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.