Читать книгу The Last Giants - Levison Wood - Страница 12
ОглавлениеA Giant’s World
There are three species of elephant alive today: the Asian elephant (Elephas maximus), the African forest elephant (Loxodonta cyclotis), and the African savannah elephant (Loxodonta africana), which is the primary subject of this book. Although some debate rumbles on about whether forest and savannah elephants really are two separate species, evidence points to the fact that they are. They look different, their behaviour is somewhat different, and recent research shows that their DNA is distinct, too. These genetics-based studies more or less confirm their separation as two individual species. They likely diverged from a common ancestor as much as 5.5 million years ago, at a time when the climate got cooler and forest habitats became smaller.
The Asian elephant is a more distant relative to the two African species – it’s estimated that they split between around 7 million years ago, with the first migration of Elephas from Africa into Asia happening some 3 million years ago, although as I mentioned in the last chapter, the two types continued to live alongside each other on the plains of Africa until only a few thousand years ago. Interestingly, genetic analysis has revealed that the closest relative of the Asian elephant is not its African cousin, but in fact the extinct woolly mammoth, from whom they diverged at a similar time to their divergence from the forest and savannah elephant. Visually, these groupings make sense, given the smaller ears, lumpy-looking heads and sloping backs shared by the two species.
Forest elephants, which inhabit the tropical jungles of central Africa, are smaller in height and weight than African savannah elephants, with thinner, straighter tusks that tend to point downwards. They consume much less grass – but more woody plant material and fruit – than savannah elephants, as you’d expect of a species that lives in dense forests, and from what we understand they probably live in smaller social groups, and are much better at climbing steep slopes. The two species overlap only rarely in the fringe areas of Africa’s tropical forest belt in places like the Congo.
Yet across these three surviving species, there are clear similarities that mark them out as elephants: the overall large size, including long limbs and broad, cushioned feet with distinct, flat toenails; the very large head and skull; the trunk; the excess growth of the incisor teeth to form tusks (in many but not all); and the phenomenon of horizontal teeth displacement.
This is a unique process whereby the molars gradually move forward from the back of the mouth to replace worn teeth at the front. There are an amazing six progressions – imagine having six sets of teeth come through! – and the final set of molars, which erupt at about thirty or forty years of age, are enormous, weighing over 3 kg, and measuring 20 cm long and 7 cm wide. The shape of African elephant teeth is how they got their Latin name: Loxodonta means sloping teeth.
But the teeth that elephants are most famous for are, of course, their second upper incisors – known universally as tusks. In Asian elephants, the females never have tusks and many males don’t either. Some female Asian elephants have what are known as ‘tushes’. They resemble very short tusks, but do not have the same tooth pulp inside, and so they never grow further. However, in the two African elephant species, both males and females generally have tusks.
The tusks of males tend to be larger – thicker and longer – than those of females. Mature male elephants in Kenya’s Amboseli National Park have an average tusk weight of around 50 kg, whilst the average female tusk of the same age weighs only 7 kg. Tusks grow for the whole of the elephant’s lifetime in both sexes, meaning that older elephants tend to have the longest tusks.
Elephants use their tusks in a variety of ways: to help forage for food by breaking or pushing branches and to strip bark from trees. They use them to dig in the ground as they forage for roots or search for water. They are a convenient lever, and are even used to carry things; elephants can often be seen using their tusks to move logs or carry grass in the same way as a forklift truck. I’ve seen elephants use their tusks as lethal weapons in fights with other elephants and indeed with plenty of other animals that make the mistake of crossing them. With the full strength of a charge, an elephant can easily pick up a fully grown buffalo using its tusks as a spear and whip it into the air.
A fellow officer in my battalion of the Parachute Regiment was once on a military exercise in Kenya. Captain Jay Courtney was leading a patrol through the bush in an area of the country where British troops often went to train before being sent on deployments to Afghanistan or Iraq. It was a warm evening in the autumn of 2018, and Jay led his four-man team on a reconnaissance mission to scout out an imaginary enemy on the far side of a dry riverbed. At around 6 p.m., as the sun was setting over the distant escarpment, the soldiers were in the process of climbing up a sandy ridge onto an open plain dotted with acacia trees and thorny scrub.
