A comparison between the diet of the franciscana and the boto-cinza is presented through the proximate-composition and caloric value of their main prey. The fish Stellifer cf. rastrifer, Pellona harroweri, Anchoa filifera, Isopisthus parvippinnis and Trichiurus lepturus and the squids Loligo sanpaulensis and L. plei were analysed for water, protein, lipid and mineral contents and gross energy (GE). The fish are more important in the diet of the boto-cinza and squids are consumed mostly by the franciscana. Loligo sanpaulensis had the higher water content and protein was the largest fraction of the organic matter in all prey species. Squids presented greater GE values than fish. The data on prey composition and energy from this study are the first for these South American dolphins.
