f you are a not a herd animal and you have poor eyesight how do you find partners or know whose been visiting your territory? For rhinos the solution is communal middens. These largish patches of dung are like cell phone masts relaying a wealth of information to passing and resident white rhinos. It’s not just rhinos who use the middens but insects, butterflies and birds as well for whom they are a treasure trove of seeds and material for breeding and food.
Middens are used by male rhinos to advertise their territory, but they don’t rush to one midden every day to reinforce their ownership, instead they appear to carefully parcel out dung droppings across the middens in their territory. To spread their message wider they compensate by kicking their dung around with their back legs after defecating, which males who don’t own the territory don’t do. The resident male will visit the same midden about once every ten days while females and non-territorial males do so only every thirty days or so.
Visitors to middens are tolerated if they are passing through but their visits are monitored and noted by the owner of a space who will spend up to 50% of his time at the midden sniffing around checking the calling cards at his feet. A male white rhino’s territory is not very large, extending to an average of two square kilometres with middens being scattered across the area and not only located on the boundaries. Territorial ownership of a midden however is just one of the messages passed on by the pile of dung. From a male point of view the reason you guard your territory is not only for food, but for breeding so if a passing female leaves a message that she is in oestrus and ready for some fun, then the male can work out her age and availability just from her dung and set off in pursuit, once he has such a female in his territory he guards her and stays with her for at least ten days making sure that her offspring will be his by letting no one else near her. It’s a benign captivity but it has one purpose, reproduction of the his genes.
White rhinos breed all year round, but tend to peak around the time when the rains start and the grass is lush so females who are in oestrus have compensated for the potential problem of their availability being washed away by rain by adding staying power to the scent in their dung. For approximately 48 hours rain or sun, the message is there for available males to pick up on. Other messages left at the midden dissipate more rapidly and are affected by the weather so a passing male might even be missed as might a female whose range is far greater than that of the male, however the age of dung can be detected by rhinos so they don’t have to waste energy on seeking out the impossible.
The odour of fresh dung is irresistible to dung beetles who are some of the main processors at the midden. They appear like an armada and get to work with the majority of them beavering away happily under the dung midden fertilising the earth in the process. They reduce the methane output of the dung in the burying and perform numerous other ecological services. From a rhino’s point of view one of the most valuable is acting as delete buttons on old messages. They reduce the white noise of the cornucopia of odours and messages that the dung conveys leaving the way clear for new and interesting messages about who is who in the zoo to be deposited. It’s a rich world not only for white rhinos but for the soil and for myriad of other creatures all of whom benefit from this message filled waste product. It is unfortunately also the place where poachers go to kill rhinos because they know that rhinos will come to deposit their message laden dung and so like puffadders who wait in one spot for their prey to arrive, poachers sit and
wait and are assured of their prey. When they murder a rhino they murder a little eco system. It is a stark reminder of the fact that rhinos are a keystone species and their loss goes far beyond anything statistics of poaching deaths conveys.