Author: sonja@afritree.com

Shortly after sunset and before sunrise, flocks of this pigeon–sized bird converge on water holes throughout Namibia. They arrive with such precision that you can set your watch by it. The synchronised drinking of Double–banded Sandgrouse provides an insight into the delicate mechanisms that ensure survival in a harsh environment.Sunset…a magical time at the water holes of Etosha. The sun dips below the horizon, its rim flaming like some giant veld fire. Searing temperatures drop with the diminishing day, promising coolness and relief. Twilight time brings a pervasive stillness that is tangible after the raucous day. The last doves dip their beaks and fly off urgently into the dusk. This is the time when it is too late for eagles and too early for owls to be at the water’s edge. I check my stopwatch, waiting expectantly for the first flying form to mirror itself above the water. It arrives punctually after sunset, winging in swiftly and landing a little distance away, creating a small puff of dust as it settles. I stop the watch, noting the exact time. Complete silence, then the calling begins when bird after bird appears, flying low and fast. Soft, rasping conversation spreads amongst the arrivals; a multi–syllabled sequence, which has been likened to the words “why do you weep so Charlie?” or a longer, drawn–out “oh no, he’s gone and done it again” (emphasis on the syllables in bold). The convergence of Double–banded Sandgrouse assumes a ritualistic ceremony as hundreds, sometimes thousands, of these secretive birds gather at Etosha’s many water holes. Found throughout Namibia, the males have a distinctive, banded black–and–white pattern on the forehead and a similar horizontal bar across their rufous breast feathers. Females are inconspicuous, with finely barred, buff–coloured feathering.

Their synchronised pattern of drinking became apparent to me while working in the Namib Desert and later in Etosha. I began associating sunset with their sudden appearance at watering places, noting that they arrive with uncanny precision during the brief window of time that divides day and darkness. Eventually, my curiosity about this predictable behaviour caused me to accurately record my earlier, casual observations. To do this, I enlisted the assistance of several people and we followed the same, strict protocol several times a week, over a period of one year. A number of factors appeared to be involved, for example, the time of sunset changes daily, albeit imperceptibly. Consequently, to accurately record this, we used a Global Positioning System (GPS) that gave the exact time of sunset at the water hole we were observing. Timing this by stopwatch, we proceeded to note: arrival of the first sandgrouse, estimated maximum number of birds present, disturbance by other animals, cloud cover, rainfall, and time when the last sandgrouse flew off. Powerful floodlights at Okaukuejo, Halali and Namutoni rest camps illuminate the water holes, so we also noted the time when these were automatically activated, to ascertain whether the artificial light had any influence.

It was fascinating work. I became absorbed by the regularity with which these swift flyers appeared, homing in to a water hole with uncanny timing. Sunset’s silence was broken for about half–an–hour as the sandgrouse vocalised, their combined voices rising in volume when their numbers reached a peak. The sound resembled a chorus of many frogs. It gave the impression that the birds were engaged in conversation and that this brief period was when they could socialise before flying away to all points of the compass. On occasions they emitted a distinctive, softer, “churring” note. Earlier research hypothesizes that this call may have evolved from imitating the Suricate, by sounding like the growling of this fierce little member of the mongoose family. It may well be that such a call would make the defenceless sandgrouse sound dangerous to would–be predators. Their airborne departure from drinking was invariably accompanied by a busy “chuk–chuk–chuk” note.

Sometimes their predictable pattern of arrival and departure was broken by the announced advent of elephants. Trumpeting and trunk–flaying, the herd encircled a water hole, chasing all and sundry away. Sandgrouse scattered in front of this wall of sound and movement, abandoning their congregation for that particular night. During full moon, when I spent the entire night at a water hole, a few birds came to drink throughout the hours of darkness. Some winged their way in as dawn was approaching but, during 35 years of observation, I have not witnessed them coming to drink during daylight hours. The technical term for this dusk–and–dawn activity is crepuscular, as opposed to animals that are nocturnally or diurnally active.

A year’s data showed, with results that are statistically highly significant, that Double–banded Sandgrouse arrive to drink 16 minutes after sunset on average, with a standard deviation time of 4 minutes either way. They spent, on average 28 minutes at water, flying away about 44 minutes after sunset. So predictable were these times that we joked we could set our watches by them! The significance of this synchrony is most likely that this species of sandgrouse has evolved a strategy, which favours their survival in an environment fraught with hazards. Surface water in Namibia is very limited for most of the year. Temperatures soar to dehydrating heights and flying in this heat requires debilitating energy outputs. Predators abound in the form of birds of prey, wild cats and jackals. Consequently, the hypothesis is that the primary signal which, figuratively speaking, “switches them on” comes with decreasing daylight intensity. Moreover, the cooler, denser twilight air saves flying energy and also reduces body water loss.

