Nick Crumpton, a PhD student at the museum, writes of one of his favourite animals, the Giant Golden Mole:
Let’s imagine you’re walking through the grasslands of South Africa and have decided to find some shade under the trees of a nearby forest. Although you might assume that the most interesting animals could be slithering through the trees above you or silently evading you behind the tree trunks, it’s the ground beneath your feet that I want you to concentrate on. Perhaps, after a while, you’re luck and see the leaf litter tremble a little. Then, suddenly, a shiny, furry, eyeless face pops up. Say hello to Chrysospalax trevelyani, the Giant Golden Mole.
But why is a mole so interesting? Well, because it’s not really a mole at all. Although scientists thought for years that golden moles were closely related to talpids (the group that includes true moles like those you find in the UK), shrews and hedgehogs, recent genetic and anatomical analyses have shown without a shadow of a doubt that Chrysospalax trevelyani and the 20 other species of golden mole share a more recent common ancestor with aardvarks, manatees, sengis and elephants than with any other type of mammal.
This is a striking case of convergent evolution where two types of animals that aren’t closely related have found themselves evolving similar adaptations. When we see how alike the lifestyles of golden moles and talpids are, this makes sense. If an animal lives underground, natural selection favours certain ‘traits’: a streamlined shape to ease moving through sand or soil; very large hands to push sediment out of the way; and strong arms with which to propel itself. We also see a decrease in the size of their eyes as vision is less important underground.
When you get down to the precise anatomical differences between talpids and golden moles, you do start to see differences. For instance, the golden moles’ eyes are completely covered by skin and fur whereas some true moles still open their relatively ‘normal’ – albeit very small – eyes. They also have different digging techniques.
Both have evolved aspects of their bodies that the other would love. For instance, talpids are the only mammals on Earth to have their noses covered in special touch-sensitive pads called Eimer’s organs, which enable them to feel the world around them better than we can with our fingertips. But some golden moles have incredibly large ear bones making them far more sensitive to vibrations as they move through the earth listening out for prey. Very recent research has also shown that golden moles have evolved a coat of hairs that lest sand and soil run straight off them, making them silky smooth so they can tunnel through the ground incredibly easily. A rather accidental byproduct of this special coat means that it also makes the mammals iridescent. But, as they’re completely blind, they can’t appreciate how attractive it makes them look.
Although little is known about golden moles in comparison to their Northern hemisphere counterparts, we do know that their habitats are fragmenting, catrs and dogs are adept at catching them and that 12 species of golden moles across Africa are now classified from ‘vulnerable’ ‘critically endangered’ by the International Union for Conservation of Nature. So the next time you come to the museum, point out the Giant Golden Mole and explain to your friends how it evolved from the same ancestor as elephants did. Perhaps if people know more about these shiny, super-hearing, insect-munching tunnelers they might live a little more securely in their subterranean homes.