Food of the platypus (Ornithorhynchus anatinus) with notes on the food of brown trout (Salmo trutta) in the Shoalhaven River,N.S.W.

Feeding in the platypus (Ornithorhynchus anatinus) was investigated by identifying material found in the cheek pouches of animals trapped in nets in a study area on the upper Shoalhaven River, N.S.W. Benthic samples were taken in the rapids and pools of the river and the relative abundance of food items available was related to the food found in the platypus cheek pouches. The main food organisms found were insect larvae, notably Trichoptera, Diptera, Coleoptera, Ephemeroptera and Odonata. Subsidiary food items found included freshwater shrimp (Paratya australiensis), bivalve mollusks (Sphaerium sp.) and one anuran. The main food items were generally taken in direct proportion to their numerical abundance in the river. Comparisons are made with the food selected by the brown trout (Salmotrutta) from the area. Estimates are made of the weights of invertebrate food necessary to maintain a platypus in various seasonal conditions.