The challenge remaining for future research is the yet–to–be answered question of how these birds are able to find their way back to the nest when they depart from a water hole after dark, flying many kilometres over trackless bush or open desert. They will have to land unerringly at the nest, a mere shallow scrape in the ground, where their helpless chicks await the bringing of water, carried in the male’s breast feathers. Finding a water hole is relatively easy, but consider the feat of flying in exactly the right direction to locate the nest. In addition, they must know the distance accurately and they must know the length of time to fly this distance. Finally, they must do all of this by moonlight, starlight or virtually no light at all when thick clouds obscure the night sky.

Just as I became intrigued by the clockwork precision with which Double–banded Sandgrouse drink, I now find myself wondering how they complete their return journey to the nest. It will require many nights of work in the veld, coupled with far more sophisticated instruments and technology than what we used, to answer this question.

Text by Dr. Hu Berry
First published in “Flamingo” June 2005

‘Gogga’ is a popular Afrikaans word used mostly in a derogatory sense, to denote a creepy-crawly, a flying insect or a near relative, such as a spider, scorpion, tick or mite. People often use the word in exasperation when irritated by buzzing flies and mosquitoes, and deal with the offender by hitting, squashing, trampling or dousing it with an aerosol spray. Paradoxically, ‘gogga’ is also used as a term of endearment, yet another linguistic quirk of the Afrikaans language.

The best definition that science is able to give for an insect is ‘an animal with six legs in the adult stage’. Applying this seemingly simple statement to all the animal species, which have been discovered and described scientifically, we find that the vast majority fit this description. An inventory of Earth’s living organisms lists a total of 1,75 million species, of which not less than 1,1 million or two-thirds are insects.

But who decides what insects belong where? This is the realm of taxonomists, people whose main interest is classifying living things into different groups, according to various scientific criteria. Thus, they have to date determined that there are at least six major types of life, which they designate as ‘Kingdoms’. The two best known are plants and animals, the remaining four being more primitive and microscopic life forms. The animal Kingdom is further divided into 33 ‘Phyla’ (singular ‘Phylum’). Of these, 32 are spineless animals and one, known as the ‘Chordata’ possesses a chord or spine in its back. Humans are Chordates or more specifically, vertebrates.

Insects have no spine or internal skeleton like vertebrates, and are relegated to the ‘Class’ Insecta (or Hexapoda, meaning six-legged). Entomologists are people who study insects and they generally agree that there are 26 groups into which insects can be divided, known as ‘Orders’. These range from primitive silverfish and fish moths to socially complex termites and highly developed honey bees. Ultimately, the Orders are made up of ‘Families’ , ‘Genera’ and ‘species’, the latter generally being the final step in classification.

To give an idea of how numerous insects are, a prominent entomologist estimates the weight (or body mass) of the world’s ants to be roughly the weight of all 6 400 million humans living today, namely 320 000 million tons. More about ants and humans: the societies of both species are remarkably similar – ants and people have highly developed social systems. Both are ‘super organisms’, meaning the ability to communicate, cooperative behaviour and altruism (unselfish sacrifice by an individual to promote the interests of other individuals). Another characteristic of a super organism is that it dominates ecosystems, which ants and humans certainly do. In tropical forests ants alone make up four times the weight of all the land vertebrates (amphibians, reptiles, birds, mammals) put together. Furthermore, ants and people exert a tremendous effect on other species. We divide our labour, we are the principle turners of the soil, we are the top predators; worse still, we are constantly at war with our own species. Ants eclipse us in this respect however, as they are the most warlike of all animals. Reflect for a moment that ants and humans behaviour supports the theory that highly evolved societies having an elevated level of altruism, tending to divide into distinct groups that then proceed to fight against each. We humans are constantly at war and have been in group conflict since prehistory. This begs the question whether complex societies and war go hand-in-hand. Can ant behaviour provide humanity with any lessons? Like us, ants do some shocking, repellent things. They scavenge, they cannibalize, and they practice slavery. They do differ in one aspect (proponents of female freedom, take note): ant colonies are all female; males are tolerated for only part of the year! One lesson we can learn is that these biblically busy little creatures (‘look to the ant thou sluggard’) keep themselves fanatically clean, so ant epidemics are rare.