Jay was point man, focused on navigating the soldiers towards the position, his mind running through all possible scenarios – would the enemy be laying an ambush, or would they be able to sneak up on them? Did his men have enough water to last in case the patrol was extended? He thought about where he would be sleeping that night, under a thin poncho beneath a star-filled African sky, and wondered whether or not he might get a faint cell phone signal so that he could message home. All sorts of things run through a soldier’s mind, especially when he’s been immersed in the wilderness for so long, and this exercise had already dragged on for six weeks.
Jay felt comfortable in the bush, and had become accustomed to the ferocious heat, the irritating flies and the daily chore of cleaning his rifle of dust and sand. This was a training exercise, and even though the soldiers carried only blank ammunition, which simply made a loud bang, it had to be treated like a real combat mission and he took his job seriously.
Like all the other paratroopers, Jay was a hardened warrior, used to the rigours of living in the wild. He’d been warned of the dangers of the wildlife and briefed on how to avoid getting on the wrong side of a lion, buffalo or elephant, but so far, he’d only seen the animals at a distance, and generally they ran away from soldiers. Most wildlife has no desire to hang around strange-looking (and smelling) men who like to blow things up and make loud noises. As Jay put it, the elephants were simply ‘part of the furniture’.
That is perhaps why, as he strode forward under the weight of his webbing and rucksack, it came as a shock to hear the man behind him start shouting frantically and waving at the confused commander. Jay shook his head and raised an upturned palm to question what on earth the raving soldier was making such a fuss about. You should never raise your voice on a patrol, let alone shout and scream, unless the enemy are already upon you and you’re under fire.
Instinctively, Jay ducked and looked around, thinking that perhaps his junior soldier had spotted the enemy troops, or maybe a shot had been fired, and somehow he’d not heard it. But then as he swung back and looked forward, he realised his mistake. It wasn’t enemy forces. In this case, it was something far more dangerous. There, not fifty metres away, was an enormous female elephant with two fat tusks. The giant was shaking her head in anger and flapping her ears, while stomping her feet on the ground.
Jay froze, glancing about him. Now he understood what had happened. Off to the side of the female were more elephants, and babies too. He had inadvertently walked right into the middle of a breeding herd. The mothers, who usually corral their youngsters into the middle of the herd to protect them from predators, had not spotted Jay. The wind had been blowing towards the patrol, so the elephants hadn’t picked up the soldiers’ scent before it was too late. Jay was almost surrounded, while the other three men scarpered to the safety of the edge of the riverbed.
For Jay, the moment seemed like an eternity, but it couldn’t have been more than a few seconds. The matriarch, startled by the presence of an armed human, was not about to take any chances with so many vulnerable calves in the herd. She gave him one ear-splitting trumpeting call as a final warning before charging at full speed right towards him. As the elephant crashed through the bushes at twenty miles an hour, Jay’s mind spun in disbelief at the surreal vision that unfolded in front of him. This doesn’t happen except in the movies, he thought, surely it will stop soon?
It was too late to run anywhere and there was nowhere to hide. In any case, he remembered what the brief had said, you can’t run from an elephant. His attention became fixated not on the bulk of mass hurtling towards him, but instead at the glistening ivory tusks that appeared like spears before him. They were cracked and patchy; one was slightly longer than the other, and, he thought to himself, decidedly blunt. Even so, the primal fear inside him took over as his body exploded with adrenaline, and he knew that whatever happened, he must avoid those tusks.
The rest is a blur, but from the accounts of the other soldiers who watched on in horror, the elephant smashed into Jay with her forehead, sending the young officer flying into the air, before the 3-tonne beast continued with the assault, ramming her tusks into the ground either side of the man. Jay remembers seeing the enormous grey hulk hovering above his head and stamping down on the earth, all the while using her trunk to flick and toss his injured body around like a piece of cloth.
He tried to crawl away from the carnage, but there was no stopping it. Then the elephant delivered her message home in the only way she knew how, by driving one of her three-foot-long tusks right through his arm, ripping the paratrooper’s limb almost in two. Despite its rounded end, the tusk speared his tricep, tearing through the flesh and muscle like a hot knife through butter. Jay’s body crumpled, and the only thought he could muster was that it might be better to play dead. He curled into a ball and hoped above all else that he might survive.
