families that farm the Kalahari. They cut down stalks of dry grass to a manageable size and drag them down into their tunnels thirty feet below—provisions against harder times. Waiting to feed upon the termites are predators like the scorpion and the ant-eating chat. Each termite, worker or soldier, is a succulent snack. For predators, they are small packets of life-sustaining moisture. Close by, a sand wasp is preparing for its future. She's paralyzed a caterpillar which she will take into a hole she dug earlier. First, she'll have to open the entrance. On the living caterpillar, she lays one egg. Soon, the paralyzed victim will be a fresh meal for her single larva. Before leaving, the small stone over the opening is replaced. She may repeat the same process a dozen times in her lifetime. Still working on the stalks of dried grass, the termite's habit of moving plant material underground plays an enormous role in nutrient cycling. Their fat-rich bodies are also a key link in the Kalahari food chain. The ant-eating chat has more than a beakful ready to bring to her brood in a very unusual home. Such a wealth of food enables the chats to nest in this dry time of year. But where? She's at the entrance to an aardvark burrow, now occupied by a brown hyena. The resident doesn't seem to mind the intrusion. Both parents are feeding the chicks whose cries are coming from a hole in the roof of the tunnel. Although it can excavate its own burrow for nesting, it more often chooses the ready-made shelter of an aardvark hole. The dry season is also nesting time for the world's largest bird. The male ostrich is about to change places with the female. It's now his turn to incubate the eggs. Heat is the biggest enemy. The temperature is high, even in the shade. Unattended, eggs can easily spoil in the Kalahari sun. Other females also lay eggs in the nest. This minimizes the risk of losing an entire clutch to predators. But each set of parents knows its own eggs and tries to keep them positioned in the center of the nest. During these daytime vigils, the ostrich can become heat-stressed. But it can tolerate the loss of up to 25% of its body weight in water without ill effect. In the heat of the day, soil temperature can rise to over 150 degrees. But in the labyrinth of burrows beneath this scorching landscape, it can be as much as 50% cooler. For the Kalahari's nocturnal creatures, this retreat is key to their survival. Daytime grazers also seek protection when temperatures are at their highest. Lying in the shade of trees or bushes helps reduce water loss and keeps body temperatures from soaring. Diurnal animals have adapted in other ways. Pound for pound, they require less water and use less energy to survive. Their body tissue can also store a much larger amount of heat. Six weeks after being laid, the ostrich eggs have hatched, sending as many as ten miniature versions of their parents out into the world. They will grow at a remarkable rate, from six inches to eight feet in their first year. But not all the eggs hatch. Sometimes, despite the best efforts of their parents, they become spoiled in the heat and are abandoned. The failures will not go to waste. The eggs represent nourishment for the less discerning of Kalahari's night life. As the dry season advances, the sun's warming rays quickly dissipate into the clear evening sky. Because of the region's relatively high altitude, temperatures in winter can drop below freezing. Cold becomes another enemy. But tonight, winter's grip has not yet taken hold, and the Kalahari's nocturnal prowlers are free to roam. The denizens of the underworld stir in their burrows. The bush babies seem less interested in grasshoppers this evening and more interested in each other. The master digger ventures out, concerned—quite literally—with sticking to its diet of ants and termites. It's just a slight distraction to the bush babies, who are keen on courtship. The prelude to mating involves the gentlest of caresses. And then, a series of gymnastic displays, leaping up to fifteen feet in a single bound. The hyena has caught the smell of rotting ostrich eggs. They're a welcome seasonal bonus. Hyenas have been observed removing over twenty eggs from a nest, one by one, hiding them for later. For all but a few animals, these eggs present a tricky problem. Ostrich eggs are designed to be broken from the inside at the right time. The hyena will need to use its bone-crushing jaws. With a little persuasion, the egg gives up its spoiled contents to an animal with just the stomach for such a pungent delicacy. Another of the Kalahari's underground creatures surfaces to find its first meal of the night. The conspicuous coloring of the striped polecat warns others to stay clear. Like the skunk, it will release a nauseating spray if threatened. Its diet is primarily insects, but it will readily consume more exotic fare. Scorpions hide in other animals' burrows as well. Like almost everything else, it's looking for a meal. It has a powerful sting, but against a much larger predator, it stands little chance of escape. To the striped polecat, the scorpion is not a difficult challenge. The larger predator first bites off the tail which can deliver a painful sting. To the scorpion, termites were thirst-quenchers. Now, it unwillingly provides the same service for the striped polecat, a link in the chain of appetites foraging in the dark. Changing seasons mean changing diets for the hunters and scavengers of the Kalahari's night. As the weather cools, it is often ants, and not termites, that are more readily-available for feasting. During the meal, the aardvark will inadvertently consume grass seed the ants have stored. Because he cannot digest the seed, it will be deposited on soil which the aardvark then buries. Beyond his title of master digger, the aardvark is one of the Kalahari's master planters as well. And so, it's on to the next job at hand, an after-dinner dig which will take the aardvark into the deepest recesses of the underworld, providing once again additional shelter for those less capable of such grand excavation. A master bedroom in the making. Familiar sounds and smells alert the nocturnal cast of the imminent sunrise. Travel-weary but well-fed, the brown hyena returns to its burrow. The others soon follow suit. Soon, the only traces left of these strange creatures will be the dark portals to their hidden world. Gone, but not forgotten. The creatures of the night play a vital role in the regeneration of this arid land. Without them, this fragile web of life would all but disappear.
ANNOUNCER: Night vision. Where we see only darkness, some animals see their next meal. How do they do it? NOVA's Web site shines a spotlight on the nocturnal eye. See for yourself at www.pbs.org. Educators can order this show for $19.95 plus shipping and handling by calling 1-800-949-8670. And, to learn more about science can solve the mysteries of our world, ask about our many other NOVA videos.
NOVA is a production of WGBH Boston. Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television. This program is funded in part by Northwestern Mutual Life, which has been protecting families and businesses for generations. Have you heard from The Quiet Company? Northwestern Mutual Life. And by the Corporation for Public Broadcasting, and viewers like you.
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Night Creatures of the Kalahari
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