But other important differences also exist, benefiting the human whose weight is huge compared to the micro-mass of an ant. We are not only physically but mentally superior to ants. Ants cannot use fire, for the simple reason that the smallest, stable fire must be much larger than an ant. Ants cannot therefore carry fuel close enough to a fire to maintain it. Ants cannot use tools like, for example, a hammer because an ant-sized hammer will have too little kinetic energy to drive an ant-sized nail. Furthermore, an ant-sized book would be impossible to open because the necessarily ultra-thin pages would be held together by inter-molecular forces that are extremely powerful at that micro-scale. Moreover, ants are unable to read – they do not possess sufficient brain cells to perform this function. And…..ants cannot wash because water’s surface tension prevents adhesion (wetting) to their bodies, plus the fact that most insects’ waxy outer layer repels water. The fastidiously clean ant overcomes this disadvantage by dry-cleaning itself.

Other ‘goggas’ perform seemingly impossible feats. Mosquito-like pond skaters can literally walk on water, using the surface tension to create a contact angle with their miniscule feet, which is so high that the surface pressure prevents them from sinking. Because the force exerted by water’s surface tension is proportional to the length of a pond skater’s feet, a human weighing a million times more than a pond skater would need feet with a perimeter of more than seven kilometres to do this.

The common housefly, which pesters you to the extent that a swatter has been designed specifically to deal with it, is aerodynamically possibly the most gifted creature on Earth. What aircraft can execute six turns a second, hover instantly, fly straight up (or down or backward), somersault and land upside-down or on a vertical surface? Its brain, by the way, is smaller than a pinhead, yet the swipe of a human hand is magnitudes slower than a fly’s ability to avoid being smacked. An ardent studier of hoverflies disputes this agility however, maintaining they are the ultimate aerial performer. We will have equaled the darting hoverfly when we develop an aircraft that can hover in one spot, hurtle through the air to another point, and return directly to precisely the previous hovering point. Using advanced technology, which involves filming at super-slow motion; researchers put another acrobat, the ubiquitous fruit fly through its paces by manipulating their visual field in a closed chamber. When the film is screened, there are 6 000 images of every second of the acrobatics performed by these densely-clustered fliers to explain how they avoid mid-air collisions. Executing 90-degree turns, they employ their total of 12 muscles in combination with compound eyes, light sensors, wind-sensitive hairs and equilibrium organs on their backs that function like gyroscopes. A mid-air collision has not yet been recorded during these experiments.

Flies have been around for hundreds of millions of years. They are also the first animals to take to the air, long before birds. When you finally flatten that pestering fly with a well-aimed swipe of the swatter or triumphantly exterminate the ant colony, which is excavating your driveway, with deadly insecticide dust, remember…there are more where they come from and they will probably outlast us as a species.

Text by Dr. Hu Berry
Originally published by Venture Publications in ‘Flamingo ’August 2006

‘The Desert is both fascinating and terrifyingIt is the great, lonely void,
And humans instinctively dread being brought face-to-face with themselves.
For you, the Desert is not a setting,It is a state of soul.
The Desert turns you inward.’ (from the writings of a Tibetan Monk)

Deserts are very special places. They embrace all continents – the Equator, the Poles, and the open sea. They can be hot or cold, on the highest mountain peaks and nearly 400 metres below sea level at the Dead Sea, where the salinity is seven times that of the oceans. At least 10 discernible deserts are named in the New World and 27 are recognized in the Old World. Add to this the frozen realms of the Arctic and Antarctic Circles, because their minimal precipitation qualifies them as arid regions. Names like Death Valley, Baja, Mojave, Arabian, Gobi, Kalahari, Namib and Sahara conjure up visions of barren isolation. If the oceans cover 71% of the Earth’s surface, then deserts vie for second place, with 61 million square kilometres or 35% of the land surface classified as ‘desert’. Definition of a desert is not as simplistic as it sounds. The Latin ‘desertus’ means abandoned, while the English dictionary describes it as ‘an uninhabited, desolate, uncultivated, barren treeless and waterless region’. This is misleading because deserts are, in parts, inhabited, cultivated, and not necessarily without trees and water. It took years of debate between climatologists, geologists, geographers and biologists to produce an acceptable definition. Thus, a desert is recognized as a geographical area where life processes are regulated by infrequent, isolated and unpredictable inputs of water.

