Edition 42: Spring 2008

Dung, droppings, faeces, excreta: whatever your euphemism of choice, there’s no escaping the fact that animals produce plenty of the stuff. However, while hunting and other feeding behaviour makes prime time viewing, what comes out the other end tends to be swept – as it were – under the carpet. And yet animal poo is a fascinating and illuminating subject, as any tracker will tell you. Not only can it reveal an animal’s identity and whereabouts, it also offers an insight into its lifestyle and is pivotal to the health of its habitat. By Mike Unwin

Midden-life crisis
Most male mammals use the whiff of dung to mark out their territory. Some plaster it on vegetation or drop it beside trails, while others pile up conspicuous mounds at strategic sites, known as middens. A territorial white rhino bull, as befits his size and appetite, maintains 20-30 massive, waist-deep middens. These serve as communication points for adults of both sexes, who make regular visits to top up the mound and sniff out the local news. But it is the territorial bull that works them the hardest, scraping deep furrows with his back feet before tramping his scent around the territory. Curiously, the smaller black rhino sometimes leaves its load on top of a white rhino’s. But the two deposits are easy to distinguish: the dung of the white rhino, a grazer, comprises nothing but fine grass, whereas that of the black rhino, a browser, is full of twigs.

Dung roamin’
Without dung beetles, the African bush would be drowning in excrement. And of the thousands of species that make up the Scarabidae family, the best known and most conspicuous are the ‘rollers’. These tank-like insects pile into the dung while it is still steaming, fashioning it into spheres – called brood balls – which they roll away backwards, usually battling competitors as they go. A mating pair gets together over a brood ball, and once they’ve buried it and mated the female lays a single egg inside. The young insect’s entire development takes place in this ball, which provides all its sustenance, until eventually it emerges above ground as an adult. Dung beetles are, relatively speaking, among the strongest creatures on the planet – a single beetle can bury 250 times its weight in a night – and 16,000 have been counted in one heap of elephant dung. This energy and abundance gives them a vital ecological role, recycling the soil nutrients that are the very foundation of the great food pyramid. 

Take two
You might find the idea of eating your own dung rather hard to swallow, so to speak. But coprophagy, to use the proper term, is an essential survival technique for rabbits and hares, such as the African scrub hare. These animals excrete two kinds of dropping: the first are normal brown faecal pellets, which they leave; the second are soft green pellets, composed of only semi-digested plant food, which they eat. The idea is to absorb the maximum amount of nutrients from the food by sending it through the gut twice. This process is not dissimilar to that of ruminants, such as cows, which return a cud of vegetation from the stomach to the mouth for a second chew. It usually happens while the hare is resting, and is a good way to refuel while hiding from predators.

Jumbo germination
Every farmer appreciates the magic of manure, and in the West African rainforest the biggest muck spreader is the elephant. Up to 30 per cent of the larger tree species in some forests depend upon pachyderm poo for seed dispersal, since only elephants can break into their thick-shelled fruits. Not only are the seeds spread far and wide, but their prospects of germination are also greatly enhanced by a journey through the animal’s gut, where the acidic conditions provide protection from predators and pathogens. Experiments with one species, Balanites wilsoniana, showed how seeds that had passed through elephants enjoyed a rate of germination nearly 20 times higher than seeds from fruits collected directly from the tree. And the nutritious pile of dung in which the seedlings find themselves gives the growing plant a head start. Without elephants, many of these tree species might disappear in the long term, taking with them a host of other creatures that depend upon the forest.

Something fishy
The fish-rich waters of the Benguela Current along Africa’s southwest coast provide abundant food for huge colonies of seabirds. What goes in must come out, and over the centuries these colonies have accumulated a mountain of guano (bird ‘poo’, to you and me). Guano is rich in nitrogen, phosphorus and potassium and, unsurprisingly, makes a fantastic fertiliser. During the 19th century vast quantities were mined from Namibia’s offshore islands. Entrepreneurs have since tried to replenish the supply by building huge wooden breeding platforms for seabirds, primarily cape cormorants, some of which still yield an annual quota.