How the elephant got its skin and other real-life 'Just So' stories
Rudyard Kipling's 'Just So' children's stories are among some of the British author's best-known works. Written back in 1902, these classics originally began as bedtime stories for his daughter and describe how animals came to acquire some of their most notable features.
Inspired by these literary tales, Elly has put together a series of real-life 'Just So' stories, based on some ground-breaking scientific discoveries, to tell you exactly why some of your favourite animals evolved their famous traits.
How the elephant got its skin:
If you look closely at an elephant's skin you will notice that it is adorned with an intricate network of cracks and crevices. From the more noticeable, large folds down to the miniscule, micrometre-wide channels; it is no coincidence that these gentle giants are sporting a rugged complexion. One thing's for sure - there is no need for anti-wrinkle cream here!
As humans, we have sweat and sebum glands which help us to regulate our temperature and keep our skin moist and flexible. Elephants, on the other hand, have few sweat glands and cannot use them for cooling down. Instead, they can be seen regularly bathing in and spraying themselves with mud on a hot day.
The elephant's wrinkled skin traps the moisture in all of the tiny hollows, in much the same way as your absorbent kitchen mop, and retains 5 to 10 times as much moisture as a flat surface. This means it takes much longer for this moisture to evaporate which, in turn, keeps the elephant cooler for longer.
This also explains why the African elephants we see on safari have a far more wrinkled epidermis than their Asian cousins. Unsurprisingly, the wetter and more shady forest canopies under which Asian elephants roam means they have less trouble staying cool than those who inhabit our dry, parched savannas.
Recent research has also found that these cracks and crevices become more intricate as the elephant ages. As the outermost layer of skin gets thicker and new skin grows beneath it, the outer layer begins to bend and new cracks form. This is clear if you look at a baby elephant, whose skin is far smoother than its older relatives.
So, not only are elephants getting more wrinkly with age, but this elderly complexion is actually their secret to staying cool under the harsh African sun. Ingenious!
How the giraffe got its neck:
Charles Darwin first puzzled over the giraffe's remarkable anatomy back in the 1800s, and scientists are still unravelling the secrets of their evolution to this day. There is no other creature on earth quite like the giraffe; its long legs and neck helping it to reach a staggering 5 to 6 metres in height and achieve the esteemed title of the world's tallest land mammal.
Its closest relative, the elusive okapi, inhabits the rainforests of central Africa and has been nicknamed the 'forest giraffe'. However, the two diverged from their common ancestor only 11 to 12 million years ago (relatively recently in evolutionary terms!), yet the okapi is a third of the giraffe's height. So, what pressures caused the giraffe to evolve its characteristically long neck?
Some scientists believe that it evolved in response to competition from other, shorter herbivores like kudu, allowing giraffes to feed on taller vegetation that their competitors could not reach. While this sensible explanation held up for about a century, we now realise it may not give us the full story...
Biologist Robert Simmons believes that giraffes developed long necks not to compete for food but for mates, allowing males to develop a special method of fighting known as 'necking'. This is when male giraffes swing their powerful necks around, slamming their heads into their opponents with immense force. Simmons argues that because giraffes often feed with their necks bent, reaching down to the lower vegetation, the reasoning behind their long necks might have more to do with these fights.
Why, then, do female giraffes have long necks if they are not fighting with one another? Great question! Simmons believes it is because they share so many genes with males. Where males add about 40kg to their necks after they become sexually mature, females do not. This is important given it is usually males with the longest, thickest necks that win these necking contests.
While the origin of the giraffe's long neck may still be a point of contention, we do know some baffling truths about their anatomy. Giraffe have the same number of bones in their neck as a human: seven. However, a single cervical vetebrae in an adult giraffe is about the same length as a human's humerus bone, which stretches from your shoulder to your elbow!
How the zebra got its stripes:
Zebras are undoubtedly one of the most striking and iconic species to see on safari, their contrasting black and white stripes making them hard to miss. However, what many people don't know is that a zebra did not always have stripes...
In fact, they evolved from a now-extinct ancestor known as a 'quagga', which was only partially striped on its head and neck. So, for these stripes to have evolved to adorn the zebra's entire body, there must have been some sort of selective advantage to this remarkable coat pattern.
Initially, researchers thought that the stripes provided a form of disruptive camouflage, breaking up the outline of the individual and making it appear more two-dimensional against its background. Others then posited that perhaps these juxtaposed bands of colour were a way of confusing predators, 'dazzling' them with flashes of stripes and making it more difficult to pick out a single zebra from a fleeing group.
While both of these ideas may be true, there are two alternative theories that have gained the most support. The first believes that the contrasting colours help a zebra to regulate it's temperature. In research published last year, scientists found that the black stripes are 12-15ºC hotter than the white stripes in the middle of the day. This temperature difference is thought to create small-scale air currents just above the hair which helps to wick away sweat from the skin so it can evaporate and keep the zebra cool.
Other fascinating research has shown that the stripes lessen the likelihood of being bitten by nasty, predatory flies, but how exactly this occurs is still not well-understood. Scientists found that horse flies landed on zebras less than 25% as often as they landed on a uniformly coloured horse.
Not only that, but the flies appeared to be making crash-landings on the zebra before flying away, implying that the stripes somehow confused the flies and prevented them from landing on, and therefore biting, the zebra. Whatever the case may be, it seems the zebras stripes are serving multiple benefits to this true icon of the African bush!
How the leopard got its spots:
Have you ever wondered why leopards have spots (or rosettes), tigers have stripes and lions have no markings at all, yet they are all from the same family of big cats? Or, perhaps more interestingly, why did leopards evolve spots but lions did not, despite sharing the exact same habitat in Africa?
Rudyard Kipling's just-so story suggests that it was because the leopard moved to an environment "full of trees and bushes and stripy, speckly, patchy-blatchy shadows," but is this really true?
Researchers at the University of Bristol set out to answer these exact questions by comparing the coat patterns of 35 different species of wild cats. They found that the answer to these beautiful and intriguing variations in appearance was down to the type of habitat the cats preferred.
Leopards are more likely to be found in dense, thickly-vegetated habitats, sometimes in the trees themselves, and are active both day and night, although mostly when light is scarce. Cats like these were far more likely to have irregular or complex coat patterns, helping them to camouflage effectively in their surroundings. Because leopards occupy a wide range of habitats, including savanna grassland, mountains, forests and even the outskirts of cities; their mesmerizing spots evolved to help conceal them among various backdrops.
Lions, on the other hand, are found mostly in savanna grasslands and are a uniform, sandy colour. This is a function of the environment they most commonly hunt in, the colour of their fur giving them a distinct camouflage advantage in the dry grass. In fact, lions cubs are born with rosettes like a leopard to help them stay hidden at a den site when they are still too small to follow their mother. They slowly lose these markings as they get older and learn how to hunt.
So, is seems Rudyard Kipling was indeed on the right track back in 1902 when he wrote his bedtime stories! However, you may be rightly thinking that the anomaly here is the cheetah, whose spotted coat pattern has evolved despite a clear preference for open habitats like grasslands. Well, you will be delighted to hear that scientists still do not have a sufficient explanation for this!
What is clear from all of these stories, however, is that nothing in nature evolves without a reason. Whether it's the elephant's wrinkly skin or the zebra's dazzling black and white stripes - every characteristic of these creatures has it's place, no matter how bizarre it may seem.
Article written by Elly Gearing with photos courtesy of Nerise Bekker and Elly Gearing.