Our Cradle of Civilization arose in the aridity of the Middle East, between the confluence of two rivers, the Tigris and Euphrates. Three great religions, Judaism, Christianity and Islam were founded in this region, all possessing the characteristic of worshipping one God only. The barren wildernesses of the Earth inspire poets, artists, writers, scientists, philosophers and the military. The brilliance of generals such as Germany’s Rommel (‘the Desert Fox’) and Britain’s Montgomery of El Alamein was displayed in the Sahara. Later, we entered the nuclear age in the desert of New Mexico. Now our civilizations threaten many deserts’ fragile ecosystems. Eventually, according to biblical prophesy, we may face our demise in the desert at Armageddon where the armed forces of this world will engage in the final, supreme conflict of nations.

Absence of moisture means that desert surfaces receive more than twice the amount of the Sun’s radiation (achieving a temperature of 580C in the Sahara) than do humid regions. Similarly, deserts lose twice as much heat at night, sometimes dropping to minus 180C. Most deserts are located around 300 latitude in both hemispheres – a result of global air circulations, which form vast cells of descending, dry, hot air in these regions. Moreover, especially in the southern hemisphere, Antarctic currents sweep northwards along the western sides of continents, giving rise to the relatively cool, coastal Atacaman, Peruvian and Namib deserts. By comparison, continental inland deserts of Asia and Australia are far from the sea, thereby greatly reducing the possibility of moisture reaching them. South America’s Andes, North America’s Rocky Mountains and India’s Himalayas craft the third type of desert. They create ‘rain shadow barriers’ that harvest the rain-bearing winds blowing in from the ocean, leaving dry air in their wake. Even the North and South Poles cannot escape the freezing dehydration and are known as ice deserts. Closer to home, Namibia’s 5 000 square kilometres Etosha Pan is classified as ‘saline desert with dwarf shrub savanna fringe’.

Far from being lifeless, deserts harbour some extreme adaptations. Recently described by science, an ancient creosote bush found in North America’s Mojave Desert may represent the oldest form of plant life at 11 000 years (6 000 years older than the Great Pyramid of Cheops in the Sahara). Arizona’s giant saguaro cactus contradicts the popular notion of a lack of water in the desert. Weighing 9 tonnes, with a height of 15 metres, its fleshy stem contains 75% to 95% moisture. What’s more, its longevity and prolific nature produces 40 million seeds in 200 years. Nevertheless, the desert decrees that only one of these will reach full maturity every two centuries, a prime example of population control. The world’s fastest land animal, the cheetah, courses across Old World deserts at 110 kilometres an hour. The speediest rodent in existence, the Mara or Patagonian ‘hare’ is a swift sprinter. Resembling, but not a true hare, it has long, rabbit-like ears and is capable of reaching 45 kilometres an hour (about the same speed as the fastest human). What about the Namib Wheel Spider’s hasty escape? When danger threatens, this eight-legged wonder forms a wheel, using its legs as spokes. The 330 angle of a dune’s slope, enables it to revolve 20 times (or one metre) per second to send it hurtling down the slipface. When it comes to outstanding resilience to dryness, few animals can match the Australian desert frog, which remains in a dormant torpor for five years. Who can equal the animal that survives the smallest geographic range known for any vertebrate? The Mojave Desert pupfish triumphs by having a geographic distribution of only 20 square metres. And Namibia’s desert-adapted elephants (that slide down sand dunes), its rhinos (that chomp and relish the deadly-to-humans milkweed Euphorbia virosa) and its beach-combing desert lions (that hunt fur seals), create a kaleidoscope of desert life which is unique on our planet.