The elephant calmed down, her bloodlust perhaps satisfied by the thought that he no longer posed a threat, but she still loomed over him, her weight crushing his chest. Then, as the creature was about to stamp on his lifeless form, the other soldiers began to fire their weapons in its direction. Despite the fact there were no actual bullets flying, the noise seemed to do the trick. The elephant, startled by the bangs, raised her trunk and trumpeted again, reversing backwards and flicking her head in disgust. The men jolted forwards, shouting and firing more shots into the air, until the creature backed off and slinked away in the direction of the rest of the herd. A few seconds later they had disappeared, and all was silent.
Luckily for Jay, he survived. The other soldiers ran to his side and held his smashed arm together, applying a tourniquet and stemming the flow of blood until the medics arrived at the scene ten minutes later. He was rushed to hospital in Nairobi, where doctors managed to put his mangled arm back together, and now he’s left with only an impressive scar and a good story to tell. One thing’s for certain, though, he won’t ever think of elephants as merely part of the furniture again. And it’s a lesson that anyone who walks on foot through Africa is advised to keep well in mind: those tusks are not just for show.
Apart from their tusks, the other defining feature of elephants is obviously their trunks. Formed by the fusion of the nose and upper lip, trunks are truly amazing appendages. Imagine having a six-foot-long nose that doubles up as a hand.
Trunks are used for gathering and picking up food and other things with remarkable precision. African elephants have two pincer-like ‘fingers’ at its tip, one at the top and bottom, whereas Asian elephants have only the one at the top. Trunks can be used to push over and break up large food items, sometimes as big as whole trees. They’re also handy for trumpeting, dusting, scratching, bathing and snorkelling, as elephants are born swimmers. It’s an enchanting sight to watch young elephants tumbling around in a watering hole, as they learn how to spray water and play with each other.
As Jay found out, the trunk is also a formidable weapon with which to smash others, and even to launch projectiles: elephants can throw things like sticks and stones, and with pretty good aim. And, of course, elephants use their trunks to drink with, sucking up litres of water before pouring it back into their mouths.
Trunks are used almost continuously to check on the rest of the social group, either in a tactile way – reaching out and touching others by way of greeting or reassurance – or by sniffing others to get information. Because above all else, trunks are fundamentally a nose – a highly mobile and phenomenally sensitive nose, at that.
The mobility and precision of the boneless trunk comes from the 40,000 or so muscles it contains. By way of a comparison, the whole human body contains just 639. The muscles of the trunk are divided into more than 100,000 fibre bundles, each served by a mass of nerves and connective tissue. And to illustrate how sensitive a nose it is, consider that elephants have five times more olfactory receptor genes than humans and more than twice as many as dogs. These are the genes associated with our sense of smell and while this does not necessarily mean that an elephant is twice as good at smelling stuff as dogs are, it certainly means they have more sensitivity to a broader range of scents.
In fact, recent experiments with Asian elephants have shown they can smell the difference between buckets containing either one or three scoops of sunflower seeds, correctly choosing the bucket with more food. Clearly, we could do the same by looking, or feeling the weight of the buckets. But by smelling only, through a sealed lid? I don’t think we’d stand a chance.
The importance of scent and smelling to elephants becomes very apparent when we begin to look at their brains. Elephants dedicate a huge area of their large brains to perceiving and processing smells. The size of various brain parts shows us that hearing sounds and producing vocalisations is also of considerable importance to elephants, whereas vision seems to be much less significant, with the areas of the brain that process visual signals being much smaller than those that deal with smell and sound.
This confirms an important point about elephants: they must perceive the world in a rather different way to us. As a species, we rely heavily on sight to get information about the world around us, but for elephants, smell and hearing are the dominant senses.
When you scale the brain against body size, humans win out. We have the largest brains relative to body size with bottlenose dolphins and chimpanzees coming after. An average person is seventy-five times smaller than an adult male savannah elephant, yet our brain is only three or four times smaller than that of an elephant. That said, when it comes to absolute terms, there is no brain bigger on land than that of the elephant. They weigh in at up to 5.5 kg in males and slightly less in females. Sperm whales and orcas do have larger brains than this – at around 7 kg – because water can support a heavier head and body. Humans by contrast have a brain that weighs just 1.3 kg.
Compared to many other mammals, the brain of the elephant is located low down in the head – in line with the eyes – while the upper skull is formed of a honeycomb-like bone structure with air pockets that reduce the weight of the head, but keep structural integrity in place. This adaptation has been the fatal undoing of many a novice hunter, who has aimed too high when attempting to kill an elephant, succeeding only in wounding and enraging the poor animal.
