The world would be a smaller place without its megaherbivores. John Doherty introduces one of the most threatened - the reticulated giraffe.
I know there is a good chance that the lions will not succeed but, even so, my heart is in my mouth. Trident is special – he was the first giraffe I learned to recognise – and now three big cats threaten both him and my scientific objectivity.
It is early morning and the light is soft but clear. From his great height, the old bull soon spots his would-be assassins, their own pinprick pupils returning his stare. For long minutes he watches, motionless, as the trio of predators moves carefully closer. Overhead, hundreds of bright-blue rollers stream towards a gap in the mountains, flying north to the Mediterranean.
Trident is with two younger bulls: Marten and Crocodile’s Eye. His towering frame bears the marks of narrow escapes in the past – the skin of his hindquarters is raked with long, parallel scars and he has lost the fly-whisk tassel at the tip of his tail.
Sheer size gives giraffes immunity to most predators (as well as to competition from other browsing animals) but, by working together, a team of lions can bring down even the largest adult males.
Suddenly, the suspense is broken: three giraffes and three lions are running, hard, and the air behind them is thick with dust thrown up by their hooves and paws. Fascinated but fearful, I follow as quickly as I can.
Walking tall no more
Dramatic encounters such as this may soon be a thing of the past because the giraffes that live here in the drylands of northern Kenya are fast disappearing. They have coped with predation by lions for hundreds of thousands of years but are now in serious trouble.
In 1998, there were thought to be 28,000 giraffes in northern Kenya, Ethiopia and Somalia, but this figure has plummeted by 80 per cent in only 10 years. My aim is to find out why – and to save these gentle giants from possible extinction.
The giraffes I study are called ‘reticulated’or ‘Somali’. They look quite different to Africa’s eight other giraffe subspecies due to their signature hide pattern: dark chestnut polygons divided by a complex tracery of narrow white lines.
Recent research suggests that they are so different from the others genetically that they deserve to be considered a separate species.
I’m based at the heart of the reticulated giraffes’ remaining range, in Samburu, Shaba and Buffalo Springs National Reserves, about 300km north of Nairobi. The landscapes here are magnificent – a mosaic of mountains and open savannahs, cut through by the great, life-giving Ewaso Ng’iro (‘brown river’).
It is a land of special animals not found in national parks to the south, including the so-called ‘Samburu Six’ – the beisa oryx, gerenuk, desert warthog, Grevy’s zebra, Somali ostrich and reticulated giraffe.
Today, I am joined by my friend Jacob Leaidura, a skilled naturalist with an encyclopedic knowledge of the area’s colourful birdlife. We are in Samburu, checking the strip of woodland that lines the banks of the Ewaso Ng’iro to see if any of our giraffes are here. And sure enough, before the lions shattered the calm of early morning, we had come across several familiar faces.
First to be located were Exclamation and Broken Blade, drinking in mid-river. Next we saw the aggressive Twin Shields slamming his bony head against the neck of another bull, Shamrock, who seemed reluctant to reciprocate but was nevertheless standing his ground.
And finally we watched a young female join a group with calves in the shade of a stand of doum (or gingerbread) palms. She was unknown to us but not, apparently, to Africa, an older female who greeted her with a brief but affectionate touching of muzzles.
The social behaviour of giraffes is something of a mystery. Casual observers tend to assume that they are highly social animals because they are so often found in what appear to be family groups. Yet these groups are extremely unstable – giraffes join and leave them apparently at random. Could it be that long-term bonds between individual giraffes are rare?
To tease out the truth, it’s necessary to be able to reliably identify hundreds of individuals in the field. I have spent countless hours staring at coat patterns, looking for unique and easily recognisable shapes among the maze-like networks of lines. And I name every known animal after the feature that most catches my eye.
I am also interested in the possibility that giraffes communicate using vocalisations below the frequency range of our hearing. They are certainly big enough to produce infrasonic signals and it has been suggested that they do so by means of Helmholtz resonance – the noise produced by blowing across the open neck of a bottle. So far, my findings seem to support this idea.
Otherwise, it is curious that giraffes are so silent. They are apparently unable even to warn their companions of the presence of predators such as lions, though they may pick up on behavioural cues such as nervousness and startling.