The Arabic word ‘sahra’ means wilderness, referring to the Sahara. It is the biggest desert, being more than seven million square kilometres in area and covering 25% of Africa. It cannot compete with the Namib however, which is 50 times smaller in size. The Namib’s success story as the desert with the most diverse life forms comes with the fog banks that drift off the cold Benguela Current. Yet most deserts are under threat from human activities. Let us remember the words of a person who loved the desert and was inspired by it. He said ‘First came the forests, then came civilization, then came the deserts…’

Text by Dr. Hu Berry
Published in “Flamingo”, January 2007

‘Is not the lion a mirror of man?
How did we get the lion’s share?
By being superior to the lion we had to be better at what the lion was best at dominating his world.’ (Randall Eaton)

‘Surely, you cannot be serious?’ I asked my friend, whilst we watched a lion pride lazing in the heat of an Etosha day. ‘Why not?’ he replied emphatically, ‘when women have too many babies we put them on the Pill’. He spoke with the authority of a medical obstetrician and gynaecologist, but also as a dedicated conservationist. I had been telling him about the explosion in lion numbers during the 1970s, a period of exceptional rains. Etosha’s ecosystem responded with grasslands that resembled a cornfield; herbivores followed and flourished on the profusion of energy available; lions did what lions do best when there is abundant prey available – they produced cubs at a prodigious rate. Moreover, their increase was aided by a high level of the dreaded bacterial disease anthrax, which decimated wildebeest and zebra numbers. Whereas herbivores are highly susceptible to anthrax, lions and other predators in Etosha are mostly resistant to infection by it. Lions can feast on an anthrax-infected carcase without any ill-effects. This is because anthrax has probably been present in the system for hundreds, if not thousands of years, giving carnivores ample time to build up antibodies against it. As biologist, I was responsible to make recommendations for managing Etosha which, even although it covers more than two million hectares, is fenced, with a liberal supply of artificially provided water. The combination of fencing, abundant waterholes and anthrax favours the ever opportunistic lions at the expense of wildebeest and zebra, their major prey.

My quandary was that the 1980s heralded a subsequent drought that took most of the country, including Etosha, into its withering grip. The notorious ‘Drought of the Century’ brought about that elephant were facing a cull. Their numbers in Etosha had increased to a level that threatened their habitat and that of the other herbivores. There were close to   3 000 elephants in Etosha and the authorities were implementing a cull, removing more than 500. Why not cull lions as well? My misgivings about doing this were strengthened by the results of a lion and spotted hyaena cull in the Kruger National Park, South Africa. There the lions regained their previous numbers within 18 months of the cessation of culling, whilst the hyaenas’ specialized and sensitive matriachal social system was significantly affected. To cull lions seemed inappropriate. We knew nothing about the effects of a cull on natural selection, loss of genetic variation and subsequent behaviour. Just the thought of culling lions in a national park did not appeal to me. Another option was to capture and translocate them, but there was at that time no market for free-ranging lions in other conservation areas or on game farms. Furthermore, translocated wild lions often caused significant problems in their new homes. The idea of contraception proposed by my companion suddenly became an attractive alternative.

‘What is more’ the gynaecologist added convincingly ‘the contraceptive has been used in millions of women, so humans are the guinea pigs, not lions. If you cull the wrong lion, it’s irrevocable. If you apply contraception, it’s reversible, it can be rotated in different lionesses, and you’re not destroying genetic material.’ Thus was born the idea of lionesses on the ‘Pill’. We both agreed that ours would be a scientifically acceptable experiment, in which we would apply contraception to random selected lionesses in different prides, leaving the majority of females untreated. They would be the reference or control animals. To satisfy statisticians we would need to treat 10 fertile females. We were convinced that the hormones to be used would render the lionesses temporarily infertile; that was not the objective. Hormones are powerful agents of behaviour and our aim was to monitor the effects of synthetic chemicals on the activity patterns of wild lions. It was critical to the success or failure of our trials because lions are the only truly social cat species in the world. We wanted to know if treated lionesses would become aggressive or submissive towards their pride members, or if males would accept or expel them from the group. Whatever the outcome, there was an interesting parallel to be made – lions and humans are both top predators and are both highly sociable.

The contraceptives came in the form of slow-release implants and the surgical procedure was simple, taking a few minutes. A small incision in the neck skin of an immobilized lioness, followed by insertion of the implant just below the surface, was the ideal site. The sutured incision healed within a fortnight. Because it was vital to locate each of the 10 lionesses in various prides, we used radio transmitters embedded in collars fitted around their necks. These emitted a distinguishing signal on our receiver. After that began hundreds of hours of intensive monitoring of six prides, which included the individual behaviour of treated and untreated lionesses. Using observers in relays, we watched and followed the lions continuously for entire days and nights, classifying their activities into 13 different categories. When statistical tests of the data showed no significant differences between lionesses on contraception and those without, we could report with confidence that, on average, all lions rested between 20 and 22 out of 24 hours (or 85% to 90% of their time). The remainder was mostly spent walking, hunting and feeding, with drinking, vocalizing and social behaviour comprising a very small amount of time.

