The Last Giants. Levison Wood
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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.
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