style="font-size:15px;"> 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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