During the three-year study, we purposefully removed the implants from five of the lionesses. They all reverted to fertility, giving birth to healthy cubs. Our trial was cut short when a large number of lions, including those on contraception, were tragically destroyed when they trespassed onto ranchland adjoining Etosha. Our resolve not to cull lions was annulled by enraged farmers, who had the final say, using bullets, gin traps and poison. In this manner at least 84 Etosha lions were destroyed in one year. Nevertheless, we maintain that contraception is preferable to capture or culling.

Text by Dr. Hu Berry
Published in “Flamingo”, June 2007

The doves flew in fast, aiming their flight pattern at the edge of the waterhole. Puffs of powder-fine dust marked the landings, each bird hurriedly dipping its beak into the cool, thirst-quenching liquid. Just as speedily as they arrived, their take-off was hasty, almost frenzied as they headed for the safety of the surrounding bush, flying fast and low to avoid predators. Watching this spectacle of drink and flee, my guest, an ornithologist of international standing, began musing about what we could learn from these birds. I listened as he advanced his hypothesis.It was based on his findings that adult doves in Cape Town, South Africa contain on average seven times more lead in their body tissues than the same species living in rural farmland only 50 kilometres from the city. These significantly higher concentrations were believed to reflect a relatively higher degree of lead in the urban air, presumably as a result of motor vehicle exhaust emissions. The rate at which doves accumulate this insidious poison in their bodies was not known however. The Professor continued ….. “if we catch doves in Etosha, keeping half of them here and half in Cape Town, we may be able to measure the build-up of lead in their muscles respectively”. His reasoning was logical and most original I thought. The method we ultimately agreed on was far from simple!

It involved trapping a large number of these fast flyers by means of nets suspended from poles near to the water’s edge. Known to ornithologists as ‘mist nets’, their fine mesh effectively camouflages them from approaching birds. I had used this method successfully in the Namib Desert to mark various bird species with numbered metal leg bands. The Etosha capture would be different – vastly different! In the Namib the likelihood of encountering potentially dangerous animals at a waterhole was as remote as the desert itself. Also, in the desert, I had hidden the nets amongst vegetation in a dry riverbed. At Etosha, the possibility of a hazardous situation developing when nets were placed close to a waterhole was very real. Elephants come to quench their massive thirsts at a pace that exceeds any scientist’s ability to furl the nets. Moreover, lions approach to drink on silent pads that don’t betray their presence until the feline form emerges from the undergrowth surrounding the drinking place. My proposal to counter this was to set the nets around a waterhole located on open ground, giving me time to remove them from the path of approaching big game. The Professor was understandably not concerned with these finer details. He wanted young doves that were growing and therefore developing their powerful breast muscles. This emergent tissue would be the ideal medium in which lead was able to deposit. The manner whereby I provided the doves was secondary.

My increasing concern for the consequences that this capture held for me was temporarily interrupted by an exclamation of excitement from the Professor who had spotted a Lanner Falcon mounting its attack on the drinking doves. Coming in high, with the Sun behind to obscure its approach, the raptor stooped on its unsuspecting prey, wingtips folded against its tail, reaching a velocity in excess of 200 kilometres an hour. Too late! The dove’s sensed danger, scrambling frantically into the air as the Lanner’s talons hit an unfortunate bird, killing it instantly in an explosion of feathers. The Professor’s words for this contact were “the falcon is binding with its prey”.  We had witnessed ancient aerial acrobatics of the highest order. Following this thrill the learned Professor’s enthusiasm knew no bounds. We, in reality meaning “I”, would provide the doves, whereafter they were to be divided into two groups and housed at Okaukuejo Rest Camp in Etosha and in Cape Town. The air they subsequently breathed would carry with it any traces of lead, depositing the heavy metal in their growing bodies.

