Save the rhino, save the plant

ALL SPECIES of rhinoceros are in trouble, as poachers kill them to take their horns. But Sumatran rhinos are . Fewer than 80 remain alive, and that handful is scattered between three groups in Sumatra and one in Borneo. This is terrible news for the species itself. But Kim McConkey and Ahimsa Campos-Arceiz at the University of Nottingham, in Britain, think it has wider ramifications—for, as they explain in a paper in , several plant species also depend on Sumatran rhinos for their survival.A large proportion of a Sumatran rhino’s diet is fruit. The evolutionary bargain between frugivores and plants is that the plants coat indigestible seeds with tasty and nutritious pulp as payment for the frugivores’ dispersal of those seeds by defecation far from the plant that produced them. Some plants, indeed, go further. Their seeds will not germinate unless they have passed through an animal’s digestive system. This arrangement works well as long as suitable frugivores are available. But for plants with large seeds, these need to be big animals. And of those, there may be a restricted supply.