This monograph provides the first comprehensive data on the current status and distribution of marine mammals in East Malaysia waters. Marine mammals are diverse, with 12 of the total 21 species confirmed in these waters observed during boat and aerial surveys. The spinner dolphin is the most commonly sighted and abundant species in open waters. In inshore waters, Irrawaddy dolphin is the most frequently sighted and the only species found upstream. The Indo-Pacific humpback dolphin and dugong are probably low in density and their distribution may be restricted to certain shallow bays. The...