With permission obtained to trap a total of 60 doves in Etosha and keep them captive, I set up mist nets at a waterhole that was away from tourist routes. My hopes that doves would not detect the finely meshed nets in the open were dashed. The slightest breeze caused the nets to billow, warning alert drinkers to divert and land safely away from my trap. Clearly this was not going to produce 60 captive doves in the time required. With rising apprehension I relocated my equipment to a waterhole surrounded by fairly dense vegetation. Then I sat and waited for the doves (and imagined elephants and lions) to come. Birds flew into the nets in numbers that I could barely handle. I cursed and removed everything from protesting Redeyed Bulbuls to irritated Pied Barbets that nipped me painfully with pincer-like beaks. Also many doves enmeshed themselves, but my catch had to be limited to juveniles whose age was estimated according to the state of moult in their primary wing feathers. The Professor required very young birds that had fledged four to seven weeks previously. It took many hundreds of doves and two months of tense waiting to secure the catch before the experiment could begin. Thirty young doves were kept in an aviary in my Okaukuejo garden and the remaining 30 were transported to Cape Town where they started to breathe the air from the city in a cage at the university’s campus. Both cages were large enough to permit the doves to fly and so exercise their flight muscles. Subsequently, on a given date at two-monthly intervals, I euthanised three doves, taken randomly, at Okaukuejo and the Professor did the same in Cape Town. These sacrificial birds were assayed for lead, using atomic absorption spectrophotometry, a method that entailed dissecting the muscle tissue whilst immersed under distilled water to prevent any possible contamination by lead in the laboratory.

The fact that we reached this stage proves I had survived the dove catching. Were there any dramatic developments at the thickly vegetated waterhole? The only memorable one was when a warthog enmeshed itself in my nets, quickly destroying one section with indignant squeals and snorts before it trotted off in apparent triumph, filaments of netting trailing from its muscular body. No elephant herd attacked my ambush for doves and no lions encircled me whilst I was engrossed in removing netted birds.

The most alarming result came from the doves kept in Cape Town. Their pectoral muscles, which power flight, had accumulated from two to five times more lead concentration in the space of a year than their counterparts housed at Okaukuejo. Lead is toxic and is a ubiquitous element in modern societies, occurring in practically all living organisms that inhabit industrialized areas, including humans. Given the virtual absence of “heavy” industry in Cape Town at that time, it is likely that the source of lead came primarily from automobile exhausts. The analyses were sensitive enough to detect traces of lead, albeit minimal, in the doves kept at Okaukuejo.  Thus, even the relatively small amount of traffic in Etosha during the 1970s, when this experiment took place, left its legacy in the wildlife. Traffic in both Etosha and Cape Town has increased by several magnitudes during the ensuing 30 years, with concomitant increases in fuel consumption. Nevertheless, the increasing introduction of unleaded petrol since then bodes well for our health. Ultimately, elimination of leaded fuel may make both doves and people breathe more easily.

Text by Dr. Hu Berry
Published in “Flamingo”, September 2005

Sky, sand and sea merge in the Bay of Sandwich, once an ancient harbour that sheltered sailing ships riding at anchor to load white gold in the form of bird guano and blubber from butchered whales. Those primitive scenes have given way to modern all-wheel drive vehicles, powered by turbo-charged diesel engines, carrying a cargo of holidaymakers. Replete with Global Positioning Systems, two-way radios, cell phones, and the latest in fishing gear, they descend on remote beaches to relax and savour the emptiness.Above them tower the dunes of the oldest desert in the world. Where does all this sand come from? Trace its origins back to the vast hinterlands of South Africa where erosion moves huge amounts of weathered rocks into streams and tributaries that merge to form the mighty Vaal and Orange Rivers. Now called the Gariep, the Orange wends its way through tortuous gorges, emptying its load into the northward-flowing Benguela Current. The basic chemistry of much of this copious discharge is silica oxide or sand, as we know it. Billions of shiny sand crystals pour into the Atlantic Ocean, entering a new world of thundering surf and rasping wind. Curling waves dump this burden back onto beaches where the Sun dries it and the wind carries it to tumble and be reborn as fresh, new pale dunes that soar above the sea. The chemical processes move on relentlessly – tiny iron particles that adhere to the sand begin to oxidize, reddening it, and the ceaseless wind moves the sand ever inland. Eventually, after millions of years, giant dunes rise skywards in the vicinity of Sossusvlei, their crests cascading onto slip-faces, leaving a knife-edge of red sand jutting more than 300 metres into the azure sky. The rusting process is complete.