Perhaps they are more communicative – and sociable – than has been supposed. Maybe they maintain extended social networks, as elephants are thought to do, by using infrasound for long-distance communication.
At the same time as trying to understand how reticulated giraffes interact with each other, I am piecing together a picture of their place in the wider ecosystem. I want to know how they use the landscapes and resources available to them and, in particular, about the pressures and threats that they face.
The chief cause of the recent decline in their numbers is probably poaching. Reticulated giraffes inhabit a volatile area characterised by a growing human population, poverty, habitat degradation and drought, regional conflicts, overstretched security forces and a widespread availability of automatic weapons.
Giraffes are tempting targets because they yield large amounts of meat, while some pastoral groups value them highly as trophies and for their hides, tail hair and bone marrow.
But there is hope. Later this year, Kenya will become the first African state to launch a national strategy for giraffe conservation. This is especially fitting in light of recent genetic evidence suggesting that modern giraffes first emerged in this part of the continent. Moreover, the country’s giraffe populations are uniquely diverse: three of the nine subspecies – Rothschild’s, Masai and reticulated – still occur here.
Echoes of the past
To me, megaherbivores such as giraffes represent echoes of a younger planet, where giant life forms were commonplace. When they are extinct, such creatures become objects of wonder (think, for example, of our fascination with mammoths, giant sloths and, especially, the dinosaurs). While they are still with us, however, it seems that we take them for granted.
But what of Trident, Marten and Crocodile’s Eye? To my enormous relief, the heat of the morning sun quickly saps the lions’ stamina. One by one, chests heaving, they give up the chase and head for the shade.
As the dust settles and the last of the migrating rollers disappears into the hazy distance, the three great bulls briefly face their pursuers, then return to the sweet acacia flowers on which they had been feasting since dawn.
SUPERSIZED AND SUPERCHARGED Size poses problems for big herbivores, but giraffes have made it a virtue.
Giraffes, it seems, don’t live by the rules. Most large herbivores have such high calorific requirements that they must eat abundant but often poor-quality food – dry grass or tough leaves, for example.
By contrast, smaller species can pick and choose, favouring the best foods such as berries and seeds. In extreme environments such as African savannahs, where food availability varies greatly with the season, this is reflected in the energy budgets of buffalos and other big animals, which can breed only during times of plenty.
But giraffes are different. Quite apart from their height – which enables them to munch the foliage of taller, deeper-rooted and thus more drought-resistant trees – their fine, tapering muzzles, mobile lips and long, prehensile tongues allow them to be unusually picky.
Add to these a highly efficient digestive system (even by ruminant standards) and the result is ‘supercharged’ giraffes with enough of an energy surplus to breed all year round.
DID YOU KNOW?
Size isn’t everything: bull giraffes are more vulnerable to predation than the smaller females. This is because they spend more time alone and are thus easier to ambush.
SEVEN THINGS YOU NEVER KNEW ABOUT GIRAFFES
- Giraffes are born with their ossicones (horns) lying flat against their heads. Later, the ossicones fuse to the skull, harden and grow. In adult males they become formidable weapons, worn bare of skin at the tips – old bulls may even have patches of bare bone elsewhere on their massive, craggy heads.
- Much of the moisture that giraffes need is produced as they metabolise their food but they also drink water directly – they shuffle awkwardly until their front legs are splayed and they can reach the water surface.
- A large body size means a long gestation period. Female giraffes carry their young for 15 months – but since they can breed all year round, they do not need to ‘resynchronise’ with the seasons each time they give birth.
- Giraffes require large quantities of calcium and phosphorus to build their skeletons. After weaning, they derive most of these minerals from their food, but they also chew on carcass bones (a behaviour known as ‘osteophagy’).
- A fully grown giraffe can raise or lower its head by up to 5m and might pass out were it not for a dense network of fine capillaries (the ‘rete mirabile’) that cushions its brain against rapid changes in blood pressure.
- Giraffes are probably the world’s largest pollinators, transferring genetic material on their muzzles from the flowers of one tree to those of another.
- The giraffe family contains only one other species: the rare okapi. This forest-dweller has a shorter neck – like the extinct species from which both it and giraffes are thought to have evolved.
To read more information on reticulated giraffe conservation, click here.
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