Landing history of 'urus' and its influence on the bird ecosystem in Dongdao Island, Xisha Islands of South China Sea

The Dongdao Island of Xisha Islands is an epitome of the island eco-system of South China Sea, and red-footed booby (Sula sula) and Pissonia grandis are typical species of the island community. However, a large herbivore 'urus' (actually cattle) is now threatening the survival of other species. We analyzed the lithology, as well as organic carbon and nitrogen concentration and isotopes of the sediment core DY2 sampled from the 'Cattle Pond' of Dongdao Island, Xisha Islands. Combined with the isotope results of modern cattle and seabird droppings, we identified the eco-geological characteristic of the 'urus'. According to the AMS14C dating of the lumpy cattle excreta and charcoal on the interface layer, we determined the landing time of 'urus' and identified a population booming after the landing as shown in the isotope profiles. The 'urus', actually cattle, is a special species in the whole island eco-system, but it could disrupt the offshore ecosystem irreversibly; therefore 'urus' population needs to be controlled on a proper level. This research proposed a possible method to study the history of invasive species.