Moving northwards past Walvis Bay, a narrow spit of land called Pelican Point grows several metres a year, its arrowhead pointing forebodingly towards the land. Eventually, given time, it will encase the present bay to form a shallow lagoon like Sandwich Bay and Conception Bay to the south have done. The evolution of this coast is dynamic and unremitting. Bays appear and disappear. So too do the dune fields. Suddenly, as if cut off by a giant knife the Namib ‘sand sea’ stops at the southern bank of the Kuiseb River, pushing a thin sliver of pale dunes past Walvis Bay to Swakopmund. Why the sudden cessation of sand? The irregular pulses of water that flood the Kuiseb River flush sand from the leading dunes, scouring it and depositing it downstream where the south-westerly wind again plays with the grains, driving them ever northwards. But even the wind has its limits. The powerful ‘wind funnels’ that are responsible for building the 34 000 km2 dune desert between Lüderitz and Walvis Bay decrease their strength towards Swakopmund, leaving the sand stranded.  Aeolian sand (the mythical Greek God of the Wind) is totally dependent on its master to proliferate into the giant dunes that make the Namib famous.

Passing Walvis (“Whale”) Bay, two square bunkers of concrete jut grotesquely from their sandy bed in the vicinity of the guano platform, on the approach to Long Beach. Built by the South African armed forces during World War II, their formidable cannons safeguarded the entrance to the harbour against German warships. Now they stand, mute and slowly disintegrating as the grains, whipped up by the persistent winds, scour them like sandpaper.

Rocks replace sand at intervals, their colours and shapes bearing testimony to the heat and pressure by which they were wrought. Jet-black dolerite dykes jut glistening into the sea, their shapes softened by millenniums of pounding waves. Next to them shafts of almost pure white and pink marble mark where liquid intrusions once forced molten magma into faults of the newly-born Earth. They are the remnants of an umbilical link with South America when it and Africa combined to form the super continent of Gondwana some 130 million years ago. Now South America has drifted thousands of kilometres westwards. Rocks of other colours range between these spectrum extremes and together the rocky banks form a kaleidoscope of pools. The rich, oxygenated seawater washes them ceaselessly by day and night with tidal fluxes. They are home to a myriad of marine diversity. Small fish dart among colourful starfish, anemones and mussel banks while sea urchins and snails slowly wend their way, grazing from the ocean floor. Further out, in the wave zone, kelp beds bob gracefully in rhythm with the sea’s urging.

Strange how one’s mind darts here and there while wandering along this paradise of life. I am reminded of a humorous geologist’s formula for describing the range of hardness in minerals found in rocks. On a rating scale of 1 (the softest) to 10 (the hardest), it proclaims that “Tall Girls Can Flirt And Other Queer Things Can Do”. This is a prompt to remember that Talc, Gypsum, Carbon, Fluorite, Andesite, Orthoclase, Quartz, Tourmaline, Carborundum and Diamond are examples of varying solidity in the mineral world.

Between the rocky outcrops sandy beaches stretch, displaying white, brown, purple and black grains. Some of these are magnetic minerals and words like magnetite, ilmenite, titanium and garnet flash through my mind. If teased by drawing a magnet across the surface these minerals will adhere, clinging to the compelling force to assume a dense cluster of fine, hair-like particles on the magnet’s smooth surface. Often the sand’s pattern is broken by the webbed imprint of a ponderous pelican waddling along the shore, or the distinctive paw print of a jackal as it patrols the tidal wash tirelessly in search of morsels thrown up by the waves.

The cry of kelp gulls brings me back to reality. I watch them collect washed up mussels, bearing them aloft and then hovering, to drop the shells within uncanny accuracy onto rocks where they shatter and provide a tasty meal for these persistent scavengers. Prompted by their behaviour I begin collecting fresh brown mussels, wrenching them from their attachment to the rocks. Washed first in seawater and then rinsed in fresh water with flour added to assist the bivalves to flush themselves of grit and other impurities, they will, boiled or grilled over an open fire, provide me with a tangible reminder that all life originated in the oceans.

There can be few experiences as rewarding as walking barefoot along the Namib shore, feeling the fresh sand and icy flush of Antarctic water swirling around your ankles. Kilometres of sand and rocks merge, receding into the distance as you pass. Suddenly, acting on a cue from the wind, a fogbank drifts shoreward enveloping you in a cool blanket of moisture. As it moves inland, lichens unfurl and change from lifeless forms to present an array of shapes and colours. The lifeblood of the Namib Desert has arrived and with it another secret – moisture that ensures it will remain the most diverse desert on Earth. A walk along the Namib coast takes you back in time as far as your thoughts are able to wander; at the same time reminding you of its present vitality and abundance of living things.

Text by Dr. Hu Berry
Published in “Namibia Holiday & Travel ”, 2006