Aside from the enlarged olfactory and auditory regions, the elephant brain also has an especially well-developed cerebellum. All mammals have a cerebellum, which is mostly involved in overseeing and coordinating movements and voluntary muscular activity. But in elephants it is huge, with many more neurons, organised in a much more complex way, compared to other mammals – including us. This makes sense, given the complexity and range of movements that the trunk is capable of performing. So elephants have brains that are specialised for smelling and hearing, with very fine motor control.
Most mammals are born with brains that already weigh around 90 per cent of what they will do when fully grown. This means that they are almost fully developed. The brain of a newborn human, in contrast, weighs only 25 per cent of what it will do as an adult.
If you think of the ‘childhood’ of the average mouse or horse, versus our own species, this makes sense. Those species are up and running soon after birth, whereas humans are pretty useless for the first year or two after birth. But a newborn elephant brain weighs 35 per cent of the adult brain weight – the same percentage as chimpanzee infant brains, and slightly lower than the 40 per cent figure for bottlenose dolphins. The brains of all these species have a lot of developing to do during their long childhood – almost as much as we do – suggesting they also have a lot to learn.
An elephant is big. Very big. A fully grown adult male can reach a shoulder height of 3.4 metres and weigh up to 7,000 kg. That’s the same as four family cars, with passengers. The largest known elephant was a male, shot in Angola in 1956, which was a colossal four metres tall, as big as some of the prehistoric species we mentioned, and is thought to have weighed 10 tonnes. And while there are other megaherbivores roaming the earth today – including four species of rhinoceroses, the common hippopotamus, and giraffes – none of them come close to the size of a full-grown African elephant.
The elephant’s enormous size has been the key to their evolutionary success. It gives them a triple whammy of survival benefits: making them less vulnerable to predators; enabling them to live in a wide range of habitats; and meaning they can eat a wide range of foods. This allows elephants to move into different areas when there’s not much food around.
All the same, there’s a big difference in size between male and female elephants, with females normally around one metre shorter than males, and topping out at around 3,000 kg.
The difference in size between males and females all comes down to sex. It’s a common feature in many animal species, and is known as sexual dimorphism. In elephants, as with many mammals, the males don’t have much to do with raising their offspring. Their role ends basically at finding and then competing for receptive females with whom to mate. Male elephants aren’t particularly choosy when thinking about the size of their partners, either, and as long as the female is in oestrus (the time when they can get pregnant and so are ‘sexually receptive’), males will try to mate with them. That means there’s no selective pressure picking out larger females over time. The only thing limiting the number of offspring a male elephant can sire is the number of females he can find and mate with, which in theory could be in the hundreds.
For females on the other hand, as is often the case, size does matter. Females put a lot of time and energy into raising their young, so they want to give each one the best chance of survival. This means they want the healthiest and strongest males to breed with, in order to ensure their offspring are more likely to be healthy.
It takes twenty-two months of pregnancy for a female elephant to produce a newborn, which can weigh more than 100 kg at birth. The female spends the next few years nursing the youngster (known as a calf), until it can be persuaded to give up milk and survive solely on solid food – often only because the mother has had a new calf that needs her milk more. So, there is usually a gap of around four or five years between each new baby. This means a female elephant who typically gives birth to her first calf when she is between the ages of eleven to fourteen years, and who lives to sixty, might raise only nine or so calves over her lifetime.
Based on the numbers alone, a female has fewer chances of offspring successfully passing her genes to the next generation, so she invests heavily in those chances. Males, on the other hand, play the numbers game – going for quantity over quality. This in turn sets up competition between males for the attentions of likely females. It usually goes no further than intimidation, because physical combat runs a high risk of injury or even death. But, if neither one backs down, male elephants will often fight for the right to mate with a female.
Ultimately, that means the largest, most dominant bulls are more likely to mate successfully than smaller males. Their genes are passed on to the next generation, and the process of natural selection therefore favours larger males. Such sexual dimorphism is common in species that compete in this way for access to mates, but elephants have one of the most pronounced size differences amongst any mammals.*
Whatever the size difference between the sexes, elephants are still gigantic when compared to other land animals. This has influenced everything from their diet and their habitat, to their effect on the environment, as we shall discover next.
* The champion of the mammal world when it comes to disparities in body size between the sexes is the southern elephant seal – where mature males can weigh up to 4,000 kg, which is seven times greater than an average adult female elephant seal.
