Analysis of Stomach Contents of Dugongs From Queensland.

Abstract

Quantitative analysis of samples of the stomach contents of 95 north Queensland dugongs, Dugong dugon, (63 from the Townsville area, 30 from the Mornington Island area and 2 from the Torres Strait area) and one dugong from south Queensland indicates that the diet of most consisted almost entirely of seagrasses of all available genera. Halodule was found in 95% of stomachs, followed by Halophila (89%). Cymodocea (61%) and Thalassia (39%). Seagrass rhizomes were present in all stomachs examined including that of a newborn calf. The generic composition of the stomach contents probably reflects that of the seagrass beds in the areas where the dugongs were captured and is not necessarily indicative of discrimination in selecting food. Non-epiphytic algae occurred in 51% of the stomachs, usually in small amounts. When seagrasses were abundant, dugongs appeared to eat algae often but only in very small amounts (<2% of food volume). Dugongs do not appear to be well adapted to utilize algae as food and probably usually consume them incidentally with seagrasses. Many of the dugongs which drowned in the shark nets near Townsville in the year after a cyclone had severely damaged the seagrass beds in the area, had eaten more of the seagrasses Cymodocea and Thalassia, less of the seagrasses Halodule and Halophila, and more algae than animals which died in other years.